Public policies targeting labour market rigidities
Directory of Open Access Journals (Sweden)
Andreea Claudia ŞERBAN
2013-02-01
Full Text Available Labour market rigidity becomes an issue of increasing importance under conditions of shocks associated with the economic crisis due to the need to increase the adaptability and responsiveness to them. Thus, labour market policies must be directed towards mitigating rigidities caused by institutional or demographic factors or certain mismatch between demand and supply of education qualifications. This paper highlights the major role of the active labour market policies targeting the increase of labour flexibility, stressing the importance and impact on the ability to adapt quickly and effectively to macroeconomic shocks. Located on a declining trend in the years preceding the crisis, spending on labour market policies increased in 2009 in all the Member States of the European Union. Spending differences are significant between countries, Romania being at the lowest end of the European Union. This requires special attention because the increased adaptability of workers through training, as active measure, is of major importance considering the increased speed of changes in the labour market.
Loading on a Rigid Target from Close Proximity Underwater Explosions
Directory of Open Access Journals (Sweden)
Mark Riley
2012-01-01
Full Text Available The study describes recent simulation results for underwater explosions in close-proximity to rigid targets. Simulations are performed using Chinook, an Eulerian computational fluid dynamics (CFD code. Predicted target loadings are compared with measurements taken from a series of experiments conducted under an international collaboration between Canada, The Netherlands, and Sweden. The simulations of the rigid target tests focused on the modelling of gas bubble collapse and water jetting behaviour. Both two-dimensional and three-dimensional simulations were performed. It was found that the two-dimensional analyses produced good bubble periods and reasonable impulse loading compared to experimental data. The time of arrival of the bubble collapse and water jetting were found to be very mesh dependent and refining the mesh did not always produce better results. The two-dimensional approach provides a good initial understanding of the problem for a reasonable computational effort. The three-dimensional simulations were found to produce improved impulse predictions. The numerical gas bubble radii time histories are also compared to empirical time histories.
Real-time non-rigid target tracking for ultrasound-guided clinical interventions
Zachiu, C.; Ries, M.; Ramaekers, P.; Guey, J.-L.; Moonen, C. T. W.; de Senneville, B. Denis
2017-10-01
Biological motion is a problem for non- or mini-invasive interventions when conducted in mobile/deformable organs due to the targeted pathology moving/deforming with the organ. This may lead to high miss rates and/or incomplete treatment of the pathology. Therefore, real-time tracking of the target anatomy during the intervention would be beneficial for such applications. Since the aforementioned interventions are often conducted under B-mode ultrasound (US) guidance, target tracking can be achieved via image registration, by comparing the acquired US images to a separate image established as positional reference. However, such US images are intrinsically altered by speckle noise, introducing incoherent gray-level intensity variations. This may prove problematic for existing intensity-based registration methods. In the current study we address US-based target tracking by employing the recently proposed EVolution registration algorithm. The method is, by construction, robust to transient gray-level intensities. Instead of directly matching image intensities, EVolution aligns similar contrast patterns in the images. Moreover, the displacement is computed by evaluating a matching criterion for image sub-regions rather than on a point-by-point basis, which typically provides more robust motion estimates. However, unlike similar previously published approaches, which assume rigid displacements in the image sub-regions, the EVolution algorithm integrates the matching criterion in a global functional, allowing the estimation of an elastic dense deformation. The approach was validated for soft tissue tracking under free-breathing conditions on the abdomen of seven healthy volunteers. Contact echography was performed on all volunteers, while three of the volunteers also underwent standoff echography. Each of the two modalities is predominantly specific to a particular type of non- or mini-invasive clinical intervention. The method demonstrated on average an accuracy of
Modeling of Micromotion and Analysis of Properties of Rigid Marine Targets
Directory of Open Access Journals (Sweden)
Chen Xiao-long
2015-12-01
Full Text Available As one of the most useful phenomena for separating sea clutter and marine targets, micro-Doppler (m-D describes the refined motion characteristics of a marine target and helps to improve the abilities of radar detection and recognition. In this study, based on maritime radar, the signal model of a target with micromotion in sea clutter is described. Initially, the definitions of micromotion and m-D are briefly reviewed with a description of their details, and a classification of rigid marine targets that exhibit micromotion is introduced. Then, according to the duration of the observation time, we establish two types of signal models, i.e., in one range unit and across range unit. According to the type of motion, we establish separate signal models for non-uniform translational motion and rotational motion. Finally, the properties of micromotion are analyzed using real radar data, and the effectiveness of the established models is verified.
Aiyegbo, Mohammed S; Shmelkov, Evgeny; Dominguez, Lorenzo; Goger, Michael; Battacharya, Shibani; deCamp, Allan C; Gilbert, Peter B; Berman, Phillip W; Cardozo, Timothy
2017-01-01
The only evidence of vaccine-induced protection from HIV acquisition in humans was obtained in the RV144 HIV vaccine clinical trial. One immune correlate of risk in RV144 was observed to be higher titers of vaccine-induced antibodies (Abs) reacting with a 23-mer non-glycosylated peptide with the same amino acid sequence as a segment in the second variable (V2) loop of the MN strain of HIV. We used NMR to analyze the dynamic 3D structure of this peptide. Distance restraints between spatially proximate inter-residue protons were calculated from NOE cross peak intensities and used to constrain a thorough search of all possible conformations of the peptide. α-helical folding was strongly preferred by part of the peptide. A high-throughput structure prediction of this segment in all circulating HIV strains demonstrated that α-helical conformations are preferred by this segment almost universally across all subtypes. Notably, α-helical conformations of this segment of the V2 loop cluster cross-subtype-conserved amino acids on one face of the helix and the variable amino acid positions on the other in a semblance of an amphipathic α-helix. Accordingly, some Abs that protected against HIV in RV144 may have targeted a specific, conserved α-helical peptide epitope in the V2 loop of HIV's surface envelope glycoprotein.
Pallavaram, Srivatsan; D'Haese, Pierre-François; Lake, Wendell; Konrad, Peter E.; Dawant, Benoit M.; Neimat, Joseph S.
2015-01-01
Background Finding the optimal location for the implantation of the electrode in Deep Brain Stimulation (DBS) surgery is crucial for maximizing therapeutic benefit to the patient. Such targeting is challenging for several reasons including anatomical variability between patients as well as lack of consensus about the location of the optimal target. Objective To compare the performance of popular manual targeting methods against a fully automatic non-rigid image registration based approach. Methods In 71 Parkinson's disease STN-DBS implantations, an experienced functional neurosurgeon selected the target manually using three different approaches; indirect targeting using standard stereotactic coordinates, direct targeting based on the patient MRI, and indirect targeting relative to the red nucleus. Targets were also automatically predicted using a leave-one-out approach to populate the CranialVault atlas using non-rigid image registration. The different targeting methods were compared against the location of the final active contact, determined through iterative clinical programming in each individual patient. Results Targeting using standard stereotactic coordinates corresponding to the center of the motor territory of the STN had the largest targeting error (3.69 mm), followed by direct targeting (3.44 mm), average stereotactic coordinates of active contacts from this study (3.02 mm), red nucleus based targeting (2.75 mm), and non-rigid image registration based automatic predictions using the CranialVault atlas (2.70 mm). The CranialVault atlas method had statistically smaller variance than all manual approaches. Conclusions Fully automatic targeting based on non-rigid image registration using the CranialVault atlas is as accurate and more precise than popular manual methods for STN-DBS. PMID:25988929
[Prostate cancer diagnostic by saturation randomized biopsy versus rigid targeted biopsy].
Defontaines, J; Salomon, L; Champy, C; Cholley, I; Chiaradia, M; de la Taille, A
2017-12-01
Optimal diagram teaming up randomized biopsy (BR) to targeted biopsy (BC) is still missing for the diagnostic of prostate cancer (CP). This study compares diagram of 6, 12 or 18 BR with or without BC rigid. Between January 2014 and May 2016, 120 patients had prostate biopsy BR and BC. Each patient had 18 BR and BC. Results compared sextant (6 BR), standard (12 BR) and saturation (18 BR) protocol with or without the adding of BC for the detection of CP. Rectal examination was normal, mean PSA at 8.99ng/mL and mean volume at 54cm 3 . It was first round for 48% of patients. Forty-four cancers were found by the group 18 BR+BC (control). The detection rate was respectively, for 6, 12 and 18 BR of 61%, 82% and 91%. The add of BC increased this detection of +27% for 6 BR+BC, +13% for 12 BR+BC and +9% for 18 BR+BC. BC found 70% of all CP. Nine percent of CP were missed by BR only. Significant CP (Gleason≥7) diagnostic was the same for 12 BR+BC and 18 BR+BC. The add of BC to BR increase the detection of CP by 10%. Twelve BR+BC is the optimal diagram for the diagnostic of CP finding 95% of CP and 97% of significant CP. 4. Copyright © 2017 Elsevier Masson SAS. All rights reserved.
McLeod, Gemma; Sherriff, Jill; Hartmann, Peter E; Nathan, Elizabeth; Geddes, Donna; Simmer, Karen
2016-02-14
The variable content of human breast milk suggests that its routine fortification may result in sub-optimal nutritional intakes and growth. In a pragmatic trial, we randomised infants born below 30 weeks of gestation to either the intervention (Igp) of fortifying milk on measured composition according to birth weight criteria and postmenstrual age (PMA) or our routine practice (RPgp) of fortifying on assumed milk composition to target 3·8-4·4 g protein/kg per d and 545-629 kJ/kg per d. Milk composition was measured using the MIRIS® Human Milk Analyser. Percentage fat mass (%FM) was measured using PEA POD (COSMED). The effects of macronutrient intakes and clinical variables on growth were assessed using mixed model analysis. Mean measured protein content (1·6 g/100 ml) was higher than the assumed value (1·4 g/100 ml), often leading to lower amounts of fortifier added to the milk of intervention infants. At discharge (Igp v. RPgp), total protein (3·2 (SD 0·3) v. 3·4 (SD 0·4) g; P=0·067) and energy (456 (SD 39) v. 481 (SD 48) kJ; P=0·079) intakes from all nutrition sources, weight gain velocity (11·4 (SD 1·4) v. 12·1 (SD 1·6) g/kg per d; P=0·135) and %FM (13·7 (SD 3·6) v.13·6 (SD 3·5) %; P=0·984) did not significantly differ between groups. A protein intake >3·4 g/kg per d reduced %FM by 2%. Nutrition and growth was not improved by targeting milk fortification according to birth weight criteria and PMA using measured milk composition, compared with routine practice. Targeting fortification on measured composition is labour intensive, requiring frequent milk sampling and precision measuring equipment, perhaps reasons for its limited practice. Guidance around safe upper levels of milk fortification is needed.
Collaboration: Assumed or Taught?
Kaplan, Sandra N.
2014-01-01
The relationship between collaboration and gifted and talented students often is assumed to be an easy and successful learning experience. However, the transition from working alone to working with others necessitates an understanding of issues related to ability, sociability, and mobility. Collaboration has been identified as both an asset and a…
Morlieras, Jessica; Dufort, Sandrine; Sancey, Lucie; Truillet, Charles; Mignot, Anna; Rossetti, Fabien; Dentamaro, Mario; Laurent, Sophie; Vander Elst, Luce; Muller, Robert N; Antoine, Rodolphe; Dugourd, Philippe; Roux, Stéphane; Perriat, Pascal; Lux, François; Coll, Jean-Luc; Tillement, Olivier
2013-09-18
Gadolinium based Small Rigid Plaforms (SRPs) have previously demonstrated their efficiency for multimodal imaging and radiosensitization. Since the RGD sequence is well-known to be highly selective for αvβ3 integrins, a cyclic pentapeptide containing the RGD motif (cRGDfK) has been grafted onto the SRP surface. An appropriate protocol led to the grafting of two targeting ligands per nano-object. The resulting nanoparticles have demonstrated a strong association with αvβ3 integrins in comparison with cRADfK grafted SRPs as negative control. Flow cytometry and fluorescence microscopy have also been used to highlight the ability of the nanoparticles to target efficiently HEK293(β3) and U87MG cells. Finally the grafted radiosensitizing nanoparticles were intravenously injected into Nude mice bearing subcutaneous U87MG tumors and the signal observed by optical imaging was twice as high for SRP-cRGDfK compared to their negative analogue.
An on-line learning tracking of non-rigid target combining multiple-instance boosting and level set
Chen, Mingming; Cai, Jingju
2013-10-01
Visual tracking algorithms based on online boosting generally use a rectangular bounding box to represent the position of the target, while actually the shape of the target is always irregular. This will cause the classifier to learn the features of the non-target parts in the rectangle region, thereby the performance of the classifier is reduced, and drift would happen. To avoid the limitations of the bounding-box, we propose a novel tracking-by-detection algorithm involving the level set segmentation, which ensures the classifier only learn the features of the real target area in the tracking box. Because the shape of the target only changes a little between two adjacent frames and the current level set algorithm can avoid the re-initialization of the signed distance function, it only takes a few iterations to converge to the position of the target contour in the next frame. We also make some improvement on the level set energy function so that the zero level set would have less possible to converge to the false contour. In addition, we use gradient boost to improve the original multi-instance learning (MIL) algorithm like the WMILtracker, which greatly speed up the tracker. Our algorithm outperforms the original MILtracker both on speed and precision. Compared with the WMILtracker, our algorithm runs at a almost same speed, but we can avoid the drift caused by background learning, so the precision is better.
The structure of rigid functions
Balka, Richárd; Elekes, Márton
2008-09-01
A function is called vertically rigid if graph(cf) is isometric to graph(f) for all c[not equal to]0. We prove Jankovic's conjecture by showing that a continuous function is vertically rigid if and only if it is of the form a+bx or a+bekx (). We answer the question of Cain, Clark and Rose by showing that there exists a Borel measurable vertically rigid function which is not of the above form. We discuss the Lebesgue and Baire measurable case, consider functions bounded on some interval and functions with at least one point of continuity. We also introduce horizontally rigid functions, and show that a certain structure theorem can be proved without assuming any regularity.
Yang, D S; Yoon, W S; Lee, J A; Lee, N K; Lee, S; Kim, C Y; Yim, H J; Lee, S H; Chung, H H; Cha, S H
2014-09-01
To achieve consistent target delineation in radiotherapy for hepatocellular carcinoma (HCC), image registration between simulation CT and diagnostic MRI was explored. Twenty patients with advanced HCC were included. The median interval between MRI and CT was 11 days. CT was obtained with shallow free breathing and MRI at exhale phase. On each CT and MRI, the liver and the gross target volume (GTV) were drawn. A rigid image registration was taken according to point information of vascular bifurcation (Method[A]) and pixel information of volume of interest only including the periphery of the liver (Method[B]) and manually drawn liver (Method[C]). In nine cases with an indefinite GTV on CT, a virtual sphere was generated at the epicenter of the GTV. The GTV from CT (VGTV[CT]) and MRI (VGTV[MR]) and the expanded GTV from MRI (V+GTV[MR]) considering geometrical registration error were defined. The underestimation (uncovered V[CT] by V[MR]) and the overestimation (excessive V[MR] by V[CT]) were calculated. Through a paired T-test, the difference between image registration techniques was analyzed. For method[A], the underestimation rates of VGTV[MR] and V+GTV[MR] were 16.4 ± 8.9% and 3.2 ± 3.7%, and the overestimation rates were 16.6 ± 8.7% and 28.4 ± 10.3%, respectively. For VGTV[MR] and V+GTV[MR], the underestimation rates and overestimation rates of method[A] were better than method[C]. The underestimation rates and overestimation rates of the VGTV[MR] were better in method[B] than method[C]. By image registration and additional margin, about 97% of HCC could be covered. Method[A] or method[B] could be recommended according to physician preference. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Steven J. Gortler
2013-12-01
Full Text Available We study the properties of affine rigidity of a hypergraph and prove a variety of fundamental results. First, we show that affine rigidity is a generic property (i.e., depends only on the hypergraph, not the particular embedding. Then we prove that a graph is generically neighborhood affinely rigid in d-dimensional space if it is (d+1-vertex-connected. We also show neighborhood affine rigidity of a graph implies universal rigidity of its squared graph. Our results, and affine rigidity more generally, have natural applications in point registration and localization, as well as connections to manifold learning.
Rigid particulate matter sensor
Hall, Matthew [Austin, TX
2011-02-22
A sensor to detect particulate matter. The sensor includes a first rigid tube, a second rigid tube, a detection surface electrode, and a bias surface electrode. The second rigid tube is mounted substantially parallel to the first rigid tube. The detection surface electrode is disposed on an outer surface of the first rigid tube. The detection surface electrode is disposed to face the second rigid tube. The bias surface electrode is disposed on an outer surface of the second rigid tube. The bias surface electrode is disposed to face the detection surface electrode on the first rigid tube. An air gap exists between the detection surface electrode and the bias surface electrode to allow particulate matter within an exhaust stream to flow between the detection and bias surface electrodes.
2010-11-01
rayon de bulle de type champ libre , d’une cible rigide. À cette distance de sécurité, l’onde de choc et la bulle de gaz contribuent de façon...bulle de type champ libre maximal. Résultats : Le présent rapport donne les résultats d’une étude utilisant le logiciel qui utilise la dynamique...Chinook software . During a presentation of this material at the 81st SAVIAC Symposium, it was brought to the authors’ attention that the divergence of
Non-rigid registration by geometry-constrained diffusion
DEFF Research Database (Denmark)
Andresen, Per Rønsholt; Nielsen, Mads
2001-01-01
Assume that only partial knowledge about a non-rigid registration is given: certain points, curves, or surfaces in one 3D image are known to map to certain points, curves, or surfaces in another 3D image. In trying to identify the non-rigid registration field, we face a generalized aperture problem...
Csermely, Peter; Hódsági, János; Korcsmáros, Tamás; Módos, Dezső; Perez-Lopez, Áron R; Szalay, Kristóf; Veres, Dániel V; Lenti, Katalin; Wu, Ling-Yun; Zhang, Xiang-Sun
2015-02-01
Cancer is increasingly perceived as a systems-level, network phenomenon. The major trend of malignant transformation can be described as a two-phase process, where an initial increase of network plasticity is followed by a decrease of plasticity at late stages of tumor development. The fluctuating intensity of stress factors, like hypoxia, inflammation and the either cooperative or hostile interactions of tumor inter-cellular networks, all increase the adaptation potential of cancer cells. This may lead to the bypass of cellular senescence, and to the development of cancer stem cells. We propose that the central tenet of cancer stem cell definition lies exactly in the indefinability of cancer stem cells. Actual properties of cancer stem cells depend on the individual "stress-history" of the given tumor. Cancer stem cells are characterized by an extremely large evolvability (i.e. a capacity to generate heritable phenotypic variation), which corresponds well with the defining hallmarks of cancer stem cells: the possession of the capacity to self-renew and to repeatedly re-build the heterogeneous lineages of cancer cells that comprise a tumor in new environments. Cancer stem cells represent a cell population, which is adapted to adapt. We argue that the high evolvability of cancer stem cells is helped by their repeated transitions between plastic (proliferative, symmetrically dividing) and rigid (quiescent, asymmetrically dividing, often more invasive) phenotypes having plastic and rigid networks. Thus, cancer stem cells reverse and replay cancer development multiple times. We describe network models potentially explaining cancer stem cell-like behavior. Finally, we propose novel strategies including combination therapies and multi-target drugs to overcome the Nietzschean dilemma of cancer stem cell targeting: "what does not kill me makes me stronger". Copyright © 2014 Elsevier Ltd. All rights reserved.
Nonlinear dynamic behavior of microscopic bubbles near a rigid wall
Suslov, Sergey A.; Ooi, Andrew; Manasseh, Richard
2012-06-01
The nonlinear dynamic behavior of microscopic bubbles near a rigid wall is investigated. Oscillations are driven by the ultrasonic pressure field that arises in various biomedical applications such as ultrasound imaging or targeted drug delivery. It is known that, when bubbles approach a blood-vessel wall, their linear dynamic response is modified. This modification may be very useful for real-time detection of bubbles that have found targets; in future therapeutic technologies, it may be useful for controlled release of medical agents encapsulating microbubbles. In this paper, the nonlinear response of microbubbles near a wall is studied. The Keller-Miksis-Parlitz equation is adopted, but modified to account for the presence of a rigid wall. This base model describes the time evolution of the bubble surface, which is assumed to remain spherical, and accounts for the effect of acoustic radiation losses owing to liquid compressibility in the momentum conservation. Two situations are considered: the base case of an isolated bubble in an unbounded medium, and a bubble near a rigid wall. In the latter case, the wall influence is modeled by including a symmetrically oscillating image bubble. The bubble dynamics is traced using a numerical solution of the model equation. Subsequently, Floquet theory is used to accurately detect the bifurcation point where bubble oscillations stop following the driving ultrasound frequency and undergo period-changing bifurcations. Of particular interest is the detection of the subcritical period-tripling and -quadrupling transition. The parametric bifurcation maps are obtained as functions of nondimensional parameters representing the bubble radius, the frequency and pressure amplitude of the driving ultrasound field, and the distance from the wall. It is shown that the presence of the wall generally stabilises the bubble dynamics, so that much larger values of the pressure amplitude are needed to generate nonlinear responses. Thus, a
Weiss, Asia; Whiteley, Walter
2014-01-01
This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme. Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology. The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...
Energy Technology Data Exchange (ETDEWEB)
Steckle, W.P. Jr. [Los Alamos National Lab., NM (United States); Mitchell, M.A. [Chemidal Corp., Palatine, IL (United States); Aspen, P.G. [Simula Inc., Phoenix, AZ (United States)
1998-12-31
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Organic analogues to inorganic zeolites would be a significant step forward in engineered porous materials and would provide advantages in range, selectivity, tailorability, and processing. Rigid molecular foams or {open_quotes}organic zeolites{close_quotes} would not be crystalline materials and could be tailored over a broader range of pore sizes and volumes. A novel process for preparing hypercrosslinked polymeric foams has been developed via a Friedel-Crafts polycondensation reaction. A series of rigid hypercrosslinked foams have been prepared using simple rigid polyaromatic hydrocarbons including benzene, biphenyl, m-terphenyl, diphenylmethane, and polystyrene, with dichloroxylene (DCX) as the pore size. After drying the foams are robust and rigid. Densities of the resulting foams can range from 0.15 g/cc to 0.75 g/cc. Nitrogen adsorption studies have shown that by judiciously selecting monomers and the crosslinking agent along with the level of crosslinking and the cure time of the resulting gel, the pore size, pore size distribution, and the total surface area of the foam can be tailored. Surface areas range from 160 to 1,200 m{sup 2}/g with pore sizes ranging from 6 {angstrom} to 2,000 {angstrom}.
Near field acoustic holography with microphones on a rigid sphere
DEFF Research Database (Denmark)
Jacobsen, Finn; Moreno-Pescador, Guillermo; Fernandez Grande, Efren
2011-01-01
Spherical near field acoustic holography (spherical NAH) is a technique that makes it possible to reconstruct the sound field inside and just outside a spherical surface on which the sound pressure is measured with an array of microphones. This is potentially very useful for source identification....... The sphere can be acoustically transparent or it can be rigid. A rigid sphere is somewhat more practical than an open sphere. However, spherical NAH based on a rigid sphere is only valid if it can be assumed that the sphere has a negligible influence on the incident sound field, and this is not necessarily...
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.
DEFF Research Database (Denmark)
Niebe, Sarah Maria
The topic of this thesis is the numerics of rigid body simulation, with focus on the contact force problem. Three contact force models are presented, followed by three contact point determination methods. To solve the contact force problem, six different numerical methods are presented, each......-Seidel (PGS), although computationally more expensive. The NNCG method has been implemented in the physics library Bullet, as of revision r2709, as an alternative to the PGS method. A subspace minimization method is developed to improve convergence of the PGS method, improving the results of large mass ratio...
Rigid Motion and Adapted Frames
Lyle, Stephen N.
The aim here is to describe the rigid motion of a continuous medium in special and general relativity. Section 7.1 defines a rigid rod in special relativity, and Sect. 7.2 shows the link with the space coordinates of a certain kind of accelerating frame in flat spacetimes. Section 7.3 then sets up a notation for describing the arbitrary smooth motion of a continuous medium in general curved spacetimes, defining the proper metric of such a medium. Section 7.4 singles out rigid motions and shows that the rod in Sect. 7.1 undergoes rigid motion in the more generally defined sense. Section 7.5 defines a rate of strain tensor for a continuous medium in general relativity and reformulates the rigidity criterion. Section 7.6 aims to classify all possible rigid motions in special relativity, reemphasizing the link with semi-Euclidean frames adapted to accelerating observers in special relativity. Then, Sects. 7.7 and 7.8 describe rigid motion without rotation and rigid rotation, respectively. Along the way we introduce the notion of Fermi-Walker transport and discuss its relevance for rigid motions. Section 7.9 brings together all the above themes in an account of a recent generalization of the notion of uniform acceleration, thereby characterizing a wide class of rigid motions.
DEFF Research Database (Denmark)
Let $U_q$ denote the quantum group associated with a finite dimensional semisimple Lie algebra. Assume that $q$ is a complex root of unity of odd order and that $U_q$ is %the quantum group version obtained via Lusztig's $q$-divided powers construction. We prove that all regular projective (tiltin...
Torsional Rigidity of Minimal Submanifolds
DEFF Research Database (Denmark)
Markvorsen, Steen; Palmer, Vicente
2006-01-01
We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...... for the torsional rigidity are actually attained and give conditions under which the geometric average of the stochastic mean exit time for Brownian motion at infinity is finite....
Energy Technology Data Exchange (ETDEWEB)
Park, Sora; Ahn, Jeung Sun; Kwon, Young-Kyun; Tomanek, David [Department of Physics and Research Institute for Basic Sciences, Kyung Hee University, Seoul, 130-701 (Korea, Republic of); Kittimanapun, Kritsada, E-mail: ykkwon@khu.ac.k, E-mail: tomanek@pa.msu.ed [Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824-2320 (United States)
2010-08-25
We use ab initio density functional calculations to study the stability, elastic properties and electronic structure of sp{sup 2} carbon minimal surfaces with negative Gaussian curvature, called schwarzites. We focus on two systems with cubic unit cells containing 152 and 200 carbon atoms, which are metallic and very rigid. The porous schwarzite structure allows for efficient and reversible doping by electron donors and acceptors, making it a promising candidate for the next generation of alkali ion batteries. We identify schwarzite structures that act as arrays of interconnected spin quantum dots or become magnetic when doped. We introduce two interpenetrating schwarzite structures that may find their use as the ultimate super-capacitor.
DEFF Research Database (Denmark)
Troiano, Giovanni Maria
Deformable and shape-changing interfaces are rapidly emerging in the field of human-computer interaction (HCI). Deformable interfaces provide users with newer input possibilities such as bending, squeezing, or stretching, which were impossible to achieve with rigid interfaces. Shape...... sensors in the five preferred objects and programmed them for controlling sounds with computer software. Finally, we ran a performance study where six musicians performed music with deformable interfaces at their studios. Results from the performance study show that musicians systematically map......, Transformation, Adaptation and Physicalization. In synthesis, the work presented in this thesis shows (1) implications of usefulness for deformable interfaces and how their new input modalities can redefine the way users interact with computers, and (2) how a systematic understanding of conventional design...
Semiclassical Theory of Spectral Rigidity
Berry, M. V.
1985-08-01
The spectral rigidity Δ(L) of a set of quantal energy levels is the mean square deviation of the spectral staircase from the straight line that best fits it over a range of L mean level spacings. In the semiclassical limit (hslash-> 0), formulae are obtained giving Δ(L) as a sum over classical periodic orbits. When L ~= Lmax, where Lmax ~ hslash-(N-1) for a system of N freedoms, Δ(L) is shown to display the following universal behaviour as a result of properties of very long classical orbits: if the system is classically integrable (all periodic orbits filling tori), Δ(L) = 1/15L (as in an uncorrelated (Poisson) eigenvalue sequence); if the system is classically chaotic (all periodic orbits isolated and unstable) and has no symmetry, Δ(L) = ln L/2π^2 + D if 1 ~= L ~= Lmax (as in the gaussian unitary ensemble of random-matrix theory); if the system is chaotic and has time-reversal symmetry, Δ(L) = ln L/π^2 + E if 1 ~= L ~= Lmax (as in the gaussian orthogonal ensemble). When L >> Lmax, Δ(L) saturates non-universally at a value, determined by short classical orbits, of order hslash-(N-1) for integrable systems and ln (hslash-1) for chaotic systems. These results are obtained by using the periodic-orbit expansion for the spectral density, together with classical sum rules for the intensities of long orbits and a semiclassical sum rule restricting the manner in which their contributions interfere. For two examples Δ(L) is studied in detail: the rectangular billiard (integrable), and the Riemann zeta function (assuming its zeros to be the eigenvalues of an unknown quantum system whose unknown classical limit is chaotic).
Quantum charged rigid membrane
Energy Technology Data Exchange (ETDEWEB)
Cordero, Ruben [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N., Unidad Adolfo Lopez Mateos, Edificio 9, 07738 Mexico, D.F. (Mexico); Molgado, Alberto [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Zacatecas Zac. (Mexico); Rojas, Efrain, E-mail: cordero@esfm.ipn.mx, E-mail: amolgado@fisica.uaz.edu.mx, E-mail: efrojas@uv.mx [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)
2011-03-21
The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.
Interaction of the rigid journal with Newtonian fluid
Michal, Havlásek; František, Pochylý
2017-09-01
This paper deals with the problem of identification of added effects of incompressible Newtonian fluid that impacts on the rigid journal performing translational motion. It considers two degrees of freedom. The axial motion of the rigid journal was neglected. It assumes small oscillations and linear model. The task was solved for two geometrical configurations of the computational domain. In the first variant of geometry, there is no flow between the bases of journal and stator. The second variant of geometry also allows liquid to flow in space between the bases of journal and stator. The introduction describes the mathematical model for the identification of added mass, damping and stiffness matrices. On the basis of the mathematical model and computational modeling of velocity and pressure fields using CFD, the force components are determined. From there, the mentioned matrices are determined depending on the eccentricity of the rigid journal.
A note on the assumed distributions in stochastic frontier models
Meesters, Aljar
2014-01-01
Stochastic frontier models all need an assumption on the distributional form of the (in)efficiency component. Generally this efficiency component is assumed to be half normally, truncated normally, or exponentially distributed. This paper shows that the exponential distribution is, just like the
Statistical motor number estimation assuming a binomial distribution
Blok, J.H.; Visser, G.H.; de Graaf, S.; Zwarts, M.J.; Stegeman, D.F.
2005-01-01
The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution.
Statistical motor number estimation assuming a binomial distribution.
Blok, J.H.; Visser, G.H.A.; Graaf, S.S.N. de; Zwarts, M.J.; Stegeman, D.F.
2005-01-01
The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution.
Significance of the shape of the assumed concrete compression ...
African Journals Online (AJOL)
In this study, the effect of assuming a parabolic-rectangular or rectangular shape of the concrete compression block on the analysis and design of reinforced concrete beams has been investigated. Analytical expressions are derived for the steel reinforcement ratio, the concrete compressive force coefficient and the design ...
Rigid therapies, rigid minds: italian professionals' perspectives on autism interventions.
Cascio, M Ariel
2015-06-01
Many therapies, interventions, and programs seek to improve outcomes and quality of life for people diagnosed with autism spectrum conditions. This paper addresses Italian professionals' perspectives on a variety of such interventions, including TEACCH, ABA, Defeat Autism Now!, and Doman-Delacato. Drawing on participant-observation and interviews collected in 2012-2013 in a northern region of Italy, it highlights the theme of "rigidity" that appears in professionals' discourses about both the characteristics of people with autism and the potential risks of adhering too strictly to any particular treatment protocol. The co-occurrence of the theme of rigidity across different domains demonstrates a way in which diagnostic characteristics become metaphors for medical practice. This paper proposes that such discursive moves may help bridge the gap between people with autism and people who work with them because a key attribute of people with autism-thinking and/or acting rigidly-is also a potential pitfall for people without autism.
The dynamical rigid body with memory
Albu, Ion Doru; Neamtu, Mihaela; Opris, Dumitru
2007-01-01
In the present paper we describe the dynamics of the revised rigid body, the dynamics of the rigid body with distributed delays and the dynamics of the fractional rigid body. We analyze the stationary states for given values of the rigid body's parameters.
Modeling turbulent/chemistry interactions using assumed pdf methods
Gaffney, R. L, Jr.; White, J. A.; Girimaji, S. S.; Drummond, J. P.
1992-01-01
Two assumed probability density functions (pdfs) are employed for computing the effect of temperature fluctuations on chemical reaction. The pdfs assumed for this purpose are the Gaussian and the beta densities of the first kind. The pdfs are first used in a parametric study to determine the influence of temperature fluctuations on the mean reaction-rate coefficients. Results indicate that temperature fluctuations significantly affect the magnitude of the mean reaction-rate coefficients of some reactions depending on the mean temperature and the intensity of the fluctuations. The pdfs are then tested on a high-speed turbulent reacting mixing layer. Results clearly show a decrease in the ignition delay time due to increases in the magnitude of most of the mean reaction rate coefficients.
Chemically reacting supersonic flow calculation using an assumed PDF model
Farshchi, M.
1990-01-01
This work is motivated by the need to develop accurate models for chemically reacting compressible turbulent flow fields that are present in a typical supersonic combustion ramjet (SCRAMJET) engine. In this paper the development of a new assumed probability density function (PDF) reaction model for supersonic turbulent diffusion flames and its implementation into an efficient Navier-Stokes solver are discussed. The application of this model to a supersonic hydrogen-air flame will be considered.
Rigidly foldable origami gadgets and tessellations.
Evans, Thomas A; Lang, Robert J; Magleby, Spencer P; Howell, Larry L
2015-09-01
Rigidly foldable origami allows for motion where all deflection occurs at the crease lines and facilitates the application of origami in materials other than paper. In this paper, we use a recently discovered method for determining rigid foldability to identify existing flat-foldable rigidly foldable tessellations, which are also categorized. We introduce rigidly foldable origami gadgets which may be used to modify existing tessellations or to create new tessellations. Several modified and new rigidly foldable tessellations are presented.
DEFF Research Database (Denmark)
Rijkhoff, Jan
2010-01-01
This article argues that in addition to the major flexible lexical categories in Hengeveld’s classification of parts of speech systems (Contentive, Non-Verb, Modifier), there are also flexible word classes within the rigid lexical category Noun (Set Noun, Sort Noun, General Noun). Members...... classes. Finally this article wants to claim that the distinction between rigid and flexible noun categories (a) adds a new dimension to current classifications of parts of speech systems, (b) correlates with certain grammatical phenomena (e.g. so-called number discord), and (c) helps to explain the parts...
Design of the new rigid endoscope distortion measurement system
Zhai, Xiaohao; Liu, Xiaohua; Liu, Ming; Hui, Mei; Dong, Liquan; Zhao, Yuejin; Wang, Yakun; Li, Yonghui; Zhou, Peng
2015-08-01
Endoscopic imaging quality affects industrial safety and medical security. Rigid endoscope distortion is of great signification as one of optical parameters to evaluate the imaging quality. This paper introduces a new method of rigid endoscope distortion measurement, which is different from the common methods with low accuracy and fussy operation. It contains a Liquid Crystal Display (LCD) to display the target, a CCD to obtain the images with distortion, and a computer to process the images. The LCD is employed instead of common white screen. The autonomous control system of LCD makes it showing the test target designed for distortion, and its parameter is known. LCD control system can change the test target to satisfy the different demand for accuracy, which avoids replacing target frequently. The test system also contains a CCD to acquire images in the exit pupil position of rigid endoscope. Rigid endoscope distortion is regarded as centrosymmetric, and the MATLAB software automatically measures it by processing the images from CCD. The MATLAB software compares target images with that without distortion on LCD and calculates the results. Relative distortion is obtained at different field of view (FOV) radius. The computer plots the curve of relative distortion, abscissa means radius of FOV, ordinate means relative distortion. The industry standard shows that, the distortion at 70% field of view is pointed on the curve, which can be taken as an evaluation standard. This new measuring method achieves advantages of high precision, high degree of intelligence, excellent repeatability and gets calculation results quickly.
Beyond an assumed mother–child symbiosis in nutritional guidelines
DEFF Research Database (Denmark)
Nielsen, Annemette; Michaelsen, Kim F.; Holm, Lotte
2014-01-01
Researchers question the implications of the way in which “motherhood” is constructed in public health discourse. Current nutritional guidelines for Danish parents of young children are part of this discourse. They are shaped by an assumed symbiotic relationship between the nutritional needs...... practical solutions for the whole family in a busy everyday life, to socialise the child into the family and society at large, and to create personal relief from the strain small children put on time and energy all served as socially acceptable reasons for knowingly departing from nutritional...... recommendations. These findings suggest that information about parental concerns is important both if we are to understand the successes and failures of existing health initiatives on child-feeding and if we are to plan effective interventions in the future. The study suggests that current Danish guidelines...
Rigid 4D N=2 supersymmetric backgrounds and actions
Energy Technology Data Exchange (ETDEWEB)
Butter, Daniel; Inverso, Gianluca; Lodato, Ivano [Nikhef Theory Group,Science Park 105, 1098 XG Amsterdam (Netherlands)
2015-09-15
We classify all N=2 rigid supersymmetric backgrounds in four dimensions with both Lorentzian and Euclidean signature that preserve eight real supercharges, up to discrete identifications. Among the backgrounds we find specific warpings of S{sup 3}×ℝ and AdS{sub 3}×ℝ, AdS{sub 2}×S{sup 2} and H{sup 2}×S{sup 2} with generic radii, and some more exotic geometries. We provide the generic two-derivative rigid vector and hypermultiplet actions and analyze the conditions imposed on the special Kähler and hyperkähler target spaces.
Rigid body dynamics of mechanisms
Hahn, Hubert
2003-01-01
The second volume of Rigid Body Dynamics of Mechanisms covers applications via a systematic method for deriving model equations of planar and spatial mechanisms. The necessary theoretical foundations have been laid in the first volume that introduces the theoretical mechanical aspects of mechatronic systems. Here the focus is on the application of the modeling methodology to various examples of rigid-body mechanisms, simple planar ones as well as more challenging spatial problems. A rich variety of joint models, active constraints, plus active and passive force elements is treated. The book is intended for self-study by working engineers and students concerned with the control of mechanical systems, i.e. robotics, mechatronics, vehicles, and machine tools. The examples included are a likely source from which to choose models for university lectures.
Elasticity of Relativistic Rigid Bodies?
Smarandache, Florentin
2013-10-01
In the classical Twin Paradox, according to the Special Theory of Relativity, when the traveling twin blasts off from the Earth to a relative velocity v =√{/3 } 2 c with respect to the Earth, his measuring stick and other physical objects in the direction of relative motion shrink to half their lengths. How is that possible in the real physical world to have let's say a rigid rocket shrinking to half and then later elongated back to normal as an elastic material when it stops? What is the explanation for the traveler's measuring stick and other physical objects, in effect, return to the same length to their original length in the Stay-At-Home, but there is no record of their having shrunk? If it's a rigid (not elastic) object, how can it shrink and then elongate back to normal? It might get broken in such situation.
DEFF Research Database (Denmark)
Rijkhoff, Jan
2008-01-01
Studies in Language 32-3 (2008), 727-752. Special issue: Parts of Speech: Descriptive tools, theoretical constructs Jan Rijkhoff - On flexible and rigid nouns This article argues that in addition to the flexible lexical categories in Hengeveld’s classification of parts-of-speech systems (Contentive...... classifications of parts-of-speech systems, (b) correlates with certain grammatical phenomena (e.g. so called number discord), and (c) helps to explain the parts-of-speech hierarchy....
Inference of directional selection and mutation parameters assuming equilibrium.
Vogl, Claus; Bergman, Juraj
2015-12-01
In a classical study, Wright (1931) proposed a model for the evolution of a biallelic locus under the influence of mutation, directional selection and drift. He derived the equilibrium distribution of the allelic proportion conditional on the scaled mutation rate, the mutation bias and the scaled strength of directional selection. The equilibrium distribution can be used for inference of these parameters with genome-wide datasets of "site frequency spectra" (SFS). Assuming that the scaled mutation rate is low, Wright's model can be approximated by a boundary-mutation model, where mutations are introduced into the population exclusively from sites fixed for the preferred or unpreferred allelic states. With the boundary-mutation model, inference can be partitioned: (i) the shape of the SFS distribution within the polymorphic region is determined by random drift and directional selection, but not by the mutation parameters, such that inference of the selection parameter relies exclusively on the polymorphic sites in the SFS; (ii) the mutation parameters can be inferred from the amount of polymorphic and monomorphic preferred and unpreferred alleles, conditional on the selection parameter. Herein, we derive maximum likelihood estimators for the mutation and selection parameters in equilibrium and apply the method to simulated SFS data as well as empirical data from a Madagascar population of Drosophila simulans. Copyright © 2015 Elsevier Inc. All rights reserved.
Wrist rigidity assessment during Deep Brain Stimulation surgery.
Costa, Pedro; Rosas, Maria José; Vaz, Rui; Cunha, João Paulo
2015-01-01
Parkinson's Disease (PD) patients often need Deep Brain Stimulation (DBS) surgery when they become intolerant to drugs or these lose efficiency. A stimulation electrode is implanted in the basal ganglia to promote the functional control of the deregulated dopaminergic motor pathways. The stimulation target is defined by medical imaging, followed by electrophysiological inspection for fine electrode position trimming and electrical stimulation tuning. Intra-operative stimulation of the target and the evaluation of wrist rigidity allows to choose the stimulation parameters which best alleviate PD symptoms without side effects. Neurologists impose a passive wrist flexion movement and qualitatively describe the perceived decrease in rigidity under different voltages, based on its experience and with subjectivity. We designed a novel, comfortable and wireless wearable motion sensor to classify the wrist rigidity by deriving a robust signal descriptor from angular speed values and a polynomial mathematical model to classify signals using a quantitative continuous scale. The descriptor significantly (pwrist rigidity, improving upon the inherent subjective clinical evaluation while using small, simple and easy to use motion sensor.
ATR discrimination-SNR for HRR assuming χ2 model of RCS variability
Holt, Craig R.; Schmidt, Steven L.; Attili, Joseph B.
2001-10-01
A discrimination SNR for predicting classification performance is developed as an analogy to the RADAR equation that is used to predict detection performance. It assumes a statistical model for the target radar cross-section (RCS) and that the resulting likelihood classifier is employed. The relationship between the probability of classification errors and the dB value of the discrimination SNR is obtained. A specific form for the likelihood classifier and the discrimination SNR is developed assuming that the variability of the target RCS is described by a (chi) 2 - distribution. The form of this (chi) 2 - based classifier is novel and significantly different from the more common Gaussian based mean-square-error classifier. It is shown that the discrimination SNR has an intuitive interpretation in terms of the number of radar samples, the average contrast between targets and the contrast-noise. The use of this tool is illustrated using compact range High Range Resolution (HRR) Doppler measurements from the U.S. Army National Ground Intelligence Center (NGIC). The sensitivity of ATR performance to radar parameters is quantified using the discrimination SNR with gains measured in meaningful dB units.
Rigidity theorems of Clifford Torus
Directory of Open Access Journals (Sweden)
SOUSA JR. LUIZ A. M.
2001-01-01
Full Text Available Let M be an n-dimensional closed minimally immersed hypersurface in the unit sphere Sn + 1. Assume in addition that M has constant scalar curvature or constant Gauss-Kronecker curvature. In this note we announce that if M has (n - 1 principal curvatures with the same sign everywhere, then M is isometric to a Clifford Torus .
Series solution for large deflections of a cantilever beam with variable flexural rigidity
DEFF Research Database (Denmark)
Kimiaeifar, Amin; Lund, Erik; Thomsen, Ole Thybo
2012-01-01
In this paper large deflection and rotation of a nonlinear Bernoulli-Euler beam with variable flexural rigidity and subjected to a static co-planar follower loading is studied. It is assumed that the angle of inclination of the force with respect to the deformed axis of the beam remains unchanged...
Rigidizing Inflatable Deployable Dwelling (RIDD) Project
National Aeronautics and Space Administration — By combining thin thermoplastic films, woven Vectran reinforcements, and heat a reliable, deployable, rigidizing space habitat can be created. Although much research...
Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces
DEFF Research Database (Denmark)
González, Alejandro González; Hemmsen, Martin Christian; Wilhjelm, Jens E.
2015-01-01
Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces......Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces...
Rigidity in Mentally Retarded and Nonretarded Children.
Kreitler, Shulamith; And Others
1990-01-01
Seven rigidity tests varying in difficulty were administered to 45 retarded subjects, with a mean age of 10, and 45 mental age-matched nonretarded subjects. Subjects did not differ on 3 easy tests, but retarded children were more rigid on 4 difficult tests. (Author/JDD)
Colpitts, Che C; Ustinov, Alexey V; Epand, Raquel F; Epand, Richard M; Korshun, Vladimir A; Schang, Luis M
2013-04-01
Entry of enveloped viruses requires fusion of viral and cellular membranes. Fusion requires the formation of an intermediate stalk structure, in which only the outer leaflets are fused. The stalk structure, in turn, requires the lipid bilayer of the envelope to bend into negative curvature. This process is inhibited by enrichment in the outer leaflet of lipids with larger polar headgroups, which favor positive curvature. Accordingly, phospholipids with such shape inhibit viral fusion. We previously identified a compound, 5-(perylen-3-yl)ethynyl-2'-deoxy-uridine (dUY11), with overall shape and amphipathicity similar to those of these phospholipids. dUY11 inhibited the formation of the negative curvature necessary for stalk formation and the fusion of a model enveloped virus, vesicular stomatitis virus (VSV). We proposed that dUY11 acted by biophysical mechanisms as a result of its shape and amphipathicity. To test this model, we have now characterized the mechanisms against influenza virus and HCV of 5-(perylen-3-yl)ethynyl-arabino-uridine (aUY11), which has shape and amphipathicity similar to those of dUY11 but contains an arabino-nucleoside. aUY11 interacted with envelope lipids to inhibit the infectivity of influenza virus, hepatitis C virus (HCV), herpes simplex virus 1 and 2 (HSV-1/2), and other enveloped viruses. It specifically inhibited the fusion of influenza virus, HCV, VSV, and even protein-free liposomes to cells. Furthermore, aUY11 inhibited the formation of negative curvature in model lipid bilayers. In summary, the arabino-derived aUY11 and the deoxy-derived dUY11 act by the same antiviral mechanisms against several enveloped but otherwise unrelated viruses. Therefore, chemically unrelated compounds of appropriate shape and amphipathicity target virion envelope lipids to inhibit formation of the negative curvature required for fusion, inhibiting infectivity by biophysical, not biochemical, mechanisms.
Semi-rigid brace and taping decrease variability of the ankle joint position sense
Directory of Open Access Journals (Sweden)
Márcia Barbanera
2014-12-01
Full Text Available The present study investigated the effect of taping and the semi-rigid ankle brace on ankle joint position sense. Sixteen healthy women (20.8 ± 2.3 years old actively placed the ankle in a target position. The experimental conditions were: 1 wearing no orthosis device, 2 using semi-rigid brace, and 3 wearing ankle taping. Absolute error (AE and variable error (VE were calculated to obtain the joint position sense. We found an interaction effect between condition and target angle at 15o of plantar flexion for the variable VE, which showed smaller errors during the use of taping and semi-rigid brace. In conclusion, the use of ankle joint orthoses, whether taping or semi-rigid brace, decrease the variability of the position sense at 15o of plantar flexion, potentially decreasing ankle sprains occurrence.
Inertial rotation of a rigid body
Butikov, Eugene
2006-07-01
A simple approach to the important problem of torque-free rotation of a symmetrical rigid body is suggested which is appropriate for teaching introductory mechanics and general physics to undergraduate students and is free from the difficulties of traditional treatment of the problem. A small simulation program (Java-applet) is developed that visualizes the investigated motion and illustrates its principal features. The program facilitates understanding of concepts behind rigid body dynamics. Simultaneously with simulating the rigid body motion, the program presents a clear geometrical interpretation of the inertial rotation.
Analysis of Switched-Rigid Floating Oscillator
Directory of Open Access Journals (Sweden)
Prabhakar R. Marur
2009-01-01
Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.
Rigid bronchoscope dilatation of postintubation tracheal stenosis
African Journals Online (AJOL)
The management modalities that have been employed for the management of. PITS include stenting, surgical resection and reconstruction, percutaneous dilatation, rigid bronchoscopic dilatation, fibreoptic assisted balloon dilatation and Nd: YAG. (neodyiniumrvttritiurn-aluniinuni garnet) laser therapy with or without stenting.
An Immersed Boundary Method for Rigid Bodies
Bhalla, Amneet Pal Singh; Kallemov, Bakytzhan; Donev, Aleksandar; Griffith, Boyce
2014-11-01
The traditional immersed boundary (IB) method is a very flexible method for coupling elastic structures to fluid flow. When rigid bodies are modeled using an IB approach, a penalty method is usually employed to approximately enforce the rigidity of the body; this requires small time step sizes and leads to difficult-to-control errors in the solution. We develop a method that exactly enforces a rigidity constraint by solving a linear system coupling a standard semi-implicit discretization of the fluid equations with a rigidity constraint. We develop a preconditioned iterative solver that combines an approximate multigrid solver for the fluid problem with an approximate direct solver for the Schur complement system. We demonstrate the efficiency and study the accuracy of the method on several test problems for both zero and finite Reynolds numbers.
Consumers' Imperfect Information and Price Rigidities
Jean-Paul L'Huillier
2012-01-01
This paper develops a model of price rigidities and information diffusion in decentralized markets with private information. First, I provide a strategic microfoundation for price rigidities, by showing that firms are better off delaying the adjustment of prices when they face a high number of uninformed consumers. Second, in an environment where consumers learn from firms' prices, the diffusion of information follows a Bernoulli differential equation. Therefore, learning follows nonlinear dy...
Nennig, Benoit; Renou, Ygaäl; Groby, Jean-Philippe; Aurégan, Yves
2012-05-01
This work investigates the acoustical properties of a multilayer porous material in which periodic inclusions are embedded. The material is assumed to be backed by a rigid wall. Most of the studies performed in this field used the multipole method and are limited to circular shape inclusions. Here, a mode matching approach, more convenient for a layered system, is adopted. The inclusions can be in the form of rigid scatterers of an arbitrary shape, in the form of an air-filled cavity or in the form of a porous medium with contrasting properties. The computational approach is validated on simple geometries against other numerical schemes and with experimental results obtained in an anechoic room on a rigid grating embedded in a porous material made of 2 mm glass beads. The method is used to study the acoustic absorption behavior of this class of materials in the low frequency range and at a range of angles of incidence.
Metrology of Non-Rigid Objects
Energy Technology Data Exchange (ETDEWEB)
Blaedel, K L; Smith, D W; Claudet, A A; Kasper, E P; Patterson, S R
2002-01-01
Dimensional characterization of non-rigid parts presents many challenges. For example, when a non-rigid part is mounted in an inspection apparatus the effects of fixturing constraints cause significant deformation of the part. If the part is not used in normal service with the same load conditions as during inspection, the dimensional characteristics in service will deviate from the reported values during inspection. Further, the solution of designing specialized fixturing to duplicate ''as-installed'' conditions does not fully resolve the problem because each inspection requires its own methodology. The goal of this project is to formulate the research problem and propose a method of assessing the dimensional characteristics of non-rigid parts. The measured dimension of a rigid component is traceable at some level of confidence to a single source (NIST in the USA). Hence the measurement of one component of an assembly can be related to the measurement of another component of that assembly. There is no generalized analog to this pedigreed process for dimensionally characterizing non-rigid bodies. For example, a measurement made on a sheet-metal automobile fender is heavily influenced by how it is held during the measurement making it difficult to determine how well that fender will assemble to the rest of the (non-rigid) car body. This problem is often overcome for specific manufacturing problems by constructing rigid fixtures that over-constrain the non-rigid parts to be assembled and then performing the dimensional measurement of the contour of each component to check whether each meets specification. Note that such inspection measurements will yield only an approximation to the assembled shape, which is a function of both the geometry and the compliance of the component parts of the assembly. As a result, non-rigid components are more difficult to specify and inspect and therefore are more difficult to purchase from outside vendors compared
Metrology of Non-Rigid Objects
Energy Technology Data Exchange (ETDEWEB)
Blaedel, K; Swift, D; Claudet, A; Kasper, E; Patterson, S
2002-01-01
Dimensional characterization of non-rigid parts presents many challenges. For example, when a non-rigid part is mounted in an inspection apparatus the effects of fixturing constraints are significant. If the part is not used in normal service with the same load conditions as during inspection, the dimensional characteristics will deviate from reported values. Further, the solution of designing specialized fixturing to duplicate ''as-installed'' conditions does not fully resolve the problem because each inspection requires its own methodology. The goal of this project is to formulate the research problem and propose a method of assessing the dimensional characteristics of non-rigid parts. The measured dimension of a rigid component is traceable at some level of confidence to a single source (NIST in the USA). Hence the measurement of one component of an assembly can be related to the measurement of another component of that assembly. There is no generalized analog to this pedigreed process for dimensionally characterizing non-rigid bodies. For example, a measurement made on a sheet-metal automobile fender is heavily influenced by how it is held during the measurement making it difficult to determine how well that fender will assemble to the rest of the (non-rigid) car body. This problem is often overcome for specific manufacturing problems by constructing rigid fixtures that over-constrain the non-rigid parts to be assembled and then performing the dimensional measurement of the contour of each component to check whether each meets specification. Note that such inspection measurements will yield only an approximation to the assembled shape, which is a function of both the geometry and the compliance of the component parts of the assembly. As a result, non-rigid components are more difficult to specify and inspect and therefore are more difficult to purchase from outside vendors compared to rigid components. The problems are compounded as the
Rigid motion artifact reduction in CT using frequency domain analysis.
Zhang, Yuan; Zhang, Liyi; Sun, Yunshan
2017-01-01
It is often unrealistic to assume that the subject remains stationary during a computed tomography (CT) imaging scan. A patient rigid motion can be decomposed into a translation and a rotation around an origin. How to minimize the motion impact on image quality is important. To eliminate artifacts caused by patient rigid motion during a CT scan, this study investigated a new method based on frequency domain analysis to estimate and compensate motion impact. Motion parameters was first determined by the magnitude correlation of projections in frequency domain. Then, the estimated parameters were applied to compensate for the motion effects in the reconstruction process. Finally, this method was extended to helical CT. In fan-beam CT experiments, the simulation results showed that the proposed method was more accurate and faster on the performance of motion estimation than using Helgason-Ludwig consistency condition method (HLCC). Furthermore, the reconstructed images on both simulated and human head experiments indicated that the proposed method yielded superior results in artifact reduction. The proposed method is a new tool for patient motion compensation, with a potential for practical application. It is not only applicable to motion correction in fan-beam CT imaging, but also to helical CT.
Origami-Inspired Folding of Thick, Rigid Panels
Trease, Brian P.; Thomson, Mark W.; Sigel, Deborah A.; Walkemeyer, Phillip E.; Zirbel, Shannon; Howell, Larry; Lang, Robert
2014-01-01
To achieve power of 250 kW or greater, a large compression ratio of stowed-to-deployed area is needed. Origami folding patterns were used to inspire the folding of a solar array to achieve synchronous deployment; however, origami models are generally created for near-zero-thickness material. Panel thickness is one of the main challenges of origami-inspired design. Three origami-inspired folding techniques (flasher, square twist, and map fold) were created with rigid panels and hinges. Hinge components are added to the model to enable folding of thick, rigid materials. Origami models are created assuming zero (or near zero) thickness. When a material with finite thickness is used, the panels are required to bend around an increasingly thick fold as they move away from the center of the model. The two approaches for dealing with material thickness are to use membrane hinges to connect the panels, or to add panel hinges, or hinges of the same thickness, at an appropriate width to enable folding.
NoRMCorre: An online algorithm for piecewise rigid motion correction of calcium imaging data.
Pnevmatikakis, Eftychios A; Giovannucci, Andrea
2017-11-01
Motion correction is a challenging pre-processing problem that arises early in the analysis pipeline of calcium imaging data sequences. The motion artifacts in two-photon microscopy recordings can be non-rigid, arising from the finite time of raster scanning and non-uniform deformations of the brain medium. We introduce an algorithm for fast Non-Rigid Motion Correction (NoRMCorre) based on template matching. NoRMCorre operates by splitting the field of view (FOV) into overlapping spatial patches along all directions. The patches are registered at a sub-pixel resolution for rigid translation against a regularly updated template. The estimated alignments are subsequently up-sampled to create a smooth motion field for each frame that can efficiently approximate non-rigid artifacts in a piecewise-rigid manner. Existing approaches either do not scale well in terms of computational performance or are targeted to non-rigid artifacts arising just from the finite speed of raster scanning, and thus cannot correct for non-rigid motion observable in datasets from a large FOV. NoRMCorre can be run in an online mode resulting in comparable to or even faster than real time motion registration of streaming data. We evaluate its performance with simple yet intuitive metrics and compare against other non-rigid registration methods on simulated data and in vivo two-photon calcium imaging datasets. Open source Matlab and Python code is also made available. The proposed method and accompanying code can be useful for solving large scale image registration problems in calcium imaging, especially in the presence of non-rigid deformations. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.
Non-rigid registration by geometry-constrained diffusion
DEFF Research Database (Denmark)
Andresen, Per Rønsholt; Nielsen, Mads
1999-01-01
Assume that only partial knowledge about a non-rigid registration is given so that certain point, curves, or surfaces in one 3D image map to certain points, curves, or surfaces in another 3D image. We are facing the aperture problem because along the curves and surfaces, point correspondences...... are not given. We will advocate the viewpoint that the aperture and the 3D interpolation problem may be solved simultaneously by finding the simplest displacement field. This is obtained by a geometry-constrained diffusion which yields the simplest displacement field in a precise sense. The point registration...... obtained may be used for growth modelling, shape statistics, or kinematic interpolation. The algorithm applies to geometrical objects of any dimensionality. We may thus keep any number of fiducial points, curves, and/or surfaces fixed while finding the simplest registration. Examples of inferred point...
Semi-rigid brace and taping decrease variability of the ankle joint position sense
Barbanera,Márcia; Mazuchi,Flávia de Andrade e Souza; Batista,José Paulo Berretta; Ultremare,Janaina de Moura; Iwashita,Juliana da Silva; Ervilha,Ulysses Fernandes
2014-01-01
The present study investigated the effect of taping and the semi-rigid ankle brace on ankle joint position sense. Sixteen healthy women (20.8 ± 2.3 years old) actively placed the ankle in a target position. The experimental conditions were: 1) wearing no orthosis device, 2) using semi-rigid brace, and 3) wearing ankle taping. Absolute error (AE) and variable error (VE) were calculated to obtain the joint position sense. We found an interaction effect between condition and target angle at 15o ...
21 CFR 876.3630 - Penile rigidity implant.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Penile rigidity implant. 876.3630 Section 876.3630...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Prosthetic Devices § 876.3630 Penile rigidity implant. (a) Identification. A penile rigidity implant is a device that consists of a pair of semi-rigid rods implanted in the...
Eigenvalue analysis of a cantilever beam-rigid-body MEMS gyroscope
Lajimi, Seyed Amir Mousavi; Abdel-Rahman, Eihab
2014-01-01
The eigenvalues of a new microbeam-rigid-body gyroscope are computed and studied to show the variation of frequencies versus the input spin rate. To this end, assuming the harmonic solution of the dynamic equation of motion the characteristic equation is obtained and solved for the natural frequencies of the system in the rotating frame. It is shown that the difference between the natural frequencies (eigenvalues) proportionally grows with the input angular displacement rate.
Algorithms for Graph Rigidity and Scene Analysis
DEFF Research Database (Denmark)
Berg, Alex Rune; Jordán, Tibor
2003-01-01
We investigate algorithmic questions and structural problems concerning graph families defined by `edge-counts'. Motivated by recent developments in the unique realization problem of graphs, we give an efficient algorithm to compute the rigid, redundantly rigid, M-connected, and globally rigid...... components of a graph. Our algorithm is based on (and also extends and simplifies) the idea of Hendrickson and Jacobs, as it uses orientations as the main algorithmic tool. We also consider families of bipartite graphs which occur in parallel drawings and scene analysis. We verify a conjecture of Whiteley...... by showing that 2d-connected bipartite graphs are d-tight. We give a new algorithm for finding a maximal d-sharp subgraph. We also answer a question of Imai and show that finding a maximum size d-sharp subgraph is NP-hard....
Measuring the Acceleration of a Rigid Body
Directory of Open Access Journals (Sweden)
Peter G. Martin
1998-01-01
Full Text Available Two methods to measure the six-degree-of-freedom acceleration of a point on a rigid body are presented. The first, referred to as the periphery scheme, makes use of three clusters of accelerometers mounted orthogonal to each other and coincident with the axes of the point. One of the clusters consists of the three accelerometers attached to a cube-shaped triaxial angular rate sensor (ARS. The second method, called the compact cube scheme, uses a single 3-accelerometer/ARS cluster that may be mounted anywhere on the rigid body. During impact tests with an instrumented rigid body, both methods produced measurements that were highly correlated near the time of peak acceleration. Whereas the compact cube scheme was more economical and easier to implement, the periphery scheme produced results that were less disrupted by instrument signal errors and noisy environments.
Torsional rigidity of submanifolds with controlled geometry
DEFF Research Database (Denmark)
Hurtado, Ana; Markvorsen, Steen; Palmer, Vicente
2009-01-01
We prove explicit upper and lower bounds for the torsional rigidity of extrinsic domains of submanifolds ^m$ with controlled radial mean curvature in ambient Riemannian manifolds ^n$ with a pole $ and with sectional curvatures bounded from above and from below, respectively. These bounds are given...... in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped product model spaces. Our main results are obtained using methods from previously established isoperimetric inequalities, as found in e.g. [MP4] and [MP5]. As in [MP4] we also characterize the geometry...... of those situations in which the bounds for the torsional rigidity are actually attained and study the behavior at infinity of the so-called geometric average of the mean exit time for Brownian motion....
Quantum mechanics of a generalised rigid body
Gripaios, Ben; Sutherland, Dave
2016-05-01
We consider the quantum version of Arnold’s generalisation of a rigid body in classical mechanics. Thus, we quantise the motion on an arbitrary Lie group manifold of a particle whose classical trajectories correspond to the geodesics of any one-sided-invariant metric. We show how the derivation of the spectrum of energy eigenstates can be simplified by making use of automorphisms of the Lie algebra and (for groups of type I) by methods of harmonic analysis. We show how the method can be extended to cosets, generalising the linear rigid rotor. As examples, we consider all connected and simply connected Lie groups up to dimension 3. This includes the universal cover of the archetypical rigid body, along with a number of new exactly solvable models. We also discuss a possible application to the topical problem of quantising a perfect fluid.
van der Put, R. W.; Kerkhof, E. M.; Raaymakers, B. W.; Jürgenliemk-Schulz, I. M.; Lagendijk, J. J. W.
2009-12-01
External beam radiation treatment for patients with cervical cancer is hindered by the relatively large motion of the target volume. A hybrid MRI-accelerator system makes it possible to acquire online MR images during treatment in order to correct for motion and deformation. To fully benefit from such a system, online delineation of the target volumes is necessary. The aim of this study is to investigate the accuracy of rigid, non-rigid and semi-automatic registrations of MR images for interfractional contour propagation in patients with cervical cancer. Registration using mutual information was performed on both bony anatomy and soft tissue. A B-spline transform was used for the non-rigid method. Semi-automatic registration was implemented with a point set registration algorithm on a small set of manual landmarks. Online registration was simulated by application of each method to four weekly MRI scans for each of 33 cervical cancer patients. Evaluation was performed by distance analysis with respect to manual delineations. The results show that soft-tissue registration significantly (P cervical cancer, online MRI imaging will allow target localization based on soft tissue visualization, which provides a significantly higher accuracy than localization based on bony anatomy. The use of limited user input to guide the registration increases overall accuracy. Additional non-rigid registration further reduces the propagation error and negates errors caused by small observer variations.
On Saturnian cosmic ray cutoff rigidities
Sauer, H. H.
1980-03-01
It has been determined that Saturn possesses a relatively pure dipolar magnetic field through magnetometer measurements made by Ness et al. (1979, private comm.) and Smith et al. (1979). The paper briefly outlines the dipole geomagnetic cutoff theory and demonstrates the scaling required for its applicability to energetic particle measurements in the vicinity of Saturn. Since the cutoff rigidity is a function of viewing direction, the effective cutoff rigidity must be determined as an integration over the finite viewing angle of a physical detector.
Evaluating a method for automated rigid registration
DEFF Research Database (Denmark)
Darkner, Sune; Vester-Christensen, Martin; Larsen, Rasmus
2007-01-01
, the influence of different norms and sampling point densities is evaluated. The performance of the two methods has been evaluated on data consisting of 178 scanned ear impressions taken from the right ear. To quantify the difference of the two methods we calculate the registration cost and the mean point......We evaluate a novel method for fully automated rigid registration of 2D manifolds in 3D space based on distance maps, the Gibbs sampler and Iterated Conditional Modes (ICM). The method is tested against the ICP considered as the gold standard for automated rigid registration. Furthermore...
Rigid origami vertices: conditions and forcing sets
Directory of Open Access Journals (Sweden)
Zachary Abel
2016-04-01
Full Text Available We develop an intrinsic necessary and sufficient condition for single-vertex origami crease patterns to be able to fold rigidly. We classify such patterns in the case where the creases are pre-assigned to be mountains and valleys as well as in the unassigned case. We also illustrate the utility of this result by applying it to the new concept of minimal forcing sets for rigid origami models, which are the smallest collection of creases that, when folded, will force all the other creases to fold in a prescribed way.
Rigidity analysis of HIV-1 protease
Heal, J. W.; Wells, S. A.; Jimenez-Roldan, E.; Freedman, R. F.; Römer, R. A.
2011-03-01
We present a rigidity analysis on a large number of X-ray crystal structures of the enzyme HIV-1 protease using the 'pebble game' algorithm of the software FIRST. We find that although the rigidity profile remains similar across a comprehensive set of high resolution structures, the profile changes significantly in the presence of an inhibitor. Our study shows that the action of the inhibitors is to restrict the flexibility of the β-hairpin flaps which allow access to the active site. The results are discussed in the context of full molecular dynamics simulations as well as data from NMR experiments.
The 'twin paradox' in relativistic rigid motion
Ben-Ya'acov, Uri
2017-01-01
Relativistic rigid motion suggests a new version for the so-called `twin paradox', comparing the ages of two astronauts on a very long spaceship. Although there is always an instantaneous inertial frame in which the whole spaceship, being rigid, is simultaneously at rest, the twins' ages, measured as the proper-times along their individual world lines, are different when they are located at remote parts of the spaceship. The age, or proper-time, difference depends on the distance at rest betw...
Rigid polyurethane and kenaf core composite foams
Rigid polyurethane foams are valuable in many construction applications. Kenaf is a bast fiber plant where the surface stem skin provides bast fibers whose strength-to-weight ratio competes with glass fiber. The higher volume product of the kenaf core is an under-investigated area in composite appli...
Settling dynamics of asymmetric rigid fibers
E.J. Tozzi; C Tim Scott; David Vahey; D.J. Klingenberg
2011-01-01
The three-dimensional motion of asymmetric rigid fibers settling under gravity in a quiescent fluid was experimentally measured using a pair of cameras located on a movable platform. The particle motion typically consisted of an initial transient after which the particle approached a steady rate of rotation about an axis parallel to the acceleration of gravity, with...
Geometric integrators for stochastic rigid body dynamics
Tretyakov, Mikhail
2016-01-05
Geometric integrators play an important role in simulating dynamical systems on long time intervals with high accuracy. We will illustrate geometric integration ideas within the stochastic context, mostly on examples of stochastic thermostats for rigid body dynamics. The talk will be mainly based on joint recent work with Rusland Davidchak and Tom Ouldridge.
Secondary structure and rigidity in model proteins.
Perticaroli, Stefania; Nickels, Jonathan D; Ehlers, Georg; O'Neill, Hugh; Zhang, Qui; Sokolov, Alexei P
2013-10-28
There is tremendous interest in understanding the role that secondary structure plays in the rigidity and dynamics of proteins. In this work we analyze nanomechanical properties of proteins chosen to represent different secondary structures: α-helices (myoglobin and bovine serum albumin), β-barrels (green fluorescent protein), and α + β + loop structures (lysozyme). Our experimental results show that in these model proteins, the β motif is a stiffer structural unit than the α-helix in both dry and hydrated states. This difference appears not only in the rigidity of the protein, but also in the amplitude of fast picosecond fluctuations. Moreover, we show that for these examples the secondary structure correlates with the temperature- and hydration-induced changes in the protein dynamics and rigidity. Analysis also suggests a connection between the length of the secondary structure (α-helices) and the low-frequency vibrational mode, the so-called boson peak. The presented results suggest an intimate connection of dynamics and rigidity with the protein secondary structure.
Analysis and Modeling of Rigid Microswimmers
Meshkati, Farshad
In this thesis, we investigate magnetically actuated rigid microswimmers based on analytical and numerical schemes. These swimming micro-robots have medical applications such as drug delivery and in vivo diagnostics. Our model employs the method of regularized Stokeslets to faithfully incorporate the low-Reynolds-number hydrodynamics of arbitrary rigid geometries. We show how these magnetized swimmers can be actuated and controlled by externally rotating uniform magnetic fields. Our model predicts the swimming characteristics such as speed and direction. We show how to determine the dynamic stability of steadily rotating microswimmers. First, we address what is the simplest geometry capable of swimming. We illustrate that, despite the common belief that rigid microswimmers need to be chiral to be able to cause propulsion, a simple achiral 3-bead geometry can exhibit appreciable propulsion and controllability. We generalize this to explain the minimum geometric requirements for rigid rotating propulsion based on a symmetry analysis. Next, we investigate the implications of the stability analysis on the control of the 3-bead swimmer. We show that by adjusting the angle between the magnetic field and its rotation, one can control the existence of multiple stable rotation modes, leading to control of swimming direction and speed.
On the combinatorics of infinitesimally rigid frameworks
Laman, G.
2000-01-01
Starting from a short survey of minimal infinitesimally rigid frameworks it is shown by an example that and why a two-dimensional characterization of them cannot be extended to higher dimensions just like that. The findings of a closer inspection of the interdependence of the rows of the relevant
A relativistic generalisation of rigid motions
Llosa, J.; Molina, A.; Soler, D.
2012-07-01
A weaker substitute for the too restrictive class of Born-rigid motions is proposed, which we call radar-holonomic motions. The definition is expressed as a set of differential equations. Integrability conditions and Cauchy problem are studied. We finally obtain an example of a radar-holonomic congruence containing a given worldline with a given value of the rotation on this line.
Reference frames and rigid motions in relativity
Llosa, J.; Soler, D.
2004-07-01
A reference frame consists of a reference space, a time scale and a spatial metric. The geometric structure induced by these objects in spacetime is developed. The existence of a class of spatial metrics which are rigid, have free mobility and can be derived as a slight deformation of the radar metric, is demonstrated.
Cracking of open traffic rigid pavement
Directory of Open Access Journals (Sweden)
Niken Chatarina
2017-01-01
Full Text Available The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken’s et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can’t accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.
The two-body problem of a pseudo-rigid body and a rigid sphere
DEFF Research Database (Denmark)
Kristiansen, Kristian Uldall; Vereshchagin, M.; Gózdziewski, K.
2012-01-01
n this paper we consider the two-body problem of a spherical pseudo-rigid body and a rigid sphere. Due to the rotational and "re-labelling" symmetries, the system is shown to possess conservation of angular momentum and circulation. We follow a reduction procedure similar to that undertaken...... in the study of the two-body problem of a rigid body and a sphere so that the computed reduced non-canonical Hamiltonian takes a similar form. We then consider relative equilibria and show that the notions of locally central and planar equilibria coincide. Finally, we show that Riemann's theorem on pseudo...
Rigid Spine Syndrome among Children in Oman
Directory of Open Access Journals (Sweden)
Roshan Koul
2015-08-01
Full Text Available Objectives: Rigidity of the spine is common in adults but is rarely observed in children. The aim of this study was to report on rigid spine syndrome (RSS among children in Oman. Methods: Data on children diagnosed with RSS were collected consecutively at presentation between 1996 and 2014 at the Sultan Qaboos University Hospital (SQUH in Muscat, Oman. A diagnosis of RSS was based on the patient’s history, clinical examination, biochemical investigations, electrophysiological findings, neuro-imaging and muscle biopsy. Atrophy of the paraspinal muscles, particularly the erector spinae, was the diagnostic feature; this was noted using magnetic resonance imaging of the spine. Children with disease onset in the paraspinal muscles were labelled as having primary RSS or rigid spinal muscular dystrophy. Secondary RSS was classified as RSS due to the late involvement of other muscle diseases. Results: Over the 18-year period, 12 children were included in the study, with a maleto- female ratio of 9:3. A total of 10 children were found to have primary RSS or rigid spinal muscular dystrophy syndrome while two had secondary RSS. Onset of the disease ranged from birth to 18 months of age. A family history was noted, with two siblings from one family and three siblings from another (n = 5. On examination, children with primary RSS had typical features of severe spine rigidity at onset, with the rest of the neurological examination being normal. Conclusion: RSS is a rare disease with only 12 reported cases found at SQUH during the study period. Cases of primary RSS should be differentiated from the secondary type.
Pre-Service Teachers' Personal Epistemic Beliefs and the Beliefs They Assume Their Pupils to Have
Rebmann, Karin; Schloemer, Tobias; Berding, Florian; Luttenberger, Silke; Paechter, Manuela
2015-01-01
In their workaday life, teachers are faced with multiple complex tasks. How they carry out these tasks is also influenced by their epistemic beliefs and the beliefs they assume their pupils hold. In an empirical study, pre-service teachers' epistemic beliefs and those they assume of their pupils were investigated in the setting of teacher…
Computer-aided rigid choledochoscopy lithotripsy for hepatolithiasis.
Fang, Chi-Hua; Li, Gang; Wang, Ping; Fan, Ying-Fang; Zhong, Shi-Zhen
2015-05-01
Hepatolithiasis is challenging for surgeons to treat especially in patients with previous hepatobiliary surgery. The aim of the study was to report our experience of rigid choledochoscopy lithotripsy in targeted treatment of hepatolithiasis under the guidance of a medical image three-dimensional visualization system, which we developed and patented (software copyright no: 2008SR18 798) by comparing it with hepatectomy without a three-dimensional (3D) reconstruction technique. Between December 2007 and March 2013, 64 patients underwent rigid choledochoscopy lithotripsy based on 3D visualization technology conducted by a medical image three-dimensional visualization system for hepatolithiasis (group A). During the same period, 61 patients with hepatolithiasis were selected for hepatectomy (group B). Comparative analysis was made of demographic and perioperative characteristics of the two groups. 3D visualization was instructive for surgeons on how the stones were distributed and what the spatial relationship was between stones and the intrahepatic vascular system. Compared with patients in group B, those in group A had a significantly lower intermediate residual stone rate, a faster operating time, a lower intraoperative blood loss and intraoperative blood transfusion, a shorter postoperative hospital stay, less postoperative complications, and more liver function reserved (P Copyright © 2015 Elsevier Inc. All rights reserved.
Rigid cohomology over Laurent series fields
Lazda, Christopher
2016-01-01
In this monograph, the authors develop a new theory of p-adic cohomology for varieties over Laurent series fields in positive characteristic, based on Berthelot's theory of rigid cohomology. Many major fundamental properties of these cohomology groups are proven, such as finite dimensionality and cohomological descent, as well as interpretations in terms of Monsky-Washnitzer cohomology and Le Stum's overconvergent site. Applications of this new theory to arithmetic questions, such as l-independence and the weight monodromy conjecture, are also discussed. The construction of these cohomology groups, analogous to the Galois representations associated to varieties over local fields in mixed characteristic, fills a major gap in the study of arithmetic cohomology theories over function fields. By extending the scope of existing methods, the results presented here also serve as a first step towards a more general theory of p-adic cohomology over non-perfect ground fields. Rigid Cohomology over Laurent Series Fields...
Financial Constraints and Nominal Price Rigidities
DEFF Research Database (Denmark)
Menno, Dominik Francesco; Balleer, Almut; Hristov, Nikolay
This paper investigates how financial market imperfections and the frequency of price adjustment interact. Based on new firm-level evidence for Germany, we document that financially constrained firms adjust prices more often than their unconstrained counterparts, both upwards and downwards. We show...... that these empirical patterns are consistent with a partial equilibrium menu-cost model with a working capital constraint. We then use the model to show how the presence of financial frictions changes profits and the price distribution of firms compared to a model without financial frictions. Our results suggest...... that tighter financial constraints are associated with higher nominal rigidities, higher prices and lower output. Moreover, in response to aggregate shocks, aggregate price rigidity moves substantially, the response of inflation is dampened, while output reacts more in the presence of financial frictions...
Lectures on formal and rigid geometry
Bosch, Siegfried
2014-01-01
A first version of this work appeared in 2005 as a Preprint of the Collaborative Research Center "Geometrical Structures in Mathematics" at the University of Münster. Its aim was to offer a concise and self-contained 'lecture-style' introduction to the theory of classical rigid geometry established by John Tate, together with the formal algebraic geometry approach launched by Michel Raynaud. These Lectures are now viewed commonly as an ideal means of learning advanced rigid geometry, regardless of the reader's level of background. Despite its parsimonious style, the presentation illustrates a number of key facts even more extensively than any other previous work. This Lecture Notes Volume is a revised and slightly expanded version of the original preprint and has been published at the suggestion of several experts in the field.
Rigidity of the magic pentagram game
Kalev, Amir; Miller, Carl A.
2017-01-01
A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.
Rigidity of the magic pentagram game
Kalev, Amir; Miller, Carl A.
2018-01-01
A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.
Rigid aleph_epsilon-saturated models of superstable theories
Shami, Ziv; Shelah, Saharon
1999-01-01
In a countable superstable NDOP theory, the existence of a rigid aleph_epsilon-saturated model implies the existence of 2^lambda rigid aleph_epsilon-saturated models of power lambda for every lambda>2^{aleph_0}.
Rank rigidity for CAT(0) cube complexes
Caprace, Pierre-Emmanuel; Sageev, Michah
2010-01-01
We prove that any group acting essentially without a fixed point at infinity on an irreducible finite-dimensional CAT(0) cube complex contains a rank one isometry. This implies that the Rank Rigidity Conjecture holds for CAT(0) cube complexes. We derive a number of other consequences for CAT(0) cube complexes, including a purely geometric proof of the Tits Alternative, an existence result for regular elements in (possibly non-uniform) lattices acting on cube complexes, and a characterization ...
Balancing of Rigid and Flexible Rotors
1986-01-01
IA14 nf~VO1lS t’ , f,~ riabtiB SVM-12 Balancing of Rigid and Flexible Rotors Neville F. Rieger Stress Technology, Inc. 1986 The Shock end Vibration...a bearing or other Atructural components by fatigue . Unbalance is therefore recognized as an important potential cause of machinery failure. A number...runout on slow rotation, stress relaxation with time often heavy vibration during rota- "tion Section of blade or vane broken Visually observable; bearing
Sternick, Marcelo Back; Dallacosta, Darlan; Bento, Daniela Águida; do Reis, Marcelo Lemos
2012-01-01
To analyze the rigidity of a platform-type external fixator assembly, according to different numbers of pins on each clamp. Computer simulation on a large-sized Cromus dynamic external fixator (Baumer SA) was performed using a finite element method, in accordance with the standard ASTM F1541. The models were generated with approximately 450,000 quadratic tetrahedral elements. Assemblies with two, three and four Schanz pins of 5.5 mm in diameter in each clamp were compared. Every model was subjected to a maximum force of 200 N, divided into 10 sub-steps. For the components, the behavior of the material was assumed to be linear, elastic, isotropic and homogeneous. For each model, the rigidity of the assembly and the Von Mises stress distribution were evaluated. The rigidity of the system was 307.6 N/mm for two pins, 369.0 N/mm for three and 437.9 N/mm for four. The results showed that four Schanz pins in each clamp promoted rigidity that was 19% greater than in the configuration with three pins and 42% greater than with two pins. Higher tension occurred in configurations with fewer pins. In the models analyzed, the maximum tension occurred on the surface of the pin, close to the fixation area.
Rocking Rotation of a Rigid Disk Embedded in a Transversely Isotropic Half-Space
Directory of Open Access Journals (Sweden)
Seyed Ahmadi
2014-06-01
Full Text Available The asymmetric problem of rocking rotation of a circular rigid disk embedded in a finite depth of a transversely isotropic half-space is analytically addressed. The rigid disk is assumed to be in frictionless contact with the elastic half-space. By virtue of appropriate Green's functions, the mixed boundary value problem is written as a dual integral equation. Employing further mathematical techniques, the integral equation is reduced to a well-known Fredholm integral equation of the second kind. The results related to the contact stress distribution across the disk region and the equivalent rocking stiffness of the system are expressed in terms of the solution of the obtained Fredholm integral equation. When the rigid disk is located on the surface or at the remote boundary, the exact closed-form solutions are presented. For verification purposes, the limiting case of an isotropic half-space is considered and the results are verified with those available in the literature. The jump behavior in the results at the edge of the rigid disk for the case of an infinitesimal embedment is highlighted analytically for the first time. Selected numerical results are depicted for the contact stress distribution across the disk region, rocking stiffness of the system, normal stress, and displacement components along the radial axis. Moreover, effects of anisotropy on the rocking stiffness factor are discussed in detail.
Stability for the Lens Rigidity Problem
Bao, Gang; Zhang, Hai
2017-09-01
Let g be a Riemannian metric for R^d ({d ≥q 3}) which differs from the Euclidean metric only in a smooth and strictly convex bounded domain M. The lens rigidity problem is concerned with recovering the metric g inside M from the corresponding lens relation on the boundary {partial M}. In this paper, the stability of the lens rigidity problem is investigated for metrics which are a priori close to a given non-trapping metric satisfying the "strong fold-regular" condition. A metric g is called strong fold-regular if for each point {x\\in M}, there exists a set of geodesics passing through x whose conormal bundle covers {T^*xM}. Moreover, these geodesics contain either no conjugate points or only fold conjugate points with a non-degeneracy condition. Examples of strong fold-regular metrics are constructed. Our main result gives the first stability result for the lens rigidity problem in the case of anisotropic metrics which allow conjugate points. The approach is based on the study of the linearized inverse problem of recovering a metric from its induced geodesic flow, which is a weighted geodesic X-ray transform problem for symmetric 2-tensor fields. A key ingredient is to show that the kernel of the X-ray transform on symmetric solenoidal 2-tensor fields is of finite dimension. It remains open whether the kernel space is trivial or not.
Rigid internal fixation of infected mandibular fractures.
Mehra, Pushkar; Van Heukelom, Emily; Cottrell, David A
2009-05-01
To evaluate the treatment outcomes of rigid internal fixation for the management of infected mandible fractures. A retrospective chart review of infected mandible fractures managed by a single oral and maxillofacial surgeon at a level I trauma center during a 7-year period was accomplished by independent examiners. All patients were treated with incision and drainage, culture and sensitivity testing, extraction of nonsalvageable teeth, placement of maxillomandibular fixation when possible, fracture reduction with bone debridement and decortication, rigid internal fixation of the mandible by an extraoral approach, and antibiotic therapy. The medical and social history was contributory in most patients. The analysis was stratified by the differentiation of the fractures into 2 groups: those with soft tissue infections in the fracture region versus those with hard tissue-infected fractures (biopsy-proven osteomyelitis). A total of 44 patients were included in this study, with an average follow-up of 18.2 months from the date of surgery (range 3 to 48). The treatment protocol was successful in all 18 patients (100%) with soft tissue infected mandibular fractures and 24 (92%) of 26 patients with hard tissue-infected fractures. A protocol consisting of concomitant incision and drainage, mandibular debridement, fracture reduction, and stabilization with rigid internal fixation can be effectively used for single-stage management of infected mandible fractures.
Mouse whole-body organ mapping by non-rigid registration approach
Xiao, Di; Zahra, David; Bourgeat, Pierrick; Berghofer, Paula; Acosta Tamayo, Oscar; Green, Heather; Gregoire, Marie Claude; Salvado, Olivier
2011-03-01
Automatic small animal whole-body organ registration is challenging because of subject's joint structure, posture and position difference and loss of reference features. In this paper, an improved 3D shape context based non-rigid registration method is applied for mouse whole-body skeleton registration and lung registration. A geodesic path based non-rigid registration method is proposed for mouse torso skin registration. Based on the above registration methods, a novel non-rigid registration framework is proposed for mouse whole-body organ mapping from an atlas to new scanned CT data. A preliminary experiment was performed to test the method on lung and skin registration. A whole-body organ mapping was performed on three target data and the selected organs were compared with the manual outlining results. The robust of the method has been demonstrated.
21 CFR 886.5916 - Rigid gas permeable contact lens.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rigid gas permeable contact lens. 886.5916 Section 886.5916 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5916 Rigid gas permeable contact lens. (a) Identification. A rigid gas permeable...
A rigid dumbbell settling under gravity in a periodic flow field
Energy Technology Data Exchange (ETDEWEB)
Piva, M F; Martino, G R [Grupo de Medios Porosos, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850 (1063), Buenos Aires Argentina (Argentina)], E-mail: mpiva@fi.uba.ar
2009-01-16
The motion of a rigid dumbbell settling under gravity in a stationary two-dimensional cellular flow field is investigated. The dumbbell is modeled as two identical beads connected by a rigid rod. Assuming that the bead radius is much shorter than the bead to bead distance, a simple model is obtained to describe the dynamical behavior of the dumbbell in terms of evolution of the dumbbell orientation and the velocity of the center of mass. The average velocity of the dumbbell in the gravity direction was found to depend on the dumbbell length, the inertia parameter and the terminal settling velocity in still fluid. For certain conditions the dumbbell remains suspended in the flow field. In one of the suspension regimes the dumbbell remains indefinitely attached to a fixed point. This behavior is related to the existence to saddle nodes in the cellular flow field.
Spherical near field acoustic holography with microphones on a rigid sphere
DEFF Research Database (Denmark)
Jacobsen, Finn; Hald, Jørgen; Fernandez Grande, Efren
2008-01-01
Spherical near field acoustic holography (SNAH) is a recently developed technique that makes it possible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible...... scattering. Because of the versatile geometry of a sphere SNAH is potentially extremely useful for source identification. On the other hand a rigid sphere is somewhat more practical than an open sphere, and it is possible to modify the SNAH theory so that a similar sound field reconstruction can be made...... with an array of microphones flush-mounted on a rigid sphere. However, this approach is only valid if it can be assumed that the sphere has a negligible influence on the incident sound field, in other words if multiple scattering can be ignored, and this is not necessarily a good assumption when the sphere...
Near field acoustic holography with microphones mounted on a rigid sphere
DEFF Research Database (Denmark)
Jacobsen, Finn; Moreno, Guillermo; Fernandez Grande, Efren
2008-01-01
Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering....... This is potentially very useful for source identification. On the other hand a rigid sphere is somewhat more practical than an open sphere, and it is possible to modify the existing spherical NAH theory so that a similar sound field reconstruction can be made with an array of microphones flush-mounted on a rigid...... is only valid if it can be assumed that the sphere has a negligible in-fluence on the incident sound field, and this is not necessarily a good assumption when the sphere is very close to a radiating surface. This paper describes the modified spherical NAH theory and examines the matter through simulations...
Influence of flock coating on bending rigidity of woven fabrics
Ozdemir, O.; Kesimci, M. O.
2017-10-01
This work presents the preliminary results of our efforts that focused on the effect of the flock coating on the bending rigidity of woven fabrics. For this objective, a laboratory scale flocking unit is designed and flocked samples of controlled flock density are produced. Bending rigidity of the samples with different flock densities are measured on both flocked and unflocked sides. It is shown that the bending rigidity depends on both flock density and whether the side to be measured is flocked or not. Adhesive layer thickness on the bending rigidity is shown to be dramatic. And at higher basis weights, flock density gets less effective on bending rigidity.
Understanding geological processes: Visualization of rigid and non-rigid transformations
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
Brownian dynamics of confined rigid bodies
Energy Technology Data Exchange (ETDEWEB)
Delong, Steven; Balboa Usabiaga, Florencio; Donev, Aleksandar, E-mail: donev@courant.nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)
2015-10-14
We introduce numerical methods for simulating the diffusive motion of rigid bodies of arbitrary shape immersed in a viscous fluid. We parameterize the orientation of the bodies using normalized quaternions, which are numerically robust, space efficient, and easy to accumulate. We construct a system of overdamped Langevin equations in the quaternion representation that accounts for hydrodynamic effects, preserves the unit-norm constraint on the quaternion, and is time reversible with respect to the Gibbs-Boltzmann distribution at equilibrium. We introduce two schemes for temporal integration of the overdamped Langevin equations of motion, one based on the Fixman midpoint method and the other based on a random finite difference approach, both of which ensure that the correct stochastic drift term is captured in a computationally efficient way. We study several examples of rigid colloidal particles diffusing near a no-slip boundary and demonstrate the importance of the choice of tracking point on the measured translational mean square displacement (MSD). We examine the average short-time as well as the long-time quasi-two-dimensional diffusion coefficient of a rigid particle sedimented near a bottom wall due to gravity. For several particle shapes, we find a choice of tracking point that makes the MSD essentially linear with time, allowing us to estimate the long-time diffusion coefficient efficiently using a Monte Carlo method. However, in general, such a special choice of tracking point does not exist, and numerical techniques for simulating long trajectories, such as the ones we introduce here, are necessary to study diffusion on long time scales.
Getino, J.; Escapa, A.; Miguel, D.
2010-05-01
This paper is the first part of an investigation where we will present an analytical general theory of the rotation of the non-rigid Earth at the second order, which considers the effects of the interaction of the rotation of the Earth with itself, also named as the spin-spin coupling. Here, and as a necessary step in the development of that theory, we derive complete, explicit, analytical formulae of the rigid Earth rotation that account for the second-order rotation-rotation interaction. These expressions are not provided in this form by any current rigid Earth model. Working within the Hamiltonian framework established by Kinoshita, we study the second-order effects arising from the interaction of the main term in the Earth geopotential expansion with itself, and with the complementary term arising when referring the rotational motion to the moving ecliptic. To this aim, we apply a canonical perturbation method to solve analytically the canonical equations at the second order, determining the expressions that provide the nutation-precession, the polar motion, and the length of day. In the case of the motion of the equatorial plane, nutation-precession, we compare our general approach with the particular study for this motion developed by Souchay et al., showing the existence of new terms whose numerical values are within the truncation level of 0.1 μas adopted by those authors. These terms emerge as a consequence of not assuming in this work the same restrictive simplifications taken by Souchay et al. The importance of these additional contributions is that, as the analytical formulae show, they depend on the Earth model considered, in such a way that the fluid core resonance could amplify them significatively when extending this theory to the non-rigid Earth models.
Rigid gas permeable lenses and patient management.
Terry, R; Schnider, C; Holden, B A
1989-01-01
The introduction of new rigid gas permeable (RGP) contact lens materials provides the practitioner with a number of alternatives for patient management. But whatever the lens materials used, problems related to the lenses, care and maintenance solutions, and patients may arise. This paper examines concerns such as parameter instability, durability of lenses, compatibility of materials and solutions, patient education and compliance, 3 and 9 o'clock staining, corneal distortion, and lid changes. Suggestions are made on ways to avoid or minimize problems related to RGP lens wear.
Mechanical Characterization of Rigid Polyurethane Foams
Energy Technology Data Exchange (ETDEWEB)
Lu, Wei-Yang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Mechanics of Materials
2014-12-01
Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.
Gabapentin for decerebrate rigidity: a case report.
Kao, Chuen-Der; Chen, Jen-Tse; Lai, Kuan-Lin; Chang, Jiun-Bin; Wu, Zin-An; Liao, Kwong-Kum
2008-01-01
A 48-year-old woman suddenly lost consciousness as a result of a right rostral pontine tegmentum haemorrhage. The patient presented with decerebrate rigidity (DR) and regained full consciousness 5 days after the initial onset. The patient was given gabapentin 1200 mg/day nasogastrically and her DR significantly improved, although other antiepileptic drugs such as phenytoin and carbamazepine were given in larger dosages to decrease muscle hypertonicity. The patients' preserved consciousness and motor-evoked potentials to transcranial magnetic stimulation indicated a derangement of the extrapyramidal tracts with preservation of the pyramidal tracts. This case report discusses the possible mechanisms of action of gabapentin in DR.
How Public High School Students Assume Cooperative Roles to Develop Their EFL Speaking Skills
Directory of Open Access Journals (Sweden)
Julie Natalie Parra Espinel
2010-12-01
Full Text Available This study describes an investigation we carried out in order to identify how the specific roles that 7th grade public school students assumed when they worked cooperatively were related to their development of speaking skills in English. Data were gathered through interviews, field notes, students’ reflections and audio recordings. The findings revealed that students who were involved in cooperative activities chose and assumed roles taking into account preferences, skills and personality traits. In the same manner, when learners worked together, their roles were affected by each other and they put into practice some social strategies with the purpose of supporting their embryonic speaking development.
Deformable image registration with local rigidity constraints for cone-beam CT-guided spine surgery
Reaungamornrat, S.; Wang, A. S.; Uneri, A.; Otake, Y.; Khanna, A. J.; Siewerdsen, J. H.
2014-07-01
Image-guided spine surgery (IGSS) is associated with reduced co-morbidity and improved surgical outcome. However, precise localization of target anatomy and adjacent nerves and vessels relative to planning information (e.g., device trajectories) can be challenged by anatomical deformation. Rigid registration alone fails to account for deformation associated with changes in spine curvature, and conventional deformable registration fails to account for rigidity of the vertebrae, causing unrealistic distortions in the registered image that can confound high-precision surgery. We developed and evaluated a deformable registration method capable of preserving rigidity of bones while resolving the deformation of surrounding soft tissue. The method aligns preoperative CT to intraoperative cone-beam CT (CBCT) using free-form deformation (FFD) with constraints on rigid body motion imposed according to a simple intensity threshold of bone intensities. The constraints enforced three properties of a rigid transformation—namely, constraints on affinity (AC), orthogonality (OC), and properness (PC). The method also incorporated an injectivity constraint (IC) to preserve topology. Physical experiments involving phantoms, an ovine spine, and a human cadaver as well as digital simulations were performed to evaluate the sensitivity to registration parameters, preservation of rigid body morphology, and overall registration accuracy of constrained FFD in comparison to conventional unconstrained FFD (uFFD) and Demons registration. FFD with orthogonality and injectivity constraints (denoted FFD+OC+IC) demonstrated improved performance compared to uFFD and Demons. Affinity and properness constraints offered little or no additional improvement. The FFD+OC+IC method preserved rigid body morphology at near-ideal values of zero dilatation ({ D} = 0.05, compared to 0.39 and 0.56 for uFFD and Demons, respectively) and shear ({ S} = 0.08, compared to 0.36 and 0.44 for uFFD and Demons
Teacher Leader Model Standards and the Functions Assumed by National Board Certified Teachers
Swan Dagen, Allison; Morewood, Aimee; Smith, Megan L.
2017-01-01
The Teacher Leader Model Standards (TLMS) were created to stimulate discussion around the leadership responsibilities teachers assume in schools. This study used the TLMS to gauge the self-reported leadership responsibilities of National Board Certified Teachers (NBCTs). The NBCTs reported engaging in all domains of the TLMS, most frequently with…
BERGSTRA, A; VANDIJK, RB; HILLEGE, HL; LIE, KI; MOOK, GA
This study was performed because of observed differences between dye dilution cardiac output and the Fick cardiac output, calculated from estimated oxygen consumption according to LaFarge and Miettinen, and to find a better formula for assumed oxygen consumption. In 250 patients who underwent left
Graddy, K.; Hamilton, J.; Pownall, R.A.J.
2012-01-01
This article proposes an alternative specification for the second stage of the Case-Shiller repeat-sales method. This specification is based on serial correlation in the deviations from the mean one-period returns on the underlying individual assets, whereas the original Case-Shiller method assumes
Similarity and assumed similarity in personality reports of well-acquainted persons.
Lee, Kibeom; Ashton, Michael C; Pozzebon, Julie A; Visser, Beth A; Bourdage, Joshua S; Ogunfowora, Babatunde
2009-02-01
The authors obtained self- and observer reports of personality from pairs of well-acquainted college students. Consistent with previous findings, results of Study 1 showed strong cross-source agreement for all 6 HEXACO personality factors (rs approximately .55). In addition, the authors found modest levels of similarity (r approximately .25) between dyad members' self-reports on each of 2 dimensions, Honesty-Humility and Openness to Experience. For these same 2 factors, dyad members' self-reports were correlated with their observer reports of the other dyad member (r approximately .40), thus indicating moderately high assumed similarity. In Study 2, Honesty-Humility and Openness to Experience were the 2 personality factors most strongly associated with the 2 major dimensions of personal values, which also showed substantial assumed similarity. In Study 3, assumed similarity was considerably stronger for close friends than for nonfriend acquaintances. Results suggest that assumed similarity for Honesty-Humility and Openness to Experience reflects a tendency to overestimate one's similarity to persons with whom one has a close relationship, but only on those personality characteristics whose relevance to values gives them central importance to one's identity.
Does the Advice to Assume the Knee-Chest Position at the 36th to ...
African Journals Online (AJOL)
of the intervention group assumed the knee-chest position for 15 minutes three times a day for one week. The control group had 53 cases. The study and control groups were reviewed after a week to assess the fetal presentation. The version rate was 61% and 20% in intervention and in control groups, respectively (P value ...
How Public High School Students Assume Cooperative Roles to Develop Their EFL Speaking Skills
Parra Espinel, Julie Natalie; Fonseca Canaría, Diana Carolina
2010-01-01
This study describes an investigation we carried out in order to identify how the specific roles that 7th grade public school students assumed when they worked cooperatively were related to their development of speaking skills in English. Data were gathered through interviews, field notes, students' reflections and audio recordings. The findings…
Vertebral Column Resection for Rigid Spinal Deformity.
Saifi, Comron; Laratta, Joseph L; Petridis, Petros; Shillingford, Jamal N; Lehman, Ronald A; Lenke, Lawrence G
2017-05-01
Broad narrative review. To review the evolution, operative technique, outcomes, and complications associated with posterior vertebral column resection. A literature review of posterior vertebral column resection was performed. The authors' surgical technique is outlined in detail. The authors' experience and the literature regarding vertebral column resection are discussed at length. Treatment of severe, rigid coronal and/or sagittal malalignment with posterior vertebral column resection results in approximately 50-70% correction depending on the type of deformity. Surgical site infection rates range from 2.9% to 9.7%. Transient and permanent neurologic injury rates range from 0% to 13.8% and 0% to 6.3%, respectively. Although there are significant variations in EBL throughout the literature, it can be minimized by utilizing tranexamic acid intraoperatively. The ability to correct a rigid deformity in the spine relies on osteotomies. Each osteotomy is associated with a particular magnitude of correction at a single level. Posterior vertebral column resection is the most powerful posterior osteotomy method providing a successful correction of fixed complex deformities. Despite meticulous surgical technique and precision, this robust osteotomy technique can be associated with significant morbidity even in the most experienced hands.
EGFR and HER2 activate rigidity sensing only on rigid matrices
Saxena, Mayur; Liu, Shuaimin; Yang, Bo; Hajal, Cynthia; Changede, Rishita; Hu, Junqiang; Wolfenson, Haguy; Hone, James; Sheetz, Michael P.
2017-07-01
Epidermal growth factor receptor (EGFR) interacts with integrins during cell spreading and motility, but little is known about the role of EGFR in these mechanosensing processes. Here we show, using two different cell lines, that in serum- and EGF-free conditions, EGFR or HER2 activity increase spreading and rigidity-sensing contractions on rigid, but not soft, substrates. Contractions peak after 15-20 min, but diminish by tenfold after 4 h. Addition of EGF at that point increases spreading and contractions, but this can be blocked by myosin-II inhibition. We further show that EGFR and HER2 are activated through phosphorylation by Src family kinases (SFK). On soft surfaces, neither EGFR inhibition nor EGF stimulation have any effect on cell motility. Thus, EGFR or HER2 can catalyse rigidity sensing after associating with nascent adhesions under rigidity-dependent tension downstream of SFK activity. This has broad implications for the roles of EGFR and HER2 in the absence of EGF both for normal and cancerous growth.
Bone marrow mesenchymal stem cells can differentiate and assume corneal keratocyte phenotype
Liu, Hongshan; Zhang, Jianhua; Liu, Chia-Yang; Hayashi, Yasuhito; Kao, Winston W-Y
2012-01-01
Abstract It remains elusive as to what bone marrow (BM) cell types infiltrate into injured and/or diseased tissues and subsequently differentiate to assume the phenotype of residential cells, for example, neurons, cardiac myocytes, keratocytes, etc., to repair damaged tissue. Here, we examined the possibility of whether BM cell invasion via circulation into uninjured and injured corneas could assume a keratocyte phenotype, using chimeric mice generated by transplantation of enhanced green fluorescent protein (EGFP)+ BM cells into keratocan null (Kera−/−) and lumican null (Lum−/−) mice. EGFP+ BM cells assumed dendritic cell morphology, but failed to synthesize corneal-specific keratan sulfate proteoglycans, that is KS-lumican and KS-keratocan. In contrast, some EGFP+ BM cells introduced by intrastromal transplantation assumed keratocyte phenotypes. Furthermore, BM cells were isolated from Kera-Cre/ZEG mice, a double transgenic mouse line in which cells expressing keratocan become EGFP+ due to the synthesis of Cre driven by keratocan promoter. Three days after corneal and conjunctival transplantations of such BM cells into Kera−/− mice, green keratocan positive cells were found in the cornea, but not in conjunctiva. It is worthy to note that transplanted BM cells were rejected in 4 weeks. MSC isolated from BM were used to examine if BM mesenchymal stem cells (BM-MSC) could assume keratocyte phenotype. When BM-MSC were intrastromal-transplanted into Kera−/− mice, they survived in the cornea without any immune and inflammatory responses and expressed keratocan in Kera−/− mice. These observations suggest that corneal intrastromal transplantation of BM-MSC may be an effective treatment regimen for corneal diseases involving dysfunction of keratocytes. PMID:21883890
Parkinson's disease rigidity: relation to brain connectivity and motor performance
Directory of Open Access Journals (Sweden)
Nazanin eBaradaran
2013-06-01
Full Text Available Objective: 1 To determine the brain connectivity pattern associated with clinical rigidity scores in Parkinson's disease (PD and 2 to determine the relation between clinically-assessed rigidity and quantitative metrics of motor performance.Background: Rigidity, the resistance to passive movement, is exacerbated in PD by asking the subject to move the contralateral limb, implying that rigidity involves a distributed brain network. Rigidity mainly affects subjects when they attempt to move; yet the relation between clinical rigidity scores and quantitative aspects of motor performance are unknown.Methods: Ten clinically diagnosed PD patients (off medication and ten controls were recruited to perform an fMRI squeeze-bulb tracking task that included both visually guided and internally guided features. The direct functional connectivity between anatomically defined regions of interest was assessed with Dynamic Bayesian Networks (DBNs. Tracking performance was assessed by fitting Linear Dynamical System (LDS models to the motor performance, and was compared to the clinical rigidity scores. A cross-validated Least Absolute Shrinkage and Selection Operator (LASSO regression method was used to determine the brain connectivity network that best predicted clinical rigidity scores.Results: The damping ratio of the LDS models significantly correlated with clinical rigidity scores (p < 10-4. An fMRI connectivity network in subcortical and primary and premotor cortical regions accurately predicted clinical rigidity scores (p < 10-5. Conclusions: A widely distributed cortical/subcortical network is associated with rigidity observed in PD patients, which reinforces the importance of altered functional connectivity in the pathophysiology of PD. PD subjects with higher rigidity scores tend to have less overshoot in their tracking performance, and damping ratio may represent a robust, quantitative marker of the motoric effects of increasing rigidity.
Virtual rigid body: a new optical tracking paradigm in image-guided interventions
Cheng, Alexis; Lee, David S.; Deshmukh, Nishikant; Boctor, Emad M.
2015-03-01
Tracking technology is often necessary for image-guided surgical interventions. Optical tracking is one the options, but it suffers from line of sight and workspace limitations. Optical tracking is accomplished by attaching a rigid body marker, having a pattern for pose detection, onto a tool or device. A larger rigid body results in more accurate tracking, but at the same time large size limits its usage in a crowded surgical workspace. This work presents a prototype of a novel optical tracking method using a virtual rigid body (VRB). We define the VRB as a 3D rigid body marker in the form of pattern on a surface generated from a light source. Its pose can be recovered by observing the projected pattern with a stereo-camera system. The rigid body's size is no longer physically limited as we can manufacture small size light sources. Conventional optical tracking also requires line of sight to the rigid body. VRB overcomes these limitations by detecting a pattern projected onto the surface. We can project the pattern onto a region of interest, allowing the pattern to always be in the view of the optical tracker. This helps to decrease the occurrence of occlusions. This manuscript describes the method and results compared with conventional optical tracking in an experiment setup using known motions. The experiments are done using an optical tracker and a linear-stage, resulting in targeting errors of 0.38mm+/-0.28mm with our method compared to 0.23mm+/-0.22mm with conventional optical markers. Another experiment that replaced the linear stage with a robot arm resulted in rotational errors of 0.50+/-0.31° and 2.68+/-2.20° and the translation errors of 0.18+/-0.10 mm and 0.03+/-0.02 mm respectively.
Theoretical modeling of a two-phase thermosyphon assuming the liquids reservoir
Energy Technology Data Exchange (ETDEWEB)
Zanardi, M.A. [UNESP, Guaratingueta, SP (Brazil). Faculdade de Engenharia. Dept. de Energia; Leite, N.G.C. [Universidade do Estado do Rio de Janeiro (UERJ), Resende, RJ (Brazil). Faculdade de Tecnologia. Dept. de Mecanica e Energia]. E-mail: nleite@fat.uerj.br
2007-06-15
A theoretical mod sling using the mass, momentum and energy conservation equations, about the intrinsic phenomena in the working of a cylindrical geometry two-phase thermosyphon operating on vertical was performed. The conservation equations were solved in steady-state operation for all the phases of the thermosyphon. Then model also assumed the presence of a liquid reservoir whose valves of the coefficient of heat transfer that determine the operation of functioning in the reservoir, were obtained from the correlation published in literature The set of conservation equations was solved by using the method of fl nite volumes. The results achieved were checked with experimental data from literature and also from specific experiments performed in laboratory. In a general view, the the oric results matched reasonably well with those ones from the experiments, and the observed deviation were assumed by a inadequate prevision of the reservoir model used, besides keeping a stable level of the reservoir of liquid. (author)
Accounting for Productivity: Is it OK to Assume that the World is Cobb-Douglas?
Shekhar Aiyar; Carl-Johan Dalgaard
2008-01-01
The development accounting literature almost always assumes a Cobb-Douglas (CD) production function. However, if in reality the elasticity of substitution between capital and labor deviates substantially from 1, the assumption is invalid, potentially casting doubt on the commonly held view that factors of production are relatively unimportant in accounting for differences in labor productivity. We use international data on relative factor shares and capital-output ratios to formulate a number...
MR findings of decerebrate rigidity with preservation of consciousness.
Kao, C-D; Guo, W-Y; Chen, J-T; Wu, Z-A; Liao, K-K
2006-05-01
We describe a case of decerebrate rigidity, with preservation of consciousness, caused by a discrete pontine tegmentum lesion identified on MR imaging. Lesions within a certain brain stem region are responsible for decerebrate rigidity in animal studies, but there has been a lack of MR imaging evidence in humans. This report also implies that a discrete lesion was responsible for the decerebrate rigidity, while consciousness was preserved.
Observational properties of rigidly rotating dust configurations
Ilyas, Batyr; Yang, Jinye
2016-01-01
We study the observational properties of a class of exact solutions of Einstein's field equations describing stationary, axially symmetric, rigidly rotating dust. We ask the question whether such solutions can describe astrophysical rotating dark matter clouds and we probe the possibility that they may constitute an alternative to supermassive black holes at the center of galaxies. We show that light emission from accretion disks in this space-time has several differences with respect to the emission of light from accretion disks around black holes. The shape of the iron K{\\alpha} line in the reflection spectrum of accretion disks can potentially distinguish this class of solution from the Kerr metric, but this may not be possible with current X-ray missions.
Settling dynamics of asymmetric rigid fibers
Tozzi, E. J.; Scott, C. T.; Vahey, D.; Klingenberg, D. J.
2011-03-01
The three-dimensional motion of asymmetric rigid fibers settling under gravity in a quiescent fluid was experimentally measured using a pair of cameras located on a movable platform. The particle motion typically consisted of an initial transient after which the particle approached a steady rate of rotation about an axis parallel to the acceleration of gravity, with its center of mass following a helical trajectory. Numerical and analytical methods were used to predict translational and angular velocities as well as the evolution of the fiber orientation as a function of time. A comparison of calculated and measured values shows that it is possible to quantitatively predict complex motions of particles that have highly asymmetric shape. The relations between particle shape and settling trajectory have potential applications for hydrodynamic characterization of fiber shapes and fiber separation.
Suspension of rigid spheres in shear flows
Rahmani, Mona; Esteghamatian, Amir; Wachs, Anthony
2017-11-01
Suspension of rigid spheres in a plane Couette flow is studied using three-dimensional particle resolved numerical simulations. We use a fixed mesh that resolves each particle diameter using 24 points and a Distributed Lagrange Multi- plier/Fictitious Domain (DLM/FD) method. The effects of particle volume fraction and particle Reynolds number on the macrcoscopic and microscopic stresses in the suspension are examined. The kinematics of particle are also studied for a range of dilute to dense suspensions and Stokes to inertial flows. For dense suspensions and also for higher particle Reynolds numbers the particle/particle and particle/wall contacts are enhanced. For such cases, lubrication forces need to be taken into account. We compare simulations with and without the lubrication forces to conclude for what range of parameters lubrication should be incorporated into the simulations.
On real structures on rigid surfaces
Energy Technology Data Exchange (ETDEWEB)
Kulikov, Vik S [Steklov Mathematical Institute, Russian Academy of Sciences (Russian Federation); Kharlamov, V M [Institut de Recherche Matematique Avanee Universite Louis Pasteur et CNRS 7 rue Rene Descartes (France)
2002-02-28
We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p{sub g}=q=0 and K{sup 2}=9. These surfaces also provide new counterexamples to the 'Dif = Def' problem.
Advanced Rigid Ablative Thermal Protection Systems
Feldman, J. D.; Gasch, M. J.; Poteet, C. C.; Szalai, Christine
2012-01-01
With the gradual increase in robotic rover sophistication and the desire for humans to explore the solar system, the need for reentry systems to deliver large payloads into planetary atmospheres is looming. Heritage ablative Thermal Protection Systems (TPS) using Viking or Pathfinder era materials are at or near their performance limits and will be inadequate for many future missions. Significant advances in TPS materials technology are needed in order to enable susequent human exploration missions. This paper summarizes some recent progress at NASA in developing families of advanced rigid ablative TPS that could be used for thermal protection in planetary entry missions. In particular, the effort focuses on technologies required to land heavy masses on Mars to facilitate exploration.
Observational properties of rigidly rotating dust configurations
Energy Technology Data Exchange (ETDEWEB)
Ilyas, Batyr; Malafarina, Daniele [Nazarbayev University, Department of Physics, Astana (Kazakhstan); Yang, Jinye [Fudan University, Center for Field Theory and Particle Physics and Department of Physics, Shanghai (China); Bambi, Cosimo [Fudan University, Center for Field Theory and Particle Physics and Department of Physics, Shanghai (China); Eberhard-Karls Universitaet Tuebingen, Theoretical Astrophysics, Tuebingen (Germany)
2017-07-15
We study the observational properties of a class of exact solutions of Einstein's field equations describing stationary, axially symmetric, rigidly rotating dust (i.e. non-interacting particles). We ask the question whether such solutions can describe astrophysical rotating dark matter clouds near the center of galaxies and we probe the possibility that they may constitute an alternative to supermassive black holes at the center of galaxies. We show that light emission from accretion disks made of ordinary baryonic matter in this space-time has several differences with respect to the emission of light from similar accretion disks around black holes. The shape of the iron Kα line in the reflection spectrum of accretion disks can potentially distinguish this class of solutions from the Kerr metric, but this may not be possible with current X-ray missions. (orig.)
The impact of assumed knowledge entry standards on undergraduate mathematics teaching in Australia
King, Deborah; Cattlin, Joann
2015-10-01
Over the last two decades, many Australian universities have relaxed their selection requirements for mathematics-dependent degrees, shifting from hard prerequisites to assumed knowledge standards which provide students with an indication of the prior learning that is expected. This has been regarded by some as a positive move, since students who may be returning to study, or who are changing career paths but do not have particular prerequisite study, now have more flexible pathways. However, there is mounting evidence to indicate that there are also significant negative impacts associated with assumed knowledge approaches, with large numbers of students enrolling in degrees without the stated assumed knowledge. For students, there are negative impacts on pass rates and retention rates and limitations to pathways within particular degrees. For institutions, the necessity to offer additional mathematics subjects at a lower level than normal and more support services for under-prepared students impacts on workloads and resources. In this paper, we discuss early research from the First Year in Maths project, which begins to shed light on the realities of a system that may in fact be too flexible.
Torsional and bending rigidity of the double helix from data on small DNA rings.
Frank-Kamenetskii, M D; Lukashin, A V; Anshelevich, V V; Vologodskii, A V
1985-02-01
We have calculated the variance of equilibrium distribution of a circular wormlike polymer chain over the writhing number, [Wr)2), as a function of the number of Kuhn statistical segments, n. For large n these data splice well with our earlier results obtained for a circular freely jointed polymer chain. Assuming that [delta Lk)2) = [delta Tw)2) we have compared our results with experimental data on the chain length dependence of the [delta Lk)2) value recently obtained by Horowitz and Wang for small DNA rings. This comparison has shown an excellent agreement between theory and experiment and yielded a reliable estimate of the torsional and bending rigidity parameters. Namely, the torsional rigidity constant is C = 3.0.10(-19) erg cm, and the bending rigidity as expressed in terms of the DNA persistence length is a = 500 A. The obtained value of C agrees well with earlier estimates by Shore and Baldwin as well as by Horowitz and Wang whereas the a value is in accord with the data of Hagerman. We have found the data of Shore and Baldwin on the chain length dependence of the [delta Lk)2) value to be entirely inconsistent with our theorectical results.
EVolution: an edge-based variational method for non-rigid multi-modal image registration
de Senneville, B. Denis; Zachiu, C.; Ries, M.; Moonen, C.
2016-10-01
Image registration is part of a large variety of medical applications including diagnosis, monitoring disease progression and/or treatment effectiveness and, more recently, therapy guidance. Such applications usually involve several imaging modalities such as ultrasound, computed tomography, positron emission tomography, x-ray or magnetic resonance imaging, either separately or combined. In the current work, we propose a non-rigid multi-modal registration method (namely EVolution: an edge-based variational method for non-rigid multi-modal image registration) that aims at maximizing edge alignment between the images being registered. The proposed algorithm requires only contrasts between physiological tissues, preferably present in both image modalities, and assumes deformable/elastic tissues. Given both is shown to be well suitable for non-rigid co-registration across different image types/contrasts (T1/T2) as well as different modalities (CT/MRI). This is achieved using a variational scheme that provides a fast algorithm with a low number of control parameters. Results obtained on an annotated CT data set were comparable to the ones provided by state-of-the-art multi-modal image registration algorithms, for all tested experimental conditions (image pre-filtering, image intensity variation, noise perturbation). Moreover, we demonstrate that, compared to existing approaches, our method possesses increased robustness to transient structures (i.e. that are only present in some of the images).
Method of control of machining accuracy of low-rigidity elastic-deformable shafts
Directory of Open Access Journals (Sweden)
Antoni Świć
Full Text Available The paper presents an analysis of the possibility of increasing the accuracy and stability of machining of low-rigidity shafts while ensuring high efficiency and economy of their machining. An effective way of improving the accuracy of machining of shafts is increasing their rigidity as a result of oriented change of the elastic-deformable state through the application of a tensile force which, combined with the machining force, forms longitudinal-lateral strains. The paper also presents mathematical models describing the changes of the elastic-deformable state resulting from the application of the tensile force. It presents the results of experimental studies on the deformation of elastic low-rigidity shafts, performed on a special test stand developed on the basis of a lathe. An estimation was made of the effectiveness of the method of control of the elastic-deformable state with the use, as the regulating effects, the tensile force and eccentricity. It was demonstrated that controlling the two parameters: tensile force and eccentricity, one can improve the accuracy of machining, and thus achieve a theoretically assumed level of accuracy.
Static and Restricted Rigid Rotor Configurations of Three Classical 12-6-Lennard-Jones Particles
Rupp, Florian
2015-03-01
Motivated by the continuous search for stable geometric configurations of atom and molecule clusters, we analyse the planar evolution of two freely movable point particles around a third immovable one subject to the 12-6-Lennard-Jones potential. This tailors our discussion to systems with one very heavy particle that can be assumed to be permanently at rest in the moving reference frame for the whole ensemble. Relating to Lennard-Jones interactions, we allow all three point particles to take different parameters. This breaks the symmetry conditions that are usually imposed on such systems. Through a classical non-regularized Hamiltonian description of our restricted three particle system, we study the existence of genuine equilibria and rigid rotor solutions around a single axis of rotation. We prove, depending on the choice of the Lennard-Jones parameters, that for these genuine equilibria, collinear alignments and triangular configurations of any shape can occur. Moreover, for the discussed type of relative equilibria a complete classification is provided by proving the existence of rigid rotor configurations in the plane of rotation (collinear cis and trans as well as triangle shaped configurations) and out of the plane of rotation (triangle shaped and flag-like configurations). Furthermore, we show that there are no further rigid rotor solutions of the underlying equations of motion.
Hippo/YAP-mediated rigidity-dependent motor neuron differentiation of human pluripotent stem cells
Sun, Yubing; Yong, Koh Meng Aw; Villa-Diaz, Luis G.; Zhang, Xiaoli; Chen, Weiqiang; Philson, Renee; Weng, Shinuo; Xu, Haoxing; Krebsbach, Paul H.; Fu, Jianping
2014-06-01
Our understanding of the intrinsic mechanosensitive properties of human pluripotent stem cells (hPSCs), in particular the effects that the physical microenvironment has on their differentiation, remains elusive. Here, we show that neural induction and caudalization of hPSCs can be accelerated by using a synthetic microengineered substrate system consisting of poly(dimethylsiloxane) micropost arrays (PMAs) with tunable mechanical rigidities. The purity and yield of functional motor neurons derived from hPSCs within 23 days of culture using soft PMAs were improved more than fourfold and tenfold, respectively, compared with coverslips or rigid PMAs. Mechanistic studies revealed a multi-targeted mechanotransductive process involving Smad phosphorylation and nucleocytoplasmic shuttling, regulated by rigidity-dependent Hippo/YAP activities and actomyosin cytoskeleton integrity and contractility. Our findings suggest that substrate rigidity is an important biophysical cue influencing neural induction and subtype specification, and that microengineered substrates can thus serve as a promising platform for large-scale culture of hPSCs.
Rigid aromatic linking moiety in cationic lipids for enhanced gene transfection efficiency.
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.
A High Rigidity Spectrometer for the Facility for Rare Isotope Beams.
Zegers, Remco
2017-01-01
The High Rigidity Spectrometer (HRS) will be the centerpiece experimental tool of the Facility for Rare-Isotope Beams (FRIB) fast-beam program. The fast-beam program has tremendous discovery potential, enabling experiments with beam intensities of a few ions per second or less through the luminosity afforded by thick targets. The high magnetic rigidity of the HRS (up to 8 Tm) will match the rigidities at which rare-isotope production yields at the FRIB fragment separator are maximum across the entire chart of nuclei and enable experiments with the most neutron-rich nuclei available at FRIB. Gain factors in luminosity of ten or more are achievable compared to running with existing spectrometers, which have a maximum rigidity of 4 Tm, with the highest gains for the most neutron-rich unstable isotopes. To enable a broad spectrum of experiments, the HRS will accommodate different ion-optical modes and provide the flexibility to run in coincidence with a diverse set of other detector systems, such as the Gamma Ray Energy Tracking Array (GRETA) and the Modular Neutron Array (MoNA-LISA). In the presentation, an overview of the scientific opportunities with the HRS and the present layout, based on ion-optical and magnet-feasibility studies, will be given. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office for Nuclear Physics, under Award Number DE-SC0014554.
Rigid-only versus combined rigid and flexible percutaneous nephrolithotomy: a systematic review.
Cracco, Cecilia M; Knoll, Thomas; Liatsikos, Evangelos N; Osther, Palle J; Smith, Arthur D; Scarpa, Roberto M; Scoffone, Cesare M
2017-08-01
Percutaneous nephrolithotomy (PNL) is usually performed worldwide with a rigid-only antegrade approach. Daily practice suggests that adding flexible nephroscopy and/or ureteroscopy to conventional rigid PNL might improve its efficacy and safety, but available evidence is weak. Appraisal of reliable outcomes of such PNL techniques would better guide intraoperative choices and optimize surgical results. Therefore, our objective was to systematically review relevant literature comparing the outcomes of rigid-only PNL and combined flexible PNLs (adding flexible nephroscopy and/or flexible ureteroscopy) for the treatment of large and/or complex upper urinary tract calculi, with regard to efficacy and safety. Ovid MedLine, PubMed, Scopus and Web of Science databases were searched in August 2016 to identify relevant studies. Article selection was performed according to the Preferred Reporting Items for Systematic Review and Meta-analysis criteria. Six articles reporting on 666 patients were included: two randomized controlled trials, two retrospective comparative studies and two case series ≥50 patients (one prospective and one retrospective). A narrative synthesis of minor evidences was also prepared. The adjunct of flexible nephroscopy and/or ureteroscopy provided better stone-free rates (range 86.7-96.97%), through a single percutaneous access most of the times and in any position, reducing the need for second-look procedures. Safety of the combined flexible procedures was improved to a variable degree, with a consensual reduction of the mean hospital stay (range 5.1-7 days). The current evidence suggests that patients with large and/or complex urolithiasis might benefit from the adjunct of flexible nephroscopy and/or ureteroscopy to rigid PNL.
Similarity, agreement, and assumed similarity in proxy end-of-life decision making.
McDade-Montez, Elizabeth; Watson, David; Beer, Andrew
2013-12-01
Medical decisions near the end of life are often made by proxies who can be inaccurate in their judgments of patient preferences. Given that accuracy in surrogate decision making is an important goal in end-of-life decision making, and in light of that previously seen levels of accuracy reflect substantial disagreement, error, or both, this study examined both relationship and individual factors that potentially affect surrogate accuracy. Specifically, this study examined similarity, agreement, and assumed similarity-a process whereby raters use their own traits and preferences to rate another person-in spousal ratings of end-of-life treatment. This study expands on previous research by examining the potential influence of relationship factors and assumed similarity on end-of-life decision making among a sample of newlyweds. Newly married couples (n = 197) completed self and spouse measures of hypothetical end-of-life preferences and scales assessing marital satisfaction, personality, and attitudes. Results indicate a moderate level of similarity on husband and wife self-rated end-of-life treatment preferences (rs = .18-.29) and a moderate level of agreement between self and proxy ratings (rs = .17-.41). The largest correlations were seen between self ratings and proxy ratings (e.g., husband self ratings and husband proxy ratings of wife preferences, rs = .46-.69), reflecting strong assumed similarity in proxy ratings. For wives, similarity with husbands on a few attitudinal variables (i.e., spirituality, moral strictness, and conservatism) influenced proxy accuracy. Recognizing the potential impact of personal preferences on proxy ratings, as well as the potential influence of relationship factors, may help improve proxy accuracy and end-of-life care for patients and families.
VizieR Online Data Catalog: Stellar parameters and assumed wind parameters (Cazorla+, 2017)
Cazorla, C.; Morel, T.; Naze, Y.; Rauw, G.; Semaan, T.; Daflon, S.; Oey, S.
2017-03-01
Stellar parameters derived for the stars in our sample and assumed wind parameters for our hotter stars. Because macroturbulent velocities cannot be determined reliably for fast rotators (Sect. 4.2), all values in column 6 are upper limits. Column 7 provides the multiplicity status (see Sect. 4.1 for the classification criterion and Appendix C for the RV studies of each individual object). The runaway status is based on literature studies (references are given on a star-to-star basis in Appendix C). Columns 15, 16, and 17 of the table presenting the results for the hotter stars list the assumed wind parameters. For stars with the lowest temperatures (typically B0.5 stars), the carbon abundance cannot be firmly determined due to the weakness of the CIII lines at these temperatures. Besides, NII lines may also be very weak for the hottest stars studied with DETAIL/SURFACE. In these cases, we provide upper limits for both carbon and nitrogen abundances. They correspond to predicted lines becoming detectable, i.e., having a depth significantly exceeding the local noise. Similarly, CMFGEN fits may converge towards very high or very low CNO abundances. In both cases, the upper or lower limits were determined from the chi2 curves and correspond to the limit of their flat minimum. Since the CNO abundances are measured relative to the hydrogen content (assumed to be constant in our study), a correction should in principle be applied to the CNO abundances of stars that exhibit a very high helium abundance (and therefore have a reduced hydrogen abundance). However, we found this correction to be negligible (<~0.1dex) even for the most He-rich stars. The 1σ errors on the parameters are given in dedicated columns. (2 data files).
Guo, Beibei; Li, Yisheng
2014-07-29
For many molecularly targeted agents, the probability of response may be assumed to either increase or increase and then plateau in the tested dose range. Therefore, identifying the maximum effective dose, defined as the lowest dose that achieves a pre-specified target response and beyond which improvement in the response is unlikely, becomes increasingly important. Recently, a class of Bayesian designs for single-arm phase II clinical trials based on hypothesis tests and nonlocal alternative prior densities has been proposed and shown to outperform common Bayesian designs based on posterior credible intervals and common frequentist designs. We extend this and related approaches to the design of phase II oncology trials, with the goal of identifying the maximum effective dose among a small number of pre-specified doses. We propose two new Bayesian designs with continuous monitoring of response rates across doses to identify the maximum effective dose, assuming monotonicity of the response rate across doses. The first design is based on Bayesian hypothesis tests. To determine whether each dose level achieves a pre-specified target response rate and whether the response rates between doses are equal, multiple statistical hypotheses are defined using nonlocal alternative prior densities. The second design is based on Bayesian model averaging and also uses nonlocal alternative priors. We conduct simulation studies to evaluate the operating characteristics of the proposed designs, and compare them with three alternative designs. In terms of the likelihood of drawing a correct conclusion using similar between-design average sample sizes, the performance of our proposed design based on Bayesian hypothesis tests and nonlocal alternative priors is more robust than that of the other designs. Specifically, the proposed Bayesian hypothesis test-based design has the largest probability of being the best design among all designs under comparison and the smallest probability of
Chulya, Abhisak; Mullen, Robert L.
1989-01-01
A linear finite strip plate element based on Mindlin-Reissner plate theory is developed. The analysis is suitable for both thin and thick plates. In the formulation, new transverse shear strains are introduced and assumed constant in each two-node linear strip. The element stiffness matrix is explicitly formulated for efficient computation and computer implementation. Numerical results showing the efficiency and predictive capability of the element for the analysis of plates are presented for different support and loading conditions and a wide range of thicknesses. No sign of shear locking is observed with the newly developed element.
Influence of rigid boundary on the propagation of torsional surface ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Earth System Science; Volume 124; Issue 1. Influence of rigid boundary on the propagation of torsional ... rigid boundary, whereas it does at the free boundary. Graphical user interface (GUI) software has been developed using MATLAB 7.5 to generalize the effect of various parameter discussed.
Anti-synchronization of the rigid body exhibiting chaotic dynamics ...
African Journals Online (AJOL)
Anti-synchronization of the rigid body exhibiting chaotic dynamics. ... Journal of the Nigerian Association of Mathematical Physics ... Global asymptotic stability and convergence of the sum of the dynamical variables representing the Eulerian state space of the two rigid bodies was verified by numerical simulations. JONAMP ...
effects of flexural rigidity of reinforcement bars on the fundamental ...
African Journals Online (AJOL)
NIJOTECH
2009-09-02
Sep 2, 2009 ... numerical method, and the results show that the flexural rigidity of the bars has significant effect on the fundamental natural frequency of heavily reinforced concrete sections. KEYWORDS: Fundamental Natural Frequency, Reinforced Concrete Slab, Flexural Rigidity,. Reinforcement Bars. INTRODUCTION.
Conflict and creativity: Threat-rigidity or motivated focus
de Dreu, C.K.W.; Nijstad, B.A.
2008-01-01
According to the traditional threat-rigidity reasoning, people in social conflict will be less flexible, less creative, more narrow-minded, and more rigid in their thinking when they adopt a conflict rather than a cooperation mental set. The authors propose and test an alternative, motivated focus
The relationship between torsional rigidity and bending strength ...
African Journals Online (AJOL)
The modulus of rigidity, G, and bending moment of elasticity, MOE, of SA pine are evaluated from a direct torsion test and bending tests. Specimens were subjected to a series of tests with the view to determining direct torsional rigidity, apparent bending modulus of elasticity and pure bending modulus of elasticity. Torsional ...
Fernández, David Lorente
2015-01-01
This chapter uses a comparative approach to examine the maintenance of Indigenous practices related with Learning by Observing and Pitching In in two generations--parent generation and current child generation--in a Central Mexican Nahua community. In spite of cultural changes and the increase of Western schooling experience, these practices persist, to different degrees, as a Nahua cultural heritage with close historical relations to the key value of cuidado (stewardship). The chapter explores how children learn the value of cuidado in a variety of everyday activities, which include assuming responsibility in many social situations, primarily in cultivating corn, raising and protecting domestic animals, health practices, and participating in family ceremonial life. The chapter focuses on three main points: (1) Cuidado (assuming responsibility for), in the Nahua socio-cultural context, refers to the concepts of protection and "raising" as well as fostering other beings, whether humans, plants, or animals, to reach their potential and fulfill their development. (2) Children learn cuidado by contributing to family endeavors: They develop attention and self-motivation; they are capable of responsible actions; and they are able to transform participation to achieve the status of a competent member of local society. (3) This collaborative participation allows children to continue the cultural tradition and to preserve a Nahua heritage at a deeper level in a community in which Nahuatl language and dress have disappeared, and people do not identify themselves as Indigenous. © 2015 Elsevier Inc. All rights reserved.
Srivastava, Sanjay; Guglielmo, Steve; Beer, Jennifer S
2010-03-01
In interpersonal perception, "perceiver effects" are tendencies of perceivers to see other people in a particular way. Two studies of naturalistic interactions examined perceiver effects for personality traits: seeing a typical other as sympathetic or quarrelsome, responsible or careless, and so forth. Several basic questions were addressed. First, are perceiver effects organized as a global evaluative halo, or do perceptions of different traits vary in distinct ways? Second, does assumed similarity (as evidenced by self-perceiver correlations) reflect broad evaluative consistency or trait-specific content? Third, are perceiver effects a manifestation of stable beliefs about the generalized other, or do they form in specific contexts as group-specific stereotypes? Findings indicated that perceiver effects were better described by a differentiated, multidimensional structure with both trait-specific content and a higher order global evaluation factor. Assumed similarity was at least partially attributable to trait-specific content, not just to broad evaluative similarity between self and others. Perceiver effects were correlated with gender and attachment style, but in newly formed groups, they became more stable over time, suggesting that they grew dynamically as group stereotypes. Implications for the interpretation of perceiver effects and for research on personality assessment and psychopathology are discussed.
Donde, Sapana D; Ragsdale, Sally K A
2017-10-01
Survivors of sexual trauma often experience pervasive adverse cognitive attributions, such as assuming responsibility for victimization. In fact, these negative outcomes were recently included in the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) criterion for posttraumatic stress disorder (PTSD) and have garnered substantial research attention devoted toward investigating the effectiveness of empirically supported trauma treatments in altering and reducing maladaptive belief systems. However, less is known about the ways that these negative cognitions may be inadvertently serving an adaptive role in young women's healing and recovery from sexual trauma. The present study examined relationships between situational aspects of sexual victimization, personal responsibility, self-esteem, perceived future control, and perceived future likelihood of assault recurrence using path analysis in a sample of college women ( n = 347) who had experienced sexual victimization. Increased physical harm, decreased intoxication of the male, increased survivor intoxication, and decreased clarity of nonconsent were associated with increased personal responsibility, which was positively associated with self-esteem and perceived future control. Self-esteem mediated a negative relationship between personal responsibility and perceived future likelihood of assault recurrence, while perceived future control mediated a positive relationship. Findings suggest that college women's tendency to assume personal responsibility for sexual victimization experiences is a complicated double-edged sword with both harmful and adaptive effects. Innovative, comprehensive, and sophisticated approaches to sexual assault prevention and treatment are needed to more effectively address this issue and support young women's healing and recovery from victimization.
Tautochrone and Brachistochrone Shape Solutions for Rocking Rigid Bodies
Glaschke, Patrick
2016-01-01
Rocking rigid bodies appear in several shapes in everyday life: As furniture like rocking chairs and rocking cradles or as toys like rocking horses or tilting dolls. The familiar rocking motion of these objects, a non-linear combination of a rigid rotation and a translation of the center of mass, gives rise to a number of interesting dynamical properties. However, their study has received little attention in the literature. This work presents a comprehensive introduction to the dynamics of rocking rigid bodies, including a concise derivation of the equations of motion as well as a general inversion procedure to construct rocking rigid body shapes with specified dynamical properties. Moreover, two novel rigid body shapes are derived - the tautochrone shape and the brachistochrone shape - which represent an intriguing generalization of the well-know tautochrone and brachistochrone curves. In particular, tautochrone shapes offer an alternative construction of a tautochrone pendulum, in addition to Huygens' cyclo...
The theory of pseudo-rigid bodies
Cohen, Harley
1988-01-01
This monograph concerns the development, analysis, and application of the theory of pseudo-rigid bodies. It collects together our work on that subject over the last five years. While some results have appeared else where, much of the work is new. Our objective in writing this mono graph has been to present a new theory of the deformation of bodies, one that has not only a firm theoretical basis, but also the simplicity to serve as an effective tool in practical problems. Consequently, the main body of the treatise is a multifaceted development of the theory, from foundations to explicit solutions to linearizations to methods of approximation. The fact that this variety of aspects, each examined in considerable detail, can be collected together in a single, unified treat ment gives this theory an elegance that we feel sets it apart from many others. While our goal has always been to give a complete treatment of the theory as it now stands, the work here is not meant to be definitive. Theories are not ent...
Spontaneous droplet trampolining on rigid superhydrophobic surfaces
Schutzius, Thomas M.; Jung, Stefan; Maitra, Tanmoy; Graeber, Gustav; Köhme, Moritz; Poulikakos, Dimos
2015-11-01
Spontaneous removal of condensed matter from surfaces is exploited in nature and in a broad range of technologies to achieve self-cleaning, anti-icing and condensation control. But despite much progress, our understanding of the phenomena leading to such behaviour remains incomplete, which makes it challenging to rationally design surfaces that benefit from its manifestation. Here we show that water droplets resting on superhydrophobic textured surfaces in a low-pressure environment can self-remove through sudden spontaneous levitation and subsequent trampoline-like bouncing behaviour, in which sequential collisions with the surface accelerate the droplets. These collisions have restitution coefficients (ratios of relative speeds after and before collision) greater than unity despite complete rigidity of the surface, and thus seemingly violate the second law of thermodynamics. However, these restitution coefficients result from an overpressure beneath the droplet produced by fast droplet vaporization while substrate adhesion and surface texture restrict vapour flow. We also show that the high vaporization rates experienced by the droplets and the associated cooling can result in freezing from a supercooled state that triggers a sudden increase in vaporization, which in turn boosts the levitation process. This effect can spontaneously remove surface icing by lifting away icy drops the moment they freeze. Although these observations are relevant only to systems in a low-pressure environment, they show how surface texturing can produce droplet-surface interactions that prohibit liquid and freezing water-droplet retention on surfaces.
THE RIGIDITY OF THE EARTH'S INNER CORE
Directory of Open Access Journals (Sweden)
K. E. BULLEN
1953-06-01
Full Text Available The purpose of this paper is to examine and assess, in the
light of recent evidence, the theory lliat the Earth's inner core has
a significant rigidity.
The presenee of an inner core in the Earth is revealed from
observations of the seismie pliase PKP in the « sliadow zone » for
which the epicentral distance A lies in the range 105" < A < 143".
Miss I. Lehmann (r in 1936, followed by Gutenberg and Richter (2
in 1938, atlrihuted these observations to tlie presence of an inner
core; and Jeffreys (3 in 1939 applied Airy's theory of diffraetion
near a caustic to sliow that the alternative theory of diffraetion
round the outer boundary of the centrai core was not capable of
explaining tlie observations in the shadow zone. The existence of the
inner core has been fairly generallv accepted sinee tliis ealculation
of Jeffreys.
Molecular rigidity and enthalpy-entropy compensation in DNA melting.
Vargas-Lara, Fernando; Starr, Francis W; Douglas, Jack F
2017-10-23
Enthalpy-entropy compensation (EEC) is observed in diverse molecular binding processes of importance to living systems and manufacturing applications, but this widely occurring phenomenon is not sufficiently understood from a molecular physics standpoint. To gain insight into this fundamental problem, we focus on the melting of double-stranded DNA (dsDNA) since measurements exhibiting EEC are extensive for nucleic acid complexes and existing coarse-grained models of DNA allow us to explore the influence of changes in molecular parameters on the energetic parameters by using molecular dynamics simulations. Previous experimental and computational studies have indicated a correlation between EEC and changes in molecular rigidity in certain binding-unbinding processes, and, correspondingly, we estimate measures of DNA molecular rigidity under a wide range of conditions, along with resultant changes in the enthalpy and entropy of binding. In particular, we consider variations in dsDNA rigidity that arise from changes of intrinsic molecular rigidity such as varying the associative interaction strength between the DNA bases, the length of the DNA chains, and the bending stiffness of the individual DNA chains. We also consider extrinsic changes of molecular rigidity arising from the addition of polymer additives and geometrical confinement of DNA between parallel plates. All our computations confirm EEC and indicate that this phenomenon is indeed highly correlated with changes in molecular rigidity. However, two distinct patterns relating to how DNA rigidity influences the entropy of association emerge from our analysis. Increasing the intrinsic DNA rigidity increases the entropy of binding, but increases in molecular rigidity from external constraints decreases the entropy of binding. EEC arises in numerous synthetic and biological binding processes and we suggest that changes in molecular rigidity might provide a common origin of this ubiquitous phenomenon in the mutual
Validation of a Non-Rigid Registration Error Detection Algorithm Using Clinical MRI Brain Data
Datteri, Ryan D.; Liu, Yuan; D’Haese, Pierre-François; Dawant, Benoit M.
2014-01-01
Identification of error in non-rigid registration is a critical problem in the medical image processing community. We recently proposed an algorithm that we call “Assessing Quality Using Image Registration Circuits” (AQUIRC) to identify non-rigid registration errors and have tested its performance using simulated cases. In this article, we extend our previous work to assess AQUIRC’s ability to detect local non-rigid registration errors and validate it quantitatively at specific clinical landmarks, namely the Anterior Commissure (AC) and the Posterior Commissure (PC). To test our approach on a representative range of error we utilize 5 different registration methods and use 100 target images and 9 atlas images. Our results show that AQUIRC’s measure of registration quality correlates with the true target registration error (TRE) at these selected landmarks with an R2 = 0.542. To compare our method to a more conventional approach, we compute Local Normalized Correlation Coefficient (LNCC) and show that AQUIRC performs similarly. However, a multi-linear regression performed with both AQUIRC’s measure and LNCC shows a higher correlation with TRE than correlations obtained with either measure alone, thus showing the complementarity of these quality measures. We conclude the article by showing that the AQUIRC algorithm can be used to reduce registration errors for all five algorithms. PMID:25095252
An assumed pdf approach for the calculation of supersonic mixing layers
Baurle, R. A.; Drummond, J. P.; Hassan, H. A.
1992-01-01
In an effort to predict the effect that turbulent mixing has on the extent of combustion, a one-equation turbulence model is added to an existing Navier-Stokes solver with finite-rate chemistry. To average the chemical-source terms appearing in the species-continuity equations, an assumed pdf approach is also used. This code was used to analyze the mixing and combustion caused by the mixing layer formed by supersonic coaxial H2-air streams. The chemistry model employed allows for the formation of H2O2 and HO2. Comparisons are made with recent measurements using laser Raman diagnostics. Comparisons include temperature and its rms, and concentrations of H2, O2, N2, H2O, and OH. In general, good agreement with experiment was noted.
Compositional Synthesis of Controllers from Scenario-Based Assume-Guarantee Specifications
DEFF Research Database (Denmark)
Greenyer, Joel; Kindler, Ekkart
2013-01-01
to avoid flaws in the product or costly iterations during its development. We propose to use Modal Sequence Diagrams (MSDs), a formal, yet intuitive formalism for specifying the interaction of a system with its environment, and developed a formal synthesis approach that allows us to detect inconsistencies...... and even to automatically synthesize controllers from MSD specifications. The technique is suited for specifications of technical systems with real-time constraints and environment assumptions. However, synthesis is computationally expensive. In order to employ synthesis also for larger specifications, we...... present, in this paper, a novel assume-guarantee-style compositional synthesis technique for MSD specifications. We provide evaluation results underlining the benefit of our approach and formally justify its correctness....
Hamiltonian theory for the non-rigid Earth: Semidiurnal terms
Getino, J.; Ferrándiz, J. M.; Escapa, A.
2001-04-01
The purpose of this paper is to determine the contributions to the nutation series arising from the triaxiality of a non-rigid Earth model composed of a rigid mantle and a liquid core. With this aim, the canonical formulation of the rotation of the non-rigid Earth developed by Getino and Ferrándiz is applied in order to study the semidiurnal terms arising from the C22 and S22 geopotential coefficients. Once the corresponding generating function is calculated, analytical expressions of the Andoyer and figure planes are derived. We also provide numerical nutation series based on the analytical formulae.
Observations on the Partial Breaking of $N=2$ Rigid Supersymmetry
Andrianopoli, Laura; Ferrara, Sergio; Trigiante, Mario
2015-01-01
We study the partial breaking of $N=2$ rigid supersymmetry for a generic rigid special geometry of $n$ abelian vector multiplets in the presence of Fayet-Iliopoulos terms induced by the Hyper-K\\"ahler momentum map. By exhibiting the symplectic structure of the problem we give invariant conditions for the breaking to occur, which rely on a quartic invariant of the Fayet-Iliopoulos charges as well as on a modification of the $N=2$ rigid symmetry algebra by a vector central charge.
Observations on the partial breaking of N=2 rigid supersymmetry
Directory of Open Access Journals (Sweden)
Laura Andrianopoli
2015-05-01
Full Text Available We study the partial breaking of N=2 rigid supersymmetry for a generic rigid special geometry of n abelian vector multiplets in the presence of Fayet–Iliopoulos terms induced by the hyper-Kähler momentum map. By exhibiting the symplectic structure of the problem we give invariant conditions for the breaking to occur, which rely on a quartic invariant of the Fayet–Iliopoulos charges as well as on a modification of the N=2 rigid symmetry algebra by a vector central charge.
From the Kochen-Specker theorem to noncontextuality inequalities without assuming determinism.
Kunjwal, Ravi; Spekkens, Robert W
2015-09-11
The Kochen-Specker theorem demonstrates that it is not possible to reproduce the predictions of quantum theory in terms of a hidden variable model where the hidden variables assign a value to every projector deterministically and noncontextually. A noncontextual value assignment to a projector is one that does not depend on which other projectors-the context-are measured together with it. Using a generalization of the notion of noncontextuality that applies to both measurements and preparations, we propose a scheme for deriving inequalities that test whether a given set of experimental statistics is consistent with a noncontextual model. Unlike previous inequalities inspired by the Kochen-Specker theorem, we do not assume that the value assignments are deterministic and therefore in the face of a violation of our inequality, the possibility of salvaging noncontextuality by abandoning determinism is no longer an option. Our approach is operational in the sense that it does not presume quantum theory: a violation of our inequality implies the impossibility of a noncontextual model for any operational theory that can account for the experimental observations, including any successor to quantum theory.
Stanke, Monika; Adamowicz, Ludwik
2013-10-01
In this work, we describe how the energies obtained in molecular calculations performed without assuming the Born-Oppenheimer (BO) approximation can be augmented with corrections accounting for the leading relativistic effects. Unlike the conventional BO approach, where these effects only concern the relativistic interactions between the electrons, the non-BO approach also accounts for the relativistic effects due to the nuclei and due to the coupling of the coupled electron-nucleus motion. In the numerical sections, the results obtained with the two approaches are compared. The first comparison concerns the dissociation energies of the two-electron isotopologues of the H2 molecule, H2, HD, D2, T2, and the HeH+ ion. The comparison shows that, as expected, the differences in the relativistic contributions obtained with the two approaches increase as the nuclei become lighter. The second comparison concerns the relativistic corrections to all 23 pure vibrational states of the HD+ ion. An interesting charge asymmetry caused by the nonadiabatic electron-nucleus interaction appears in this system, and this effect significantly increases with the vibration excitation. The comparison of the non-BO results with the results obtained with the conventional BO approach, which in the lowest order does not describe the charge-asymmetry effect, reveals how this effect affects the values of the relativistic corrections.
Oseso, Linda; Magaret, Amalia S; Jerome, Keith R; Fox, Julie; Wald, Anna
2016-09-01
Current treatment of genital herpes is focused on ameliorating signs and symptoms but is not curative. However, as potential herpes simplex virus (HSV) cure approaches are tested in the laboratory, we aimed to assess the interest in such studies by persons with genital herpes and the willingness to assume risks associated with experimental therapy. We constructed an anonymous online questionnaire that was posted on websites that provide information regarding genital herpes. The questions collected demographic and clinical information on adults who self-reported as having genital herpes, and assessed attitudes toward and willingness to participate in HSV cure clinical research. Seven hundred eleven participants provided sufficient responses to be included in the analysis. Sixty-six percent were women; the median age was 37 years, and the median time since genital HSV diagnosis was 4.7 years. The willingness to participate in trials increased from 59.0% in phase 1 to 68.5% in phase 2, and 81.2% in phase 3 trials, and 40% reported willingness to participate even in the absence of immediate, personal benefits. The most desirable outcome was the elimination of risk for transmission to sex partner or neonate. The mean perceived severity of receiving a diagnosis of genital HSV-2 was 4.2 on a scale of 1 to 5. Despite suppressive therapy available, persons with genital herpes are interested in participating in clinical research aimed at curing HSV, especially in more advanced stages of development.
Approximate natural vibration analysis of rectangular plates with openings using assumed mode method
Directory of Open Access Journals (Sweden)
Dae Seung Cho
2013-09-01
Full Text Available Natural vibration analysis of plates with openings of different shape represents an important issue in naval architecture and ocean engineering applications. In this paper, a procedure for vibration analysis of plates with openings and arbitrary edge constraints is presented. It is based on the assumed mode method, where natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. The presented solution represents an extension of a procedure for natural vibration analysis of rectangular plates without openings, which has been recently presented in the literature. The effect of an opening is taken into account in an intuitive way, i.e. by subtracting its energy from the total plate energy without opening. Illustrative numerical examples include dynamic analysis of rectangular plates with rectangular, elliptic, circular as well as oval openings with various plate thicknesses and different combinations of boundary conditions. The results are compared with those obtained by the finite element method (FEM as well as those available in the relevant literature, and very good agreement is achieved.
Trujillo, Anna C.; Gregory, Irene M.
2014-01-01
Control-theoretic modeling of human operator's dynamic behavior in manual control tasks has a long, rich history. There has been significant work on techniques used to identify the pilot model of a given structure. This research attempts to go beyond pilot identification based on experimental data to develop a predictor of pilot behavior. Two methods for pre-dicting pilot stick input during changing aircraft dynamics and deducing changes in pilot behavior are presented This approach may also have the capability to detect a change in a subject due to workload, engagement, etc., or the effects of changes in vehicle dynamics on the pilot. With this ability to detect changes in piloting behavior, the possibility now exists to mediate human adverse behaviors, hardware failures, and software anomalies with autono-my that may ameliorate these undesirable effects. However, appropriate timing of when au-tonomy should assume control is dependent on criticality of actions to safety, sensitivity of methods to accurately detect these adverse changes, and effects of changes in levels of auto-mation of the system as a whole.
Sound propagation over rigid porous layers
Howorth, Craig
Two related topics are discussed: (1) the measurement of the acoustical characteristics of rigid porous materials, that is the impedance and propagation constant; and (2) the propagation of sound over the surface of a hard backed layer of such a material. A review of impedance measurement leads to the selection of an indirect method which is employed successfully on a wide range of surfaces. A numerical comparison of impedance models follows including a one-parameter semi-empirical model, a phenomenological model, and a microstructural model which relates several physical parameters of a material to the acoustical properties of a surface. The models differ in their prediction of the acoustical properties of a low porosity material. A numerical comparison of the solutions of point source propagation in the presence of a porous media indicates that the 'extended' Weyl van der Pol approximation is reliable over short source receiver distances. The study is extended to examine the phenomenon of the acoustical surface wave. Three experimental techniques are used to produce new evidence for the existence of such a wave which shows good agreement with the theoretical predictions. The indirect method is used to obtain impedances and model parameters for a wide variety of surfaces varying from soils to fiberglass and which are compared with the results of an impedance technique and with standing wave tube measurements. The indirect method of impedance is employed together with the microstructural model and the propagation model examined earlier in studies of the acoustical properties of porous road surfaces. It proves possible to use the indirect method both to determine the microstructural parameters and to classify the acoustical properties of such a previous surface when the sound source is either a loudspeaker point source or a vehicle. The results of the parameter determination are validated by a series of non-acoustical measurements. With regard only to the excess
Glass fiber and silica reinforced rigid polyurethane foams
National Research Council Canada - National Science Library
M W Kim; S H Kwon; H Park; B K Kim
2017-01-01
Ternary composites of rigid polyurethane foam (RPUF)/glass fiber/silica as well as RPUF/glass fiber have been fabricated from glass fiber, silica, polymeric 4,4'-di-phenylmethane diisocyanate (PMDI...
Stabilization of Rigid Body Dynamics by Internal and External Torques
National Research Council Canada - National Science Library
Bloch, A. M; Krishnaprasad, P. S; Marsden, J. E; Sanchez de Alvarez, G
1990-01-01
...] with quadratic feedback torques for internal rotors. We show that with such torques, the equations for the rigid body with momentum wheels are Hamiltonian with respect to a Lie-Poisson bracket structure. Further...
Resin Infusion Rigidized Inflatable Concept Development and Demonstration Project
National Aeronautics and Space Administration — Utilizing resin infusion to rigidize an inflatable structure and form fiber-reinforced composites on-orbit is a novel concept that builds on current NASA technology...
A Concise Introduction to Mechanics of Rigid Bodies Multidisciplinary Engineering
Huang, L
2012-01-01
A Concise Introduction to Mechanics of Rigid Bodies: Multidisciplinary Engineering presents concise, key concepts of kinematics and dynamics of rigid bodies. This compact volume bridges the steep gap between introductory texts on engineering mechanics, which focus on one and two dimensional motions of particles and rigid bodies, and advanced texts on multi-body dynamics in high dimension spaces found in multidisciplinary areas like mechatronics, robotics and biomechanics. In the book, rigid body motions in the spaces with different dimensions are described in addition to studies in a uniform framework supported by vector and matrix operations. Rigorous mathematic tools and explanations are provided to clarify the most complex concepts. This book also: Provides practical examples from different engineering areas, offering a link between theoretical fundamentals and everyday applications Offers simplified mathematical equations to clearly present essential theories in robotics and mechanics Presents statics...
[Arterial rigidity in patients with chronic obstructive pulmonary disease].
Karoli, N A; Dolishniaia, G R; Rebrov, A P
2012-01-01
The aim of this open study was to estimate arterial rigidity in patients with chronic obstructive pulmonary disease (COPD). It included 105 patients above 40 years of age. Exclusion criteria were clinical signs of CHD, peripheral atherosclerosis, and other severe chronic diseases in the exacerbation phase. The control group was comprised of 27 practically healthy volunteers. The arterial fluid was detected using a Tensioclinic arteriograph (Tensiomed, Hungary). Arterial rigidity was estimated in patients of two age groups (below and above 60 years) with COPD of different severity The results suggest the development of arterial wall lesions in proportion to the patients' age and COPD severity. It was shown that excessive arterial rigidity and accelerated pulse wave reflection (increased speed of pulse wave propagation and augmentation index) exert significant influence on the elevation of central arterial pressure. Enhanced rigidity of the arterial wall being a cardiovascular risk factor further prospective studies are needed.
Dynamic Simulation of Rigid Guide Structure Based on ANSYS
National Research Council Canada - National Science Library
Zhang Xin; Wang Zhe
2017-01-01
... commonly used calculation model of rigid guide and bunton by ANSYS. Simulation of the horizontal force through a section of the guide evenly, and the deflection curves of each model are obtained...
Invariant scrambled sets, uniform rigidity and weak mixing
Foryś, Magdalena; Huang, Wen; Li, Jian; Oprocha, Piotr
2014-01-01
We show that for a non-trivial transitive dynamical system, it has a dense Mycielski invariant strongly scrambled set if and only if it has a fixed point, and it has a dense Mycielski invariant $\\delta$-scrambled set for some $\\delta>0$ if and only if it has a fixed point and not uniformly rigid. We also provide two methods for the construction of completely scrambled systems which are weakly mixing, proximal and uniformly rigid.
Observability/Identifiability of Rigid Motion under Perspective Projection
Soatto, Stefano
1994-01-01
The "visual motion estimation" problem concerns the reconstruction of the motion of an object viewed under projection. This paper addresses the feasibility of such a problem when the object is represented as a "rigid" set of point-features in the Euclidean 3D space. We represent rigid motion as a point on the so-called "essential manifold" and show that it is globally observable from perspective projections under some general position conditions. Such conditions hold when the path of the view...
A sequence-dependent rigid-base model of DNA.
Gonzalez, O; Petkevičiūtė, D; Maddocks, J H
2013-02-07
A novel hierarchy of coarse-grain, sequence-dependent, rigid-base models of B-form DNA in solution is introduced. The hierarchy depends on both the assumed range of energetic couplings, and the extent of sequence dependence of the model parameters. A significant feature of the models is that they exhibit the phenomenon of frustration: each base cannot simultaneously minimize the energy of all of its interactions. As a consequence, an arbitrary DNA oligomer has an intrinsic or pre-existing stress, with the level of this frustration dependent on the particular sequence of the oligomer. Attention is focussed on the particular model in the hierarchy that has nearest-neighbor interactions and dimer sequence dependence of the model parameters. For a Gaussian version of this model, a complete coarse-grain parameter set is estimated. The parameterized model allows, for an oligomer of arbitrary length and sequence, a simple and explicit construction of an approximation to the configuration-space equilibrium probability density function for the oligomer in solution. The training set leading to the coarse-grain parameter set is itself extracted from a recent and extensive database of a large number of independent, atomic-resolution molecular dynamics (MD) simulations of short DNA oligomers immersed in explicit solvent. The Kullback-Leibler divergence between probability density functions is used to make several quantitative assessments of our nearest-neighbor, dimer-dependent model, which is compared against others in the hierarchy to assess various assumptions pertaining both to the locality of the energetic couplings and to the level of sequence dependence of its parameters. It is also compared directly against all-atom MD simulation to assess its predictive capabilities. The results show that the nearest-neighbor, dimer-dependent model can successfully resolve sequence effects both within and between oligomers. For example, due to the presence of frustration, the model can
On the inertial motions of liquid-filled rigid bodies
Mazzone, Giusy; Galdi, Giovanni; Zunino, Paolo
2013-11-01
We consider a rigid body with a cavity completely filled by a viscous liquid and study the inertial motions of the system liquid-filled rigid body S . The equations governing the motion of this coupled system are given by the Navier-Stokes equations and the equations of the balance of the total angular momentum of S in absence of external forces and torques. Given any initial motion to the coupled system, characterized by an initial relative velocity of the fluid and an initial total angular momentum, we give a complete description of the behavior that the system liquid-filled rigid body will show at large times. From both analytical and numerical viewpoints, we are able to prove a longstanding conjecture stated by Zhukovskii, namely that S will eventually reach a steady state which is a rigid body permanent rotation. In other words, the liquid goes to rest with respect to the rigid body and the coupled system will rotate as a whole rigid body, with a constant angular velocity that is directed along one of the principal axes of inertia of the system.
Augmented reality for non-rigid surfaces
Pilet, Julien
2008-01-01
Augmented Reality (AR) is the process of integrating virtual elements in reality, often by mixing computer graphics into a live video stream of a real scene. It requires registration of the target object with respect to the cameras. To this end, some approaches rely on dedicated hardware, such as magnetic trackers or infra-red cameras, but they are too expensive and cumbersome to reach a large public. Others are based on specifically designed markers which usually look like bar-codes. However...
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.
Toplis, M. J.; Mizzon, H.; Forni, O.; Monnereau, M.; Prettyman, T. H.; McSween, H. Y.; McCoy, T. J.; Mittlefehldt, D. W.; DeSanctis, M. C.; Raymond, C. A.;
2012-01-01
Bulk composition (including oxygen content) is a primary control on the internal structure and mineralogy of differentiated asteroids. For example, oxidation state will affect core size, as well as Mg# and pyroxene content of the silicate mantle. The Howardite-Eucrite-Diogenite class of meteorites (HED) provide an interesting test-case of this idea, in particular in light of results of the Dawn mission which provide information on the size, density and differentiation state of Vesta, the parent body of the HED's. In this work we explore plausible bulk compositions of Vesta and use mass-balance and geochemical modelling to predict possible internal structures and crust/mantle compositions and mineralogies. Models are constrained to be consistent with known HED samples, but the approach has the potential to extend predictions to thermodynamically plausible rock types that are not necessarily present in the HED collection. Nine chondritic bulk compositions are considered (CI, CV, CO, CM, H, L, LL, EH, EL). For each, relative proportions and densities of the core, mantle, and crust are quantified. Considering that the basaltic crust has the composition of the primitive eucrite Juvinas and assuming that this crust is in thermodynamic equilibrium with the residual mantle, it is possible to calculate how much iron is in metallic form (in the core) and how much in oxidized form (in the mantle and crust) for a given bulk composition. Of the nine bulk compositions tested, solutions corresponding to CI and LL groups predicted a negative metal fraction and were not considered further. Solutions for enstatite chondrites imply significant oxidation relative to the starting materials and these solutions too are considered unlikely. For the remaining bulk compositions, the relative proportion of crust to bulk silicate is typically in the range 15 to 20% corresponding to crustal thicknesses of 15 to 20 km for a porosity-free Vesta-sized body. The mantle is predicted to be largely
Validation of Fick cardiac output calculated with assumed oxygen consumption : a study of cardiac output during epoprostenol
Bergstra, A; van den Heuvel, A F M; Zijlstra, F; Berger, R M F; Mook, G A; van Veldhuisen, D J
OBJECTIVE: To test the validity of using assumed oxygen consumption for Fick cardiac output during administration of epoprostenol. METHODS: In 24 consecutive patients Fick cardiac output calculated with assumed oxygen consumption according to LaFarge and Miettinen (COLM) and according to Bergstra et
2010-04-01
... Requirements § 224.64 How may a tribe assume management of development of different types of energy resources... 25 Indians 1 2010-04-01 2010-04-01 false How may a tribe assume management of development of different types of energy resources? 224.64 Section 224.64 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF...
Rotation of a rigid satellite with a fluid component: a new light onto Titan's obliquity
Boué, Gwenaël; Rambaux, Nicolas; Richard, Andy
2017-12-01
We revisit the rotation dynamics of a rigid satellite with either a liquid core or a global subsurface ocean. In both problems, the flow of the fluid component is assumed inviscid. The study of a hollow satellite with a liquid core is based on the Poincaré-Hough model which provides exact equations of motion. We introduce an approximation when the ellipticity of the cavity is low. This simplification allows to model both types of satellite in the same manner. The analysis of their rotation is done in a non-canonical Hamiltonian formalism closely related to Poincaré's "forme nouvelle des équations de la mécanique". In the case of a satellite with a global ocean, we obtain a seven-degree-of-freedom system. Six of them account for the motion of the two rigid components, and the last one is associated with the fluid layer. We apply our model to Titan for which the origin of the obliquity is still a debated question. We show that the observed value is compatible with Titan slightly departing from the hydrostatic equilibrium and being in a Cassini equilibrium state.
Rigidity analysis of protein biological assemblies and periodic crystal structures
2013-01-01
Background We initiate in silico rigidity-theoretical studies of biological assemblies and small crystals for protein structures. The goal is to determine if, and how, the interactions among neighboring cells and subchains affect the flexibility of a molecule in its crystallized state. We use experimental X-ray crystallography data from the Protein Data Bank (PDB). The analysis relies on an effcient graph-based algorithm. Computational experiments were performed using new protein rigidity analysis tools available in the new release of our KINARI-Web server http://kinari.cs.umass.edu. Results We provide two types of results: on biological assemblies and on crystals. We found that when only isolated subchains are considered, structural and functional information may be missed. Indeed, the rigidity of biological assemblies is sometimes dependent on the count and placement of hydrogen bonds and other interactions among the individual subchains of the biological unit. Similarly, the rigidity of small crystals may be affected by the interactions between atoms belonging to different unit cells. We have analyzed a dataset of approximately 300 proteins, from which we generated 982 crystals (some of which are biological assemblies). We identified two types of behaviors. (a) Some crystals and/or biological assemblies will aggregate into rigid bodies that span multiple unit cells/asymmetric units. Some of them create substantially larger rigid cluster in the crystal/biological assembly form, while in other cases, the aggregation has a smaller effect just at the interface between the units. (b) In other cases, the rigidity properties of the asymmetric units are retained, because the rigid bodies did not combine. We also identified two interesting cases where rigidity analysis may be correlated with the functional behavior of the protein. This type of information, identified here for the first time, depends critically on the ability to create crystals and biological assemblies
A comparison of regulatory impacts to real target impacts
Energy Technology Data Exchange (ETDEWEB)
Ammerman, D.J.
1998-05-01
The purpose of this paper is to discuss the relative severity of regulatory impacts onto an essentially rigid target to impacts at higher velocities onto real targets. For impacts onto the essentially rigid target all of the kinetic energy of the package is absorbed by deformation of the package. For impacts onto real targets the kinetic energy is absorbed by deformation of the target as well as by deformation of the package. The amount of kinetic energy absorbed by the target does not increase the severity of the impact.
General terms and rigidity: another solution to the trivialization problem
Directory of Open Access Journals (Sweden)
Eleonora Orlando
2014-06-01
Full Text Available In this paper I am concerned with the problem of applying the notion of rigidity to general terms. In Naming and Necessity, Kripke has clearly suggested that we should include some general terms among the rigid ones, namely, those common nouns semantically correlated with natural substances, species and phenomena, in general, natural kinds -'water', 'tiger', 'heat'- and some adjectives -'red', 'hot', 'loud'. However, the notion of rigidity has been defined for singular terms; after all, the notion that Kripke has provided us with is the notion of a rigid designator. But general terms do not designate single individuals: rather, they apply to many of them. In sum, the original concept of rigidity cannot be straightforwardly applied to general terms: it has to be somehow redefined in order to make it cover them. As is known, two main positions have been put forward to accomplish that task: the identity of designation conception, according to which a rigid general term is one that designates the same property or kind in all possible worlds, and the essentialist conception, which conceives of a rigid general term as an essentialist one, namely, a term that expresses an essential property of an object. My purpose in the present paper is to defend a particular version of the identity of designation conception: on the proposed approach, a rigid general term will be one that expresses the same property in all possible worlds and names the property it expresses. In my opinion, the position can be established on the basis of an inference to the best explanation of our intuitive interpretation and evaluation, relative to counterfactual circumstances, of statements containing different kinds of general terms, which is strictly analogous to our intuitive interpretation and evaluation, relative to such circumstances, of statements containing different kinds of singular ones. I will argue that it is possible to offer a new solution to the trivialization
Unified Creep Plasticity Damage (UCPD) Model for Rigid Polyurethane Foams.
Energy Technology Data Exchange (ETDEWEB)
Neilsen, Michael K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lu, Wei-Yang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Scherzinger, William M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hinnerichs, Terry D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lo, Chi S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-06-01
Numerous experiments were performed to characterize the mechanical response of several different rigid polyurethane foams (FR3712, PMDI10, PMDI20, and TufFoam35) to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant volumetric and deviatoric plasticity when they are compressed. Rigid polyurethane foams were also found to be very strain-rate and temperature dependent. These foams are also rather brittle and crack when loaded to small strains in tension or to larger strains in compression. Thus, a new Unified Creep Plasticity Damage (UCPD) model was developed and implemented into SIERRA with the name Foam Damage to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments and experimental findings. Next, development of a UCPD model for rigid, polyurethane foams is described. Selection of material parameters for a variety of rigid polyurethane foams is then discussed and finite element simulations with the new UCPD model are compared with experimental results to show behavior that can be captured with this model.
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.
Efficient computation of root mean square deviations under rigid transformations.
Hildebrandt, Anna K; Dietzen, Matthias; Lengauer, Thomas; Lenhof, Hans-Peter; Althaus, Ernst; Hildebrandt, Andreas
2014-04-15
The computation of root mean square deviations (RMSD) is an important step in many bioinformatics applications. If approached naively, each RMSD computation takes time linear in the number of atoms. In addition, a careful implementation is required to achieve numerical stability, which further increases runtimes. In practice, the structural variations under consideration are often induced by rigid transformations of the protein, or are at least dominated by a rigid component. In this work, we show how RMSD values resulting from rigid transformations can be computed in constant time from the protein's covariance matrix, which can be precomputed in linear time. As a typical application scenario is protein clustering, we will also show how the Ward-distance which is popular in this field can be reduced to RMSD evaluations, yielding a constant time approach for their computation. Copyright © 2014 Wiley Periodicals, Inc.
Correlated rigidity percolation and gelation of colloidal particles
Zhang, Shang; Zhang, Leyou; Rocklin, D. Zeb; Mao, Xiaoming
Rigidity percolation on a lattice with sites or bonds randomly diluted is controlled by the isostatic point, where the degrees of freedom and constraints balance, and the system is at the verge of mechanical instability. In the case of triangular lattice rigidity percolation occurs very close to p = 2 / 3 as predicted from isostaticity. Interestingly, we found that when the site dilution is correlated, this transition occurs at a lower p, meaning that less material is needed for rigidity in the disordered structure. This correlation may be seen as a consequence of short range attraction between the particles which makes them cluster. We characterized critical scaling associated with the site correlation parameter, and will discuss implication to understand experimental systems such as gelation of colloidal particles.
A concise introduction to mechanics of rigid bodies multidisciplinary engineering
Huang, L
2017-01-01
This updated second edition broadens the explanation of rotational kinematics and dynamics — the most important aspect of rigid body motion in three-dimensional space and a topic of much greater complexity than linear motion. It expands treatment of vector and matrix, and includes quaternion operations to describe and analyze rigid body motion which are found in robot control, trajectory planning, 3D vision system calibration, and hand-eye coordination of robots in assembly work, etc. It features updated treatments of concepts in all chapters and case studies. The textbook retains its comprehensiveness in coverage and compactness in size, which make it easily accessible to the readers from multidisciplinary areas who want to grasp the key concepts of rigid body mechanics which are usually scattered in multiple volumes of traditional textbooks. Theoretical concepts are explained through examples taken from across engineering disciplines and links to applications and more advanced courses (e.g. industrial rob...
Friction effects on lateral loading behavior of rigid piles
DEFF Research Database (Denmark)
Zania, Varvara; Hededal, Ole
2012-01-01
The adequacy of the p -y curves used in the current practice for the design of rigid pile foundations with large diameter, like in the case of monopile foundations of offshore wind turbines, has been widely questioned. The current study aims at analyzing the lateral behavior of rigid piles, while...... taking into account the shear frictional resistance along the pile. For this purpose efficient three dimensional finite element models of different diameter have been developed. The increase of the side friction and of the diameter of the pile is shown to alter the failure pattern and increase...... the lateral capacity of the pile. The obtained p - y curves demonstrate the importance of the aforementioned parameters in the design of rigid piles, as the reduction of friction along the interface reduces not only the ultimate load but also the stiffness of the soil-pile response. Read More: http...
Toxicity evaluation and hazard review for Rigid Foam
Energy Technology Data Exchange (ETDEWEB)
Archuleta, M.M.; Stocum, W.E.
1994-02-01
Rigid Foam is a chemical delay foam used to completely encapsulate an object or to block access to an area. Prior studies have indicated that the final foam product is essentially non-toxic. The purpose of this study was to evaluate and summarize the current chemical and toxicological data available on the components of Rigid Foam and to update the information available on the toxicity of the final Rigid Foam product. Since the possibility exists for a partial deployment of Rigid Foam where only one of the components is released, this study also examined the toxicity of its chemical constituents. Rigid Foam is composed of an {open_quotes}A{close_quotes} and {open_quotes}B{close_quotes} Component. The {open_quotes}A{close_quotes} component is primarily a polymeric isocyanate and the {open_quotes}B{close_quotes} component is a mixture of polyols. In addition to the primary constituents, dichlorodifluoromethane and trichlorofluoromethane are present as blowing agents along with catalysts and silicone surfactants necessary for foaming. The pre-deployed {open_quotes}A{close_quotes} and {open_quotes}B{close_quotes} components are stored in separate vessels and are brought together in static mixing nozzles for dispersal. The results of this evaluation indicate that a completely deployed Rigid Foam under normal conditions is essentially non-toxic as determined previously. However, in the event of a partial deployment or deployment of an individual component directly at an unprotected individual, the degree of hazard is increased due to the toxic and corrosive nature of the individual constituents. The health hazard would depend on the properties of the material to which the person was exposed.
Topology-Preserving Rigid Transformation of 2D Digital Images.
Ngo, Phuc; Passat, Nicolas; Kenmochi, Yukiko; Talbot, Hugues
2014-02-01
We provide conditions under which 2D digital images preserve their topological properties under rigid transformations. We consider the two most common digital topology models, namely dual adjacency and well-composedness. This paper leads to the proposal of optimal preprocessing strategies that ensure the topological invariance of images under arbitrary rigid transformations. These results and methods are proved to be valid for various kinds of images (binary, gray-level, label), thus providing generic and efficient tools, which can be used in particular in the context of image registration and warping.
Shear-induced rigidity in spider silk glands
Koski, Kristie J.; McKiernan, Keri; Akhenblit, Paul; Yarger, Jeffery L.
2012-09-01
We measure the elastic stiffnesses of the concentrated viscous protein solution of the dehydrated Nephila clavipes major ampullate gland with Brillouin light scattering. The glandular material shows no rigidity but possesses a tensile stiffness similar to that of spider silk. We show, however, that with application of a simple static shear, the mechanical properties of the spider gland protein mixture can be altered irreversibly, lowering symmetry and enabling shear waves to be supported, thus, giving rise to rigidity and yielding elastic properties similar to those of the naturally spun (i.e., dynamically sheared) silk.
Quadratic Twists of Rigid Calabi–Yau Threefolds Over
DEFF Research Database (Denmark)
Gouvêa, Fernando Q.; Kiming, Ian; Yui, Noriko
2013-01-01
We consider rigid Calabi–Yau threefolds defined over Q and the question of whether they admit quadratic twists. We give a precise geometric definition of the notion of a quadratic twists in this setting. Every rigid Calabi–Yau threefold over Q is modular so there is attached to it a certain newform...... of weight 4 on some Γ 0(N). We show that quadratic twisting of a threefold corresponds to twisting the attached newform by quadratic characters and illustrate with a number of obvious and not so obvious examples. The question is motivated by the deeper question of which newforms of weight 4 on some Γ 0(N...
Non-rigid image registration using bone growth model
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Gramkow, Claus; Kreiborg, Sven
1997-01-01
Non-rigid registration has traditionally used physical models like elasticity and fluids. These models are very seldom valid models of the difference between the registered images. This paper presents a non-rigid registration algorithm, which uses a model of bone growth as a model of the change...... between time sequence images of the human mandible. By being able to register the images, this paper at the same time contributes to the validation of the growth model, which is based on the currently available medical theories and knowledge...
Reference Frames and Rigid Motions in Relativity: Applications
Soler, D.
2006-11-01
The concept of rigid reference frame and of constricted spatial metric, given in the previous work [\\emph{Class. Quantum Grav.} {\\bf 21}, 3067,(2004)] are here applied to some specific space-times: In particular, the rigid rotating disc with constant angular velocity in Minkowski space-time is analyzed, a new approach to the Ehrenfest paradox is given as well as a new explanation of the Sagnac effect. Finally the anisotropy of the speed of light and its measurable consequences in a reference frame co-moving with the Earth are discussed.
Hussein, Ayman A; Oberti, Carlos; Wazni, Oussama M; Hegrenes, Jami A; Sral, John A; Lopez, John; Kowalewski, William; Kattar, Jacqueline; Kanj, Mohamed; Lindsay, Bruce; Saliba, Walid
2015-10-01
The flexible-tip irrigated ablation catheter Cool Flex™ (St. Jude Medical, St. Paul, MN, USA) was introduced to enhance cooling of the catheter-tissue interface and to conform to endocardial surface with better contact. Little is known about the performance of such catheter design compared to the widely used rigid-tip catheters. In a thigh muscle preparation, ablation using the flexible-tip and rigid-tip catheters was performed in seven pigs across a range of ablation settings and catheter orientation. Postprocedure, the thigh muscle was stained with 2,3,5-triphenyltetrazolium-chloride injected into the femoral artery. The muscle was excised, fixed with formalin, and examined grossly. A total of 196 lesions (95 flexible tip, 101 rigid tip) were evaluated. The flexible-tip catheter was associated with enhanced cooling of catheter-tissue interface (31.1 ± 3.3°C vs 36.3 ± 3.7°C, P = 0.0001) in both perpendicular and nonperpendicular catheter orientations. This allowed more energy delivery (37.3 ± 8.9 W vs 33.7 ± 8.1 W, P = 0.004) to targeted tissue and resulted in larger lesions (median 194.7 [interquartile range: 113.1-333.8] mm(3) vs 170.9 [88.7-261.6] mm(3) , P = 0.03) than the rigid-tip catheter with larger maximum diameter (11.1 ± 2.6 mm vs 10.3 ± 2.1 mm, P = 0.03) and larger diameter at tissue surface (10.3 ± 2.4 mm vs 9.6 ± 1.7 mm, P = 0.01). Catheter orientation during ablation affected the efficiency of rigid-tip but not the flexible-tip catheter. The use of the flexible-tip catheter was associated with significantly less char formation on tissue (none vs 5.1% with rigid tip, P = 0.009). The Cool Flex™ catheter performed better than a rigid-tip catheter with enhanced cooling, larger ablation lesions, and no charring of targeted tissue. © 2015 Wiley Periodicals, Inc.
Reaungamornrat, S.; Wang, A. S.; Uneri, A.; Otake, Y.; Zhao, Z.; Khanna, A. J.; Siewerdsen, J. H.
2014-03-01
Purpose: Deformable registration of preoperative and intraoperative images facilitates accurate localization of target and critical anatomy in image-guided spine surgery. However, conventional deformable registration fails to preserve the morphology of rigid bone anatomy and can impart distortions that confound high-precision intervention. We propose a constrained registration method that preserves rigid morphology while allowing deformation of surrounding soft tissues. Method: The registration method aligns preoperative 3D CT to intraoperative cone-beam CT (CBCT) using free-form deformation (FFD) with penalties on rigid body motion imposed according to a simple intensity threshold. The penalties enforced 3 properties of a rigid transformation - namely, constraints on affinity (AC), orthogonality (OC), and properness (PC). The method also incorporated an injectivity constraint (IC) to preserve topology. Physical experiments (involving phantoms, an ovine spine, and a human cadaver) as well as digital simulations were performed to evaluate the sensitivity to registration parameters, preservation of rigid body morphology, and overall registration accuracy of constrained FFD in comparison to conventional unconstrained FFD (denoted uFFD) and Demons registration. Result: FFD with orthogonality and injectivity constraints (denoted FFD+OC+IC) demonstrated improved performance compared to uFFD and Demons. Affinity and properness constraints offered little or no additional improvement. The FFD+OC+IC method preserved rigid body morphology at near-ideal values of zero dilatation (D = 0.05, compared to 0.39 and 0.56 for uFFD and Demons, respectively) and shear (S = 0.08, compared to 0.36 and 0.44 for uFFD and Demons, respectively). Target registration error (TRE) was similarly improved for FFD+OC+IC (0.7 mm), compared to 1.4 and 1.8 mm for uFFD and Demons. Results were validated in human cadaver studies using CT and CBCT images, with FFD+OC+IC providing excellent preservation
Melchinger, Albrecht E; Technow, Frank; Dhillon, Baldev S
2011-12-01
Recent progress in genotyping and doubled haploid (DH) techniques has created new opportunities for development of improved selection methods in numerous crops. Assuming a finite number of unlinked loci (ℓ) and a given total number (n) of individuals to be genotyped, we compared, by theory and simulations, three methods of marker-assisted selection (MAS) for gene stacking in DH lines derived from biparental crosses: (1) MAS for high values of the marker score (T, corresponding to the total number of target alleles) in the F(2) generation and subsequently among DH lines derived from the selected F(2) individual (Method 1), (2) MAS for augmented F(2) enrichment and subsequently for T among DH lines from the best carrier F(2) individual (Method 2), and (3) MAS for T among DH lines derived from the F(1) generation (Method 3). Our objectives were to (a) determine the optimum allocation of resources to the F(2) ([Formula: see text]) and DH generations [Formula: see text] for Methods 1 and 2 by simulations, (b) compare the efficiency of all three methods for gene stacking by simulations, and (c) develop theory to explain the general effect of selection on the segregation variance and interpret our simulation results. By theory, we proved that for smaller values of ℓ, the segregation variance of T among DH lines derived from F(2) individuals, selected for high values of T, can be much smaller than expected in the absence of selection. This explained our simulation results, showing that for Method 1, it is best to genotype more F(2) individuals than DH lines ([Formula: see text]), whereas under Method 2, the optimal ratio [Formula: see text] was close to 0.5. However, for ratios deviating moderately from the optimum, the mean [Formula: see text] of T in the finally selected DH line ([Formula: see text]) was hardly reduced. Method 3 had always the lowest mean [Formula: see text] of [Formula: see text] except for small numbers of loci (ℓ = 4) and is favorable only if
High Resolution Quantification of Cellular Forces for Rigidity Sensing
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
Sauton, Nicolas; Lagorce, David; Villoutreix, Bruno O; Miteva, Maria A
2008-04-10
The number of protein targets with a known or predicted tri-dimensional structure and of drug-like chemical compounds is growing rapidly and so is the need for new therapeutic compounds or chemical probes. Performing flexible structure-based virtual screening computations on thousands of targets with millions of molecules is intractable to most laboratories nor indeed desirable. Since shape complementarity is of primary importance for most protein-ligand interactions, we have developed a tool/protocol based on rigid-body docking to select compounds that fit well into binding sites. Here we present an efficient multiple conformation rigid-body docking approach, MS-DOCK, which is based on the program DOCK. This approach can be used as the first step of a multi-stage docking/scoring protocol. First, we developed and validated the Multiconf-DOCK tool that generates several conformers per input ligand. Then, each generated conformer (bioactives and 37970 decoys) was docked rigidly using DOCK6 with our optimized protocol into seven different receptor-binding sites. MS-DOCK was able to significantly reduce the size of the initial input library for all seven targets, thereby facilitating subsequent more CPU demanding flexible docking procedures. MS-DOCK can be easily used for the generation of multi-conformer libraries and for shape-based filtering within a multi-step structure-based screening protocol in order to shorten computation times.
Accuracy limit of rigid 3-point water models
Izadi, Saeed
2016-01-01
Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed. PMID:27544113
Buffers Affect the Bending Rigidity of Model Lipid Membranes
DEFF Research Database (Denmark)
Bouvrais, H.; Duelund, L.; Ipsen, J. H.
2014-01-01
vesicles, of a more complex behavior, where the buffering molecules may considerably affect the bending rigidity of phosphatidylcholine bilayers. Furthermore, a synergistic effect on the bending modulus is observed in the presence of both salt and buffer molecules, which serves as a warning...
Flexibility versus rigidity in the practice of Islamic Family law
N.Y. Shehada (Nahda)
2009-01-01
textabstractThe last decades have witnessed a sustained critique of the mainstream Orientalist notion that classical Islamic family law was rigid, inflexible, and homogeneous. Many historians have used innovative methods to demonstrate that jurists and judges in precodification times enjoyed the
Rigidity of unilateral external fixators - A biomechanical study
P.T.P.W. Burgers (Paul); M.P.J.M. Riel (Marcel); L.M.M. Vogels (Lucas); R.W. Stam (Ronald); P. Patka (Peter); E.M.M. van Lieshout (Esther)
2011-01-01
textabstractIntroduction: External fixation is the primary choice of temporary fracture stabilisation for specific polytrauma patients. Adequate initial fracture healing requires sufficient stability at the fracture site. The purpose of this study was to compare the rigidity of the Dynafix
Behaviour and Modelling of Semi-rigid Structural Frame Systems ...
African Journals Online (AJOL)
A computational finite element model is developed to predict the load-deflection characteristic of portal frames with semi-rigid welded and bolted joints. Plate components of frame ... The modelling of friction effect between the contact surfaces of bolted joints is verified to be the most important factor. The comparative analysis ...
Dielectric relaxation phenomena of rigid polar liquid molecules ...
Indian Academy of Sciences (India)
The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate () in benzene, -hexane and -heptane () under 4.2, 9.8 and 24.6 GHz electric ﬁelds at 30°C are studied to show the possible existence of double relaxation times 2 and 1 for rotations of the whole and the ﬂexible ...
Rigid Biobased Building Blocks: Current Developments and Outlook
Es, van D.S.
2013-01-01
In this perspectives paper we will look at the state-of-the-art in rigid renewable building blocks for biobased materials, with a focus on two types of carbohydrate-based difunctional monomers, i.e.,isohexides and furan-2,5-dicarboxylic acid (FDCA).
A mixed elastoplastic/rigid-plastic material model
Huetink, Han; van den Boogaard, Antonius H.; Rietman, Bert; Lof, J.; Meinders, Vincent T.
1999-01-01
In forming process simulations, the rigid-plastic material model is widely used because of its numerically robust behaviour. The model yields accurate results, as long as the strain increments are large compared to the elastic limit strain. In cases where the strain increments are small e.g. in dead
The rigid pendulum - an antique but evergreen physical model
Butikov, Eugene I.
1999-11-01
Various kinds of motion of a rigid pendulum (including swinging with arbitrarily large amplitudes and complete revolutions) are investigated both analytically and with the help of computerized simulations. The simulation experiments reveal many interesting peculiarities of this famous physical model and complement the analytical study of the subject in a manner that is mutually reinforcing.
Substructural Identification of Flexural Rigidity for Beam-Like Structures
Directory of Open Access Journals (Sweden)
Ki-Young Koo
2015-01-01
Full Text Available This study proposes a novel substructural identification method based on the Bernoulli-Euler beam theory with a single variable optimization scheme to estimate the flexural rigidity of a beam-like structure such as a bridge deck, which is one of the major structural integrity indices of a structure. In ordinary bridges, the boundary condition of a superstructure can be significantly altered by aging and environmental variations, and the actual boundary conditions are generally unknown or difficult to be estimated correctly. To efficiently bypass the problems related to boundary conditions, a substructural identification method is proposed to evaluate the flexural rigidity regardless of the actual boundary conditions by isolating an identification region within the internal substructure. The proposed method is very simple and effective as it utilizes the single variable optimization based on the transfer function formulated utilizing Bernoulli Euler beam theory for the inverse analysis to obtain the flexural rigidity. This novel method is also rigorously investigated by applying it for estimating the flexural rigidity of a simply supported beam model with different boundary conditions, a concrete plate-girder bridge model with different length of an internal substructure, a cantilever-type wind turbine tower structure with different type of excitation, and a steel box-girder bridge model with internal structural damages.
Numerical rigid plastic modelling of shear capacity of keyed joints
DEFF Research Database (Denmark)
Herfelt, Morten Andersen; Poulsen, Peter Noe; Hoang, Linh Cao
2015-01-01
Keyed shear joints are currently designed using simple and conservative design formulas, yet these formulas do not take the local mechanisms in the concrete core of the joint into account. To investigate this phenomenon a rigid, perfectly plastic finite element model of keyed joints is used. The ...
Impulsive and rigid temperament subtypes and executive functioning
African Journals Online (AJOL)
The results indicate that the rigid temperament subtype reacted slower to both complex (executive functioning) and less complex tasks (attention and working memory) than the impulsive temperament subtype. ... Significant differences were maintained with analyses of intelligence and parental education as covariates.
Rigid rod spaced fullerene as building block for nanoclusters
Indian Academy of Sciences (India)
By using phenylacetylene based rigid-rod linkers (PhA), we have successfully synthesized two fullerene derivatives, C60-PhA and C60-PhA-C60. The absorption spectral features of C60, as well as that of the phenylacetylene moiety are retained in the monomeric forms of these fullerene derivatives, ruling out the possibility ...
On the mechanism of gas transport in rigid polymer membranes
Hensema, E.R.; Hensema, E.R.; Mulder, M.H.V.; Smolders, C.A.; Smolders, C.A.
1993-01-01
Conventional polymers are compared as gas separation membrane materials with tailormade polymers. The increased permeability of the latter are due to their higher free volume available for gas transport. The increased free volume is associated with the rigidity polymer backbone. Free volume is
Assessment of Lumped-Parameter Models for Rigid Footings
DEFF Research Database (Denmark)
Andersen, Lars
2010-01-01
The quality of consistent lumped-parameter models of rigid footings is examined. Emphasis is put on the maximum response during excitation and the geometrical damping related to free vibrations. The optimal order of a lumped-parameter model is determined for each degree of freedom, i.e. horizontal...
Patient satisfaction related to rigid external distraction osteogenesis
van Eggermont, Bas; Jansma, J.; Bierman, M. W. J.; Stegenga, B.
2007-01-01
The aim of this study was to evaluate satisfaction with treatment among cleft lip and palate patients who underwent maxillary advancement using a rigid external distraction (RED) device. Nine patients (four boys, five girls), mean age 17.7 years (SD 4.0), were included in the study. Outcome measures
Nonlinear optical properties of rigid-rod polymers
Trimmer, Mark S.; Wang, Ying
1992-01-01
The purpose of this research project was to integrate enhanced third order nonlinear optical (NLO) properties, especially high x(exp (3)) (greater than 10(exp -8) esu), into Maxdem's novel conjugated rigid-rod polymers while retaining their desirable processing, mechanical, and thermal properties. This work primarily involved synthetic approaches to optimized materials.
Rigidly connected magnetic lines: twisting and winding of magnetic lines
Prasad, G.
2017-10-01
The dynamical process of magnetic flux variation in a fluid's stream tube is described by constructing 1+1+ (2) decomposition of the gradient of fluid's 4-velocity. The necessary and sufficient conditions are obtained for a spacelike congruence to be a congruence of rigidly connected spacelike curves. The evolution of magnetic flux in a magnetic tube is explored under the assumptions that magnetic lines are rigidly connected and the chemical potential of the fluid is constant along a magnetic tube. The interplay between magnetic and stream tubes is demonstrated. It is shown that the growth of magnetic energy in a magnetic tube cannot exceed to that of a stream tube. It is found that the proper time variation of twist of magnetic lines is caused by gravitation inside a neutron star if magnetic lines are rigidly connected and charge neutrality condition holds. Helmholtz-like magnetic vorticity flux conservation in a magnetic tube constituted by rigidly connected geodetic magnetic lines is derived under the assumption that the charge neutrality condition holds. It is shown that the winding of frozen-in poloidal magnetic field due to differential rotation requires meridional circulation in an axisymmetric stationary hydromagnetic configuration.
Rigid-plastic seismic design of reinforced concrete structures
DEFF Research Database (Denmark)
Costa, Joao Domingues; Bento, R.; Levtchitch, V.
2007-01-01
In this paper a new seismic design procedure for Reinforced Concrete (R/C) structures is proposed-the Rigid-Plastic Seismic Design (RPSD) method. This is a design procedure based on Non-Linear Time-History Analysis (NLTHA) for systems expected to perform in the non-linear range during a lifetime ...
Behaviour and Modelling of Semi-rigid Structural Frame Systems ...
African Journals Online (AJOL)
A computational finite element model is developed to predict the load-deflection characteristic of portal frames with semi-rigid welded and bolted joints. Plate components of frame members and joints are modelled by thin shell finite elements while bolt connectors by springs with the force-deformation characteristic ...
Influence of rigid boundary on the propagation of torsional surface ...
Indian Academy of Sciences (India)
The present work illustrates a theoretical study on the effect of rigid boundary for the propagation of torsional surface wave in an inhomogeneous crustal layer over an inhomogeneous half space. It is believed that the inhomogeneity in the half space arises due to hyperbolic variation in shear modulus and density whereas ...
Connect-disconnect coupling for preadjusted rigid shafts
Bajkowski, F. W.; Holmberg, A.
1969-01-01
Coupling device enables a rigid shaft to be connected to or disconnected from a fixed base without disturbing the point of adjustment of the shaft in a socket or causing the shaft to rotate. The coupling consists of an externally threaded, internally slotted boss extending from the fixed base.
Mizuno, Ichiro; Komiya, Akira; Watanabe, Akihiko; Fuse, Hideki
2010-01-01
The aim of this prospective study was to evaluate the usefulness of measurement of axial penile rigidity, compared with radial penile rigidity. Twenty-two patients, aged 21-75 years old (a mean of 50), with erectile dysfunction underwent axial penile rigidity measurements by the digital inflection rigidometer (DIR) as well as radial penile rigidity measurements by the RigiScan Plus during intracavernous pharmacological erection testing. A significant correlation was recognized between axial rigidity, and radial rigidity at the tip (p = 0.0024) and base (p = 0.0098) of the penis. In 10 patients, the DIR revealed axial rigidity of 550 g or more, and they also had radial rigidity of 60% or more at the tip and base. In 14 and 17 subjects, radial rigidity of 60% or more was observed at the tip and base, respectively. Four of the former 14 and 7 of the latter 17 had axial rigidity <550 g. A RigiScan results of radial rigidity of 60% or more should be interpreted cautiously and not necessarily regarded as normal. Copyright (c) 2010 S. Karger AG, Basel.
Directory of Open Access Journals (Sweden)
Kut S.
2015-09-01
Full Text Available This paper presents the results of the numerical analysis and experimental research of the forming process of aviation drawpiece made from 0.6 mm thick Inconel 625 sheet metal. First phase of testing was conducted using rigid steel tools for drawpiece forming. Results of conducted simulations show that during rigid tool forming, the middle of the drawpiece losses stability. In consequence, rigid tool forming leads to the formation of unacceptable wrinkles on the drawpiece. Subsequent experimental research confirmed wrinkles of the metal drawpiece in this area. It was assumed that in order to eliminate this negative phenomenon, minor changes in technology and tool construction would have to be made. The drawpiece will be shaped by means of a flexible tool, than re-shaped using rigid tools. In the second phase of the research, tooling design changes have been made. They consisted of replacing the steel punch with a specially designed stamp susceptible for deformation. FEM numerical simulations were performed for flexible punch forming made of polyurethane elastomer with different hardness (50, 70, 85 and 90 Sh A. On their basis, the effect on the mechanical characteristics of the elastomeric drawing process and the formation of wrinkles was shown. They can be effectively eliminated by the use of a punch with hardness of 90 Sh A, which has also been confirmed by experimental research. In addition, the paper presents a comparative analysis of the deformations in selected actual drawpiece areas and in the elastomeric punch with hardness 90 Sh A computer model. The actual drawpiece deformation schedule and the values were determined using photogrammetric system Argus v.6.3., while the computer modeled drawpiece was based on FEM calculations performed in the MARC / Mentat system. In conclusion the difficulties as well as the advantages and disadvantages in determining the deformation of sheet metal parts were indicated using photogrammetric system
Initial Development of an Electronic Testis Rigidity Tester
Directory of Open Access Journals (Sweden)
Petros Mirilas
2011-01-01
Full Text Available We aimed to develop our previously presented mechanical device, the Testis Rigidity Tester (TRT, into an electronic system (Electronic Testis Rigidity Tester, ETRT by applying tactile imaging, which has been used successfully with other solid organs. A measuring device, located at the front end of the ETRT incorporates a tactile sensor comprising an array of microsensors. By application of a predetermined deformation of 2 mm, increased pressure alters linearly the resistance of each microsensor, producing changes of voltage. These signals were amplified, filtered, and digitized, and then processed by an electronic collector system, which presented them as a color-filled contour plot of the area of the testis coming into contact with the sensor. Testis models of different rigidity served for initial evaluation of ETRT; their evacuated central spaces contained different, increasing glue masses. An independent method of rigidity measurement, using an electric weight scale and a micrometer, showed that the more the glue injected, the greater the force needed for a 2-mm deformation. In a preliminary test, a single sensor connected to a multimeter showed similar force measurement for the same deformation in these phantoms. For each of the testis models compressed in the same manner, the ETRT system offered a map of pressures, represented by a color scale within the contour plot of the contact area with the sensor. ETRT found certain differences in rigidity between models that had escaped detection by a blind observer. ETRT is easy to use and provides a color-coded “insight“ of the testis internal structure. After experimental testing, it could be valuable in intraoperative evaluation of testes, so that the surgeon can decide about orchectomy or orcheopexy.
Deformable registration of multi-modal data including rigid structures
Energy Technology Data Exchange (ETDEWEB)
Huesman, Ronald H.; Klein, Gregory J.; Kimdon, Joey A.; Kuo, Chaincy; Majumdar, Sharmila
2003-05-02
Multi-modality imaging studies are becoming more widely utilized in the analysis of medical data. Anatomical data from CT and MRI are useful for analyzing or further processing functional data from techniques such as PET and SPECT. When data are not acquired simultaneously, even when these data are acquired on a dual-imaging device using the same bed, motion can occur that requires registration between the reconstructed image volumes. As the human torso can allow non-rigid motion, this type of motion should be estimated and corrected. We report a deformation registration technique that utilizes rigid registration for bony structures, while allowing elastic transformation of soft tissue to more accurately register the entire image volume. The technique is applied to the registration of CT and MR images of the lumbar spine. First a global rigid registration is performed to approximately align features. Bony structures are then segmented from the CT data using semi-automated process, and bounding boxes for each vertebra are established. Each CT subvolume is then individually registered to the MRI data using a piece-wise rigid registration algorithm and a mutual information image similarity measure. The resulting set of rigid transformations allows for accurate registration of the parts of the CT and MRI data representing the vertebrae, but not the adjacent soft tissue. To align the soft tissue, a smoothly-varying deformation is computed using a thin platespline(TPS) algorithm. The TPS technique requires a sparse set of landmarks that are to be brought into correspondence. These landmarks are automatically obtained from the segmented data using simple edge-detection techniques and random sampling from the edge candidates. A smoothness parameter is also included in the TPS formulation for characterization of the stiffness of the soft tissue. Estimation of an appropriate stiffness factor is obtained iteratively by using the mutual information cost function on the result
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Kennedy, Nadia Stoyanova
2012-01-01
Students are often encouraged to work on problems "like mathematicians"--to be persistent, to investigate different approaches, and to evaluate solutions. This behavior, regarded as problem solving, is an essential component of mathematical practice. Some crucial aspects of problem solving include defining and interpreting problems, working with…
Eye tracking a self-moved target with complex hand-target dynamics.
Landelle, Caroline; Montagnini, Anna; Madelain, Laurent; Danion, Frederic
2016-10-01
Previous work has shown that the ability to track with the eye a moving target is substantially improved when the target is self-moved by the subject's hand compared with when being externally moved. Here, we explored a situation in which the mapping between hand movement and target motion was perturbed by simulating an elastic relationship between the hand and target. Our objective was to determine whether the predictive mechanisms driving eye-hand coordination could be updated to accommodate this complex hand-target dynamics. To fully appreciate the behavioral effects of this perturbation, we compared eye tracking performance when self-moving a target with a rigid mapping (simple) and a spring mapping as well as when the subject tracked target trajectories that he/she had previously generated when using the rigid or spring mapping. Concerning the rigid mapping, our results confirmed that smooth pursuit was more accurate when the target was self-moved than externally moved. In contrast, with the spring mapping, eye tracking had initially similar low spatial accuracy (though shorter temporal lag) in the self versus externally moved conditions. However, within ∼5 min of practice, smooth pursuit improved in the self-moved spring condition, up to a level similar to the self-moved rigid condition. Subsequently, when the mapping unexpectedly switched from spring to rigid, the eye initially followed the expected target trajectory and not the real one, thereby suggesting that subjects used an internal representation of the new hand-target dynamics. Overall, these results emphasize the stunning adaptability of smooth pursuit when self-maneuvering objects with complex dynamics. Copyright © 2016 the American Physiological Society.
2010-10-01
... 42 Public Health 1 2010-10-01 2010-10-01 false May Self-Governance Tribes carry out construction... OF HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.291 May Self-Governance Tribes carry out construction projects without assuming these Federal environmental...
2010-10-01
... 42 Public Health 1 2010-10-01 2010-10-01 false Do Self-Governance Tribes become Federal agencies... HEALTH AND HUMAN SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.286 Do Self-Governance... Self-Governance Tribes are required to assume Federal environmental responsibilities for projects in...
Towards accurate modeling of noncovalent interactions for protein rigidity analysis.
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
Bromfield, Stephen M; Posocco, Paola; Fermeglia, Maurizio; Tolosa, Juan; Herreros-López, Ana; Pricl, Sabrina; Rodríguez-López, Julián; Smith, David K
2014-07-28
This study investigates transgeden (TGD) dendrimers (polyamidoamine (PAMAM)-type dendrimers modified with rigid polyphenylenevinylene (PPV) cores) and compares their heparin-binding ability with commercially available PAMAM dendrimers. Although the peripheral ligands are near-identical between the two dendrimer families, their heparin binding is very different. At low generation (G1), TGD outperforms PAMAM, but at higher generation (G2 and G3), the PAMAMs are better. Heparin binding also depends strongly on the dendrimer/heparin ratio. We explain these effects using multiscale modelling. TGD dendrimers exhibit "shape-persistent multivalency"; the rigidity means that small clusters of surface amines are locally well optimised for target binding, but it prevents the overall nanoscale structure from rearranging to maximise its contacts with a single heparin chain. Conversely, PAMAM dendrimers exhibit "adaptive multivalency"; the flexibility means individual surface ligands are not so well optimised locally to bind heparin chains, but the nanostructure can adapt more easily and maximise its binding contacts. As such, this study exemplifies important new paradigms in multivalent biomolecular recognition. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effect of matrix rigidity on organ-specific capture of tumor cells by flow.
Ma, P; Shen, X; Tan, P; Yang, L; Liu, W
2017-04-29
Accumulating evidences have suggested that tumor metastasis exists prominent organ discrepancy. In this progression, the capture of intravascular tumor cells (TCs) to endothelium in distant tissues and organs plays a decisive role in the organ-specific metastasis formation. However, the mechanism of tumor cells preferentially arrest and adhere to endothelial cells (ECs) of target organ still remains elusive. By using the parallel plate flow chamber and the polyacrylamide gels with different matrix stiffness, we here explored the combined effects of matrix rigidity, shear stress, and chemokine SDF-1 on the capture of circulating tumor cells to ECs in the bloodstream. In addition, the expression and the role of integrin β1 on the tumor cells surface were also detected by SDF-1 treatment. The results show that breast tumor cells MDA-MB-231 display an increasing number of adherent cells on the preferred substrate, which is similar to the matrix rigidity of breast cancer tissue (about 5kPa), under a certain shear stress. Moreover, ECs exacerbates the preferred capture of tumor cells compared with the FN-coated substrate alone. Besides, SDF-1 upregulates the number of adherent tumor cells by responding to matrix stiffness via promoting the expression of integrin β1, which is abolished by blocking of integrin β1. These results may provide a novel point of view for the mechanism of "organ specificity" phenomenon in tumor metastasis, which in turn contribute to a rational development of new drugs for cancer.
The ‘twin paradox’ in relativistic rigid motion
Ben-Ya'acov, Uri
2016-09-01
Relativistic rigid motion suggests a new version for the so-called ‘twin paradox’, comparing the ages of two astronauts on a very long spaceship. Although there is always an instantaneous inertial frame in which the whole spaceship, being rigid, is simultaneously at rest, the twins’ ages, measured as the proper-times along their individual world lines, are different when they are located at remote parts of the spaceship. The age, or proper-time, difference depends on the distance at rest between the astronauts and the rapidity difference between start to end. The relation of the age difference with the relative Doppler shift of light signals transmitted between the astronauts and implications for the possibility to assign a common age (proper-time) to complex, spatially extended, relativistic systems are also discussed.
A density-independent rigidity transition in biological tissues
Bi, Dapeng; Lopez, J. H.; Schwarz, J. M.; Manning, M. Lisa
2015-12-01
Cell migration is important in many biological processes, including embryonic development, cancer metastasis and wound healing. In these tissues, a cell’s motion is often strongly constrained by its neighbours, leading to glassy dynamics. Although self-propelled particle models exhibit a density-driven glass transition, this does not explain liquid-to-solid transitions in confluent tissues, where there are no gaps between cells and therefore the density is constant. Here we demonstrate the existence of a new type of rigidity transition that occurs in the well-studied vertex model for confluent tissue monolayers at constant density. We find that the onset of rigidity is governed by a model parameter that encodes single-cell properties such as cell-cell adhesion and cortical tension, providing an explanation for liquid-to-solid transitions in confluent tissues and making testable predictions about how these transitions differ from those in particulate matter.
LENUS (Irish Health Repository)
Ahmad, Nasir Zaheer
2012-06-01
Rigid sigmoidoscopy is sometimes performed at first presentation in colorectal clinics. We assessed the feasibility of flexible sigmoidoscopy in similar situations by comparing it with rigid sigmoidoscopy as a first investigative tool.
On Polya's inequality for torsional rigidity and first Dirichlet eigenvalue
Berg, M. van den; Ferone, V.; Nitsch, C.; Trombetti, C.
2016-01-01
Let $\\Omega$ be an open set in Euclidean space with finite Lebesgue measure $|\\Omega|$. We obtain some properties of the set function $F:\\Omega\\mapsto \\R^+$ defined by $$ F(\\Omega)=\\frac{T(\\Omega)\\lambda_1(\\Omega)}{|\\Omega|} ,$$ where $T(\\Omega)$ and $\\lambda_1(\\Omega)$ are the torsional rigidity and the first eigenvalue of the Dirichlet Laplacian respectively. We improve the classical P\\'olya bound $F(\\Omega)\\le 1,$ and show that $$F(\\Omega)\\le 1- \
NOLB: Nonlinear Rigid Block Normal Mode Analysis Method
Hoffmann, Alexandre; Grudinin, Sergei
2017-01-01
International audience; We present a new conceptually simple and computationally efficient method for non-linear normal mode analysis called NOLB. It relies on the rotations-translations of blocks (RTB) theoretical basis developed by Y.-H. Sanejouand and colleagues. We demonstrate how to physically interpret the eigenvalues computed in the RTB basis in terms of angular and linear velocities applied to the rigid blocks and how to construct a non-linear extrapolation of motion out of these velo...
Alternative Material Dowel Bars for Rigid Pavement Joints
ECT Team, Purdue
2007-01-01
Over the last thirty to forty years, dowel support of the joint in Rigid Joint Pavement (RJP) has been widely used. The problem of deterioration of concrete pavement joints has resulted in the search for alternate solutions. Fiber-reinforced polymer (FRP) and stainless steel represent corrosion resistant alternatives to conventional galvanized steel in this application. The recently study by the FHWA of Alternative Materials for Highway Construction demonstrated that even with extended wet-dr...
Nonlinear dynamics mathematical models for rigid bodies with a liquid
Lukovsky, Ivan A
2015-01-01
This book is devoted to analytically approximate methods in the nonlinear dynamics of a rigid body with cavities partly filled by liquid. It combines several methods and compares the results with experimental data. It is useful for experienced and early-stage readers interested in analytical approaches to fluid-structure interaction problems, the fundamental mathematical background and modeling the dynamics of such complex mechanical systems.
Stability characterizations of fixtured rigid bodies with Coulomb friction
Energy Technology Data Exchange (ETDEWEB)
PANG,J.S.; TRINKLE,JEFFREY C.
2000-02-15
This paper formally introduces several stability characterizations of fixtured three-dimensional rigid bodies initially at rest and in unilateral contact with Coulomb friction. These characterizations, weak stability and strong stability, arise naturally from the dynamic model of the system, formulated as a complementarity problem. Using the tools of complementarity theory, these characterizations are studied in detail to understand their properties and to develop techniques to identify the stability classifications of general systems subjected to known external loads.
Oscillation of a rigid rod in the special relativity
Paiva, F M
2012-01-01
In the special relativity, a rigid rod slides upon itself, with one extremity oscillating harmonically. We discovered restrictions in the amplitude of the motion and in the length of the rod, essential to eliminate unphysical solutions. ------- Cxe la speciala relativeco, rigida stango movigxas sur si mem, kun unu fino oscilante harmonie. Ni malkovris limigajn kondicxojn pri la amplitudo de movado kaj pri la longo de stango, necesegaj por elimini ne-fizikajn solvojn.
Theory of the rotation of the rigid earth
Kinoshita, H.
1977-01-01
Equations of motion for a triaxial rigid earth are derived in Andoyer variables. The reference plane is the ecliptic of date which is moving as a result of planetary perturbations. By using this noninertial system, the development of the disturbing function for the sun and moon is simplified, with an additional term appearing in the Hamiltonian which, however, contributes only to precessional motion. The nutation terms derived are compared with those of Woolard.
As-Rigid-As-Possible molecular interpolation paths
Nguyen, Minh Khoa; Jaillet, Léonard; Redon, Stéphane
2017-04-01
This paper proposes a new method to generate interpolation paths between two given molecular conformations. It relies on the As-Rigid-As-Possible (ARAP) paradigm used in Computer Graphics to manipulate complex meshes while preserving their essential structural characteristics. The adaptation of ARAP approaches to the case of molecular systems is presented in this contribution. Experiments conducted on a large set of benchmarks show how such a strategy can efficiently compute relevant interpolation paths with large conformational rearrangements.
Rigid bronchoscOpic dilatation of postintubation tracheal stenosis
African Journals Online (AJOL)
trice, dilatation percutanée, dilatation bronchospique rigide, dilatation de la technologie des ﬁbres optiques de la bulle ct. Nd;YAG (neodymium yttritium - aluminium garnet) la théra- pie laser avec ou sans le stenting. Méthodes: Trois malade du sexe féminins avec une histoire des périodes diverscs d'intubation endotrachée ...
Rigidity theorem for Willmore surfaces in a sphere
Indian Academy of Sciences (India)
compact non-minimal flat Willmore surfaces in S3, and Castro and Urbano [2] constructed many compact non-minimal Willmore surfaces in S4. In [6], Li obtained the following rigidity theorem for Willmore surfaces in a unit sphere. Theorem A. Let M be a compact Willmore surface in S2+p. Then. ∫M ρ2 (2 − 2B ρ2) dv ≤ 0,.
A model of the soft tissue artefact rigid component.
Camomilla, V; Bonci, T; Dumas, R; Chèze, L; Cappozzo, A
2015-07-16
When using stereophotogrammetry and skin-markers, the reconstruction of skeletal movement is affected by soft-tissue artefact (STA). This may be described by considering a marker-cluster as a deformable shape undergoing a geometric transformation formed by a non-rigid (change in size and shape) and a rigid component (translation and rotation displacements). A modal decomposition of the STA, relative to an appropriately identified basis, allows the separation of these components. This study proposes a mathematical model of the STA that embeds only its rigid component and estimates the relevant six mode amplitudes as linear functions of selected proximal and distal joint rotations during the analysed task. This model was successfully calibrated for thigh and shank using simultaneously recorded pin- and skin-marker data of running volunteers. The root mean square difference between measured and model-estimated STA rigid component was 1.1(0.8)mm (median (inter-quartile range) over 3 subjects × 5 trials × 33 markers coordinates), and it was mostly due to the wobbling not included in the model. Knee joint kinematics was estimated using reference pin-marker data and skin-marker data, both raw and compensated with the model-estimated STA. STA compensation decreased inaccuracy on average from 6% to 1% for flexion/extension, from 43% to 18% for the other two rotations, and from 69% to 25% for the linear displacements. Thus, the proposed mathematical model provides an STA estimate which can be effectively used within optimal bone pose and joint kinematics estimators for artefact compensation, and for simulations aimed at their comparative assessments. Copyright © 2015 Elsevier Ltd. All rights reserved.
Crack identification for rigid pavements using unmanned aerial vehicles
Bahaddin Ersoz, Ahmet; Pekcan, Onur; Teke, Turker
2017-09-01
Pavement condition assessment is an essential piece of modern pavement management systems as rehabilitation strategies are planned based upon its outcomes. For proper evaluation of existing pavements, they must be continuously and effectively monitored using practical means. Conventionally, truck-based pavement monitoring systems have been in-use in assessing the remaining life of in-service pavements. Although such systems produce accurate results, their use can be expensive and data processing can be time consuming, which make them infeasible considering the demand for quick pavement evaluation. To overcome such problems, Unmanned Aerial Vehicles (UAVs) can be used as an alternative as they are relatively cheaper and easier-to-use. In this study, we propose a UAV based pavement crack identification system for monitoring rigid pavements’ existing conditions. The system consists of recently introduced image processing algorithms used together with conventional machine learning techniques, both of which are used to perform detection of cracks on rigid pavements’ surface and their classification. Through image processing, the distinct features of labelled crack bodies are first obtained from the UAV based images and then used for training of a Support Vector Machine (SVM) model. The performance of the developed SVM model was assessed with a field study performed along a rigid pavement exposed to low traffic and serious temperature changes. Available cracks were classified using the UAV based system and obtained results indicate it ensures a good alternative solution for pavement monitoring applications.
A Convertible Spinal Orthosis for Controlled Torso Rigidity
Directory of Open Access Journals (Sweden)
Nicole I. Kern
2013-01-01
Full Text Available A traditional spinal orthosis in conjunction with a hip-knee-ankle-foot orthosis (HKAFO improves posture in persons with paraplegia during standing and walking. It also limits the wearer's range of motion when worn during other activities, such as vehicle transfer or sitting and reaching for objects. In order to regain full torso flexibility the user would need to remove the spinal orthosis which can be arduous and time consuming. A Convertible Spinal Orthosis (CSO that allows the user to switch between Locked rigid torso support and Unlocked free motion has been designed, fabricated and tested. It shows promise for increasing functionality, wear time and subject comfort. Analysis of movement has been performed with an able-bodied and a paraplegic subject wearing a rigid spinal orthosis, the CSO in both states, and without any bracing. Configuration state had the most impact on lateral bending. Mean values for the paraplegic subject of 27°, 38°, 48°, and 48° and for the able-bodied subject of 22°, 26°, 48°, and 45° were found for lateral bending of the upper torso relative to the thighs in the Rigid, Locked, Unlocked, and No-Brace states, respectively.
Symmetrical Parameterization of Rigid Body Transformations for Biomolecular Structures.
Kim, Jin Seob; Chirikjian, Gregory S
2018-01-01
Assessing preferred relative rigid body position and orientation is important in the description of biomolecular structures (such as proteins) and their interactions. In this article, we extend and apply the "symmetrical parameterization," which we recently introduced in the kinematics community, to address problems in structural biology. We also review parameterization methods that are widely used in structural biology to describe relative rigid body motions (in particular, orientations) as a basis for comparison. The new symmetrical parameterization is useful in describing the relative biomolecular rigid body motions, where the parameters are symmetrical in the sense that the subunits of a complex biomolecular structure are described in the same way for the corresponding motion and its inverse. The properties of this new parameterization, singularity analysis, and inverse kinematics are also investigated in more detail. Finally, parameterization is applied to real biomolecular structures and a potential application to structure modeling of symmetric macromolecules to show the efficacy of the symmetrical parameterization in the field of computational structural biology.
Chiral Orientation of Skeletal Muscle Cells Requires Rigid Substrate
Directory of Open Access Journals (Sweden)
Ninghao Zhu
2017-06-01
Full Text Available Reconstitution of tissue morphology with inherent left–right (LR asymmetry is essential for tissue/organ functions. For skeletal muscle, the largest tissue in mammalian organisms, successful myogenesis requires the regulation of the LR asymmetry to form the appropriate muscle alignment. However, the key factor for reproducing the LR asymmetry of skeletal tissues in a controllable, engineering context remains largely unknown. Recent reports indicate that cell chirality may underlie the LR development in tissue morphogenesis. Here, we report that a rigid substrate is required for the chirality of skeletal muscle cells. By using alternating micropatterned cell-adherent and cell-repellent stripes on a rigid substrate, we found that C2C12 skeletal muscle myoblasts exhibited a unidirectional tilted orientation with respect to the stripe boundary. Importantly, such chiral orientation was reduced when soft substrates were used instead. In addition, we demonstrated the key role of actin stress fibers in the formation of the chiral orientation. This study reveals that a rigid substrate is required for the chiral pattern of myoblasts, paving the way for reconstructing damaged muscle tissue with inherent LR asymmetry in the future.
Green waste cooking oil-based rigid polyurethane foam
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.
Coarse-grained rigid blob model for soft matter simulations.
Chao, Sheng D; Kress, Joel D; Redondo, Antonio
2005-06-15
We have developed a coarse-grained multiscale molecular simulation method for soft matter systems that directly incorporates stereochemical information. We divide the material into disjoint groups of atoms or particles that move as separate rigid bodies; we call these groups "rigid blobs," hence the name coarse-grained rigid blob model. The method is enabled by the construction of transferable interblob potentials that approximate the net intermolecular interactions, as obtained from ab initio electronic structure calculations, other all-atom empirical potentials, experimental data, or any combination of the above. We utilize a multipolar expansion to obtain the interblob potential-energy functions. The series, which contains controllable approximations that allow us to estimate the errors, approaches the original intermolecular potential as the number of terms increases. Using a novel numerical algorithm, we can calculate the interblob potentials very efficiently in terms of a few interaction moment tensors. This reduces the labor well beyond what is required in standard molecular-dynamics calculations and allows large-scale simulations for temporal scales commensurate with characteristic times of nano- and mesoscale systems. A detailed derivation of the formulas is presented, followed by illustrative applications to several systems showing that the method can effectively capture realistic microscopic details and can easily extend to large-scale simulations.
Operator Algebras in Rigid C*-Tensor Categories
Jones, Corey; Penneys, David
2017-11-01
In this article, we define operator algebras internal to a rigid C*-tensor category C. A C*/W*-algebra object in C is an algebra object A in ind-C whose category of free modules {FreeMod_C(A)} is a C-module C*/W*-category respectively. When C= Hilb_fd, the category of finite dimensional Hilbert spaces, we recover the usual notions of operator algebras. We generalize basic representation theoretic results, such as the Gelfand-Naimark and von Neumann bicommutant theorems, along with the GNS construction. We define the notion of completely positive morphisms between C*-algebra objects in C and prove the analog of the Stinespring dilation theorem. As an application, we discuss approximation and rigidity properties, including amenability, the Haagerup property, and property (T) for a connected W*-algebra M in C. Our definitions simultaneously unify the definitions of analytic properties for discrete quantum groups and rigid C*-tensor categories.
Integrable Problems of the Dynamics of Coupled Rigid Bodies
Bogoyavlenskiĭ, O. I.
1993-06-01
Several classical problems of dynamics are shown to be integrable for the special systems of coupled rigid bodies introduced in this paper and called Ck-central configurations. It is proved that the dynamics of an arbitrary Ck-central configuration in the Newtonian gravitational field with an arbitrary quadratic potential is integrable in the Liouville sense and in theta-functions of Riemann surfaces. A hidden symmetry of the inertial dynamics of these configurations is found, and reductions of the corresponding Lagrange equations to the Euler equations on the direct sums of Lie coalgebras SO(3) are obtained. Reductions and integrable cases of the equations for the rotation of a heavy Ck-central configuration about a fixed point are indicated. Separation of rotations of a space station type orbiting system, which is a Ck-central configuration of rigid bodies, is proved. This result leads to the possibility of independent stabilization of rotations of the rigid bodies in such orbiting configurations. Integrability of the inertial dynamics of CRn-central configurations of coupled gyrostats is proved.
Predicting Protein Hinge Motions and Allostery Using Rigidity Theory
Sljoka, Adnan; Bezginov, Alexandr
2011-11-01
Understanding how a 3D structure of a protein functions depends on predicting which regions are rigid, and which are flexible. One recent approach models molecules as a structure of fixed units (atoms with their bond angles as rigid units, bonds as hinges) plus biochemical constraints coming from the local geometry. This generates a `molecular graph' in the theory of combinatorial rigidity. The 6|V|-6 counting condition for 3-dimensional body-hinge structures (modulo molecular theorem), and a fast `pebble game' algorithm which tracks this count in the multigraph, have led to the development of the program FIRST, for rapid predictions of the flexibility of proteins. In this study we develop a novel protein hinge prediction algorithm via our extension of the pebble game algorithm (relevant regions detection algorithm). We have tested our hinge prediction algorithm on several proteins chosen from the dataset of manually annotated hinges available on the MOLMOV server. Many of our predictions are in very good agreement with this data set. Our algorithms can also predict `allosteric' interactions in proteins—where binding on one site of a molecule changes the shape or binding at a distance `active site' of the molecule. We also give some promising results which support the sliding piston-like movement of helices with respect to one another as a plausible mechanism by which GCPR receptors propagate conformational changes across membranes.
On the Existence and Utility of Rigid Quasilocal Frames
Epp, Richard J; McGrath, Paul L
2013-01-01
The notion of a rigid quasilocal frame (RQF) provides a geometrically natural way to define a system in general relativity, and a new way to analyze the problem of motion. An RQF is defined as a two-parameter family of timelike worldlines comprising the boundary (topologically R x S^2) of the history of a finite spatial volume, with the rigidity conditions that the congruence of worldlines be expansion- and shear-free. In other words, the size and shape of the system do not change. In previous work, such systems in Minkowski space were shown to admit precisely the same six degrees of freedom of rigid body motion that we are familiar with in Newtonian space-time, without any constraints, circumventing a century-old theorem due to Herglotz and Noether. This is a consequence of the fact that a two-sphere of any shape always admits precisely six conformal Killing vector fields, which generate an action of the Lorentz group on the sphere. Here we review the previous work in flat spacetime and extend it in three di...
Measuring membrane rigidity and viscosity: New methods, and new insights
Parthasarathy, Raghuveer
2014-03-01
Lipid membranes are remarkable materials: flexible, two-dimensional fluids whose physical properties guide cellular function. Bending rigidity and viscosity are two of the key mechanical parameters that characterize membranes. Both, however, are challenging to measure. I describe improvements in experimental techniques to quantify the bending modulus and the two-dimensional viscosity of lipid membranes. First, I show that using selective plane illumination microscopy (SPIM, also known as light sheet fluorescence microscopy) to image the thermal fluctuations of freely suspended giant lipid vesicles enables straightforward measurements of membrane rigidity, and also provides insights into changes in rigidity induced by cargo trafficking proteins. Second, I show that tracking both the rotational and translational diffusion of membrane-anchored tracer particles allows quantification of membrane viscosity, measurement of the effective radii of the tracers, and assessment of theoretical models of membrane hydrodynamics. Surprisingly, we find a wide distribution of effective tracer sizes, due presumably to a wide variety of couplings to the membrane. I also provide an example of protein-mediated changes in lipid viscosity.
The diagnostic role of thoracoscope in undiagnosed pleural effusion: Rigid versus flexible
Directory of Open Access Journals (Sweden)
Mostafa Mahmoud Abdel Mageid Shaheen
2014-07-01
Conclusions: Thoracoscopy using either fibreoptic bronchoscope or rigid thoracoscope is safe and well tolerated. Rigid thoracoscope has a higher diagnostic yield, easier handling, better orientation and is less expensive. Nevertheless, fibreoptic bronchoscope is an alternative technique if rigid thoracoscopy is not available.
Xiang, Shang; Jiang, Weikang; Jiang, Hao; Gao, Jianzheng
2016-09-01
An acoustic source identification technique with single layer pressure measurement is presented to reconstruct normal velocities of target sources in noisy environments. The theory for this reconstruction is developed from the inverse patch transfer functions method which is supposed to combine measurements of pressure and velocity on a surface surrounding the source. The rigid microphone array is called an acoustic mask, which is designed to obtain pressure on the Neumann boundary condition and realized by microphones flush mounted on the aluminum plate. The validity of the proposed method is demonstrated by giving the normal velocities of two baffled loudspeakers in a noisy environment in the simulation and experiment. Another experiment of a clamped steel plate is further presented to illustrate the ability of the acoustic mask to obtain the partial velocity field of interest without reconstruction of the whole source surface velocity. The accuracy of this technique is demonstrated by comparison with the accelerometer method.
Separation of Target Rigid Body and Micro-Doppler Effects in ISAR/SAR Imaging
2006-09-01
cible radar. I1 peut d6grader l’image ISAR/SAR. Toutefois, il est 6galement porteur d’information sur les caract ~ristiques de ces parties mobiles. La...l’analyse de signatures de cibles. Ces caract ~ristiques compl~tent celles que fournissent les m~thodes existantes. L’effet micro-Doppler peut servir A...tr~s importantes de donn6es SAR/ISAR exp~rimentales. Par contre, l’effet micro-Doppler fournit aussi de l’informnation sur les caract ~ristiques des
Rigidized Deployable Lifting Brake for Atmospheric Entry Project
National Aeronautics and Space Administration — Aerobraking to reduce velocity for planetary capture and landing has long been assumed for use on Mars missions because Mars has an atmosphere, and the use of...
Till, Bernie C.; Driessen, Peter F.
2014-01-01
Starting from first principles, we derive the telegraph equation to describe the propagation of sound waves in rigid tubes by using a simple approach that yields a lossy transmission line model with frequency-independent parameters. The approach is novel in the sense that it has not been found in the literature or textbooks. To derive the lossy acoustic telegraph equation from the lossless wave equation, we need only to relax the assumption that the dynamical variables are constant over the entire cross-sectional area of the tube. In this paper, we do this by introducing a relatively narrow boundary layer at the wall of the tube, over which the dynamical variables decrease linearly from the constant value to zero. This allows us to make very simple corrections to the lossless case, and to express them in terms of two parameters, namely the viscous diffusion time constant and the thermal diffusion time constant. The coefficients of the resulting telegraph equation are frequency-independent. A comparison with the telegraph equation for the electrical transmission line establishes precise relationships between the electrical circuit elements and the physical properties of the fluid. These relationships are thus proven a posteriori rather than asserted a priori. In this way, we arrive at an instructive and useful derivation of the acoustic telegraph equation, which takes viscous damping and thermal dissipation into account, and is accessible to students at the undergraduate level. This derivation does not resort to the combined heavy machinery of fluid dynamics and thermodynamics, does not assume that the waveforms are sinusoidal, and does not assume any particular cross-sectional shape of the tube. Surprisingly, we have been unable to find a comparable treatment in the standard introductory physics and acoustics texts, or in the literature.
Sim, Jaehyun; Sim, Jun; Park, Eunsung; Lee, Julian
2015-06-01
Many proteins undergo large-scale motions where relatively rigid domains move against each other. The identification of rigid domains, as well as the hinge residues important for their relative movements, is important for various applications including flexible docking simulations. In this work, we develop a method for protein rigid domain identification based on an exhaustive enumeration of maximal rigid domains, the rigid domains not fully contained within other domains. The computation is performed by mapping the problem to that of finding maximal cliques in a graph. A minimal set of rigid domains are then selected, which cover most of the protein with minimal overlap. In contrast to the results of existing methods that partition a protein into non-overlapping domains using approximate algorithms, the rigid domains obtained from exact enumeration naturally contain overlapping regions, which correspond to the hinges of the inter-domain bending motion. The performance of the algorithm is demonstrated on several proteins. © 2015 Wiley Periodicals, Inc.
Huang, J; Vieland, V J
2001-01-01
It is well known that the asymptotic null distribution of the homogeneity lod score (LOD) does not depend on the genetic model specified in the analysis. When appropriately rescaled, the LOD is asymptotically distributed as 0.5 chi(2)(0) + 0.5 chi(2)(1), regardless of the assumed trait model. However, because locus heterogeneity is a common phenomenon, the heterogeneity lod score (HLOD), rather than the LOD itself, is often used in gene mapping studies. We show here that, in contrast with the LOD, the asymptotic null distribution of the HLOD does depend upon the genetic model assumed in the analysis. In affected sib pair (ASP) data, this distribution can be worked out explicitly as (0.5 - c)chi(2)(0) + 0.5chi(2)(1) + cchi(2)(2), where c depends on the assumed trait model. E.g., for a simple dominant model (HLOD/D), c is a function of the disease allele frequency p: for p = 0.01, c = 0.0006; while for p = 0.1, c = 0.059. For a simple recessive model (HLOD/R), c = 0.098 independently of p. This latter (recessive) distribution turns out to be the same as the asymptotic distribution of the MLS statistic under the possible triangle constraint, which is asymptotically equivalent to the HLOD/R. The null distribution of the HLOD/D is close to that of the LOD, because the weight c on the chi(2)(2) component is small. These results mean that the cutoff value for a test of size alpha will tend to be smaller for the HLOD/D than the HLOD/R. For example, the alpha = 0.0001 cutoff (on the lod scale) for the HLOD/D with p = 0.05 is 3.01, while for the LOD it is 3.00, and for the HLOD/R it is 3.27. For general pedigrees, explicit analytical expression of the null HLOD distribution does not appear possible, but it will still depend on the assumed genetic model. Copyright 2001 S. Karger AG, Basel
L.A. Dobrzański; J. Trzaska
2006-01-01
Purpose: The aim of the study is to establish a system that supports the choice of steel grade for quenching and tempering at a required hardness curve as function of cooling rate from the austenitising temperature.Design/methodology/approach: It has been assumed that the steel will meet the criterion provided that the hardness curve, defined by the user, is included within the range of hardness change that is characteristic of a certain steel grade. In order to determine the steel hardness r...
Energy Technology Data Exchange (ETDEWEB)
Park, Jeong Soo; Kim, Jong Min; Kang, Seon Ye; Park, Sung Ho; Sohn, Gap Heon [Korea Power Engineering Company, Inc., Daejeon (Korea, Republic of)
2008-07-01
Out-of-limit transients due to thermal stratification are discovered in the pressurizer of the nuclear power plants supplied by Westinghouse. The occurring of out-of-limit transients are not reported in the pressurizer of OPR1000. However, the occurring of out-of-limit transients are assumed for the pressurizer of OPR1000 and are evaluated for the pressurizer surge nozzle structural integrity. The evaluation results show that the ASME Code requirements are met even though out-of-limit transients are considered additionally.
[A case of rigid spine syndrome with rimmed vacuole].
Onodera, O; Yamazaki, M; Atsumi, T; Miyatake, T; Izumi, T
1990-05-01
A case of rigid spine syndrome associated with rimmed vacuoles in muscle biopsy is reported. A 36-year-old man was admitted to our hospital because of gait disturbance and limited mortality of the spine. His family was free from any neuromuscular disorders. He was born in normal pregnancy and delivery. His physical development was normal. At age 7, he was unable to run fast. At age 36, he had right hemiparesis and dysarthria. He was diagnosed as cerebral infarction of the left basal ganglia by brain CT. Neurological examination revealed moderate proximal dominant muscular atrophy and weakness. His spine was straight, showing loss of physiological cervical and lumbar lordosis. The neck flexion was limited but the extension was full. And he had contracture of bilateral ankle joint. Laboratory findings were all normal. The electrocardiogram showed negative T wave in V4, V5 and QT interval elongation. The echocardiogram showed diffuse decrease of ventricular wall motion. Respiratory function test revealed decrease of vital capacity. Arterial blood gases on room air showed that the PaO2 and PaCO2 were 70 mmHg and 49 mmHg, respectively. The findings of electromyogram were compatible with myopathic change. Biopsy specimen of the biceps brachii muscle showed marked variation in fiber size, type 1 fiber predominancy and atrophy, and type 2B fiber deficiency. Numerous rimmed vaculoes were found in the same muscle. Four cases of the rigid spine syndrome with rimmed vacuoles have been described. Among them, three patients died in young ages and two suffered from constrictive respiratory failure. In rigid spine syndrome with rimmed vacuole formation, the cardiac and respiratory problems must be taken account intensively.
Accurate free and forced rotational motions of rigid Venus
Cottereau, L.; Souchay, J.; Aljbaae, S.
2010-06-01
Context. The precise and accurate modelling of a terrestrial planet like Venus is an exciting and challenging topic, all the more interesting because it can be compared with that of Earth for which such a modelling has already been achieved at the milli-arcsecond level. Aims: We aim to complete a previous study, by determining the polhody at the milli-arcsecond level, i.e. the torque-free motion of the angular momentum axis of a rigid Venus in a body-fixed frame, as well as the nutation of its third axis of figure in space, which is fundamental from an observational point of view. Methods: We use the same theoretical framework as Kinoshita (1977, Celest. Mech., 15, 277) did to determine the precession-nutation motion of a rigid Earth. It is based on a representation of the rotation of a rigid Venus, with the help of Andoyer variables and a set of canonical equations in Hamiltonian formalism. Results: In a first part we computed the polhody, we showed that this motion is highly elliptical, with a very long period of 525 cy compared with 430 d for the Earth. This is due to the very small dynamical flattening of Venus in comparison with our planet. In a second part we precisely computed the Oppolzer terms, which allow us to represent the motion in space of the third Venus figure axis with respect to the Venus angular momentum axis under the influence of the solar gravitational torque. We determined the corresponding tables of the nutation coefficients of the third figure axis both in longitude and in obliquity due to the Sun, which are of the same order of amplitude as for the Earth. We showed that the nutation coefficients for the third figure axis are significantly different from those of the angular momentum axis on the contrary of the Earth. Our analytical results have been validated by a numerical integration, which revealed the indirect planetary effects.
Gaussian Curvature as an Identifier of Shell Rigidity
Harutyunyan, Davit
2017-11-01
In the paper we deal with shells with non-zero Gaussian curvature. We derive sharp Korn's first (linear geometric rigidity estimate) and second inequalities on that kind of shell for zero or periodic Dirichlet, Neumann, and Robin type boundary conditions. We prove that if the Gaussian curvature is positive, then the optimal constant in the first Korn inequality scales like h, and if the Gaussian curvature is negative, then the Korn constant scales like h 4/3, where h is the thickness of the shell. These results have a classical flavour in continuum mechanics, in particular shell theory. The Korn first inequalities are the linear version of the famous geometric rigidity estimate by Friesecke et al. for plates in Arch Ration Mech Anal 180(2):183-236, 2006 (where they show that the Korn constant in the nonlinear Korn's first inequality scales like h 2), extended to shells with nonzero curvature. We also recover the uniform Korn-Poincaré inequality proven for "boundary-less" shells by Lewicka and Müller in Annales de l'Institute Henri Poincare (C) Non Linear Anal 28(3):443-469, 2011 in the setting of our problem. The new estimates can also be applied to find the scaling law for the critical buckling load of the shell under in-plane loads as well as to derive energy scaling laws in the pre-buckled regime. The exponents 1 and 4/3 in the present work appear for the first time in any sharp geometric rigidity estimate.
Atmospheric Entry Studies for Venus Missions: 45 Sphere-Cone Rigid Aeroshells and Ballistic Entries
Prabhu, Dinesh K.; Spilker, Thomas R.; Allen, Gary A., Jr.; Hwang, Helen H.; Cappuccio, Gelsomina; Moses, Robert W.
2013-01-01
The present study considers direct ballistic entries into the atmosphere of Venus using a 45deg sphere-cone rigid aeroshell, a legacy shape that has been used successfully in the past in the Pioneer Venus Multiprobe Mission. For a number of entry mass and heatshield diameter combinations (i.e., various ballistic coefficients) and entry velocities, the trajectory space in terms of entry flight path angles between skip out and -30deg is explored with a 3DoF trajectory code, TRAJ. From these trajectories, the viable entry flight path angle space is determined through the use of mechanical and thermal performance limits on the thermal protection material and science payload; the thermal protection material of choice is entry-grade carbon phenolic, for which a material thermal response model is available. For mechanical performance, a 200 g limit is placed on the peak deceleration load experienced by the science instruments, and 10 bar is assumed as the pressure limit for entry-grade carbon-phenolic material. For thermal performance, inflection points in the total heat load distribution are used as cut off criteria. Analysis of the results shows the existence of a range of critical ballistic coefficients beyond which the steepest possible entries are determined by the pressure limit of the material rather than the deceleration load limit.
Numerical study of acoustically driven bubble cloud dynamics near a rigid wall.
Ma, Jingsen; Hsiao, Chao-Tsung; Chahine, Georges L
2018-01-01
The dynamics of a bubble cloud excited by a sinusoidal pressure field near a rigid wall is studied using a novel Eulerian/Lagrangian two-phase flow model. The effects of key parameters such as the amplitude and frequency of the excitation pressure, the cloud and bubble sizes, the void fraction, and the initial standoff distance on the bubbles' collective behavior and the resulting pressure loads on the nearby wall are investigated. The study shows that nonlinear bubble cloud dynamics becomes more pronounced and results in higher pressure loading at the wall as the excitation pressure amplitude increases. The strongest collective bubble behavior occurs at a preferred resonance frequency. At this resonance frequency, pressure peaks orders of magnitudes higher than the excitation pressure result from the bubble interaction when the amplitude of the pressure excitation is high. The numerically obtained resonance frequency is significantly different from the reported natural frequency of a spherical cloud derived from linear theory, which assumes small amplitude oscillations in an unbounded medium. At high amplitudes of the excitation, the resonance frequency decreases almost linearly with the ratio of excitation pressure amplitude to ambient pressure until the ratio is larger than one. Copyright © 2017 Elsevier B.V. All rights reserved.
iCub Whole-body Control through Force Regulation on Rigid Noncoplanar Contacts
Directory of Open Access Journals (Sweden)
Francesco eNori
2015-03-01
Full Text Available This paper details the implementation on the humanoid robot iCub of state-of-the-art algorithms for whole-body control. We regulate the forces between the robot and its surrounding environment to stabilize a desired robot posture. We assume that the forces and torques are exerted on rigid contacts. The validity of this assumption is guaranteed by constraining the contact forces and torques, e.g. the contact forces must belong to the associated friction cones. The implementation of this control strategy requires to estimate the external forces acting on the robot, and the internal joint torques. We then detail algorithms to obtain these estimations when using a robot with an iCub-like sensor set, i.e. distributed six-axis force-torque sensors and whole-body tactile sensors. A general theory for identifying the robot inertial parameters is also presented. From an actuation standpoint, we show how to implement a joint torque control in the case of DC brushless motors. In addition, the coupling mechanism of the iCub torso is investigated. The soundness of the entire control architecture is validated in a real scenario involving the robot iCub balancing and making contacts at both arms.
Sound radiation from a resilient spherical cap on a rigid sphere.
Aarts, Ronald M; Janssen, Augustus J E M
2010-04-01
It has been argued that the sound radiation of a loudspeaker is modeled realistically by assuming the loudspeaker cabinet to be a rigid sphere with a resilient spherical cap. Series expansions, valid in the whole space outside the sphere, for the pressure due to a harmonically excited cap with an axially symmetric velocity distribution are presented. The velocity profile is expanded in functions orthogonal on the cap, rather than on the whole sphere. As a result, only a few expansion coefficients are sufficient to accurately describe the velocity profile. An adaptation of the standard solution of the Helmholtz equation to this particular parametrization is required. This is achieved by using recent results on argument scaling of orthogonal (Zernike) polynomials. The approach is illustrated by calculating the pressure due to certain velocity profiles that vanish at the rim of the cap to a desired degree. The associated inverse problem, in which the velocity profile is estimated from pressure measurements around the sphere, is also feasible as the number of expansion coefficients to be estimated is limited. This is demonstrated with a simulation.
A generic detailed rigid-body lumbar spine model
DEFF Research Database (Denmark)
De Zee, Mark; Hansen, Lone; Wong, Christian
2007-01-01
the literature. The work resulted in a detailed lumbar spine model with seven rigid segments with 18 degrees-of-freedom and 154 muscles. The model is able to produce a maximum extension moment of 238 Nm around L5/S1. Moreover, a comparison was made with in vivo intradiscal pressure measurements of the L4-5 disc...... available from the literature. The model is based on inverse dynamics, where the redundancy problem is solved using optimization in order to compute the individual muscle forces and joint reactions. With the presented model it is possible to investigate a range of research questions, because the model...
Dynamic phase separation of fluid membranes with rigid inclusions.
Weikl, Thomas R
2002-12-01
Membrane shape fluctuations induce attractive interactions between rigid inclusions. Previous analytical studies showed that the fluctuation-induced pair interactions are rather small compared to thermal energies, but also that multibody interactions cannot be neglected. In this paper, it is shown numerically that shape fluctuations indeed lead to the dynamic separation of the membrane into phases with different inclusion concentrations. The tendency of lateral phase separation strongly increases with the inclusion size. Large inclusions aggregate at very small inclusion concentrations and for relatively small values of the inclusions' elastic modulus.
Centrifuge modelling of rigid piles in soft clay
DEFF Research Database (Denmark)
Klinkvort, R.T.; Poder, M.; Truong, P.
2016-01-01
of this study is to employ centrifuge modelling in order to derive experimental p-y curves for rigid piles embedded in over-consolidated soft clay. A kaolin clay sample was prepared and pre-consolidated by applying a constant pressure at the soil surface, while different over-consolidation ratios were achieved...... within the clay sample by carrying out the experiments at different g fields. The findings suggest that the normalised shape of the p-y curves can be predicted within a sufficient accuracy using the current methodology but that the ultimate lat-eral resistance is underestimated at shallow depths...
Spectral rigidity of vehicular streams (random matrix theory approach)
Energy Technology Data Exchange (ETDEWEB)
Krbalek, Milan [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague (Czech Republic); Seba, Petr [Doppler Institute for Mathematical Physics and Applied Mathematics, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague (Czech Republic)
2009-08-28
Using a method originally developed for the random matrix theory, we derive an approximate mathematical formula for the number variance {delta}{sub N}(L) describing the rigidity of particle ensembles with a power-law repulsion. The resulting relation is compared with the relevant statistics of the single-vehicle data measured on the Dutch freeway A9. The detected value of the inverse temperature {beta}, which can be identified as a coefficient of the mental strain of the car drivers, is then discussed in detail with the relation to the traffic density {rho} and flow J.
Control of the rigid body and dynamics with symmetry
Lum, Kai-Yew
This dissertation explores various problems in the control of the rigid body and related dynamical systems with symmetry, utilizing various modeling approaches and control techniques. We first derive a control law that asymptotically stabilizes an unbalanced top to the sleeping motion. We rewrite the classical Euler-Poisson equations by projecting the phase space onto IRsp5. The control law is based on the Hamilton-Jacobi-Bellman theory with zero dynamics and partial stability. Lyapunov techniques are used in the analysis. Next, the control of rotor imbalance with magnetic bearings is considered in the adaptive virtual autobalancing and adaptive autocentering approaches. We derive single-plane and two-plane balancing control algorithms that provide asymptotic estimates of the rotor imbalance, and that guarantee consistent performance under varying spin rate. These algorithms are based on emulation of the mechanical autobalancer. We discuss the theory based on linear analysis, and simulation and experimental results. We go on to investigate symmetry properties associated with mechanical control systems and certain nonlinear control systems. First, we generalize the classical Serret-Andoyer transformation for the free rigid body to left-invariant, hyperregular Hamiltonian systems on Tsp*SO(3), employing the notion of symplectic (Marsden-Weinstein) reduction. We then apply this result to the controlled rigid body, and show that for Hamiltonian controls that preserve the rigid body structure, the generalized Serret-Andoyer transformation yields a two dimensional representation of the closed-loop motion in canonical form. Applications to the stability analysis of relative equilibria and numerical integration are also discussed. Finally, we apply the concept of reduction to certain regulation problems on smooth manifolds. Following the works of Van der Schaft (1981) and Grizzle and Marcus (1985), we show that an output feedback regulation problem possessing certain
Symmetry and Reduction for Coordinated Rigid Body Networks
Hanszligmann, H; Smith, T R
2004-01-01
Motivated by interest in the collective behavior of autonomous agents, we study networks of rigid bodies and the problem of coordinated orientation and position across the group. Our main result is the reduction of the networked system in the case that individuals are coupled by control inputs that depend only on relative configuration. We use reduction theory based on semi-direct products; this yields flat Poisson spaces which enable efficient formulation of control laws. In the second part of the paper, we apply the reduction results to particular choices of kinetic energy and prove stability of coordinated behaviors.
Rigid supersymmetry from conformal supergravity in five dimensions
Energy Technology Data Exchange (ETDEWEB)
Pini, Alessandro [Department of Physics, Universidad de Oviedo, Avda. Calvo Sotelo 18, 33007, Oviedo (Spain); Centre for Research in String Theory, School of Physics, Queen Mary University of London,Mile End Road, London, E1 4NS (United Kingdom); Rodriguez-Gomez, Diego; Schmude, Johannes [Department of Physics, Universidad de Oviedo, Avda. Calvo Sotelo 18, 33007, Oviedo (Spain)
2015-09-17
We study the rigid limit of 5d conformal supergravity with minimal supersymmetry on Riemannian manifolds. The necessary and sufficient condition for the existence of a solution is the existence of a conformal Killing vector. Whenever a certain SU(2) curvature becomes abelian the backgrounds define a transversally holomorphic foliation. Subsequently we turn to the question under which circumstances these backgrounds admit a kinetic Yang-Mills term in the action of a vector multiplet. Here we find that the conformal Killing vector has to be Killing. We supplement the discussion with various appendices.
The market for large rigid haul trucks in surface mining
Energy Technology Data Exchange (ETDEWEB)
Gilewicz, P.
2002-04-15
Originally published in 2001 this updated report provides a definition of the market for large rigid haulers in surface mining. The analysis covers changes to the mining market segments buying these machines including the gains made by coal producers, retrenchment in copper mining, the consolidation taking place among gold mining companies, and the expansion of iron ore producers in Australia and Brazil. It includes a detailed accounting of 2001 truck shipments, and an analysis of trends in the Ultra-truck segment. It concludes with a revised forecast for shipments through 2006. 12 charts, 56 tabs., 2 apps.
Ivanovska, Irena L; Swift, Joe; Spinler, Kyle; Dingal, Dave; Cho, Sangkyun; Discher, Dennis E
2017-07-07
Synergistic cues from extracellular matrix and soluble factors are often obscure in differentiation. Here the rigidity of cross-linked collagen synergizes with retinoids in the osteogenesis of human marrow mesenchymal stem cells (MSCs). Collagen nanofilms serve as a model matrix that MSCs can easily deform unless the film is enzymatically cross-linked, which promotes the spreading of cells and the stiffening of nuclei as both actomyosin assembly and nucleoskeletal lamin-A increase. Expression of lamin-A is known to be controlled by retinoic acid receptor (RAR) transcription factors, but soft matrix prevents any response to any retinoids. Rigid matrix is needed to induce rapid nuclear accumulation of the RARG isoform and for RARG-specific antagonist to increase or maintain expression of lamin-A as well as for RARG-agonist to repress expression. A progerin allele of lamin-A is regulated in the same manner in iPSC-derived MSCs. Rigid matrices are further required for eventual expression of osteogenic markers, and RARG-antagonist strongly drives lamin-A-dependent osteogenesis on rigid substrates, with pretreated xenografts calcifying in vivo to a similar extent as native bone. Proteomics-detected targets of mechanosensitive lamin-A and retinoids underscore the convergent synergy of insoluble and soluble cues in differentiation. © 2017 Ivanovska et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
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.
Zito, Sarah; Morton, John; Vankan, Dianne; Paterson, Mandy; Bennett, Pauleen C; Rand, Jacquie; Phillips, Clive J C
2016-01-01
Most cats surrendered to nonhuman animal shelters are identified as unowned, and the surrender reason for these cats is usually simply recorded as "stray." A cross-sectional study was conducted with people surrendering cats to 4 Australian animal shelters. Surrenderers of unowned cats commonly gave surrender reasons relating to concern for the cat and his/her welfare. Seventeen percent of noncaregivers had considered adopting the cat. Barriers to assuming ownership most commonly related to responsible ownership concerns. Unwanted kittens commonly contributed to the decision to surrender for both caregivers and noncaregivers. Nonowners gave more surrender reasons than owners, although many owners also gave multiple surrender reasons. These findings highlight the multifactorial nature of the decision-making process leading to surrender and demonstrate that recording only one reason for surrender does not capture the complexity of the surrender decision. Collecting information about multiple reasons for surrender, particularly reasons for surrender of unowned cats and barriers to assuming ownership, could help to develop strategies to reduce the number of cats surrendered.
Reinoso, J.; Paggi, M.; Linder, C.
2017-06-01
Fracture of technological thin-walled components can notably limit the performance of their corresponding engineering systems. With the aim of achieving reliable fracture predictions of thin structures, this work presents a new phase field model of brittle fracture for large deformation analysis of shells relying on a mixed enhanced assumed strain (EAS) formulation. The kinematic description of the shell body is constructed according to the solid shell concept. This enables the use of fully three-dimensional constitutive models for the material. The proposed phase field formulation integrates the use of the (EAS) method to alleviate locking pathologies, especially Poisson thickness and volumetric locking. This technique is further combined with the assumed natural strain method to efficiently derive a locking-free solid shell element. On the computational side, a fully coupled monolithic framework is consistently formulated. Specific details regarding the corresponding finite element formulation and the main aspects associated with its implementation in the general purpose packages FEAP and ABAQUS are addressed. Finally, the applicability of the current strategy is demonstrated through several numerical examples involving different loading conditions, and including linear and nonlinear hyperelastic constitutive models.
Segel, Michael J; Bobrovsky, Ben-Zion; Gabbay, Itay E; Ben-Dov, Issahar; Reuveny, Ronen; Gabbay, Uri
2017-05-01
The Cardio-vascular reserve index (CVRI) had been empirically validated in diverse morbidities as a quantitative estimate of the reserve assumed by the cardiovascular reserve hypothesis. This work evaluates whether CVRI during exercise complies with the cardiovascular reserve hypothesis. Retrospective study based on a database of patients who underwent cardio-pulmonary exercise testing (CPX) for diverse indications. Patient's physiological measurements were retrieved at four predefined CPX stages (rest, anaerobic threshold, peak exercise and after 2min of recovery). CVRI was individually calculated retrospectively at each stage. Mean CVRI at rest was 0.81, significantly higher (p0.05). CVRI after 2min of recovery rose considerably, most in the group with the best exercise capacity and least in those with the lowest exercise capacity. CVRI during exercise fits the pattern predicted by the cardiovascular reserve hypothesis. CVRI decreased with exercise reaching a minimum at peak exercise and rising with recovery. The CVRI nadir at peak exercise, similar across groups classified by exercise capacity, complies with the assumed exhaustion threshold. The clinical utility of CVRI should be further evaluated. Copyright © 2017 Elsevier B.V. All rights reserved.
Cruz-Osorio, A.; Sánchez-Salcedo, F. J.; Lora-Clavijo, F. D.
2017-11-01
We study the relativistic Bondi-Hoyle-Lyttleton accretion on to a Schwarzschild black hole (BH), which is surrounded by rigid and small, randomly distributed, bodies. These bodies are idealized representations of substructure like stars passing close to the BH, bubbles created by stellar winds or cold clumps. We explore cases where the filling factor of these bodies is small. The flow is assumed to be adiabatic and move supersonically towards the BH. The interaction with these rigid obstacles transforms ram pressure of the flow into thermal pressure through bow shocks, slowing down the flow and making the accreting gas turbulent. As a consequence, although the flow reaches a statistically steady state, the accretion rate presents some variability. For a flow Mach number at infinity of 4, a few of these objects (5-10) are enough to increase the accretion rate about 50 per cent over the accretion rate without bodies, even though the gas is adiabatic and the filling factor of the obstacles is small.
Shafiekhani, Soraya; Zamindar, Nafiseh; Hojatoleslami, Mohammad; Toghraie, Davood
2016-06-01
Pasteurization of canned apple puree was simulated for a 3-D geometry in a semi-rigid aluminum based container which was heated from all sides at 378 K. The computational fluid dynamics code Ansys Fluent 14.0 was used and the governing equations for energy, momentum, and continuity were computed using a finite volume method. The food model was assumed to have temperature-dependent properties. To validate the simulation, the apple puree was pasteurized in a water cascading retort. The effect of the mesh structures was studied for the temperature profiles during thermal processing. The experimental temperature in the slowest heating zone in the container was compared with the temperature predicted by the model and the difference was not significant. The study also investigated the impact of head space (water-vapor) on heat transfer.
Reopening modes of a collapsed elasto-rigid channel
Ducloué, Lucie; Thompson, Alice B; Juel, Anne
2016-01-01
Motivated by the reopening mechanics of strongly collapsed airways, we study the steady propagation of an air finger through a collapsed oil-filled channel with a single compliant wall. In a previous study using fully-compliant elastic tubes, a `pointed' air finger was found to propagate at high speed and low pressure, which may enable rapid reopening of highly collapsed airways with minimal tissue damage (Heap & Juel 2008). In this paper, we identify the selection mechanism of that pointed finger, which remained unexplained, by conducting an experimental study in a rigid rectangular Hele-Shaw channel with an elastic top boundary. The constitutive behaviour of this elasto-rigid channel is broadly similar to that of an elastic tube, but unlike the tube the channel's cross-section adopts self-similar shapes from the undeformed state to the point of first near wall contact. The simplification of the vessel geometry enables the systematic investigation of the reopening dynamics in terms of initial collapse. W...
Synthesis of rigid polyurethane foams from phosphorylated biopolyols.
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 H3PO4. The formation of phosphate polyesters was confirmed by FT-IR and 31P-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.
Collisions of Constrained Rigid Body Systems with Friction
Directory of Open Access Journals (Sweden)
Haijun Shen
1998-01-01
Full Text Available A new approach is developed for the general collision problem of two rigid body systems with constraints (e.g., articulated systems, such as massy linkages in which the relative tangential velocity at the point of contact and the associated friction force can change direction during the collision. This is beyond the framework of conventional methods, which can give significant and very obvious errors for this problem, and both extends and consolidates recent work. A new parameterization and theory characterize if, when and how the relative tangential velocity changes direction during contact. Elastic and dissipative phenomena and different values for static and kinetic friction coefficients are included. The method is based on the explicitly physical analysis of events at the point of contact. Using this method, Example 1 resolves (and corrects a paradox (in the literature of the collision of a double pendulum with the ground. The method fundamentally subsumes other recent models and the collision of rigid bodies; it yields the same results as conventional methods when they would apply (Example 2. The new method reformulates and extends recent approaches in a completely physical context.
Polynomials for crystal frameworks and the rigid unit mode spectrum
Power, S. C.
2014-01-01
To each discrete translationally periodic bar-joint framework in , we associate a matrix-valued function defined on the d-torus. The rigid unit mode (RUM) spectrum of is defined in terms of the multi-phases of phase-periodic infinitesimal flexes and is shown to correspond to the singular points of the function and also to the set of wavevectors of harmonic excitations which have vanishing energy in the long wavelength limit. To a crystal framework in Maxwell counting equilibrium, which corresponds to being square, the determinant of gives rise to a unique multi-variable polynomial . For ideal zeolites, the algebraic variety of zeros of on the d-torus coincides with the RUM spectrum. The matrix function is related to other aspects of idealized framework rigidity and flexibility, and in particular leads to an explicit formula for the number of supercell-periodic floppy modes. In the case of certain zeolite frameworks in dimensions two and three, direct proofs are given to show the maximal floppy mode property (order N). In particular, this is the case for the cubic symmetry sodalite framework and some other idealized zeolites. PMID:24379422
Dynamics of parallel robots from rigid bodies to flexible elements
Briot, Sébastien
2015-01-01
This book starts with a short recapitulation on basic concepts, common to any types of robots (serial, tree structure, parallel, etc.), that are also necessary for computation of the dynamic models of parallel robots. Then, as dynamics requires the use of geometry and kinematics, the general equations of geometric and kinematic models of parallel robots are given. After, it is explained that parallel robot dynamic models can be obtained by decomposing the real robot into two virtual systems: a tree-structure robot (equivalent to the robot legs for which all joints would be actuated) plus a free body corresponding to the platform. Thus, the dynamics of rigid tree-structure robots is analyzed and algorithms to obtain their dynamic models in the most compact form are given. The dynamic model of the real rigid parallel robot is obtained by closing the loops through the use of the Lagrange multipliers. The problem of the dynamic model degeneracy near singularities is treated and optimal trajectory planning for cro...
Statistics of admixture distribution in flows through rigid foams
Denissenko, Petr; Le Fur, Pierre; Vlaskamp, Jozef; Williams, Mark; Fan, Xiaolei; Lapkin, Alexei
2014-11-01
Diffusion and dispersion of admixture in flows through rigid foams need to be accounted for when modelling catalytic reactions on the foam surface. We study diffusion of admixture and scaling exponents of admixture concentration both experimentally and by numerical simulations. A liquid admixture was continuously released from a point source at the upstream boundary of a block of rigid SiC foam. Foam thickness was varied from 20 to 80 average pore sizes. A flow with Re of up to 300 based on the pore size was imposed by a progressive cavity pump. The distribution of the tracer at the exit from the foam was measured using LIF and the concentration moments have been calculated. Numerical simulation of the flow in laminar regime has been performed within OpenFoam for the Re from 1 to 100. Geometry of the sample was acquired by Micro Computed Tomography scanning of the actual foam sample. A steady-state SIMPLE method was used to solve the incompressible steady flow in the volume of 20 × 20 × 40 average pore sizes. Diffusion and dispersion of passive scalar has been studied by following individual streamlines. Results are interpreted in terms of mixing, heat transfer, and selectivity of catalytic reactions at the foam surface. This Research is supported by European Commission under the 7th Framework Program.
Rigidity-induced scale invariance in polymer ejection from capsid
Linna, R. P.; Suhonen, P. M.; Piili, J.
2017-11-01
While the dynamics of a fully flexible polymer ejecting a capsid through a nanopore has been extensively studied, the ejection dynamics of semiflexible polymers has not been properly characterized. Here we report results from simulations of ejection dynamics of semiflexible polymers ejecting from spherical capsids. Ejections start from strongly confined polymer conformations of constant initial monomer density. We find that, unlike for fully flexible polymers, for semiflexible polymers the force measured at the pore does not show a direct relation to the instantaneous ejection velocity. The cumulative waiting time t (s ) , that is, the time at which a monomer s exits the capsid the last time, shows a clear change when increasing the polymer rigidity κ . The major part of an ejecting polymer is driven out of the capsid by internal pressure. At the final stage the polymer escapes the capsid by diffusion. For the driven part there is a crossover from essentially exponential growth of t with s of the fully flexible polymers to a scale-invariant form. In addition, a clear dependence of t on polymer length N0 was found. These findings combined give the dependence t (s ) ∝N00.55s1.33 for the strongly rigid polymers. This crossover in dynamics where κ acts as a control parameter is reminiscent of a phase transition. This analogy is further enhanced by our finding a perfect data collapse of t for polymers of different N0 and any constant κ .
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Modyfication of the Rigid Polyurethane-Polyisocyanurate Foams
Directory of Open Access Journals (Sweden)
Bogusław Czupryński
2014-01-01
Full Text Available The effect of polyethylene glycol 1500 on physicomechanical properties of rigid polyurethane-polyisocyanurate (PUR-PIR foams has been studied. It was found that application of polyethylene glycol 1500 for synthesis of foams in amount from 0% to 20% w/w had an effect on reduction of brittleness and softening point, while the greater the increase in compressive strength the higher its content in foam composition was. Wastes from production of these foams were ground and subjected to glycolysis in diethylene glycol with the addition of ethanolamine and zinc stearate. Liquid brown products were obtained. Properties of the resulting products were defined in order to determine their suitability for synthesis of new foams. It was found that glycolysate 6 was the most suitable for reuse and its application in different amounts allowed us to prepare 4 new foams (nos. 25, 26, 27, and 28. Properties of foams prepared in this manner were determined and, on their basis, the suitability of glycolysates for production of rigid PUR-PIR foams was evaluated.
A Soft Gripper with Rigidity Tunable Elastomer Strips as Ligaments.
Nasab, Amir Mohammadi; Sabzehzar, Amin; Tatari, Milad; Majidi, Carmel; Shan, Wanliang
2017-12-01
Like their natural counterparts, soft bioinspired robots capable of actively tuning their mechanical rigidity can rapidly transition between a broad range of motor tasks-from lifting heavy loads to dexterous manipulation of delicate objects. Reversible rigidity tuning also enables soft robot actuators to reroute their internal loading and alter their mode of deformation in response to intrinsic activation. In this study, we demonstrate this principle with a three-fingered pneumatic gripper that contains "programmable" ligaments that change stiffness when activated with electrical current. The ligaments are composed of a conductive, thermoplastic elastomer composite that reversibly softens under resistive heating. Depending on which ligaments are activated, the gripper will bend inward to pick up an object, bend laterally to twist it, and bend outward to release it. All of the gripper motions are generated with a single pneumatic source of pressure. An activation-deactivation cycle can be completed within 15 s. The ability to incorporate electrically programmable ligaments in a pneumatic or hydraulic actuator has the potential to enhance versatility and reduce dependency on tubing and valves.
Rigid spherical particles in highly turbulent Taylor-Couette flow
Bakhuis, Dennis; Verschoof, Ruben A.; Mathai, Varghese; Huisman, Sander G.; Lohse, Detlef; Sun, Chao
2016-11-01
Many industrial and maritime processes are subject to enormous frictional losses. Reducing these losses even slightly will already lead to large financial and environmental benefits. The understanding of the underlying physical mechanism of frictional drag reduction is still limited, for example, in bubbly drag reduction there is an ongoing debate whether deformability and bubble size are the key parameters. In this experimental study we report high precision torque measurements using rigid non-deformable spherical particles in highly turbulent Taylor-Couette flow with Reynolds numbers up to 2 ×106 . The particles are made of polystyrene with an average density of 1.036 g cm-3 and three different diameters: 8mm, 4mm, and 1.5mm. Particle volume fractions of up to 6% were used. By varying the particle diameter, density ratio of the particles and the working fluid, and volume fraction of the particles, the effect on the torque is compared to the single phase case. These systematic measurements show that adding rigid spherical particles only results in very minor drag reduction. This work is financially supported by Netherlands Organisation for Scientific Research (NWO) by VIDI Grant Number 13477.
Horizontal fall arrest systems: rigid systems vs. flexible line systems.
Lough, David
2004-09-01
There are many types of flexible and rigid systems on the market, both permanent and temporary. This article does not mean to encompass all possible systems or hazards and only intends to give an outline of what at a minimum should be examined to make an educated purchasing decision. In many instances, the buyer will use the same type of horizontal system for all situations. This is a good idea in some cases because it will reduce the need for training on a number of different systems, reduce system compatibility issues, and may reduce costs for installation, supply, and maintenance. This may not be the best idea if the hazard areas differ a great deal; as we have illustrated, one system may not function for all areas and tasks. The rigid system is typically the best solution simply based on the fact the worker won't fall as far as when he is connected to a flexible system, because of the elimination of any dynamic sag and horizontal energy absorber deployment. In any case, where you stop the worker from falling farther, you decrease the chance there may be an incident where the worker is injured. From a cost standpoint, flexible fall arrest systems typically are cheapest. In the end, safety professionals must balance the cost and effectiveness of the system to prevent an injury.
Directory of Open Access Journals (Sweden)
Heike Wendt
2017-03-01
Full Text Available Abstract Background Large-scale cross-national studies designed to measure student achievement use different social, cultural, economic and other background variables to explain observed differences in that achievement. Prior to their inclusion into a prediction model, these variables are commonly scaled into latent background indices. To allow cross-national comparisons of the latent indices, measurement invariance is assumed. However, it is unclear whether the assumption of measurement invariance has some influence on the results of the prediction model, thus challenging the reliability and validity of cross-national comparisons of predicted results. Methods To establish the effect size attributed to different degrees of measurement invariance, we rescaled the ‘home resource for learning index’ (HRL for the 37 countries ( $$n=166,709$$ n = 166 , 709 students that participated in the IEA’s combined ‘Progress in International Reading Literacy Study’ (PIRLS and ‘Trends in International Mathematics and Science Study’ (TIMSS assessments of 2011. We used (a two different measurement models [one-parameter model (1PL and two-parameter model (2PL] with (b two different degrees of measurement invariance, resulting in four different models. We introduced the different HRL indices as predictors in a generalized linear mixed model (GLMM with mathematics achievement as the dependent variable. We then compared three outcomes across countries and by scaling model: (1 the differing fit-values of the measurement models, (2 the estimated discrimination parameters, and (3 the estimated regression coefficients. Results The least restrictive measurement model fitted the data best, and the degree of assumed measurement invariance of the HRL indices influenced the random effects of the GLMM in all but one country. For one-third of the countries, the fixed effects of the GLMM also related to the degree of assumed measurement invariance. Conclusion The
Rengarajan, Govind; Aminpour, Mohammad A.; Knight, Norman F., Jr.
1992-01-01
An improved four-node quadrilateral assumed-stress hybrid shell element with drilling degrees of freedom is presented. The formulation is based on Hellinger-Reissner variational principle and the shape functions are formulated directly for the four-node element. The element has 12 membrane degrees of freedom and 12 bending degrees of freedom. It has nine independent stress parameters to describe the membrane stress resultant field and 13 independent stress parameters to describe the moment and transverse shear stress resultant field. The formulation encompasses linear stress, linear buckling, and linear free vibration problems. The element is validated with standard tests cases and is shown to be robust. Numerical results are presented for linear stress, buckling, and free vibration analyses.
Directory of Open Access Journals (Sweden)
Kookhyun Kim
2012-09-01
Full Text Available An approximate method based on an assumed mode method has been presented for the free vibration analysis of a rectangular plate with arbitrary edge constraints. In the presented method, natural frequencies and their mode shapes of the plate are calculated by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. Characteristic orthogonal polynomials having the property of Timoshenko beam functions which satisfies edge constraints corresponding to those of the objective plate are used. In order to examine the accuracy of the proposed method, numerical examples of the rectangular plates with various thicknesses and edge constraints have been presented. The results have shown good agreement with those of other methods such as an analytic solution, an approximate solution, and a finite element analysis.
Estimation of the variation in target strength of objects in the air
Gudra, Tadeusz; Opielinski, Krzysztof J.; Jankowski, Jakub
2010-01-01
Target strength is one of the key values for sonar systems. The parameter is very useful in activities related to detection and estimation of marine organisms, object identification and sonar calibration. The essential difference between detection and ranging performed in water and air results from characteristics of those media. A common feature for both water and air is the fact that only longitudinal wave propagates in them. Ultrasonic wave propagation velocity in air changes when the medium's physical conditions alter (e.g. temperature, humidity, pressure, presence of other gases or pollution and gas medium heterogeneity). In water environment not all solid state objects can be assumed to be rigid and motionless-this approximation works better in case of air. This aspect is especially vital when analyzing waves penetrating objects reflecting ultrasonic wave. This paper presents calculation and measurement results of target strength of objects, shaped as spheres and cylinders of infinite and finite length, placed in air medium. The difference between the calculated and measured target strength was analyzed and escalation of difference in case of heterogeneous objects was pointed out.
Non-rigid registration of medical images based on estimation of deformation states
Marami, Bahram; Sirouspour, Shahin; Capson, David W.
2014-11-01
A unified framework for automatic non-rigid 3D-3D and 3D-2D registration of medical images with static and dynamic deformations is proposed in this paper. The problem of non-rigid image registration is approached as a classical state estimation problem using a generic deformation model for the soft tissue. The registration technique employs a dynamic linear elastic continuum mechanics model of the tissue deformation, which is discretized using the finite element method. In the proposed method, the registration is achieved through a Kalman-like filtering process, which incorporates information from the deformation model and a vector of observation prediction errors computed from an intensity-based similarity/distance metric between images. With this formulation, single and multiple-modality, 3D-3D and 3D-2D image registration problems can all be treated within the same framework. The performance of the proposed registration technique was evaluated in a number of different registration scenarios. First, 3D magnetic resonance (MR) images of uncompressed and compressed breast tissue were co-registered. 3D MR images of the uncompressed breast tissue were also registered to a sequence of simulated 2D interventional MR images of the compressed breast. Finally, the registration algorithm was employed to dynamically track a target sub-volume inside the breast tissue during the process of the biopsy needle insertion based on registering pre-insertion 3D MR images to a sequence of real-time simulated 2D interventional MR images. Registration results indicate that the proposed method can be effectively employed for the registration of medical images in image-guided procedures, such as breast biopsy in which the tissue undergoes static and dynamic deformations.
A randomized clinical trial of treatment for lumbar segmental rigidity.
Mayer, Tom G; Gatchel, Robert J; Keeley, Janice; McGeary, Don; Dersh, Jeffrey; Anagnostis, Christopher
2004-10-15
A randomized single-blind clinical trial of facet injections plus exercise, versus exercise alone, in chronic disabling work-related lumbar spinal disorders (CDWRLSD), accompanied by pilot interrater reliability and facet syndrome prevalence studies. To systematically investigate the use of facet injections as an adjunct to supervised lumbar stretching exercises in regaining lumbar range of motion (ROM) following prolonged deconditioning after work-related lumbar injuries. To assess interrater reliability of visual assessment of segmental rigidity (SR), and to evaluate the prevalence of facet syndrome in cases of lumbar SR. Corticosteroid joint injections have often been used to reduce musculoskeletal inflammation to facilitate joint mobilization in the presence of degenerative arthritis. Lumbar segmental rigidity is a recently described entity usually associated with painful chronic spinal disorders and postoperative spine surgery. Previous work has shown that SR and lumbar ROM improves with a brief intervention consisting of facet injections followed by specific stretching exercises. No systematic study has investigated the potential benefits of a combination of facet injections and exercise over supervised exercises alone to treat lumbar SR. Similarly, no study has assessed the association between SR and the facet syndrome. From a group of consecutive patients (n = 421) with CDWRLSD referred for tertiary rehabilitation between November 1999 and January 2001, 70 were noted to have SR on intake physical examination. The first part of this study assessed interrater reliability for detecting SR, and intrarater reliability for 3-segment true lumbar ROM measurements. Patients randomly assigned to participate in supervised stretching exercises with the addition of fluoroscopically guided bilateral facet injections at the involved levels (Group A, n = 36) also underwent facet syndrome prevalence assessment at the time of injection. They were compared to a randomly
Structure and properties of a new rigid tripodal oxime ligand
Premužić, Dejan; Filarowski, Aleksander; Hołyńska, Małgorzata
2017-05-01
Synthesis and properties of a new rigid tripodal oxime ligand are reported. The ligand is a derivative of phloroglucine with three carboxime arms alternate with hydroxyl groups and three intramolecular Osbnd H⋯N hydrogen bonds. Intermolecular Osbnd H⋯O hydrogen bonds result in formation of a characteristic three-dimensional network. The structure of the compound is further analyzed and confirmed by NMR, IR and MS-techniques. DFT calculations were employed to accomplish the analysis of both the hydrogen bonding and the conformational state of the ligand under study. Additionally, the study addresses the way the conformational state and metal-replacement influence the tautomeric equilibrium OH⋯N ⇆ O-⋯+HN in the studied moieties.
Confining rigid balls by mimicking quadrupole ion trapping
Fan, Wenkai; Du, Li; Wang, Sihui; Zhou, Huijun
2017-11-01
The rotating saddle not only is an interesting system that is able to trap a ball near its saddle point, but can also intuitively illustrate the operating principles of quadrupole ion traps in modern physics. Unlike the conventional models based on the mass-point approximation, we study the stability of a ball in a rotating-saddle trap using rigid-body dynamics. The stabilization condition of the system is theoretically derived and subsequently verified by experiments. The results are compared with the previous mass-point model, giving large discrepancy as the curvature of the ball is comparable to that of the saddle. We also point out that the spin angular velocity of the ball is analogous to the cyclotron frequency of ions in an external magnetic field utilized in many prevailing ion-trapping schemes.
Dynamics of Rigid Bodies and Flexible Beam Structures
DEFF Research Database (Denmark)
Nielsen, Martin Bjerre
of rigid bodies and flexible beam structures with emphasis on the rotational motion. The first part deals with motion in a rotating frame of reference. A novel approach where the equations of motion are formulated in a hybrid state-space in terms of local displacements and global velocities is presented...... quaternion parameters or nine convected base vector components. In both cases, the equations of motion are obtained via Hamilton’s equations by including the kinematic constraints associated with the redundant rotation description by means of Lagrange multipliers. A special feature of the formulation...... of the global components of the position vectors and associated convected base vectors for the element nodes. The kinematics is expressed in a homogeneous quadratic form and the constitutive stiffness is derived from complementary energy of a set of equilibrium modes, each representing a state of constant...
Percutaneous antegrade ureteric stent removal using a rigid alligator forceps.
LENUS (Irish Health Repository)
Given, M F
2008-12-01
To evaluate the safety and efficacy of percutaneous antegrade ureteric stent removal using a rigid alligator forceps. Twenty patients were included in our study. Indications for ureteric stent insertion included stone disease (n = 7), malignancy (n = 8) and transplant anastomotic strictures (n = 5). Stent retrieval was carried out for proximal stent placement\\/migration in seven patients and encrustation in the remaining 13. Twenty-two stents were successfully retrieved in 20 patients. There was one technical failure (5%). There were no major complications. We had four minor complications, which included nephrostomy site pain (n = 2), periprocedural sepsis (n = 1) and a small urinoma (n = 1). All patients settled with conservative management. Percutaneous radiologically guided antegrade ureteric stent removal with an alligator forceps is safe and effective, particularly when initial surgical removal has failed.
Controlling elastic waves with small phononic crystals containing rigid inclusions
Peng, Pai
2014-05-01
We show that a two-dimensional elastic phononic crystal comprising rigid cylinders in a solid matrix possesses a large complete band gap below a cut-off frequency. A mechanical model reveals that the band gap is induced by negative effective mass density, which is affirmed by an effective medium theory based on field averaging. We demonstrate, by two examples, that such elastic phononic crystals can be utilized to design small devices to control low-frequency elastic waves. One example is a waveguide made of a two-layer anisotropic elastic phononic crystal, which can guide and bend elastic waves with wavelengths much larger than the size of the waveguide. The other example is the enhanced elastic transmission of a single-layer elastic phononic crystal loaded with solid inclusions. The effective mass density and reciprocal of the modulus of the single-layer elastic phononic crystal are simultaneously near zero. © CopyrightEPLA, 2014.
Testing the disturbed zone around a rigid inclusion in salt
Energy Technology Data Exchange (ETDEWEB)
Knowles, M.K.; Borns, D.; Fredrich, J.; Holcomb, D.; Price, R.; Zeuch, D. [Sandia National Labs., Albuquerque, NM (United States); Dale, T.; Van Pelt, R.S. [INTERA, Inc., Austin, TX (United States)
1996-12-01
Deformational processes within a zone of rock surrounding excavations in salt result in alteration of the geophysical and hydrologic properties as compared to the undisturbed condition. The disturbed rock zone offers little resistance to fluid flow. It is hypothesized that rigid inclusions such as concrete seals will arrest and subsequently reverse the disturbance process and induce healing in the disturbed This experiment gathered in situ data that substantiates this hypothesis. A series of tests was conducted in a volume of rock surrounding concrete seals that were placed in a 1-m borehole approximately eight years ago. Fluid flow measurements, measurements of geophysical parameters of the surrounding rock and petrographic analyses on core samples were performed to characterize the rock. This paper presents the testing methodology and summarizes the data gathered from the field test program.
Random Matrix Theory of Rigidity in Soft Matter
Yamanaka, Masanori
2015-06-01
We study the rigidity or softness of soft matter using the characteristic scale of coupling formation developed in random matrix theory. The eigensystems of the timescale-dependent cross-correlation matrix, which are obtained from the time series data of the atomic coordinates of a protein produced by the all-atom molecular dynamics of the solvent, are analyzed. As an example, we present a result for a protein lysozyme, PDBID:1AKI. We find that there are at least three different time scales involved in the coupling formation of correlated sectors of atoms and at least two different time scales for the size of the correlated sectors. These five time scales coexist simultaneously. We compare the results with those of the normal mode analysis and find a crossover of the distribution of the dominant vibrational components.
Asynchronous oscillations of rigid rods drive viscous fluid to swirl
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.
Inertial and viscoelastic forces on rigid colloids in microfluidic channels.
Howard, Michael P; Panagiotopoulos, Athanassios Z; Nikoubashman, Arash
2015-06-14
We perform hybrid molecular dynamics simulations to study the flow behavior of rigid colloids dispersed in a dilute polymer solution. The underlying Newtonian solvent and the ensuing hydrodynamic interactions are incorporated through multiparticle collision dynamics, while the constituent polymers are modeled as bead-spring chains, maintaining a description consistent with the colloidal nature of our system. We study the cross-stream migration of the solute particles in slit-like channels for various polymer lengths and colloid sizes and find a distinct focusing onto the channel center under specific solvent and flow conditions. To better understand this phenomenon, we systematically measure the effective forces exerted on the colloids. We find that the migration originates from a competition between viscoelastic forces from the polymer solution and hydrodynamically induced inertial forces. Our simulations reveal a significantly stronger fluctuation of the lateral colloid position than expected from thermal motion alone, which originates from the complex interplay between the colloid and polymer chains.
Slip Morphology of Elastic Strips on Frictional Rigid Substrates.
Sano, Tomohiko G; Yamaguchi, Tetsuo; Wada, Hirofumi
2017-04-28
The morphology of an elastic strip subject to vertical compressive stress on a frictional rigid substrate is investigated by a combination of theory and experiment. We find a rich variety of morphologies, which-when the bending elasticity dominates over the effect of gravity-are classified into three distinct types of states: pinned, partially slipped, and completely slipped, depending on the magnitude of the vertical strain and the coefficient of static friction. We develop a theory of elastica under mixed clamped-hinged boundary conditions combined with the Coulomb-Amontons friction law and find excellent quantitative agreement with simulations and controlled physical experiments. We also discuss the effect of gravity in order to bridge the difference in the qualitative behaviors of stiff strips and flexible strings or ropes. Our study thus complements recent work on elastic rope coiling and takes a significant step towards establishing a unified understanding of how a thin elastic object interacts vertically with a solid surface.
Complexity management theory: motivation for ideological rigidity and social conflict.
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.
Plasma surface modification of rigid contact lenses decreases bacterial adhesion.
Wang, Yingming; Qian, Xuefeng; Zhang, Xiaofeng; Xia, Wei; Zhong, Lei; Sun, Zhengtai; Xia, Jing
2013-11-01
Contact lens safety is an important topic in clinical studies. Corneal infections usually occur because of the use of bacteria-carrying contact lenses. The current study investigated the impact of plasma surface modification on bacterial adherence to rigid contact lenses made of fluorosilicone acrylate materials. Boston XO and XO2 contact lenses were modified using plasma technology (XO-P and XO2-P groups). Untreated lenses were used as controls. Plasma-treated and control lenses were incubated in solutions containing Staphylococcus aureus or Pseudomonas aeruginosa. MTT colorimetry, colony-forming unit counting method, and scanning electron microscopy were used to measure bacterial adhesion. MTT colorimetry measurements showed that the optical density (OD) values of XO-P and XO2-P were significantly lower than those of XO and XO2, respectively, after incubation with S. aureus (P plasma technology in contact lens surface modification.
Osseous adaptation to continuous loading of rigid endosseous implants
Roberts, W. E.; Smith, R. K.; Mozsary, P. G.; Zilberman, Y.; Smith, R. S.
1984-01-01
The effect of loading on etched Ti implants in the femurs of young (3 mo) and adult (6 mo) rabbits is investigated experimentally. The results are presented in photographs, fluorescence and polarization micrographs, radiographs, and drawings and discussed. Implantation is followed by formation of coarse woven bone within 3 d and mature lamellar bone by 6 wks, with nonspecific subperiosteal bony hypertrophy in the young rabbits only. Spring loading at 100 g produces spontaneous spiral-type fractures when applied immediately, but the implants remain rigid when loads are applied after 6-12 wks of healing. The mechanisms of bone formation involved are examined, and the potential of endosseous implants as anchors in orthodontics or dentofacial-orthopedics is confirmed.
Impedances of rigid cylindrical foundations embedded in transversely isotropic soils
Barros, P. L. A.
2006-06-01
A complete formulation and implementation for assessment of the response to dynamic loads of cylindrical rigid structures embedded in transversely isotropic elastic half-spaces is presented. The analysis is performed in the frequency domain and the steady-state structure response is obtained. The method is based on a non-singular version of the indirect boundary element method which uses influence functions, instead of Green's functions, as fundamental solutions. These influence functions are the response of an elastic half-space to distributed, internally applied loads. The proposed method imposes full bonding contact between the foundation and the surrounding soil. Numerical results for displacement (vertical and horizontal) and rotation (twisting and rocking) impedances, showing the influence of the soil anisotropy, are presented. Results for the soil-structure interface tractions and for the displacement field throughout the half-space are also shown.
A rigid motion correction method for helical computed tomography (CT)
Kim, J.-H.; Nuyts, J.; Kyme, A.; Kuncic, Z.; Fulton, R.
2015-03-01
We propose a method to compensate for six degree-of-freedom rigid motion in helical CT of the head. The method is demonstrated in simulations and in helical scans performed on a 16-slice CT scanner. Scans of a Hoffman brain phantom were acquired while an optical motion tracking system recorded the motion of the bed and the phantom. Motion correction was performed by restoring projection consistency using data from the motion tracking system, and reconstructing with an iterative fully 3D algorithm. Motion correction accuracy was evaluated by comparing reconstructed images with a stationary reference scan. We also investigated the effects on accuracy of tracker sampling rate, measurement jitter, interpolation of tracker measurements, and the synchronization of motion data and CT projections. After optimization of these aspects, motion corrected images corresponded remarkably closely to images of the stationary phantom with correlation and similarity coefficients both above 0.9. We performed a simulation study using volunteer head motion and found similarly that our method is capable of compensating effectively for realistic human head movements. To the best of our knowledge, this is the first practical demonstration of generalized rigid motion correction in helical CT. Its clinical value, which we have yet to explore, may be significant. For example it could reduce the necessity for repeat scans and resource-intensive anesthetic and sedation procedures in patient groups prone to motion, such as young children. It is not only applicable to dedicated CT imaging, but also to hybrid PET/CT and SPECT/CT, where it could also ensure an accurate CT image for lesion localization and attenuation correction of the functional image data.
Rigidity and Fluidity in Living and Nonliving Matter
Lopez, Jorge H.
Many of the standard equilibrium statistical mechanics techniques do not readily apply to non-equilibrium phase transitions such as the fluid-to-disordered solid transition found in repulsive particulate systems. Examples of repulsive particulate systems are sand grains and colloids. The first part of this thesis contributes to methods beyond equilibrium statistical mechanics to ultimately understand the nature of the fluid-to-disordered solid transition, or jamming, from a microscopic basis. In Chapter 2 we revisit the concept of minimal rigidity as applied to frictionless, repulsive soft sphere packings in two dimensions with the introduction of the jamming graph. Minimal rigidity is a purely combinatorial property encoded via Laman's theorem in two dimensions. It constrains the global, average coordination number of the graph, for instance. Minimal rigidity, however, does not address the geometry of local mechanical stability. The jamming graph contains both properties of global mechanical stability at the onset of jamming and local mechanical stability. We demonstrate how jamming graphs can be constructed using local rules via the Henneberg construction such that these graphs are of the constraint percolation type, where percolation is the study of connected structures in disordered networks. We then probe how jamming graphs destabilize, or become fluid-like, by deleting an edge/contact in the graph and computing the resulting rigid cluster distribution. We also uncover a new potentially diverging lengthscale associated with the random deletion of contacts. In Chapter 3 we study several constraint percolation models, such as k-core percolation and counter-balance percolation, on hyperbolic lattices to better understand the role of loops in such models. The constraints in these percolation models incorporate aspects of local mechanical rigidity found in jammed systems. The expectation is that since these models are indeed easier to analyze than the more
Rigid-Plastic Post-Buckling Analysis of Columns and Quadratic Plates
DEFF Research Database (Denmark)
Jönsson, Jeppe
2008-01-01
the compressive load as a function of the transverse displacement. An estimate of the magnitude of the transverse displacement prior to the forming of the collapse mechanism is introduced into the compressive load function, determined by the virtual work equation, thereby revealing a qualified estimate...... yield lines accommodate differential rotations of rigid parts and the area “collapse” yield lines accommodate local area changes of the rigid parts thereby preserving compatibility of the rigid parts of a plate. The approach will be illustrated for rigid plastic column analysis and for a quadratic plate...
SU-F-I-51: CT/MR Image Deformation: The Clinical Assessment QA in Target Delineation
Energy Technology Data Exchange (ETDEWEB)
Yang, C; Chen, Y [Monmouth Medical Center, Long Branch, NJ (United States)
2016-06-15
Purpose: To study the deformation effects in CT/MR image registration of head and neck (HN) cancers. We present a clinical indication in guiding and simplifying registration procedures of this process while CT images possessed artifacts. Methods: CT/MR image fusion provides better soft tissue contrast in intracranial GTV definition with artifacts. However, whether the fusion process should include the deformation process is questionable and not recommended. We performed CT/MR image registration of a HN patient with tonsil GTV and nodes delineation on Varian Velocity™ system. Both rigid transformation and deformable registration of the same CT/MR imaging data were processed separately. Physician’s selection of target delineation was implemented to identify the variations. Transformation matrix was shown with visual identification, as well as the deformation QA numbers and figures were assessed. Results: The deformable CT/MR images were traced with the calculated matrix, both translation and rotational parameters were summarized. In deformable quality QA, the calculated Jacobian matrix was analyzed, which the min/mean/max of 0.73/0/99/1.37, respectively. Jacobian matrix of right neck node was 0.84/1.13/1.41, which present dis-similarity of the nodal area. If Jacobian = 1, the deformation is at the optimum situation. In this case, the deformation results have shown better target delineation for CT/MR deformation than rigid transformation. Though the root-mean-square vector difference is 1.48 mm, with similar rotational components, the cord and vertebrae position were aligned much better in the deformable MR images than the rigid transformation. Conclusion: CT/MR with/without image deformation presents similar image registration matrix; there were significant differentiate the anatomical structures in the region of interest by deformable process. Though vendor suggested only rigid transformation between CT/MR assuming the geometry remain similar, our findings
High mortality risk among individuals assumed to be TB-negative can be predicted using a simple test
DEFF Research Database (Denmark)
Rabna, Paulo; Andersen, Andreas; Wejse, Christian
2009-01-01
OBJECTIVES: To determine mortality among assumed TB negative (aTBneg) individuals in Guinea-Bissau and to investigate whether plasma levels of soluble urokinase receptor (suPAR) can be used to determine post-consultation mortality risk. METHODS: This prospective West-African cohort study included......-up, mortality was 21 per 100 person-year-observation (PYO) among aTBneg individuals and three per 100 PYO among the control population [mortality rate ratio (MRR) = 6.92 (95% CI 4.48-10.7)]. SuPAR values ranged between 0.9 and 45 ng/ml in aTBneg individuals. A log-linear relationship was found between su......PAR levels mortality. In the log-linear range, a 1 ng/ml increase was associated with a 46% increase in the mortality rate: MRR = 1.46 (95% CI 1.34-1.59). The area under the ROC curves was 0.88 for HIV-positive individuals and 0.79 for HIV-negative individuals. CONCLUSIONS: Our study showed...
Wildhaber, Mark L.; Lamberson, Peter J.
2004-01-01
Various mechanisms of habitat choice in fishes based on food and/or temperature have been proposed: optimal foraging for food alone; behavioral thermoregulation for temperature alone; and behavioral energetics and discounted matching for food and temperature combined. Along with development of habitat choice mechanisms, there has been a major push to develop and apply to fish populations individual-based models that incorporate various forms of these mechanisms. However, it is not known how the wide variation in observed and hypothesized mechanisms of fish habitat choice could alter fish population predictions (e.g. growth, size distributions, etc.). We used spatially explicit, individual-based modeling to compare predicted fish populations using different submodels of patch choice behavior under various food and temperature distributions. We compared predicted growth, temperature experience, food consumption, and final spatial distribution using the different models. Our results demonstrated that the habitat choice mechanism assumed in fish population modeling simulations was critical to predictions of fish distribution and growth rates. Hence, resource managers who use modeling results to predict fish population trends should be very aware of and understand the underlying patch choice mechanisms used in their models to assure that those mechanisms correctly represent the fish populations being modeled.
Bourke, Ca
2015-03-01
An astrocyte-associated motor neurone syndrome was produced in molybdenum-deprived sheep fed xanthosine. Mo-deprived sheep fed inosine, adenosine or guanosine would be also expected to develop astrocyte-associated motor neurone syndromes, because all these purine nucleosides can act as neuromodulators and all depend on the Mo-associated enzyme xanthine oxidase-dehydrogenase for their catabolism. To investigate the relationship between inosine ingestion and low Mo concentration, eight sheep were fed lucerne chaff with a Mo value neurone syndrome was produced in three sheep 18-27 months later. It was characterised by diaphragmatic, laryngeal, lingual and pharyngeal muscle weakness. The diaphragmatic muscle weakness was the most severe and potentially lethal. These findings suggest that purinergic neuromodulation of respiration, vocalisation and swallowing is different to that of limb movement. The syndrome produced, and assumed to be caused by the treatment given, has not been reported in livestock. A similar syndrome is seen in human motor neurone disease, but not in equine motor neurone disease, and this is consistent with it being an upper, not a lower, motor neurone effect. © 2015 Australian Veterinary Association.
Directory of Open Access Journals (Sweden)
Ángela Camargo-Uribe
2016-06-01
Full Text Available The paper reports a research that was carried out in order to identify teaching profiles based on the analysis of different ways of assuming communicative interaction in the classroom. Six Science teachers from two public schools of Bogotá, Colombia, participated in the study. They teach Science to 6th, 7th and 8th graders. A sequence of three classes was videotaped for each teacher. Each class was then analyzed to identify the school activities that composed it. Afterwards, each school activity (a total of 138 was described by means of a group of variables that consider the activity as a communicative event. The comparison of the main features that characterize the six teachers’ class activities and an additional multivariate analysis of the descriptions led to the identification of four teaching profiles: the scientific teacher, the classroom teacher, the frontal teacher and the circular teacher. These profiles are described and discuss with respect to the teaching profession.
Federal Laboratory Consortium — [Part of the ATLAS user facility.] The Physics Division operates a target development laboratory that produces targets and foils of various thickness and substrates,...
Kneller, E. A.; Johnson, C. A.; Queffelec, T. A.; Nachtegaele, L.
2010-12-01
Non-rigid deformation in regions of continental extension and compression can lead to large lateral strain and changes in the shape and surface area of continental plates. This large lateral strain in turn leads to vertical strain in the lithosphere, which is a fundamental control on mechanical and thermal subsidence. Traditional plate reconstruction approaches only describe 2D changes in the shape of tectonic plates and do not include lateral strain gradients and vertical strain. Incorporating lateral and vertical strain into kinematic plate tectonic models is necessary for quantifying the past configuration of tectonic plates, modeling paleogeography and for linking subsidence and heat flow to lateral plate motion. Furthermore, traditional approaches are limited to describing processes at the surface of the Earth and cannot be used to investigate 3D slab kinematics. We build on previous work and overcome the limitations of traditional methods by developing an inverse non-rigid continuum-based plate reconstruction approach that links lateral plate tectonic motion to large-scale 4D deformation of continental plates and subducting slabs. We also describe how this approach can be implemented in open source 3D animation software that can be used to create extendable and easily maintained interactive tools. These tools allow the modeler to rapidly reconstruct deformation and map data and constrain plate models with 3D information. The methods presented in this work can improve paleogeographic reconstructions, help visualize complicated 4D deformation processes in a reconstructed framework, and constrain subsidence and lithospheric stretching, all of which are important for understanding thermal history and estimating heat flow in sedimentary basins.
Automatic quantification of multi-modal rigid registration accuracy using feature detectors.
Hauler, F; Furtado, H; Jurisic, M; Polanec, S H; Spick, C; Laprie, A; Nestle, U; Sabatini, U; Birkfellner, W
2016-07-21
In radiotherapy, the use of multi-modal images can improve tumor and target volume delineation. Images acquired at different times by different modalities need to be aligned into a single coordinate system by 3D/3D registration. State of the art methods for validation of registration are visual inspection by experts and fiducial-based evaluation. Visual inspection is a qualitative, subjective measure, while fiducial markers sometimes suffer from limited clinical acceptance. In this paper we present an automatic, non-invasive method for assessing the quality of intensity-based multi-modal rigid registration using feature detectors. After registration, interest points are identified on both image data sets using either speeded-up robust features or Harris feature detectors. The quality of the registration is defined by the mean Euclidean distance between matching interest point pairs. The method was evaluated on three multi-modal datasets: an ex vivo porcine skull (CT, CBCT, MR), seven in vivo brain cases (CT, MR) and 25 in vivo lung cases (CT, CBCT). Both a qualitative (visual inspection by radiation oncologist) and a quantitative (mean target registration error-mTRE-based on selected markers) method were employed. In the porcine skull dataset, the manual and Harris detectors give comparable results but both overestimated the gold standard mTRE based on fiducial markers. For instance, for CT-MR-T1 registration, the mTREman (based on manually annotated landmarks) was 2.2 mm whereas mTREHarris (based on landmarks found by the Harris detector) was 4.1 mm, and mTRESURF (based on landmarks found by the SURF detector) was 8 mm. In lung cases, the difference between mTREman and mTREHarris was less than 1 mm, while the difference between mTREman and mTRESURF was up to 3 mm. The Harris detector performed better than the SURF detector with a resulting estimated registration error close to the gold standard. Therefore the Harris detector was shown to be the more suitable
Weight-bearing ankle dorsiflexion range of motion-can side-to-side symmetry be assumed?
Rabin, Alon; Kozol, Zvi; Spitzer, Elad; Finestone, Aharon S
2015-01-01
In clinical practice, the range of motion (ROM) of the non involved side often serves as the reference for comparison with the injured side. Previous investigations of non-weight-bearing (NWB) ankle dorsiflexion (DF) ROM measurements have indicated bilateral symmetry for the most part. Less is known about ankle DF measured under weight-bearing (WB) conditions. Because WB and NWB ankle DF are not strongly correlated, there is a need to determine whether WB ankle DF is also symmetrical in a healthy population. To determine whether WB ankle DF is bilaterally symmetrical. A secondary goal was to further explore the correlation between WB and NWB ankle DF ROM. Cross-sectional study. Training facility of the Israeli Defense Forces. A total of 64 healthy males (age = 19.6 ± 1.0 years, height = 175.0 ± 6.4 cm, and body mass = 71.4 ± 7.7 kg). Dorsiflexion ROM in WB was measured with an inclinometer and DF ROM in NWB was measured with a universal goniometer. All measurements were taken bilaterally by a single examiner. Weight-bearing ankle DF was greater on the nondominant side compared with the dominant side (P < .001). Non-weight-bearing ankle DF was not different between sides (P = .64). The correlation between WB and NWB DF was moderate, with the NWB DF measurement accounting for 30% to 37% of the variance of the WB measurement. Weight-bearing ankle DF ROM should not be assumed to be bilaterally symmetrical. These findings suggest that side-to-side differences in WB DF may need to be interpreted while considering which side is dominant. The difference in bilateral symmetry between the WB and NWB measurements, as well as the only moderate level of correlation between them, suggests that both measurements should be performed routinely.
Weight-Bearing Ankle Dorsiflexion Range of Motion—Can Side-to-Side Symmetry Be Assumed?
Rabin, Alon; Kozol, Zvi; Spitzer, Elad; Finestone, Aharon S.
2015-01-01
Context: In clinical practice, the range of motion (ROM) of the noninvolved side often serves as the reference for comparison with the injured side. Previous investigations of non–weight-bearing (NWB) ankle dorsiflexion (DF) ROM measurements have indicated bilateral symmetry for the most part. Less is known about ankle DF measured under weight-bearing (WB) conditions. Because WB and NWB ankle DF are not strongly correlated, there is a need to determine whether WB ankle DF is also symmetrical in a healthy population. Objective: To determine whether WB ankle DF is bilaterally symmetrical. A secondary goal was to further explore the correlation between WB and NWB ankle DF ROM. Design: Cross-sectional study. Setting: Training facility of the Israeli Defense Forces. Patients or Other Participants: A total of 64 healthy males (age = 19.6 ± 1.0 years, height = 175.0 ± 6.4 cm, and body mass = 71.4 ± 7.7 kg). Main Outcome Measure(s): Dorsiflexion ROM in WB was measured with an inclinometer and DF ROM in NWB was measured with a universal goniometer. All measurements were taken bilaterally by a single examiner. Results: Weight-bearing ankle DF was greater on the nondominant side compared with the dominant side (P < .001). Non–weight-bearing ankle DF was not different between sides (P = .64). The correlation between WB and NWB DF was moderate, with the NWB DF measurement accounting for 30% to 37% of the variance of the WB measurement. Conclusions: Weight-bearing ankle DF ROM should not be assumed to be bilaterally symmetrical. These findings suggest that side-to-side differences in WB DF may need to be interpreted while considering which side is dominant. The difference in bilateral symmetry between the WB and NWB measurements, as well as the only moderate level of correlation between them, suggests that both measurements should be performed routinely. PMID:25329350
Lee, Hyung Joo; Aparecida de Mattias Sartori, Ivete; Alcântara, Paola Rebelatto; Vieira, Rogéria Acedo; Suzuki, Dalton; Gasparini Kiatake Fontão, Flávia; Tiossi, Rodrigo
2012-12-01
Primary and secondary stabilities of immediately loaded mandibular implants restored with fixed prostheses (FP) using rigid or semi-rigid splinting systems were clinically and radiographically evaluated. Fifteen edentulous patients were rehabilitated using hybrid FP; each had 5 implants placed between the mental foramens. Two groups were randomly divided: group 1-FP with the conventional rigid bar splinting the implants and group 2-semi-rigid cantilever extension system with titanium bars placed in the 2 distal abutment cylinders. Primary stability was evaluated using resonance frequency analysis after installation of the implant abutments. The measurements were made at 3 times: T0, at baseline; T1, 4 months after implant placement; and T2, 8 months after implant placement. Presence of mobility and inflammation in the implant surrounding regions were checked. Stability data were submitted to statistical analysis for comparison between groups (P < 0.05). Implant survival rate for the implants was of 100% in both groups. No significant differences in the mean implant stability quotient values were found for both groups from baseline and after the 8-month follow-up. The immediate loading of the implants was satisfactory, and both splinting conditions (rigid and semi-rigid) can be successfully used for the restoration of edentulous mandibles.
Oxygen diffusion and edema with modern scleral rigid gas permeable contact lenses.
Compañ, Vicente; Oliveira, Cristina; Aguilella-Arzo, Marcel; Mollá, Sergio; Peixoto-de-Matos, Sofia C; González-Méijome, José M
2014-09-04
We defined the theoretical oxygen tension behind modern scleral contact lenses (CLs) made of different rigid gas permeable (RGP) materials, assuming different thickness of the tear layer behind the lens. A second goal was to show clinically the effect of the postlens tear film on corneal swelling. We simulated the partial pressure of oxygen across the cornea behind scleral CLs made of different lens materials (oxygen permeability Dk, 75-200 barrer) and different thickness (Tav, 100-300 μm). Postlens tear film thicknesses (Tpost-tear) ranging from 150 to 350 μm were considered. Eight healthy subjects were fitted randomly with a scleral lens with a thin and a thick postlens tear layer in two different sessions for a period of 3 hours under open-eye conditions. The CLs with less than 125 barrer of Dk and a thickness over 200 μm depleted the oxygen availability at the lens-cornea interface below 55 mm Hg for a postlens tear film of 150 μm. For a postlens tear film thickness of 350 μm, no combination of material or lens thickness will meet the criteria of 55 mm Hg. Our clinical measures of corneal edema showed that this was significantly higher (P oxygen permeability and up to 200 μm thick to avoid hypoxic effects even under open eye conditions. Postlens tear film layer should be below 150 μm to avoid clinically significant edema. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.
Large scale Brownian dynamics of confined suspensions of rigid particles.
Sprinkle, Brennan; Balboa Usabiaga, Florencio; Patankar, Neelesh A; Donev, Aleksandar
2017-12-28
We introduce methods for large-scale Brownian Dynamics (BD) simulation of many rigid particles of arbitrary shape suspended in a fluctuating fluid. Our method adds Brownian motion to the rigid multiblob method [F. Balboa Usabiaga et al., Commun. Appl. Math. Comput. Sci. 11(2), 217-296 (2016)] at a cost comparable to the cost of deterministic simulations. We demonstrate that we can efficiently generate deterministic and random displacements for many particles using preconditioned Krylov iterative methods, if kernel methods to efficiently compute the action of the Rotne-Prager-Yamakawa (RPY) mobility matrix and its "square" root are available for the given boundary conditions. These kernel operations can be computed with near linear scaling for periodic domains using the positively split Ewald method. Here we study particles partially confined by gravity above a no-slip bottom wall using a graphical processing unit implementation of the mobility matrix-vector product, combined with a preconditioned Lanczos iteration for generating Brownian displacements. We address a major challenge in large-scale BD simulations, capturing the stochastic drift term that arises because of the configuration-dependent mobility. Unlike the widely used Fixman midpoint scheme, our methods utilize random finite differences and do not require the solution of resistance problems or the computation of the action of the inverse square root of the RPY mobility matrix. We construct two temporal schemes which are viable for large-scale simulations, an Euler-Maruyama traction scheme and a trapezoidal slip scheme, which minimize the number of mobility problems to be solved per time step while capturing the required stochastic drift terms. We validate and compare these schemes numerically by modeling suspensions of boomerang-shaped particles sedimented near a bottom wall. Using the trapezoidal scheme, we investigate the steady-state active motion in dense suspensions of confined microrollers, whose
Large scale Brownian dynamics of confined suspensions of rigid particles
Sprinkle, Brennan; Balboa Usabiaga, Florencio; Patankar, Neelesh A.; Donev, Aleksandar
2017-12-01
We introduce methods for large-scale Brownian Dynamics (BD) simulation of many rigid particles of arbitrary shape suspended in a fluctuating fluid. Our method adds Brownian motion to the rigid multiblob method [F. Balboa Usabiaga et al., Commun. Appl. Math. Comput. Sci. 11(2), 217-296 (2016)] at a cost comparable to the cost of deterministic simulations. We demonstrate that we can efficiently generate deterministic and random displacements for many particles using preconditioned Krylov iterative methods, if kernel methods to efficiently compute the action of the Rotne-Prager-Yamakawa (RPY) mobility matrix and its "square" root are available for the given boundary conditions. These kernel operations can be computed with near linear scaling for periodic domains using the positively split Ewald method. Here we study particles partially confined by gravity above a no-slip bottom wall using a graphical processing unit implementation of the mobility matrix-vector product, combined with a preconditioned Lanczos iteration for generating Brownian displacements. We address a major challenge in large-scale BD simulations, capturing the stochastic drift term that arises because of the configuration-dependent mobility. Unlike the widely used Fixman midpoint scheme, our methods utilize random finite differences and do not require the solution of resistance problems or the computation of the action of the inverse square root of the RPY mobility matrix. We construct two temporal schemes which are viable for large-scale simulations, an Euler-Maruyama traction scheme and a trapezoidal slip scheme, which minimize the number of mobility problems to be solved per time step while capturing the required stochastic drift terms. We validate and compare these schemes numerically by modeling suspensions of boomerang-shaped particles sedimented near a bottom wall. Using the trapezoidal scheme, we investigate the steady-state active motion in dense suspensions of confined microrollers, whose
Space geodetic constraints on plate rigidity and global plate motions
Sella, Giovanni Federico
The Global Positioning System (GPS) has emerged over the last 10 years as the premier space geodetic technique for geologic observation with the benefits of both accuracy and economy. GPS data from more than 260 stations were processed utilizing GIPSY-OASIS software, and all available RINEX files for these stations beginning on January 1, 1993. The uniform processing strategy, combined with a rigorous independent error estimate of site velocities and the broad geographical distribution of these sites resulted in a global high-precision surface velocity data set. This data set has been used to: (1) compare the effects of different GPS antenna and monument types on data noise; (2) examine in detail the rigidity of the North America plate; (3) constrain the rate of deformation in the northern Gulf of Mexico; (4) define a model for Recent (Holocene) time global plate motions. The weighted root mean square scatter about the best fit line through the daily position estimates are used to assess the effects of different antenna and monument types on North America. The data set is sensitive to glacial isostatic adjustment as indicated by the decrease in chinu 2 from 1.3 to 1.0 by excluding those sites on rigid North America within a radius of 1,800 km of Hudson Bay. The resulting 64 site solution for the angular velocity of North America give a mean rate residual of 1 mm/yr. GULFNET, a regional GPS network created in 1997 in the northern Gulf Coast to measure strain across this active "passive margin" is described. Preliminary results suggest that deformation is occurring as predicted by the regional paradigm for deformation, i.e. Gulfward motion along normal faults. A new model for Recent global plate velocities (REVEL) describes the relative velocities of 14 plates. For several plate pairs, statistically significant differences are observed between the geodetically and geologically determined velocities reflecting changes in plate velocity through time. Some of the rate
[Aphakia correction with rigid contact lenses in congenital cataract].
Loudot, C; Jourdan, F; Benso, C; Denis, D
2012-10-01
To describe follow-up and evaluate functional results of rigid gas-permeable contact lens wear for the correction of aphakia in infants after surgery for congenital cataract. This retrospective study was performed on 23 eyes of 17 children (12 boys and five girls), between three days and 36 months of age (median 3.5 months), undergoing cataract extraction without primary intraocular lens implantation and fitted only with Menicon(®) Z material contact lenses. Initial fitting visits included history and family education. Subsequent examinations were performed at eight days, 15 days, 1 month, 6 months and 1 year. The four main parameters studied were fit characteristics, ease of manipulation, ocular integrity and lens integrity. Concurrently, functional results (visual acuity, oculomotor balance) and various prognostic factors (associated pathology, age at time of surgery, cataract density, unilaterality versus bilaterality, postoperative complications) were evaluated. Rigorous systematic amblyopia rehabilitation was performed. At the one-month exam, 60% of parents demonstrated proficiency with manipulating the lens. On one-year follow-up, three cases of failure were attributable to difficulties with lens manipulation. At one year, one infectious complication was detected. The lens material demonstrated good resistance to breakage (9% at one month) and only a mild tendency toward deposits (few or no deposits in 95% of cases at 1 month). With regard to visual outcome, among the children old enough to cooperate, visual acuity was better than 3/10 for nine out of 12 eyes, of which five eyes were 10/10. With regard to alignment, we noted 12 cases (70.6%) of strabismus postoperatively (ten esotropia, two exotropia). The factors predictive of good visual acuity correlated with those described in the literature: partial cataract, bilateral cataract, and absence of postoperative oculomotor disturbance. The characteristics of rigid gas-permeable contact lenses provide safety
Port-Based Modeling and Simulation of Mechanical Systems With Rigid and Flexible Links
Macchelli, A.; Melchiorri, C.; Stramigioli, Stefano
2009-01-01
In this paper, a systematic procedure for the defi- nition of the dynamical model in port-Hamiltonian form of me- chanical systems is presented as the result of the power-conserving interconnection of a set of basic components (rigid bodies, flexible links, and kinematic pairs). Since rigid bodies
Risk of perforation using rigid oesophagoscopy in the distal part of oesophagus
DEFF Research Database (Denmark)
Wennervaldt, Kasper; Melchiors, Jacob
2012-01-01
Endoscopic examination and treatment of disorders in the oesophagus have been a part of the otolaryngological specialty since the introduction of the rigid endoscope. Today, both flexible and rigid oesophagoscopy (RO) is used to that end. The aim of this study was to evaluate the safety of the RO....
30 CFR 7.28 - Test for flame resistance of rigid ventilation tubing.
2010-07-01
... material that falls on the floor of the test gallery during the igniting period. However, the suspended... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Test for flame resistance of rigid ventilation... and Ventilation Tubing § 7.28 Test for flame resistance of rigid ventilation tubing. (a) Test...
Mental set and creative thought in social conflict : Threat rigidity versus motivated focus
De Dreu, Carsten K. W.; Nijstad, Bernard A.
According to the traditional threat-rigidity reasoning, people in social conflict will be less flexible, less creative, more narrow-minded, and more rigid in their thinking when they adopt a conflict rather than a cooperation mental set. The authors propose and test an alternative, motivated focus
Rigid covariance as a natural extension of Painlev\\'e--Gullstrand space-times: gravitational waves
Jaén, Xavier
2016-01-01
The group of rigid motions is considered to guide the search for a natural system of space-time coordinates in General Relativity. This search leads us to a natural extension of the space-times that support Painlev\\'{e}--Gullstrand synchronization. As an interesting example, here we describe a system of rigid coordinates for the cross mode of gravitational linear plane waves.
21 CFR 886.5918 - Rigid gas permeable contact lens care products.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rigid gas permeable contact lens care products. 886.5918 Section 886.5918 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5918 Rigid gas permeable contact lens care products. (a)...
The general motion of three mutually-interacting, axisymmetric spherical rigid bodies
El-Shaboury, S. M.; Dessoky, A. E. A.
1991-05-01
In this paper, the translational-rotational motions of an axisymmetric rigid body and two spherical rigid bodies under the influence of their mutual gravitational attraction are considered. The equations of motion in the canonical elements of Delaunay-Andoyer are obtained. The elements of motion in the zero and first approximations can be determined.
Effect of various factors on the rigidity of furniture cases | Tankut ...
African Journals Online (AJOL)
In general, the stiffer the end connection, the less the deflection of the case was observed. The results also indicated that rigidity of case furniture comes mainly from the gluing of the joining surfaces. Therefore, knowing the rigidity of the case furniture made of wood composites is fundamental to the design of safe, cost ...
Understanding Behavioural Rigidity in Autism Spectrum Conditions: The Role of Intentional Control
Poljac, Edita; Hoofs, Vincent; Princen, Myrthe M.; Poljac, Ervin
2017-01-01
Although behavioural rigidity belongs to the core symptoms of autism spectrum conditions, little is known about its underlying cognitive mechanisms. The current study investigated the role of intentional control mechanisms in behavioural rigidity in autism. Autistic individuals and their matched controls were instructed to repeatedly choose…
A new cantilever beam-rigid-body MEMS gyroscope: mathematical model and linear dynamics
Lajimi, Seyed Amir Mousavi; Abdel-Rahman, Eihab
2014-01-01
A new microbeam-rigid-body gyroscope is introduced and its static and dynamic behaviours are studied. The main structure includes a microbeam and an eccentric end-rigid-body influencing the dynamic and static characteristics of the sensor. The sensitivity of the device and the effect of system parameters on the microsystem's response are investigated.
21 CFR 177.1010 - Acrylic and modified acrylic plastics, semirigid and rigid.
2010-04-01
... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylic and modified acrylic plastics, semirigid... Acrylic and modified acrylic plastics, semirigid and rigid. Semirigid and rigid acrylic and modified acrylic plastics may be safely used as articles intended for use in contact with food, in accordance with...
21 CFR 178.3790 - Polymer modifiers in semirigid and rigid vinyl chloride plastics.
2010-04-01
... chloride plastics. 178.3790 Section 178.3790 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF... modifiers in semirigid and rigid vinyl chloride plastics. The polymers identified in paragraph (a) of this... semirigid and rigid vinyl chloride plastic food-contact articles prepared from vinyl chloride homopolymers...
The shape of a drop between two rigid fibers
Protiere, Suzie; Duprat, Camille; Stone, Howard A.
2012-11-01
Wetting of fibrous media is observed in many engineered systems, e.g. filters, textiles, paper etc. and may also be found in Nature (e.g. hair or feathers). To understand the basic response of such material when interacting with a liquid we study the model system of a finite volume of liquid on two parallel rigid fibers. A liquid wetting the fibers can adopt two distinct equilibrium shapes: a compact hemispherical drop shape or a long liquid column of constant cross-section. These two morphologies depend on the inter-fiber distance, the liquid volume, the fiber radius and the liquid-fiber contact angle. We study the transitions between a drop shape and a column by incrementally varying the inter-fiber distance and find that the transition depends on the global geometry of the system as well as on the volume of liquid. More surprisingly we find that these two morphological states may coexist for certain parameter values. These switches in morphologies may be used to manipulate or transport liquid at a small scale.
Bevel toric multicurve rigid gas-permeable lens for keratoconus.
Yanai, Ryoji; Ueda, Kiichi; Sonoda, Koh-Hei
2013-03-01
To evaluate the efficacy and safety of Twinbel bevel toric, a newly designed rigid gas-permeable (RGP) lens with a toric bevel curvature, for keratoconus. A retrospective analysis of nine eyes of patients with keratoconus who had been wearing RGP contact lenses and were switched to Twinbel bevel toric at Yamaguchi University Hospital. Visual acuity and contrast sensitivity were measured under photopic conditions. Complaint symptoms were recorded as primary outcome measures at follow-up visits. Efficacy and safety were evaluated at 12 weeks after the switch to Twinbel bevel toric or later. Five eyes (55.6 %) showed an improvement in visual acuity with Twinbel bevel toric compared with the previous lens, whereas four eyes (44.4 %) maintained the same visual acuity as before. The mean best corrected visual acuity ± SD with Twinbel bevel toric was 0.01 ± 0.40 logMAR, significantly better (P = 0.044, paired Student's t test) than that (0.23 ± 0.51 logMAR) with the previous lens. Contrast sensitivity and subjective complaint scores did not differ significantly between Twinbel bevel toric and the previous lens. No serious complications of Twinbel bevel toric wear were observed. Fitting of Twinbel bevel toric improved visual acuity in eyes affected by keratoconus, thus providing a viable alternative for management of such eyes.
Non-rigid registration of cervical spine MRI volumes.
Aktar, Mst Nargis; Alam, Md Jahangir; Pickering, Mark; Webb, Alexandra; Perriman, Diana
2015-01-01
Whiplash is the colloquial term for neck injuries caused by sudden extension of the cervical spine. Patients with chronic whiplash associated disorder (WAD) can experience neck pain for many years after the original injury. Researchers have found some evidence to suggest that chronic whiplash is related to the amount of intra-muscular fat in the cervical spine muscles. Hence, an important step towards developing a treatment for chronic WAD is a technique to accurately and efficiently measure the amount of intra-muscular fat in the muscles of the cervical spine. Our proposed technique for making this measurement is to automatically segment the cervical spine muscles using a fused volume created from multi-modal MRI volumes of the cervical spine. Multiple modes are required to enhance the boundaries between the different muscles to assist the following automatic segmentation process. However, before these multiple modes can be fused it is first necessary to accurately register these volumes. Hence, in this paper, we have proposed a new non-rigid multi-modal registration algorithm using the sum of conditional variance (SCV) with partial volume interpolation (PVI) similarity measure and Gauss-Newton (GN) optimization for the accurate registration of multi-modal cervical spine MRI volumes. The performance of the proposed approach is compared with the existing SCV based registration algorithm and the sum of the conditional squared deviation from the mode (SCSDM) method. The experimental results demonstrate that the proposed approach provides superior performance than the best existing approaches.
Rigid sphere room impulse response simulation: algorithm and applications.
Jarrett, D P; Habets, E A P; Thomas, M R P; Naylor, P A
2012-09-01
Simulated room impulse responses have been proven to be both useful and indispensable for comprehensive testing of acoustic signal processing algorithms while controlling parameters such as the reverberation time, room dimensions, and source-array distance. In this work, a method is proposed for simulating the room impulse responses between a sound source and the microphones positioned on a spherical array. The method takes into account specular reflections of the source by employing the well-known image method, and scattering from the rigid sphere by employing spherical harmonic decomposition. Pseudocode for the proposed method is provided, taking into account various optimizations to reduce the computational complexity. The magnitude and phase errors that result from the finite order spherical harmonic decomposition are analyzed and general guidelines for the order selection are provided. Three examples are presented: an analysis of a diffuse reverberant sound field, a study of binaural cues in the presence of reverberation, and an illustration of the algorithm's use as a mouth simulator.
Non-rigid registration for qualitiy control of printed materials
Badshah, Amir; O'Leary, Paul; Harker, Matthew; Sallinger, Christian
2011-07-01
This paper presents a new approach to non-rigid elastic registration. The method is applied to hyper spectral imaging data for the automatic quality control of decorative foils which are subject to deformation during lamination. A new image decimation procedure based on Savitzky-Golay smoothing is presented and applied in a multiresolution pyramid. Modified Fourier basis functions implemented by projection onto the orthogonal complement of a truncated Gram polynomial basis are presented. The modified functions are used to compute spectra whereby the Gibbs error associated with local gradients in the image are reduced. The paper also presents the first direct linear solution to weighted tensor product polynomial approximation. This method is used to regularize the patch coordinates, the solution is equivalent to a Galerkin type solution to a partial differential equations. The new solution is applied to published standard data set and to data acquired in a production environment. The speed of the new solution justifies explicit reference: the present solution implemented in MATLAB requires approximatly 1.3s to register an image of size 800 ×× 500 pixels. This is approximately a factor 10 to 100 faster than previously published results for the same data set.
A Condition Number for Non-Rigid Shape Matching
Ovsjanikov, Maks
2011-08-01
© 2011 The Author(s). Despite the large amount of work devoted in recent years to the problem of non-rigid shape matching, practical methods that can successfully be used for arbitrary pairs of shapes remain elusive. In this paper, we study the hardness of the problem of shape matching, and introduce the notion of the shape condition number, which captures the intuition that some shapes are inherently more difficult to match against than others. In particular, we make a connection between the symmetry of a given shape and the stability of any method used to match it while optimizing a given distortion measure. We analyze two commonly used classes of methods in deformable shape matching, and show that the stability of both types of techniques can be captured by the appropriate notion of a condition number. We also provide a practical way to estimate the shape condition number and show how it can be used to guide the selection of landmark correspondences between shapes. Thus we shed some light on the reasons why general shape matching remains difficult and provide a way to detect and mitigate such difficulties in practice.
Rigid fibrescope Bonfils: use in simulated difficult airway by novices
Directory of Open Access Journals (Sweden)
Piepho Tim
2009-07-01
Full Text Available Abstract Background The Bonfils intubation fibrescope is a promising alternative device for securing the airway. We examined the success rate of intubation and the ease of use in standardized simulated difficult airway scenarios by physicians. We compared the Bonfils to a classical laryngoscope with Macintosh blade. Methods 30 physicians untrained in the use of rigid fibrescopes but experienced in airway management performed endotracheal intubation in an airway manikin (SimMan, Laerdal, Kent, UK with three different airway conditions. We evaluated the success rate using the Bonfils (Karl Storz, Tuttlingen, Germany or the Macintosh laryngoscope, the time needed for securing the airway, and subjective rating of both techniques. Results In normal airway all intubations were successful using laryngoscope (100% vs. 82% using the Bonfils (p Conclusion The Bonfils can be successfully used by physicians unfamiliar with this technique in an airway manikin. The airway could be secured with at least the same success rate as using a Macintosh laryngoscope in difficult airway scenarios. Use of the Bonfils did not delay intubation in the presence of a difficult airway. These results indicate that intensive special training is advised to use the Bonfils effectively in airway management.
Impact of a Liquid Cone on a Plain Rigid Wall
Directory of Open Access Journals (Sweden)
A.A. Aganin
2016-03-01
Full Text Available A numerical study of high-speed (with the velocity of 250 m/s impact of a liquid cone (cone-like jet on a plain rigid wall has been performed. The range of the angles of inclination of the cone surface to the wall corresponds to that of their variation in the process of impact on the wall of a cylindrical jet with the semi-spherical end. The direct numerical simulation has been used on the basis of the gas dynamics equations by the CIP-CUP method on the dynamically adaptive Soroban-grids without explicit tracking of the interphase boundary. It has been found that three regimes of impact are set in the examined range of the angles. At the small angles the impact with shock wave attached to the wall without liquid spreading is realized. An abrupt transition to the regime with the shock wave detached from the wall together with the radial jet of the liquid spreading on the wall takes place with increasing the angle. A smooth transition to the shockless regime with the radial liquid jet is realized with further increasing the angle.
Optical characterization and polarization calibration for rigid endoscopes
Garcia, Missael; Gruev, Viktor
2017-02-01
Polarization measurements give orthogonal information to spectral images making them a great tool in the characterization of environmental parameters in nature. Thus, polarization imagery has proven to be remarkably useful in a vast range of biomedical applications. One such application is the early diagnosis of flat cancerous lesions in murine colorectal tumor models, where polarization data complements NIR fluorescence analysis. Advances in nanotechnology have led to compact and precise bio-inspired imaging sensors capable of accurately co-registering multidimensional spectral and polarization information. As more applications emerge for these imagers, the optics used in these instruments get very complex and can potentially compromise the original polarization state of the incident light. Here we present a complete optical and polarization characterization of three rigid endoscopes of size 1.9mm x 10cm (Karl Storz, Germany), 5mm x 30cm, and 10mm x 33cm (Olympus, Germany), used in colonoscopy for the prevention of colitis-associated cancer. Characterization results show that the telescope optics act as retarders and effectively depolarize the linear component. These incorrect readings can cause false-positives or false-negatives leading to an improper diagnosis. In this paper, we offer a polarization calibration scheme for these endoscopes based on Mueller calculus. By modeling the optical properties from training data as real-valued Mueller matrices, we are able to successfully reconstruct the initial polarization state acquired by the imaging system.
Glass fiber and silica reinforced rigid polyurethane foams
Directory of Open Access Journals (Sweden)
M. W. Kim
2017-05-01
Full Text Available Ternary composites of rigid polyurethane foam (RPUF/glass fiber/silica as well as RPUF/glass fiber have been fabricated from glass fiber, silica, polymeric 4,4′-di-phenylmethane diisocyanate (PMDI and polyol using HFC 365mfc as blowing agent. Foam formation kinetics, morphology, thermal conductivity, glass transition temperature, decomposition temperatures as well as the mechanical strengths of the foam have been studied. With the addition an increasing amount of glass fiber cream time, rise time, gel time, tack free time, density, compression strength, thermal conductivity (k monotonically increased while the glass transition temperature showed a maximum at 2%. At constant glass fiber content (2%, addition of silica further increased the process times, density and compression strength while the Tg and thermal decomposition temperature showed a maximum at 3% silica. The k value of RFUF/glass fiber composite decreased with the addition of silica up to 3%, where it was even lower than the virgin RPUF. However, beyond the content k value increased. Overall, the variation of k value with silica content showed identical tendency with cells size and closed cells content.
Collapsed fat navigators for brain 3D rigid body motion.
Engström, Mathias; Mårtensson, Magnus; Avventi, Enrico; Norbeck, Ola; Skare, Stefan
2015-10-01
To acquire high-resolution 3D multi-slab echo planar imaging data without motion artifacts, using collapsed fat navigators. A fat navigator module (collapsed FatNav) was added to a diffusion-weighted 3D multi-slab echo planar imaging (DW 3D-MS EPI) sequence, comprising three orthogonal echo planar imaging readouts to track rigid body head motion in the image domain and performing prospective motion correction. The stability, resolution and accuracy of the navigator were investigated on phantoms and healthy volunteers. The experiments on phantoms and volunteers show that the navigator, depicting projections of the subcutaneous fat in of the head, is capable of correcting for head motion with insignificant bias compared to motion estimates derived from the water-signaling DWI images. Despite that this projection technique implies a non-sparse image appearance, collapsed FatNav data could be highly accelerated with parallel imaging, allowing three orthogonal 2D EPI readouts in about 6ms. By utilizing signal from the leading fat saturation RF pulse of the diffusion sequence, only the readout portion of the navigator needs to be added, resulting in a scan time penalty of only about 5%. Motion can be detected and corrected for with a 5-10Hz update frequency when combined with a sequence like the DW 3D-MS EPI. Copyright © 2015 Elsevier Inc. All rights reserved.
Canonical formalism for modelling and control of rigid body dynamics.
Gurfil, P
2005-12-01
This paper develops a new paradigm for stabilization of rigid-body dynamics. The state-space model is formulated using canonical elements, known as the Serret-Andoyer (SA) variables, thus far scarcely used for engineering applications. The main feature of the SA formalism is the reduction of the dynamics via the underlying symmetry stemming from conservation of angular momentum and rotational kinetic energy. The controllability of the system model is examined using the notion of accessibility, and is shown to be accessible from all points. Based on the accessibility proof, two nonlinear asymptotic feedback stabilizers are developed: a damping feedback is designed based on the Jurdjevic-Quinn method, and a Hamiltonian controller is derived by using the Hamiltonian as a natural Lyapunov function for the closed-loop dynamics. It is shown that the Hamiltonian control is both passive and inverse optimal with respect to a meaningful performance index. The performance of the new controllers is examined and compared using simulations of realistic scenarios from the satellite attitude dynamics field.
Unifying Rigid and Soft Bodies Representation: The Sulfur Physics Engine
Directory of Open Access Journals (Sweden)
Dario Maggiorini
2014-01-01
Full Text Available Video games are (also real-time interactive graphic simulations: hence, providing a convincing physics simulation for each specific game environment is of paramount importance in the process of achieving a satisfying player experience. While the existing game engines appropriately address many aspects of physics simulation, some others are still in need of improvements. In particular, several specific physics properties of bodies not usually involved in the main game mechanics (e.g., properties useful to represent systems composed by soft bodies, are often poorly rendered by general-purpose engines. This issue may limit game designers when imagining innovative and compelling video games and game mechanics. For this reason, we dug into the problem of appropriately representing soft bodies. Subsequently, we have extended the approach developed for soft bodies to rigid ones, proposing and developing a unified approach in a game engine: Sulfur. To test the engine, we have also designed and developed “Escape from Quaoar,” a prototypal video game whose main game mechanic exploits an elastic rope, and a level editor for the game.
Obstacles to developing sustainable cities: the real estate rigidity trap
Directory of Open Access Journals (Sweden)
V. Kelly Turner
2017-06-01
Full Text Available Sprawl patterns of urbanization have large environmental consequences, and sustainable alternatives to conventional urban patterns of development have been promoted by a subset of planners, design professionals, and municipalities. These alternatives have not been widely adopted among real estate developers, actors with large influence over urban form and function. Existing explanations for this failure enumerate market and regulatory barriers but do not sufficiently describe the institutional structures that allow conventional approaches to prevail. A failure of real estate developers to adopt alternative forms of development can best be described in terms of a rigidity trap. Specifically, norms of practice within the real estate development industry combine with market and regulatory factors to favor existing practices and limit innovation. Moreover, these institutional factors also buffer the real estate development industry from feedback mechanisms and external signals that might otherwise trigger adaptation. Addressing the environmental consequences of urbanization not only requires novel approaches to urban design, but will also necessitate addressing systemic pathologies in the design implementation process.
Microscopic theory of topologically entangled fluids of rigid macromolecules
Sussman, Daniel M.; Schweizer, Kenneth S.
2011-06-01
We present a first-principles theory for the slow dynamics of a fluid of entangling rigid crosses of zero excluded volume based on a generalization of the dynamic mean-field approach of Szamel for infinitely thin nonrotating rods. The latter theory exactly includes topological constraints at the two-body collision level and self-consistently renormalizes an effective diffusion tensor to account for many-body effects. Remarkably, it predicts scaling laws consistent with the phenomenological reptation-tube predictions of Doi and Edwards for the long-time diffusion and the localization length in the heavily entangled limit. We generalize this approach to a different macromolecular architecture, infinitely thin three-dimensional crosses, and also extend the range of densities over which a dynamic localization length can be calculated for rods. Ideal gases of nonrotating crosses have recently received attention in computer simulations and are relevant as a simple model of both a strong-glass former and entangling star-branched polymers. Comparisons of our theory with these simulations reveal reasonable agreement for the magnitude and reduced density dependence of the localization length and also the self-diffusion constant if the consequences of local density fluctuations are taken into account.
Active elastic dimers: Cells moving on rigid tracks
Lopez, J. H.; Das, Moumita; Schwarz, J. M.
2014-09-01
Experiments suggest that the migration of some cells in the three-dimensional extracellular matrix bears strong resemblance to one-dimensional cell migration. Motivated by this observation, we construct and study a minimal one-dimensional model cell made of two beads and an active spring moving along a rigid track. The active spring models the stress fibers with their myosin-driven contractility and α-actinin-driven extendability, while the friction coefficients of the two beads describe the catch and slip-bond behaviors of the integrins in focal adhesions. In the absence of active noise, net motion arises from an interplay between active contractility (and passive extendability) of the stress fibers and an asymmetry between the front and back of the cell due to catch-bond behavior of integrins at the front of the cell and slip-bond behavior of integrins at the back. We obtain reasonable cell speeds with independently estimated parameters. We also study the effects of hysteresis in the active spring, due to catch-bond behavior and the dynamics of cross linking, and the addition of active noise on the motion of the cell. Our model highlights the role of α-actinin in three-dimensional cell motility and does not require Arp2/3 actin filament nucleation for net motion.
Finite Element Investigation of the Deterioration of Doweled Rigid Pavements
Ghauch, Ziad G
2011-01-01
The purpose of this study is to describe the failure of concrete around dowel bars in jointed rigid pavements, and the resulting effect on the pavement performance. In fact, under repetitive vehicle loading, concrete in contact with the dowel bar deteriorates, particularly at the joint face. The degradation of concrete around the dowel negatively affects the latter's performance in terms of transferring wheel loads through vertical shear action. In this context, a nonlinear 3D Finite Element analysis was performed using the commercial FE code Abaqus (v-6.11). The FE model was validated with classical analytical solutions of shear and moment along the dowel. A concrete damaged plasticity model was used for the PCC slab to model the degradation of concrete matrix around the dowels under incremental loading. Results obtained show, among other things, that the degradation of concrete matrix around the dowel was found to initiate at the face of the joint and propagate towards the interior of the dowel. Also, resul...
Thermally-Induced Structural Disturbances of Rigid Panel Solar Arrays
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.
Semi-Implicit Reversible Algorithms for Rigid Body Rotational Dynamics
Energy Technology Data Exchange (ETDEWEB)
Nukala, Phani K [ORNL; Shelton Jr, William Allison [ORNL
2006-09-01
This paper presents two semi-implicit algorithms based on splitting methodology for rigid body rotational dynamics. The first algorithm is a variation of partitioned Runge-Kutta (PRK) methodology that can be formulated as a splitting method. The second algorithm is akin to a multiple time stepping scheme and is based on modified Crouch-Grossman (MCG) methodology, which can also be expressed as a splitting algorithm. These algorithms are second-order accurate and time-reversible; however, they are not Poisson integrators, i.e., non-symplectic. These algorithms conserve some of the first integrals of motion, but some others are not conserved; however, the fluctuations in these invariants are bounded over exponentially long time intervals. These algorithms exhibit excellent long-term behavior because of their reversibility property and their (approximate) Poisson structure preserving property. The numerical results indicate that the proposed algorithms exhibit superior performance compared to some of the currently well known algorithms such as the Simo-Wong algorithm, Newmark algorithm, discrete Moser-Veselov algorithm, Lewis-Simo algorithm, and the LIEMID[EA] algorithm.
Use of Terrestrial Laser Scanner for Rigid Airport Pavement Management.
Barbarella, Maurizio; D'Amico, Fabrizio; De Blasiis, Maria Rosaria; Di Benedetto, Alessandro; Fiani, Margherita
2017-12-26
The evaluation of the structural efficiency of airport infrastructures is a complex task. Faulting is one of the most important indicators of rigid pavement performance. The aim of our study is to provide a new method for faulting detection and computation on jointed concrete pavements. Nowadays, the assessment of faulting is performed with the use of laborious and time-consuming measurements that strongly hinder aircraft traffic. We proposed a field procedure for Terrestrial Laser Scanner data acquisition and a computation flow chart in order to identify and quantify the fault size at each joint of apron slabs. The total point cloud has been used to compute the least square plane fitting those points. The best-fit plane for each slab has been computed too. The attitude of each slab plane with respect to both the adjacent ones and the apron reference plane has been determined by the normal vectors to the surfaces. Faulting has been evaluated as the difference in elevation between the slab planes along chosen sections. For a more accurate evaluation of the faulting value, we have then considered a few strips of data covering rectangular areas of different sizes across the joints. The accuracy of the estimated quantities has been computed too.
Use of Terrestrial Laser Scanner for Rigid Airport Pavement Management
Directory of Open Access Journals (Sweden)
Maurizio Barbarella
2017-12-01
Full Text Available The evaluation of the structural efficiency of airport infrastructures is a complex task. Faulting is one of the most important indicators of rigid pavement performance. The aim of our study is to provide a new method for faulting detection and computation on jointed concrete pavements. Nowadays, the assessment of faulting is performed with the use of laborious and time-consuming measurements that strongly hinder aircraft traffic. We proposed a field procedure for Terrestrial Laser Scanner data acquisition and a computation flow chart in order to identify and quantify the fault size at each joint of apron slabs. The total point cloud has been used to compute the least square plane fitting those points. The best-fit plane for each slab has been computed too. The attitude of each slab plane with respect to both the adjacent ones and the apron reference plane has been determined by the normal vectors to the surfaces. Faulting has been evaluated as the difference in elevation between the slab planes along chosen sections. For a more accurate evaluation of the faulting value, we have then considered a few strips of data covering rectangular areas of different sizes across the joints. The accuracy of the estimated quantities has been computed too.
Non-Invasive Ocular Rigidity Measurement: A Differential Tonometry Approach
Directory of Open Access Journals (Sweden)
Efstathios T. Detorakis
2015-12-01
Full Text Available Purpose: Taking into account the fact that Goldmann applanation tonometry (GAT geometrically deforms the corneal apex and displaces volume from the anterior segment whereas Dynamic Contour Tonometry (DCT does not, we aimed at developing an algorithm for the calculation of ocular rigidity (OR based on the differences in pressure and volume between deformed and non-deformed status according to the general Friedenwald principle of differential tonometry. Methods: To avoid deviations of GAT IOP from true IOP in eyes with corneas different from the “calibration cornea” we applied the previously described Orssengo-Pye algorithm to calculate an error coefficient “C/B”. To test the feasibility of the proposed model, we calculated the OR coefficient (r in 17 cataract surgery candidates (9 males and 8 females. Results: The calculated r according to our model (mean ± SD, range was 0.0174 ± 0.010 (0.0123–0.022 mmHg/μL. A negative statistically significant correlation between axial length and r was detected whereas correlations between r and other biometric parameters examined were statistically not significant. Conclusions: The proposed method may prove a valid non-invasive tool for the measurement method of OR, which could help in introducing OR in the decision-making of the routine clinical practice.
Determination of Weight Suspension Rigidity in the Transport-Erector Aggregates
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V. A. Zverev
2016-01-01
Full Text Available The aim is to determine weight suspension rigidity in aggregates designed to perform technological transport-erector operations at the miscellaneous launch complexes.We consider the weight suspension comprising the following distinctive structural components: the executive weight-lowering mechanism, polyspast mechanism, rope, traverse, and rods. A created structural dynamic model of suspension allowed us to define weight suspension rigidity. Within the framework of design analysis of a dynamic model we determined the rigidity of its structural units, i.e. traverse, rope, and polyspast.Known analytical relationships were used to calculate the rope rigidity. To determine rigidity of polyspast and traverse have been created special models based on the finite element method. For each model deformation in the specific points under the test load have been defined. Data obtained were used to determine trigidity of traverses and polyspast, and also rigidity of suspension in total. The rigidity models of polispast mechanism and traverse have been developed and calculated using the software complex "Zenit-95".As the research results, the paper presents a dynamic model of the weight suspension of the transport-erector aggregate, the finite element models of the polispast mechanism and traverse, an algorithm for determining the weight suspension rigidity and relevant analytical relationships.Independent calculation of weight suspension rigidity enables us to simplify further dynamic calculation of the aggregate-weight system because it allows attaining a simpler model of the aggregate-weight system that uses the weight suspension model as an element of equivalent rigidity. Despite this simplification the model allows us to determine correctly weight movement parameters and overloads in the aggregate-weight system in the process of technical operations.
Xu, Chunyan; Chang, Jingcai; Meng, Zhen; Wang, Xiang; Zhang, Jing; Cui, Lin; Ma, Chunyuan
2016-10-01
The fine particles are considered a significant pollution problem. The wet electrostatic precipitators (ESPs) have advantages of efficient collection of the fine particles with lower pressure drop and eliminating reentrainment. The wetting properties of the collector surfaces have significantly important effect on wet ESPs' stable and secure operation. The modified rigid collector (MRC) was modified by coating specific vinyl ester resin composites and loose glass fiber cloth over the conventional carbon steel in a certain way. The rigid collector surfaces before and after modification had been characterized by scanning electron microscopy (SEM) and interface tensiometer. The effect of operating temperatures on the wetting properties of the rigid collector surfaces before and after modification was investigated. The temperature range was 40~90 °C, and the wetting properties contained liquid holdup, surface flow rate, film rate, average film thickness, and critical saturation time. The modified rigid collector surface exhibited excellent wetting properties at the operating temperatures. The fine particles collection performance compared among the MRC, the conventional rigid collector (CRC), and the flexible collector (FC) in the wet ESPs was investigated. The effects of the applied voltage, the water film, corona power, and the specific collecting area on the fine particles collection were evaluated. The modified rigid collector provided high fine particles collection effect with lower energy and water consumption. To improve the submicron particles collection efficiency and decrease energy and water consumption, the formation of uniform water film over the collector surfaces has been widely studied. The modified rigid collector was modified by coating specific vinyl ester resin composites and loose glass fiber cloth (ERGF) over the conventional carbon steel (CCS) in a certain way. The modified rigid collector surface exhibited excellent wetting properties. The wet
Euler-Poincare Reduction of Externall Forced Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2004-01-01
If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system affected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincaré reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modelling, estimation and control of mechanical systems...
Euler-Poincaré Reduction of a Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2004-01-01
If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system affected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincaré reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modelling, estimation and control of mechanical systems...
Euler-Poincare Reduction of a Rigid Body Motion
DEFF Research Database (Denmark)
Wisniewski, Rafal; Kulczycki, P.
2005-01-01
|If a mechanical system experiences symmetry, the Lagrangian becomes invariant under a certain group action. This property leads to substantial simplification of the description of movement. The standpoint in this article is a mechanical system afected by an external force of a control action....... Assuming that the system possesses symmetry and the configuration manifold corresponds to a Lie group, the Euler-Poincare reduction breaks up the motion into separate equations of dynamics and kinematics. This becomes of particular interest for modeling, estimation and control of mechanical systems...
Rigid limit for hypermultiplets and five-dimensional gauge theories arXiv
Alexandrov, Sergei; Longhi, Pietro
We study the rigid limit of a class of hypermultiplet moduli spaces appearing in Calabi-Yau compactifications of type IIB string theory, which is induced by a local limit of the Calabi-Yau. We show that the resulting hyperkahler manifold is obtained by performing a hyperkahler quotient of the Swann bundle over the moduli space, along the isometries arising in the limit. Physically, this manifold appears as the target space of the non-linear sigma model obtained by compactification of a five-dimensional gauge theory on a torus. This allows to compute dyonic and stringy instantons of the gauge theory from the known results on D-instantons in string theory. Besides, we formulate a simple condition on the existence of a non-trivial local limit in terms of intersection numbers of the Calabi-Yau, and find an explicit form for the hypermultiplet metric including corrections from all mutually non-local D-instantons, which can be of independent interest.
Efficient convex optimization approach to 3D non-rigid MR-TRUS registration.
Sun, Yue; Yuan, Jing; Rajchl, Martin; Qiu, Wu; Romagnoli, Cesare; Fenster, Aaron
2013-01-01
In this study, we propose an efficient non-rigid MR-TRUS deformable registration method to improve the accuracy of targeting suspicious locations during a 3D ultrasound (US) guided prostate biopsy. The proposed deformable registration approach employs the multi-channel modality independent neighbourhood descriptor (MIND) as the local similarity feature across the two modalities of MR and TRUS, and a novel and efficient duality-based convex optimization based algorithmic scheme is introduced to extract the deformations which align the two MIND descriptors. The registration accuracy was evaluated using 10 patient images by measuring the TRE of manually identified corresponding intrinsic fiducials in the whole gland and peripheral zone, and performance metrics (DSC, MAD and MAXD) for the apex, mid-gland and base of the prostate were also calculated by comparing two manually segmented prostate surfaces in the registered 3D MR and TRUS images. Experimental results show that the proposed method yielded an overall mean TRE of 1.74 mm, which is favorably comparable to a clinical requirement for an error of less than 2.5 mm.
Inertial Motions of a Rigid Body with a Cavity Filled with a Viscous Liquid
Disser, Karoline; Galdi, Giovanni P.; Mazzone, Giusy; Zunino, Paolo
2016-07-01
We study inertial motions of the coupled system, {S}, constituted by a rigid body containing a cavity entirely filled with a viscous liquid. We show that for arbitrary initial data having only finite kinetic energy, every corresponding weak solution (à la Leray-Hopf) converges, as time goes to infinity, to a uniform rotation, unless two central moments of inertia of {S} coincide and are strictly greater than the third one. This corroborates a famous "conjecture" of N.Ye. Zhukovskii in several physically relevant cases. Moreover, we show that, in a known range of initial data, this rotation may only occur along the central axis of inertia of {S} with the larger moment of inertia. We also provide necessary and sufficient conditions for the rigorous nonlinear stability of permanent rotations, which improve and/or generalize results previously given by other authors under different types of approximation. Finally, we present results obtained by a targeted numerical simulation that, on the one hand, complement the analytical findings, whereas, on the other hand, point out new features that the analysis is yet not able to catch, and, as such, lay the foundation for interesting and challenging future investigation.
Effects of an assumed cosmic ray-modulated low global cloud cover on the Earth's temperature
Energy Technology Data Exchange (ETDEWEB)
Ramirez, J.; Mendoza, B. [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Mendoza, V.; Adem, J. [Centro de Ciencias de la Atmosfera, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)]. E-mail: victor@atmosfera.unam.mx
2006-07-15
We have used the Thermodynamic Model of the Climate to estimate the effect of variations in the low cloud cover on the surface temperature of the Earth in the Northern Hemisphere during the period 1984-1994. We assume that the variations in the low cloud cover are proportional to the variation of the cosmic ray flux measured during the same period. The results indicate that the effect in the surface temperature is more significant in the continents, where for July of 1991, we have found anomalies of the order of 0.7 degrees Celsius for the southeastern of Asia and 0.5 degrees Celsius for the northeast of Mexico. For an increase of 0.75% in the low cloud cover, the surface temperature computed by the model in the North Hemisphere presents a decrease of {approx} 0.11 degrees Celsius; however, for a decrease of 0.90% in the low cloud cover, the model gives an increase in the surface temperature of {approx} 0.15 degrees Celsius, these two cases correspond to a climate sensitivity factor for the case of forcing by duplication of atmospheric CO{sub 2}. These decreases or increases in surface temperature by increases of decreases in low clouds cover are ten times greater than the overall variability of the non-forced model time series. [Spanish] Hemos usado el Modelo Termodinamico del Clima para estimar el efecto de variaciones en la cubierta de nubes bajas sobre la temperatura superficial de la Tierra en el Hemisferio Norte durante el periodo 1984 - 1994. Suponemos que las variaciones en la cubierta de nubes bajas son proporcionales a las variaciones del flujo de rayos cosmicos medido durante el mismo periodo. Los resultados indican que el efecto en la temperatura es mas significativo en los continentes, donde para julio de 1991, hemos encontrado anomalias del orden de 0.7 grados Celsius sobre el sureste de Asia y 0.5 grados Celsius al noreste de Mexico. Para un incremento de 0.75% en la cubierta de nubes bajas, la temperatura de la superficie calculada por el modelo en
Xiao, Di; Zahra, David; Bourgeat, Pierrick; Berghofer, Paula; Acosta Tamayo, Oscar; Wimberley, Catriona; Gregoire, Marie C.; Salvado, Olivier
2011-03-01
Small animal image registration is challenging because of its joint structure, and posture and position difference in each acquisition without a standard scan protocol. In this paper, we face the issue of mouse whole-body skeleton registration from CT images. A novel method is developed for analyzing mouse hind-limb and fore-limb postures based on geodesic path descriptor and then registering the major skeletons and fore limb skeletons initially by thin-plate spline (TPS) transform based on the obtained geodesic paths and their enhanced correspondence fields. A target landmark correction method is proposed for improving the registration accuracy of the improved 3D shape context non-rigid registration method we previously proposed. A novel non-rigid registration framework, combining the skeleton posture analysis, geodesic path based initial alignment and 3D shape context model, is proposed for mouse whole-body skeleton registration. The performance of the proposed methods and framework was tested on 12 pairs of mouse whole-body skeletons. The experimental results demonstrated the flexibility, stability and accuracy of the proposed framework for automatic mouse whole body skeleton registration.
Energy Technology Data Exchange (ETDEWEB)
Zhu, Kai-Li [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China); College of Chemistry and Life Science, Gansu Normal University for Nationalities, Hezuo, 747000 Gansu (China); Liu, Le-Yan [College of Chemistry and Life Science, Gansu Normal University for Nationalities, Hezuo, 747000 Gansu (China); Geng, Zhi-Yuan, E-mail: zhiyuangeng@126.com [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China); Yan, Pen-Ji; Lu, Yan-Hong; Liu, Rui-Rui [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China)
2015-07-15
Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations have been carried out to explore the underlying origin of merits for rigid π-spacer based on reference dyes C255 and C254. The results demonstrate that higher short-circuit current density (J{sub SC}) of C255 is primarily ascribed to the lower EBE, while the biggish short-circuit current density (V{sub OC}) mainly originates from the larger μ{sub normal} compared to C254. Besides, a novel index integral of overlap between hole and electron (S) is firstly introduced to quantitatively estimate the facility of intramolecular charge transfer (ICT) and preliminarily confirmed to be effective for the research target of this work. Furthermore, three series of dyes (C-series, A-series, AC-series) have been designed and characterized to screen promising sensitizer candidates and design strategies, while delightful results have been achieved including 6 promising candidates, design stratagem on efficiently reducing the charge recombination and combinational tactics on screening new dyes with excellent spectral properties or outstanding DSSC performance. - Graphical abstract: Display Omitted - Highlights: • Novel S index was introduced in and confirmed to be effective to estimate ICT. • The merits of rigid π bridge have been theoretically revealed. • Six promising candidates have been screened out. • New strategy on reduce charge recombination was reported. • Novel combinational tactics were acquired and justified to be feasible.
Flexible Versus Rigid Methods Of Intravenous Thrombolysis In Iran
Directory of Open Access Journals (Sweden)
Kavian Ghandehari
2017-02-01
exclusion critera as illustrated above. This method will increase the probability of symptomatic intracerebral hemorrhage and death and may increase numbers of legal condemnations for treating physician. Rigid method is prohibition of violations from standard protocols of thrombolysis which decreases both numbers of managed patients and thrombolysis contraindications. Physicians who prefer the first therapeutic strategy refer to data of published articles and guidelines of American and European stroke societies. There are two points of view; first, the Iranian neurologists do not have thrombolysis experience as well as western neurologusts. For instance very limited number of Iranian neurologists have enough experience for detection of ASPECT score. Second, due to some social factors number of legal condemnations due to medical malpractice has been hugely increased in recent two decades in Iran. Based on these points second strategy is more wise for Iranian neurologists. The speaker has made a standard protocol of thrombolysis based on international gudelines and his experience. This standard protocol which is designed according to the rigid method is available by search in Google engine and is provided in Persian language.
Rigid polyurethane/oil palm fibre biocomposite foam
Alis, Adilah; Majid, Rohah A.; Nasir, Izzah Athirah Ahmad; Mustaffa, Nor Syatika; Hassan, Wan Hasamuddin Wan
2017-07-01
Rigid polyurethane (PU) biocomposite foam had been successfully prepared by reacting palm oil-derived polyol (PO-p) with polymeric 4, 4-diphenylmethane diisocynate (p-MDI). Two types of alkali-treated oil palm fibres namely, empty fruit bunch (EFB) and palm pressed fibre (PPF) were used as fillers to be incorporated into PU foam at 2.5 wt%, 5 wt% and 7.5 wt% fibre loadings. The effects of these fibres on surface morphology, compressive strength and thermal transition behaviours of biocomposite foams were investigated. Fourier transform infra-red (FTIR) analysis confirmed the formation of urethane linkages (-NHCOO) in all samples at 1530-1540 cm-1. Differential scanning calorimetry (DSC) analysis showed the average melting peak temperature (Tm) of biocomposite foams (132°C) were lower Tm than that of pure PU foam (161.67°C) and the increase amount of fibres did not give significant effect on the Tm of both biocomposite systems. Meanwhile, the microscopic images of PU-PPF foams exhibited smaller and uniform cell size morphologies compared with the PU-EFB foams that had coarse and irregular cell sizes, especially at 7.5wt% EFB. These findings were manifested with the gradually increase of compressive strength of PU-PPF at all PPF ratios while for PU-EFB system, the compressive strength increased up to 5 wt% before reduced at 7.5 wt% loading. It was thought due to the residual oil in PPF fibre had plasticized the PU matrix to a little extent, thus helping the dispersion of PPF fibre across the matrix.
Diagnostic value of rigid body rotation in noncompaction cardiomyopathy.
van Dalen, Bas M; Caliskan, Kadir; Soliman, Osama I I; Kauer, Floris; van der Zwaan, Heleen B; Vletter, Wim B; van Vark, Laura C; Ten Cate, Folkert J; Geleijnse, Marcel L
2011-05-01
The diagnosis of noncompaction cardiomyopathy (NCCM) remains subject to controversy. Because NCCM is probably caused by an intrauterine arrest of the myocardial fiber compaction during embryogenesis, it may be anticipated that the myocardial fiber helices, normally causing left ventricular (LV) twist, will also not develop properly. The resultant LV rigid body rotation (RBR) may strengthen the diagnosis of NCCM. The purpose of the current study was to explore the diagnostic value of RBR in a large group of patients with prominent trabeculations. The study comprised 15 patients with dilated cardiomyopathy, 52 healthy subjects, and 52 patients with prominent trabeculations, of whom a clinical expert in NCCM defined 34 as having NCCM. LV rotation patterns were determined by speckle-tracking echocardiography and defined as follows: pattern 1A, completely normal rotation (initial counterclockwise basal and clockwise apical rotation, followed by end-systolic clockwise basal and counterclockwise apical rotation); pattern 1B, partly normal rotation (normal end-systolic rotation but absence of initial rotation in the other direction); and pattern 2, RBR (rotation at the basal and apical level predominantly in the same direction). The majority of normal subjects had LV rotation pattern 1A (98%), whereas the 18 subjects with hypertrabeculation not fulfilling diagnostic criteria for NCCM predominantly had pattern 1B (71%), and the 34 patients with NCCM predominantly had pattern 2 (88%). None of the patients with dilated cardiomyopathy showed RBR. Sensitivity and specificity of RBR for differentiating NCCM from "hypertrabeculation" were 88% and 78%, respectively. RBR is an objective, quantitative, and reproducible functional criterion with good predictive value for the diagnosis of NCCM as determined by expert opinion. Copyright © 2011 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.
Apical clearance rigid contact lenses induce corneal steepening.
Swarbrick, Helen A; Hiew, Ross; Kee, Ai Vy; Peterson, Sophia; Tahhan, Nina
2004-06-01
Anecdotal reports suggest that steeply fitted rigid contact lenses can induce corneal steepening and myopic shifts in refraction. This study investigated changes in corneal topography, corneal thickness, and refraction after short-term wear of apical clearance lenses. : Ten young adults participated in the study in which apical clearance lenses (Conoid, Hydron Pty. Ltd., Frenchs Forest, NSW, Australia), fitted approximately 0.3 mm steeper than the flattest keratometric reading, were worn for 4 h. A polymethyl methacrylate (PMMA) lens was worn in one eye, and a Boston XO lens (Bausch & Lomb, Rochester, NY) was worn in the other. Lenses were nonfenestrated in the first trial, and a single midperipheral fenestration was incorporated for a second trial. Corneal topography was monitored using the EyeSys topographic analysis system (EyeSys Vision, Inc., Houston, TX); central corneal thickness was quantified using ultrasonic pachometry; and refraction and anterior ocular response were also monitored. Significant central corneal edema (8.2 +/- 2.2%) was demonstrated in the PMMA lens-wearing eye only. Fenestration did not reduce the edema response. We found significant corneal steepening over a 5- to 6-mm central zone, which was more pronounced in the PMMA lens-wearing eye and was modified by lens fenestration. The curvature changes altered central corneal shape from prolate (Q = -0.06 +/- 0.10) to oblate (Q = -0.26 +/- 0.31). A slight myopic shift in refraction (-0.38 +/- 0.60 D) was found with the PMMA lenses only. : Apical clearance lenses induce corneal steepening after short-term wear. Although corneal molding is implicated as the primary factor driving the shape change, corneal edema and postlens tear film pressures can modify this response.
Success of Rigid Gas Permeable Contact Lens Fitting.
Ortiz-Toquero, Sara; Martin, Mario; Rodriguez, Guadalupe; de Juan, Victoria; Martin, Raul
2017-05-01
To assess the percentage of successful rigid gas permeable (GP) contact lenses (CLs) fit for both refractive and therapeutic reasons. New CLs (soft or GP) fittings were retrospectively analyzed and divided into refractive and therapeutic prescriptions. A standardized fitting protocol that included complete CLs information after a first eye examination, a diagnostic fitting visit, a dispensing visit, and a prescribing visit was used in all fittings. A GP fitting was defined as successful if full-time wear and optimal ocular surface physiology were both achieved at the review assessment 2 to 3 weeks after lens dispensing. Of 232 new CLs fittings analyzed, 166 were refractive fittings (71.6%) and 66 were therapeutic (28.4%). Of the refractive fittings, 88 subjects (53%) were initially fitted with GP CLs and 61 (69.3%) of these met the criteria for successful GP fitting. Within this group, a different percentage of successful fits were found for neophyte (72%), previous soft lens wearers (62%), and previous GP wearers (92.3%). Of the therapeutic fittings, 61 subjects (92.4%) were initially fitted with GP CLs and 59 (96.7%) of these met the criteria for successful GP fitting. Following a standardized CLs fitting protocol, a relatively high percentage of successful GP fits was achieved for refractive (7/10 subjects) and therapeutic (9/10 subjects) prescriptions. These results will improve the information available to patients and aid in their CL choices by providing them with a realistic attitude. It will also help eye care practitioners in their clinical activities by providing evidence-based information.
Survey of Non-Rigid Registration Tools in Medicine.
Keszei, András P; Berkels, Benjamin; Deserno, Thomas M
2017-02-01
We catalogue available software solutions for non-rigid image registration to support scientists in selecting suitable tools for specific medical registration purposes. Registration tools were identified using non-systematic search in Pubmed, Web of Science, IEEE Xplore® Digital Library, Google Scholar, and through references in identified sources (n = 22). Exclusions are due to unavailability or inappropriateness. The remaining (n = 18) tools were classified by (i) access and technology, (ii) interfaces and application, (iii) living community, (iv) supported file formats, and (v) types of registration methodologies emphasizing the similarity measures implemented. Out of the 18 tools, (i) 12 are open source, 8 are released under a permissive free license, which imposes the least restrictions on the use and further development of the tool, 8 provide graphical processing unit (GPU) support; (ii) 7 are built on software platforms, 5 were developed for brain image registration; (iii) 6 are under active development but only 3 have had their last update in 2015 or 2016; (iv) 16 support the Analyze format, while 7 file formats can be read with only one of the tools; and (v) 6 provide multiple registration methods and 6 provide landmark-based registration methods. Based on open source, licensing, GPU support, active community, several file formats, algorithms, and similarity measures, the tools Elastics and Plastimatch are chosen for the platform ITK and without platform requirements, respectively. Researchers in medical image analysis already have a large choice of registration tools freely available. However, the most recently published algorithms may not be included in the tools, yet.
Single homopolypeptide chains collapse into mechanically rigid conformations
Dougan, Lorna; Li, Jingyuan; Badilla, Carmen L.; Berne, B. J.; Fernandez, Julio M.
2009-01-01
Huntington's disease is linked to the insertion of glutamine (Q) in the protein huntingtin, resulting in polyglutamine (polyQ) expansions that self-associate to form aggregates. While polyQ aggregation has been the subject of intense study, a correspondingly thorough understanding of individual polyQ chains is lacking. Here we demonstrate a single molecule force-clamp technique that directly probes the mechanical properties of single polyQ chains. We have made polyQ constructs of varying lengths that span the length range of normal and diseased polyQ expansions. Each polyQ construct is flanked by the I27 titin module, providing a clear mechanical fingerprint of the molecule being pulled. Remarkably, under the application of force, no extension is observed for any of the polyQ constructs. This is in direct contrast with the random coil protein PEVK of titin, which readily extends under force. Our measurements suggest that polyQ chains form mechanically stable collapsed structures. We test this hypothesis by disrupting polyQ chains with insertions of proline residues and find that their mechanical extensibility is sensitive to the position of the proline interruption. These experiments demonstrate that polyQ chains collapse to form a heterogeneous ensemble of conformations that are mechanically resilient. We further use a heat-annealing molecular dynamics protocol to extensively search the conformation space and find that polyQ can exist in highly mechanically stable compact globular conformations. The mechanical rigidity of these collapsed structures may exceed the functional ability of eukaryotic proteasomes, resulting in the accumulation of undigested polyQ sequences in vivo. PMID:19549822
Rigid Polyurethane Foam Thermal Insulation Protected with Mineral Intumescent Mat
Directory of Open Access Journals (Sweden)
Kirpluks Mikelis
2014-12-01
Full Text Available One of the biggest disadvantages of rigid polyurethane (PU foams is its low thermal resistance, high flammability and high smoke production. Greatest advantage of this thermal insulation material is its low thermal conductivity (λ, which at 18-28 mW/(m•K is superior to other materials. To lower the flammability of PU foams, different flame retardants (FR are used. Usually, industrially viable are halogenated liquid FRs but recent trends in EU regulations show that they are not desirable any more. Main concern is toxicity of smoke and health hazard form volatiles in PU foam materials. Development of intumescent passive fire protection for foam materials would answer problems with flammability without using halogenated FRs. It is possible to add expandable graphite (EG into PU foam structure but this increases the thermal conductivity greatly. Thus, the main advantage of PU foam is lost. To decrease the flammability of PU foams, three different contents 3%; 9% and 15% of EG were added to PU foam formulation. Sample with 15% of EG increased λ of PU foam from 24.0 to 30.0 mW/(m•K. This paper describes the study where PU foam developed from renewable resources is protected with thermally expandable intumescent mat from Technical Fibre Products Ltd. (TFP as an alternative to EG added into PU material. TFP produces range of mineral fibre mats with EG that produce passive fire barrier. Two type mats were used to develop sandwich-type PU foams. Also, synergy effect of non-halogenated FR, dimethyl propyl phosphate and EG was studied. Flammability of developed materials was assessed using Cone Calorimeter equipment. Density, thermal conductivity, compression strength and modulus of elasticity were tested for developed PU foams. PU foam morphology was assessed from scanning electron microscopy images.
Patient preferences and comparative ocular responses to rigid and soft contact lenses.
Fonn, D; Gauthier, C A; Pritchard, N
1995-12-01
Patient preferences and ocular responses were compared between rigid and soft contact lenses by randomly fitting 32 neophyte subjects with a rigid lens in 1 eye and a soft lens in the contralateral eye. Twenty-seven of 32 subjects completed the 3-month study and 16 subjects were willing to continue for an additional 3-month extension. Subjects preferred the comfort and handling of the soft lens but preferred the vision provided by the rigid lens and initially its ease of maintenance. There was also a marked preference for the soft lens when all aspects of lens wear were compared. Objectively, the rigid lenses were responsible for more ocular changes than the soft lenses. Palpebral aperture sizes of the rigid gas permeable (RGP) wearing eyes decreased significantly (0.5 mm; p lens wearing eyes. The incidence of corneal staining was significantly greater in the rigid lens wearing eye (50% RGP vs. 22% soft) but limbal injection was greater in the soft lens wearing eye (18% soft vs. 6% RGP). Refractive sphere, cylinder, and corneal astigmatism decreased in the rigid lens wearing eye after 3 months. This daily wear clinical trial has shown a marked subjective preference for wearing soft lenses with fewer short-term ocular effects.
Comparison of elastic versus rigid suture material for peripheral sutures in tendon repair.
Nozaki, Kenji; Mori, Ryuji; Ryoke, Koji; Uchio, Yuji
2012-06-01
For secure tendon repair, while core suture materials have been previously investigated, the optimum material for peripheral sutures remains unclear. Transected bovine gastrocnemius tendons were repaired by 2-strand side-locking loop technique using no.2 braided polyblend polyethylene thread for the core suture. Then, 8-strand peripheral cross-stitches were added using either 2-0 rigid sutures (braided polyblend polyethylene) or USP 2-0-sized elastic sutures (nylon). The holding area of each peripheral suture was set at either 3 × 1 mm (shallow holding) or 6 × 2 mm (deep holding). Therefore, 4 groups were compared (the shallow-rigid, deep-rigid, shallow-elastic, and deep-elastic groups). The gap formation, ultimate tensile strength, and suture migration state were measured after 500 cyclic loadings (from 10 to 200 N). The shallow-rigid group had inferior outcomes compared to the other groups. Although the deep-rigid group had the smallest gap and highest ultimate strength, all peripheral sutures had failure prior to core suture rupture. The two elastic groups showed no significant differences, irrespective of the size of the holding area. Suture migration did not occur in the two elastic groups until the ultimate strength was reached and the core suture ruptured. Depending on the suturing method, rigid suture material may not be appropriate for peripheral sutures, when accompanying rigid core suture material. If peripheral sutures can be made with accurate deep holding, rigid suture material will provide favorable outcome. However, in other cases, elastic suture material is considered best for supporting a rigid core suture, as elasticity is another important factor for peripheral sutures. Copyright © 2011 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Kostic, Ana; Sap, Jan; Sheetz, Michael P
2007-01-01
Receptor-like protein tyrosine phosphatase alpha (RPTPalpha)-knockout mice have severe hippocampal abnormalities similar to knockouts of the Src family kinase Fyn. These enzymes are linked to the matrix-rigidity response in fibroblasts, but their function in neurons is unknown. The matrix...... response in hippocampal neuron growth cones, like in fibroblasts. In control neurons, rigid FN surfaces inhibit neurite extension and neuron differentiation relative to soft surfaces. In RPTPalpha(-/-) neurons, no inhibition of extension and differentiation is found on both rigid and soft surfaces...
Multivalent, high-relaxivity MRI contrast agents using rigid cysteine-reactive gadolinium complexes.
Garimella, Praveena D; Datta, Ankona; Romanini, Dante W; Raymond, Kenneth N; Francis, Matthew B
2011-09-21
MRI contrast agents providing very high relaxivity values can be obtained through the attachment of multiple gadolinium(III) complexes to the interior surfaces of genome-free viral capsids. In previous studies, the contrast enhancement was predicted to depend on the rigidity of the linker attaching the MRI agents to the protein surface. To test this hypothesis, a new set of Gd-hydroxypyridonate based MRI agents was prepared and attached to genetically introduced cysteine residues through flexible and rigid linkers. Greater contrast enhancements were seen for MRI agents that were attached via rigid linkers, validating the design concept and outlining a path for future improvements of nanoscale MRI contrast agents.
Maldonado-Codina, Carole; Morgan, Philip B; Efron, Nathan; Efron, Suzanne
2005-06-01
The purpose of this study is to investigate the comparative clinical performance of two hyper Dk contact lenses: a silicone hydrogel lens (Focus Night & Day, Ciba Vision) and a rigid lens (Z-alpha, Menicon Co. Ltd.) when worn for up to 30 days of continuous wear (CW). The rigid lens was worn on an unplanned replacement basis, whereas the soft lens was replaced monthly. One hundred subjects were recruited. Fifty neophyte subjects were randomly assigned into one of the lens types (25 subjects per lens type). Twenty-five existing daily wear (DW) rigid lens users wore the rigid study lens and 25 existing DW soft lens users wore the soft study lens. Visual acuity, lens fit, keratometry, refraction, lens surface assessment, physiological response, and subjective response were investigated at baseline and after 1 week of DW and 24 hours, 1 week, and 1, 3, 6, 9, and 12 months of CW. Analysis compared lens type (rigid vs. soft) and subject group (experienced vs. neophyte). Sixty-eight subjects completed the study. Visual acuity was similar for the two lens types and subject groups. Lens fit was judged to be adequate in all subjects. Corneal curvature of subjects in the rigid groups became flatter by 0.13 mm compared with 0.04 mm for subjects in the soft lens groups (F = 14.7, p = 0.0003); the refractive findings mirrored these corneal changes. The increasing rate of deposition on rigid lenses was consistent with the fact that these lenses were not replaced during the study. Conjunctival hyperemia and staining were similar for the two lens types but greater among experienced wearers at baseline (F = 13.8, p = 0.0005; F = 5.3, p = 0.02, respectively). Corneal staining was higher for the rigid lens wearers (F = 5.6, p = 0.02) but this was mainly the result of the initial higher scores in the rigid lens experienced group. The change in papillary conjunctivitis was greater for subjects in the soft lens groups than rigid lens groups (F = 4.6, p = 0.04). Comfort was initially
Free surface flow of a suspension of rigid particles in a non-Newtonian fluid
DEFF Research Database (Denmark)
Svec, Oldrich; Skocek, Jan; Stang, Henrik
2012-01-01
A numerical framework capable of predicting the free surface flow of a suspension of rigid particles in a non-Newtonian fluid is described. The framework is a combination of the lattice Boltzmann method for fluid flow, the mass tracking algorithm for free surface representation, the immersed...... boundary method for two-way coupled interactions between fluid and rigid particles and an algorithm for the dynamics and mutual interactions of rigid particles. The framework is able to simulate the flow of suspensions at the level of the largest suspended particles and, at the same time, the model is very...
Predictors of Difficult Intubation with the Bonfils Rigid Fiberscope.
Nowakowski, Michal; Williams, Stephan; Gallant, Jason; Ruel, Monique; Robitaille, Arnaud
2016-06-01
Endotracheal intubation is commonly performed via direct laryngoscopy (DL). However, in certain patients, DL may be difficult or impossible. The Bonfils Rigid Fiberscope® (BRF) is an alternative intubation device, the design of which raises the question of whether factors that predict difficult DL also predict difficult BRF. We undertook this study to determine which demographic, morphologic, and morphometric factors predict difficult intubation with the BRF. Four hundred adult patients scheduled for elective surgery were recruited. Patients were excluded if awake intubation, rapid sequence induction, or induction without neuromuscular blocking agents was planned. Data were recorded, including age, sex, weight, height, American Society of Anesthesiologist classification, history of snoring and sleep apnea, Mallampati class, upper lip bite test score, interincisor, thyromental and sternothyroid distances, manubriomental distances in flexion and extension, neck circumference, maximal neck flexion and extension, neck skinfold thickness at the cricoid cartilage, and Cormack and Lehane grade obtained via DL after paralysis was confirmed. Quality of glottic visualization (good or poor), as well as the number of intubation attempts and time to successful intubation with the BRF, was noted. Univariate analyses were performed to evaluate the association between patient characteristics and time required for intubation. Variables that exhibited a significant correlation were included in a multivariate analysis using a standard least squares model. A P 1 attempt; 4 patients could not be intubated by using the BRF alone. These 4 patients were intubated by using a combination of DL and BRF (2 patients), DL and a Frova bougie (1 patient), and DL and an endotracheal tube shaped with a semirigid stylet (1 patient). Mean time for successful intubation was 26 ± 13 seconds. Multivariate analysis showed that decreased mouth opening (P = 0.008), increased body mass index (P = 0
PiSQRD: a web server for decomposing proteins into quasi-rigid dynamical domains.
Aleksiev, T; Potestio, R; Pontiggia, F; Cozzini, S; Micheletti, C
2009-10-15
The PiSQRD web resource can be used to subdivide protein structures in quasi-rigid dynamical domains. The latter are groups of amino acids behaving as approximately rigid units in the course of protein equilibrium fluctuations. The PiSQRD server takes as input a biomolecular structure and the desired fraction of protein internal fluctuations that must be accounted for by the relative rigid-body motion of the dynamical domains. Next, the lowest energy modes of fluctuation of the protein (optionally provided by the user) are calculated and used to identify the rigid subunits. The resulting optimal subdivision is returned through a web page containing both interactive graphics and detailed data output. The PiSQRD web server, which requires Java, is available free of charge for academic users at http://pisqrd.escience-lab.org.
Fiber Optic Systems for Light Curing Rigidization of Inflatable Structures Project
National Aeronautics and Space Administration — Light (UV and visible) curing composite matrix resins are being explored as an attractive means for rigidizing inflatable spacecraft for large space-deployed...
Water retention of rigid soils from a two-factor model for clay
Chertkov, V Y
2014-01-01
Water retention is one of the key soil characteristics. Available models of soil water retention relate to the curve-fitting type. The objective of this work is to suggest a physical model of water retention (drying branch) for soils with a rigid matrix. "Physical" means the prediction based on the a priori measured or estimated soil parameters with a clear physical meaning. We rely on the two-factor model of clay that takes into account the factors of capillarity and shrinkage. The key points of the model to be proposed are some weak pseudo shrinkage that the rigid soils demonstrate according to their experimental water retention curves, and some specific properties of the rigid grain matrix. The three input parameters for prediction of soil water retention with the rigid grain matrix include inter-grain porosity, as well as maximum and minimum grain sizes. The comparison between measured and predicted sand water retention curves for four different sands is promising.
A Sensitivity Analysis of the Rigid Pavement Life-Cycle Cost Analysis Program
2000-12-01
Original Report Date: September 1999. This report describes the sensitivity analysis performed on the Rigid Pavement Life-Cycle Cost Analysis program, a computer program developed by the Center for Transportation Research for the Texas Department of ...
NUMERICAL SIMULATIONS FOR THE CASE OF RIGID ROTATING KINEMATIC COUPLING WITH BIG CLEARANCE
Directory of Open Access Journals (Sweden)
Jan-Cristian GRIGORE
2010-10-01
Full Text Available In this paper an algorithm based on [1] [2] are numerical simulations, achieving generalized coordinates of motion, positions, speeds of a rigid rotating kinematic coupling with big clearance in joint, case without friction
An Algorithmic Approach to Wireless Sensor Networks Localization Using Rigid Graphs
Directory of Open Access Journals (Sweden)
Shamantha Rai B
2016-01-01
Full Text Available In this work estimating the position coordinates of Wireless Sensor Network nodes using the concept of rigid graphs is carried out in detail. The range based localization approaches use the distance information measured by the RSSI, which is prone to noise, due to effects of path loss, shadowing, and so forth. In this work, both the distance and the bearing information are used for localization using the trilateration technique. Rigid graph theory is employed to analyze the localizability, that is, whether the nodes of the WSN are uniquely localized. The WSN graph is divided into rigid patches by varying appropriately the communication power range of the WSN nodes and then localizing the patches by trilateration. The main advantage of localizing the network using rigid graph approach is that it overcomes the effect of noisy perturbed distance. Our approach gives a better performance compared to robust quads in terms of percentage of localizable nodes and computational complexity.
Sauvageau, Anny; Kelly, Sean; Ambrosi, Corinne
2012-06-01
The study of filmed hangings in the recent has reveal a striking similarity in the agonal sequences, with a sequence of rapid loss of consciousness, convulsions, and then a complex pattern of decerebrate rigidity and decorticate rigidity. We report a case of filmed hanging not presenting with decerebrate and decorticate rigidity. A 52-year-old man stepped off a stool, hanging himself in a complete suspension in an upright position. The movement of the body stepping off the stool created a rotary movement around the ceiling's ring and the body of the hanging man immediately started to revolve around the ring. Apart for the rolling around the ceiling's ring, the body stayed motionless for the duration of the movie, without any evidence of decerebrate or decorticate rigidity. A review of the pathophysiology of these reflex posturing gives some insight as to the possible elucidation for their absence in this specific case.
Comparison of the effect of semi-rigid ankle bracing on performance ...
African Journals Online (AJOL)
Comparison of the effect of semi-rigid ankle bracing on performance among injured v. non-injured adolescent female hockey players. TJ Ellapen, N Acampora, S Dawson, J Arling, C van Niekerk, HJ van Heerden ...
Level set motion assisted non-rigid 3D image registration
Yang, Deshan; Deasy, Joseph O.; Low, Daniel A.; El Naqa, Issam
2007-03-01
Medical imaging applications of rigid and non-rigid elastic deformable image registration are undergoing wide scale development. Our approach determines image deformation maps through a hierarchical process, from global to local scales. Vemuri (2000) reported a registration method, based on levelset evolution theory, to morph an image along the motion gradient until it deforms to the reference image. We have applied this level set motion method as basis to iteratively compute the incremental motion fields and then we approximated the field using a higher-level affine and non-rigid motion model. In such a way, we combine sequentially the global affine motion, local affine motion and local non-rigid motion. Our method is fully automated, computationally efficient, and is able to detect large deformations if used together with multi-grid approaches, potentially yielding greater registration accuracy.
Anaesthesia and peri-interventional morbidity of rigid bronchoscopy: A retrospective analysis
Directory of Open Access Journals (Sweden)
Jerry Tan
2017-07-01
Conclusion: The choice of anaesthetic technique possibly affects the complication of patients undergoing rigid bronchoscopy. Volatile anaesthetics appeared to be driven by presumably shorter procedure, but was associated with higher systemic complication.
Building America Top Innovations 2013 Profile – Exterior Rigid Insulation Best Practices
Energy Technology Data Exchange (ETDEWEB)
none,
2013-09-01
In this Top Innovation profile, field and lab studies by BSC, PHI, and NorthernSTAR characterize the thermal, air, and vapor resistance properties of rigid foam insulation and describe best practices for their use on walls, roofs, and foundations.
Heat Transfer Measurement and Modeling in Rigid High-Temperature Reusable Surface Insulation Tiles
Daryabeigi, Kamran; Knutson, Jeffrey R.; Cunnington, George R.
2011-01-01
Heat transfer in rigid reusable surface insulations was investigated. Steady-state thermal conductivity measurements in a vacuum were used to determine the combined contribution of radiation and solid conduction components of heat transfer. Thermal conductivity measurements at higher pressures were then used to estimate the effective insulation characteristic length for gas conduction modeling. The thermal conductivity of the insulation can then be estimated at any temperature and pressure in any gaseous media. The methodology was validated by comparing estimated thermal conductivities with published data on a rigid high-temperature silica reusable surface insulation tile. The methodology was also applied to the alumina enhanced thermal barrier tiles. Thermal contact resistance for thermal conductivity measurements on rigid tiles was also investigated. A technique was developed to effectively eliminate thermal contact resistance on the rigid tile s cold-side surface for the thermal conductivity measurements.
Convergent Synthesis of Rigid Macrocycles Containing One and Two Tetrathiafulvalene Units
DEFF Research Database (Denmark)
Simonsen, Klaus B.; Thorup, Niels; Becher, Jan
1997-01-01
The synthesis of rigid tetrathiafulvalenophanes containing one or two tetrathiafulvalene units is presented, together with a stepwise convergent synthesis of macrocyclic bis-tetrathiafulvalenes via several open dimeric tetrathiafulvalenes. These systems were investigated by cyclic voltammetry...
Positive semidefinite matrix completion, universal rigidity and the Strong Arnold Property
M. Laurent (Monique); A. Varvitsiotis (Antonios)
2014-01-01
htmlabstractThis paper addresses the following three topics: positive semidefinite (psd) matrix completions, universal rigidity of frameworks, and the Strong Arnold Property (SAP). We show some strong connections among these topics, using semidefinite programming as unifying theme. Our main
Positive semidefinite matrix completion, universal rigidity and the Strong Arnold Property
M. Laurent (Monique); A. Varvitsiotis (Antonios)
2013-01-01
htmlabstractThis paper addresses the following three topics: positive semidefinite (psd) matrix completions, universal rigidity of frameworks, and the Strong Arnold Property (SAP). We show some strong connections among these topics, using semidefinite programming as unifying theme. Our main
Market structure, price rigidity, and performance in the Indonesian food and beverages industry
Setiawan, M.
2012-01-01
Keywords: industrial concentration, price rigidity, technical efficiency, price-cost margin, Structure-Conduct-Performance (SCP), new empirical industrial organization (NEIO), Indonesian food and beverages industry, Data Envelopment Analysis (DEA), system of equations The
He, Daping; He, Dong Sheng; Yang, Jinlong; Low, Ze-Xian; Malpass-Evans, Richard; Carta, Mariolino; McKeown, Neil B; Marken, Frank
2016-08-31
A molecularly rigid polyamine based on a polymer of intrinsic microporosity (PIM-EA-TB) is shown to capture and stabilize platinum nanoparticles during colloid synthesis in the rigid framework. Stabilization here refers to avoiding aggregation without loss of surface reactivity. In the resulting rigid framework with embedded platinum nanoparticles, the volume ratio of platinum to PIM-EA-TB in starting materials is varied systematically from approximately 1.0 to 0.1 with the resulting platinum nanoparticle diameter varying from approximately 4.2 to 3.1 nm, respectively. Elemental analysis suggests that only a fraction of the polymer is "captured" to give nanocomposites rich in platinum. A transition occurs from electrically conducting and electrochemically active (with shorter average interparticle distance) to nonconducting and only partially electrochemically active (with longer average interparticle distance) polymer-platinum composites. The conducting nanoparticle network in the porous rigid macromolecular framework could be beneficial in electrocatalysis and in sensing applications.
Correlation of impression removal force with elastomeric impression material rigidity and hardness.
Walker, Mary P; Alderman, Nick; Petrie, Cynthia S; Melander, Jennifer; McGuire, Jacob
2013-07-01
Difficult impression removal has been linked to high rigidity and hardness of elastomeric impression materials. In response to this concern, manufacturers have reformulated their materials to reduce rigidity and hardness to decrease removal difficulty; however, the relationship between impression removal and rigidity or hardness has not been evaluated. The purpose of this study was to determine if there is a positive correlation between impression removal difficulty and rigidity or hardness of current elastomeric impression materials. Light- and medium-body polyether (PE), vinylpolysiloxane (VPS), and hybrid vinyl polyether siloxane (VPES) impression materials were tested (n = 5 for each material/consistency/test method). Rigidity (elastic modulus) was measured via tensile testing of dumbbell-shaped specimens (Die C, ASTM D412). Shore A hardness was measured using disc specimens according to ASTM D2240-05 test specifications. Impressions were also made of a custom stainless steel model using a custom metal tray that could be attached to a universal tester to measure associated removal force. Within each impression material consistency, one-factor ANOVA and Tukey's post hoc analyses (α = 0.05) were used to compare rigidity, hardness, and removal force of the three types of impression materials. A Pearson's correlation (α = 0.05) was used to evaluate the association between impression removal force and rigidity or hardness. With medium-body materials, VPS exhibited significantly higher (p ≤ 0.05) rigidity and hardness than VPES or PE, while PE impressions required significantly higher (p ≤ 0.05) removal force than VPS or VPES impressions. With light-body materials, VPS again demonstrated significantly higher (p ≤ 0.05) hardness than VPES or PE, while the rigidity of the light-body materials did not significantly differ between materials (p > 0.05); however, just as with the medium-body materials, light-body PE impressions required significantly higher (p
Evaluation of surgical performance with standard rigid and flexible-tip laparoscopes.
Perrone, J M; Ames, C D; Yan, Y; Landman, J
2005-10-01
Flexible-tip laparoscopes have recently been introduced into clinical practice, with the goal of improving surgeon performance during complex laparoscopic procedures. We used objective and subjective performance parameters to compare standard rigid 0 degrees and 30 degrees lens laparoscopes two flexible-tip laparoscopes in an in vitro model. Twenty-nine subjects with varied levels of surgical experience performed complex laparoscopic tasks in three different models simulating (a) prostate dissection from the rectum, (b) cystic duct clipping, and (c) distal posterior rectum dissection. Each task was performed using two Storz rigid laparoscopes (0 degrees and 30 degrees) and two flexible-tip laparoscopes, the Olympus LTF-V3 and the Fujinon EL2-TF310. The sequence of application of the two flexible-tip laparoscopes was randomized. In each case, an experienced laparoscopic camera driver controlled the field of vision. Time to complete each task, operative precision, and subjective surgeon rating scores were compared. Statistical analysis was performed with analysis of variance (ANOVA) and a two-sided fisher's exact test. In all three models, the flexible laparoscopes offered no advantage in terms of procedure time, surgical precision, or subjective surgeon rating score when compared with the 30 degrees lens rigid laparoscope. The 30 degrees rigid lens laparoscope and the two flexible-tip laparoscopes were superior to the 0 degrees lens rigid laparoscope for all parameters evaluated, with the exception of subjective rating in the cystic duct model and procedure time in the colorectal model. In this in vitro experimental model, the flexible-tip laparoscopes found to have no advantage over the standard rigid 30 degrees lens laparoscope. These models were validated, as the 0 degrees lens rigid laparoscope was surpassed by the 30 degrees lens rigid laparoscope and the flexible-tip laparoscopes. Both flexible-tip laparoscopes produced similar results and excellent image
Precast Slabs for Contingency Rigid Airfield Pavement Damage Repairs (BRIEFING SLIDES)
2010-04-01
efficiency of using different precast concrete panel installation techniques for contingency repair of damaged airfield pavements . Fast-setting polymer ...AFRL-RX-TY-TP-2010-0055 PRECAST SLABS FOR CONTINGENCY RIGID AIRFIELD PAVEMENT DAMAGE REPAIRS (BRIEFING SLIDES) Reza Ashtiani Applied...Rigid Airfield Pavement Damage Repairs (BRIEFING SLIDES) FA4819-09-C-0028 62102F 4915 D1 4915D14E Ashtiani, Reza; *Hammons, Michael I. Applied Research
Contact point generation for convex polytopes in interactive rigid body dynamics
DEFF Research Database (Denmark)
Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny
When computing contact forces in rigid body dynamics systems, most state-of-the-art solutions use iterative methods such as the projected Gauss–Seidel (PGS) method. Methods such as the PGS method are preferred for their robustness. However, the time-critical nature of interactive applications...... for convex polytopes. A novel contact point generation method is presented, which is based on growth distances and Gauss maps. We demonstrate improvements when using our method in the context of interactive rigid body simulation...
Pre-Cast Concrete Panels for Contingency Rigid Airfield Pavement Damage Repairs
2010-06-01
Micro- texture of the particle plays an important role in aggregate interlock. Therefore, mixes consisting of less polished aggregates are expected to...AFRL-RX-TY-TR-2010-0095 PRECAST CONCRETE PANELS FOR CONTINGENCY RIGID AIRFIELD PAVEMENT DAMAGE REPAIRS Reza S. Ashtiani, Christopher J...Final Technical Report 01-JAN-2008 -- 30-APR-2010 Pre-Cast Concrete Panels for Rapid Repair of Airfield Rigid Pavements FA4819-09-C-0028 62102F 4915 D1
Analysis of viscoelastic properties of wrist joint for quantification of parkinsonian rigidity.
Park, Byung Kyu; Kwon, Yuri; Kim, Ji-Won; Lee, Jae-Ho; Eom, Gwang-Moon; Koh, Seong-Beom; Jun, Jae-Hoon; Hong, Junghwa
2011-04-01
This study aims to analyze viscoelastic properties of the wrist in patients with Parkinson's disease (PD) in comparison with the clinical score of severity. Forty-five patients with PD and 12 healthy volunteers participated in this study. Severity of rigidity at the wrist was rated by a neurologist just before the experiment. Wrist joint torque resistive to the imposed movement was measured. Three different models, (identical in structure, only different in the number of parameters for extension and flexion phases) were used in identification of viscoelastic properties: 1) one damping constant and one spring constant throughout all phases, 2) two damping constants for each phase and one spring constant throughout all phases, and 3) two damping constants and two spring constants for each phase. Normalized work and impulse suggested in the literature were also calculated. Spring constants of different models and phases showed comparable correlation with rigidity score ( r=0.68-0.73). In terms of the correlation of damping constant with clinical rigidity score, model 1 ( r = 0.90) was better than models 2 and 3 ( r=0.59 - 0.71). These results suggest that the clinical rigidity score is better represented by the mean viscosity during both flexion and extension. In models with two dampers (model 2 and 3), the damping constant was greater during extension than flexion in patients , in contrast that there was no phase difference in normal subjects. This suggests that in contrast with normal subjects, phase-dependent viscosity may be an inherent feature of PD. Although work and impulse were correlated with clinical rigidity score ( r = 0.11 - 0.84), they could not represent the phase-dependent rigidity inherent in PD. In conclusion, the viscosity of model 1 would be appropriate for quantification of clinical ratings of rigidity and that of model 2 for distinction of PD and also for investigation of phase-dependent characteristics in parkinsonian rigidity.
The Serret-Andoyer Formalism in Rigid-Body Dynamics: I. Symmetries and Perturbations
Gurfil, Pini; Elipe, Antonio; Tangren, William; Efroimsky, Michael
2006-01-01
This paper reviews the Serret-Andoyer (SA) canonical formalism in rigid-body dynamics and presents some new results. As is well known, the problem of unsupported and unperturbed rigid rotator can be reduced. The availability of this reduction is offered by the underlying symmetry, which stems from conservation of the angular momentum and rotational kinetic energy. When a perturbation is turned on, these quantities are no longer preserved. Nonetheless, the language of reduced description remai...
Eman A. Embaby; Eman M.A. Abdalgwad
2016-01-01
Background: Rigid and kinesio taping is commonly used in the rehabilitation and prevention of subacromial impingement syndrome (SIS). It is proposed to have positive effects on shoulder function and scapular kinematics. However, there is a paucity of literature regarding the effectiveness of rigid versus elastic taping on scapular upward rotation and forward head posture (FHP), which is commonly adopted in SIS. Purpose: This study was designed to investigate the effect of taping with post...
Page 1 Rigidity problem for lattices in solvable Lie groups 513 . in ...
Indian Academy of Sciences (India)
º f i.1 º group as a lattice. Now we may give an example of a rigid lattice T in olvable Lie group G of (I)-type. This lattice will be constructed with the help of a weakly rigid lattice in a splittable Lie. £º. : ~! ~1?? 1 - 4.4.2 group of (I)-type fro. Superrigid” lattice from the corollary above. (I)-type from example 2.8 and a. Example 8.3.
ANALYTIC EVALUATION OF RECTILINEARITY OF LOW RIGIDITY SHAFT DURING HARDENING PROCESS
Directory of Open Access Journals (Sweden)
Antoni Świć
2013-03-01
Full Text Available The essential influence of the unevenness of temperature distribution while heating in the technological process on dimensions stability of low rigidity elements was shown. The new approach was applied to formulate mathematical models, which describe the elastic and inelastic behaviour of piece using transfer functions and block diagrams, allowing to use frequency method for evaluation of the behaviour of dynamic semi-finished element as the rigid body.
Comparison and Implementation of a Rigid and a Flexible Multibody Planetary Gearbox Model
DEFF Research Database (Denmark)
Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær
2014-01-01
We propose algorithms for developing (1) a rigid (constrained) and (2) a flexible planetary gearbox model. The two methods are compared against each other and advantages/disadvantages of each method are discussed. The rigid model (1) has gear tooth reaction forces expressed by Lagrange multipliers...... between one and two gear teeth in mesh. The final results are from modelling the planetary gearbox in a 500 kW wind turbine which we also described in Jørgensen et al. (2013)....
Liu, Chi; Qiu, Yi; Griffin, Michael J
2017-08-16
Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8Hz. Around 3-7Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8-10Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation. Copyright © 2017 Elsevier Ltd. All rights reserved.
Technical Note: Semi-rigid chambers for methane gas flux measurements on tree-stems
Siegenthaler, A.; Welch, B.; Pangala, S. R.; Peacock, M.; Gauci, V.
2015-09-01
There is increasing interest in the measurement of methane (CH4) emissions from tree stems in a wide range of ecosystems so as to determine how they contribute to the total ecosystem flux. To date, tree CH4 fluxes are commonly measured using rigid closed chambers (static or dynamic), which often pose challenges as these are bulky and limit measurement of CH4 fluxes to only a very narrow range of tree stem sizes and shapes. To overcome these challenges we aimed to design, describe and test new semi-rigid stem-flux chambers (or sleeves). We compared semi-rigid chamber's gas permeability to CH4 against the traditional rigid chamber approach, in the laboratory and in the field, with continuous flow or syringe injections. We found that the semi-rigid chambers performed well, and had numerous benefits including reduced gas permeability and optimal stem gas exchange surface to total chamber volume ratio (Sc/Vtot) allowing better headspace mixing, especially when connected in a dynamic mode to a continuous flow gas analyser. Semi-rigid sleeves can easily be constructed and transported in multiple sizes, are extremely light, cheap to build and fast to deploy. This makes them ideal for use in remote ecosystems where access logistics are complicated.
Numerical Simulation of Dry Granular Flow Impacting a Rigid Wall Using the Discrete Element Method.
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.
Directory of Open Access Journals (Sweden)
John A. Onofrey
2016-01-01
Full Text Available This paper describes a framework for learning a statistical model of non-rigid deformations induced by interventional procedures. We make use of this learned model to perform constrained non-rigid registration of pre-procedural and post-procedural imaging. We demonstrate results applying this framework to non-rigidly register post-surgical computed tomography (CT brain images to pre-surgical magnetic resonance images (MRIs of epilepsy patients who had intra-cranial electroencephalography electrodes surgically implanted. Deformations caused by this surgical procedure, imaging artifacts caused by the electrodes, and the use of multi-modal imaging data make non-rigid registration challenging. Our results show that the use of our proposed framework to constrain the non-rigid registration process results in significantly improved and more robust registration performance compared to using standard rigid and non-rigid registration methods.
Echenique, Pablo; Calvo, Iván; Alonso, J L
2006-11-15
If constraints are imposed on a macromolecule, two inequivalent classical models may be used: the stiff and the rigid one. This work studies the effects of such constraints on the conformational equilibrium distribution (CED) of the model dipeptide HCO-L-Ala-NH(2)without any simplifying assumption. We use ab initio quantum mechanics calculations including electron correlation at the MP2 level to describe the system, and we measure the conformational dependence of all the correcting terms to the naive CED based in the potential energy surface that appear when the constraints are considered. These terms are related to mass-metric tensors determinants and also occur in the Fixman's compensating potential. We show that some of the corrections are non-negligible if one is interested in the whole Ramachandran space. On the other hand, if only the energetically lower region, containing the principal secondary structure elements, is assumed to be relevant, then, all correcting terms may be neglected up to peptides of considerable length. This is the first time, as far as we know, that the analysis of the conformational dependence of these correcting terms is performed in a relevant biomolecule with a realistic potential energy function. (c) 2006 Wiley Periodicals, Inc. J Comput Chem, 2006.
Liang, Dong; Song, Yimin; Sun, Tao; Jin, Xueying
2017-09-01
A systematic dynamic modeling methodology is presented to develop the rigid-flexible coupling dynamic model (RFDM) of an emerging flexible parallel manipulator with multiple actuation modes. By virtue of assumed mode method, the general dynamic model of an arbitrary flexible body with any number of lumped parameters is derived in an explicit closed form, which possesses the modular characteristic. Then the completely dynamic model of system is formulated based on the flexible multi-body dynamics (FMD) theory and the augmented Lagrangian multipliers method. An approach of combining the Udwadia-Kalaba formulation with the hybrid TR-BDF2 numerical algorithm is proposed to address the nonlinear RFDM. Two simulation cases are performed to investigate the dynamic performance of the manipulator with different actuation modes. The results indicate that the redundant actuation modes can effectively attenuate vibration and guarantee higher dynamic performance compared to the traditional non-redundant actuation modes. Finally, a virtual prototype model is developed to demonstrate the validity of the presented RFDM. The systematic methodology proposed in this study can be conveniently extended for the dynamic modeling and controller design of other planar flexible parallel manipulators, especially the emerging ones with multiple actuation modes.
Near real-time robust non-rigid registration of volumetric ultrasound images for neurosurgery.
Rivaz, Hassan; Collins, D Louis
2015-02-01
Ultrasound images are acquired before and after the resection of brain tumors to help the surgeon to localize the tumor and its extent and to minimize the amount of residual tumor after the resection. Because the brain undergoes large deformation between these two acquisitions, deformable image-based registration of these data sets is of substantial clinical importance. In this work, we present an algorithm for non-rigid registration of ultrasound images (RESOUND) that models the deformation with free-form cubic B-splines. We formulate a regularized cost function that uses normalized cross-correlation as the similarity metric. To optimize the cost function, we calculate its analytic derivative and use the stochastic gradient descent technique to achieve near real-time performance. We further propose a robust technique to minimize the effect of non-corresponding regions such as the resected tumor and possible hemorrhage in the post-resection image. Using manually labeled corresponding landmarks in the pre- and post-resection ultrasound volumes, we illustrate that our registration algorithm reduces the mean target registration error from an initial value of 3.7 to 1.5 mm. We also compare RESOUND with the previous work of Mercier et al. (2013) and illustrate that it has three important advantages: (i) it is fully automatic and does not require a manual segmentation of the tumor, (ii) it produces smaller registration errors and (iii) it is about 30 times faster. The clinical data set is available online on the BITE database website. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.
Flexible explicit but rigid implicit learning in a visuomotor adaptation task
Bond, Krista M.
2015-01-01
There is mounting evidence for the idea that performance in a visuomotor rotation task can be supported by both implicit and explicit forms of learning. The implicit component of learning has been well characterized in previous experiments and is thought to arise from the adaptation of an internal model driven by sensorimotor prediction errors. However, the role of explicit learning is less clear, and previous investigations aimed at characterizing the explicit component have relied on indirect measures such as dual-task manipulations, posttests, and descriptive computational models. To address this problem, we developed a new method for directly assaying explicit learning by having participants verbally report their intended aiming direction on each trial. While our previous research employing this method has demonstrated the possibility of measuring explicit learning over the course of training, it was only tested over a limited scope of manipulations common to visuomotor rotation tasks. In the present study, we sought to better characterize explicit and implicit learning over a wider range of task conditions. We tested how explicit and implicit learning change as a function of the specific visual landmarks used to probe explicit learning, the number of training targets, and the size of the rotation. We found that explicit learning was remarkably flexible, responding appropriately to task demands. In contrast, implicit learning was strikingly rigid, with each task condition producing a similar degree of implicit learning. These results suggest that explicit learning is a fundamental component of motor learning and has been overlooked or conflated in previous visuomotor tasks. PMID:25855690
Tsaousoglou, Phoebus; Michalakis, Konstantinos; Kang, Kiho; Weber, Hans-Peter; Sculean, Anton
2017-07-01
To assess survival, as well as technical and biological complication rates of partial fixed dental prostheses (FDPs) supported by implants and teeth. An electronic Medline search was conducted to identify articles, published in dental journals from January 1980 to August 2015, reporting on partial FDPs supported by implants and teeth. The search terms were categorized into four groups comprising the PICO question. Manual searches of published full-text articles and related reviews were also performed. The initial database search produced 3587 relevant titles. Three hundred and eighty-six articles were retrieved for abstract review, while 39 articles were selected for full-text review. A total of 10 studies were selected for inclusion. Overall survival rate for implants ranged between 90% and 100%, after follow-up periods with a mean range of 18-120 months. The survival of the abutment teeth was 94.1-100%, while the prostheses survival was 85-100% for the same time period. The most frequent complications were "periapical lesions" (11.53%). The most frequent technical complication was "porcelain occlusal fracture" (16.6%), followed by "screw loosening" (15%). According to the meta-analysis, no intrusion was noted on the rigid connection group, while five teeth (8.19%) were intruded in the non-rigid connection group [95% CI (0.013-0.151)]. The tooth-implant FDP seems to be a possible alternative to an implant-supported FDP. There is limited evidence that rigid connection between teeth and implants presents better results when compared with the non-rigid one. The major drawback of non-rigidly connected FDPs is tooth intrusion. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Lin, Chun-Han; Pelissier, Fanny A.; Zhang, Hui; Lakins, Jon; Weaver, Valerie M.; Park, Catherine; LaBarge, Mark A.
2015-01-01
Stiffness is a biophysical property of the extracellular matrix that modulates cellular functions, including proliferation, invasion, and differentiation, and it also may affect therapeutic responses. Therapeutic durability in cancer treatments remains a problem for both chemotherapies and pathway-targeted drugs, but the reasons for this are not well understood. Tumor progression is accompanied by changes in the biophysical properties of the tissue, and we asked whether matrix rigidity modulated the sensitive versus resistant states in HER2-amplified breast cancer cell responses to the HER2-targeted kinase inhibitor lapatinib. The antiproliferative effect of lapatinib was inversely proportional to the elastic modulus of the adhesive substrata. Down-regulation of the mechanosensitive transcription coactivators YAP and TAZ, either by siRNA or with the small-molecule YAP/TEAD inhibitor verteporfin, eliminated modulus-dependent lapatinib resistance. Reduction of YAP in vivo in mice also slowed the growth of implanted HER2-amplified tumors, showing a trend of increasing sensitivity to lapatinib as YAP decreased. Thus we address the role of stiffness in resistance to and efficacy of a HER2 pathway–targeted therapeutic via the mechanotransduction arm of the Hippo pathway. PMID:26337386
Koumi, Koffi Espoir; Chaise, Thibaut; Nelias, Daniel
2015-07-01
In this paper, the frictionless rolling contact problem between a rigid sphere and a viscoelastic half-space containing one elastic inhomogeneity is solved. The problem is equivalent to the frictionless sliding of a spherical tip over a viscoelastic body. The inhomogeneity may be of spherical or ellipsoidal shape, the later being of any orientation relatively to the contact surface. The model presented here is three dimensional and based on semi-analytical methods. In order to take into account the viscoelastic aspect of the problem, contact equations are discretized in the spatial and temporal dimensions. The frictionless rolling of the sphere, assumed rigid here for the sake of simplicity, is taken into account by translating the subsurface viscoelastic fields related to the contact problem. Eshelby's formalism is applied at each step of the temporal discretization to account for the effect of the inhomogeneity on the contact pressure distribution, subsurface stresses, rolling friction and the resulting torque. A Conjugate Gradient Method and the Fast Fourier Transforms are used to reduce the computation cost. The model is validated by a finite element model of a rigid sphere rolling upon a homogeneous vciscoelastic half-space, as well as through comparison with reference solutions from the literature. A parametric analysis of the effect of elastic properties and geometrical features of the inhomogeneity is performed. Transient and steady-state solutions are obtained. Numerical results about the contact pressure distribution, the deformed surface geometry, the apparent friction coefficient as well as subsurface stresses are presented, with or without heterogeneous inclusion.
1980-01-01
Antiproton target used for the AA (antiproton accumulator). The first type of antiproton production target used from 1980 to 1982 comprised a rod of copper 3mm diameter and 120mm long embedded in a graphite cylinder that was itself pressed into a finned aluminium container. This assembly was air-cooled and it was used in conjunction with the Van der Meer magnetic horn. In 1983 Fermilab provided us with lithium lenses to replace the horn with a view to increasing the antiproton yield by about 30%. These lenses needed a much shorter target made of heavy metal - iridium was chosen for this purpose. The 50 mm iridium rod was housed in an extension to the original finned target container so that it could be brought very close to the entrance to the lithium lens. Picture 1 shows this target assembly and Picture 2 shows it mounted together with the lithium lens. These target containers had a short lifetime due to a combination of beam heating and radiation damage. This led to the design of the water-cooled target in...
Jacobs, Donald J; Wood, Gregory G
2004-09-01
Thermodynamic stability in polypeptides is described using a novel Distance Constraint Model (DCM). Here, microscopic interactions are represented as constraints. A topological arrangement of constraints define a mechanical framework. Each constraint in the framework is associated with an enthalpic and entropic contribution. All accessible topological arrangements of distance constraints form an ensemble of mechanical frameworks, each representing a microstate of the polypeptide. A partition function is calculated exactly using a transfer matrix approach, where in many respects the DCM is similar to the Lifson-Roig model. The crucial difference is that the effect of network rigidity is explicitly calculated for each mechanical framework in the ensemble. Network rigidity is a mechanical interaction that provides a mechanism for long-range molecular cooperativity and enables a proper treatment of the nonadditivity of a microscopic free energy decomposition. Accounting for (1) helix coil conformation changes along the backbone similar to the Lifson-Roig model, (2) i to i + 4 hydrogen-bond formation breaking similar to the Zimm-Bragg model, and (3) structured unstructured solvent interaction (hydration effects), a six-parameter DCM describes normal and inverted helix-coil transitions in polypeptides. Under suitable mixed solvent conditions heat and cold denaturation is predicted. Model parameters are fitted to experimental data showing different degrees of cold denaturation in monomeric polypeptides in aqueous hexafluoroisopropanol (HFIP) solution at various HFIP concentrations. By assuming a linear HFIP concentration dependence (up to 6% by mole fraction) on model parameters, all essential experimentally observed features are captured.
Chen, Liang-Wei; Yung, Kin-Lam; Chan, Ying-Shing
2005-11-01
Parkinson' disease (PD) is a most common and debilitating degenerative disease resulted from massive loss of dopamine neurons in the substantia nigra pars compacta, which is characterized by severe motor symptoms of tremor, bradykinesia, rigidity and postural instability. Protection of nigral dopamine neurons from progressive degenerative death and cell replacement of novel dopamine neurons are hopeful strategies against PD in humans. The reactive astrocytes or functional activation of astrocytes abundantly occurred in brain insults including trauma, ischemia, and 6-OHDA or MPTP-treated PD animal models. Although they were traditionally assumed to impede neuronal regeneration by forming glial scars, growing evidence has indicated that reactive astrocytes do offer crucial benefits in functional recovery of brain injuries. The reactive astrocytes can produce various neurotrophic factors for neuron survival, synthesize extracellular substrates for axonal outgrowth and synaptogenesis, act as scavengers for free radical and excess glutamate, and promote neurogenesis of neural progenitor cells in the adult brains. We thereafter hypothesize that reactive astrocytes may also play important roles in the protection of nigral dopamine neurons or transplanted dopamine cells through their neurotrophic functions and active interaction with dopamine neurons or neural progenitor cells. Future approaches deserve to target on neurotrophic functions of reactive astrocytes in the basal ganglia and interventions to facilitate survival and axonal regeneration of dopamine neurons or differentiation of dopamine progenitor cells. Novel pharmaceutical and cell replacement strategies will hopefully be developed by potential manipulation of reactive astrocytes in the basal ganglia in prevention and treatment of Parkinson's disease.
Evaluation of Rigid Cochlear Models for Measuring Cochlear Implant Electrode Position.
Cakir, Ahmet; Labadie, Robert F; Zuniga, M Geraldine; Dawant, Benoit M; Noble, Jack H
2016-12-01
To investigate the accuracy of rigid cochlear models in measuring intra-cochlear positions of cochlear implant (CI) electrodes. Ninety three adults who had undergone CI and pre- and postoperative computed tomographic (CT) imaging. Seven rigid models of cochlear anatomy were constructed using micro-CTs of cochlear specimens. Using each of the seven models, the position of each electrode in each of the 98 ears in our dataset was measured as its depth along the length of the cochlea, its distance to the basilar membrane, and its distance to the modiolus. Cochlear duct length was also measured using each model. Standard deviation (SD) across rigid cochlear models in measures of electrode depth, distance to basilar membrane, distance to modiolus, and length of the cochlear duct at two turns were 0.68, 0.11, 0.15, and 1.54 mm. Comparing the estimated position of the electrodes with respect to the basilar membrane, i.e., deciding whether an electrode was located within the scala tympani (ST) or the scala vestibuli (SV), there was not a unanimous agreement between the models for 19% of all the electrodes. With respect to the modiolus, each electrode was classified into one of the three groups depending on its modiolar distance: close, medium, and far. Rigid models did not unanimously agree on modiolar distance for approximately 50% of the electrodes tested. Inter-model variance of rigid cochlear models exists, demonstrating that measurements made using rigid cochlear models are limited in terms of accuracy because of non-rigid inter-subject variations in cochlear anatomy.
Ignasiak, Dominika; Ferguson, Stephen J; Arjmand, Navid
2016-09-06
A number of musculoskeletal models of the human spine have been used for predictions of lumbar and muscle forces. However, the predictive power of these models might be limited by a commonly made assumption; thoracic region is represented as a single lumped rigid body. This study hence aims to investigate the impact of such assumption on the predictions of spinal and muscle forces. A validated thoracolumbar spine model was used with a flexible thorax (T1-T12), a completely rigid one or rigid with thoracic posture updated at each analysis step. The simulations of isometric forward flexion up to 80°, with and without a 20kg hand load, were performed, based on the previously measured kinematics. Depending on the simulated task, the rigid model predicted slightly or moderately lower compressive loading than the flexible one. The differences were relatively greater at the upper lumbar levels (average underestimation of 14% at the T12L1 for flexion tasks and of 18% for flexion tasks with hand load) as compared to the lower levels (3% and 8% at the L5S1 for unloaded and loaded tasks, respectively). The rigid model with updated thoracic posture predicted compressive forces similar to those of the rigid model. Predicted muscle forces were, however, very different between the three models. This study indicates that the lumbar spine models with a rigid thorax definition can be used for loading investigations at the lowermost spinal levels. For predictions of upper lumbar spine loading, using models with an articulated thorax is advised. Copyright © 2016 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Octavian PREOTU
2011-06-01
Full Text Available The paper analyzes, in parallel, common aspects and differences in the behavior of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage. The effects of the main constructional dimensions of the horizontal empennage on lift cancelling and horizontal empennage control are being analyzed
Jasak, Hrvoje; Gatin, Inno; Vukčević, Vuko
2017-10-01
In Fluid Structure Interaction (FSI) problems encountered in marine hydrodynamics, the pressure field and the velocity of the rigid body are tightly coupled. This coupling is traditionally resolved in a partitioned manner by solving the rigid body motion equations once per nonlinear correction loop, updating the position of the body and solving the fluid flow equations in the new configuration. The partitioned approach requires a large number of nonlinear iteration loops per time-step. In order to enhance the coupling, a monolithic approach is proposed in Finite Volume (FV) framework, where the pressure equation and the rigid body motion equations are solved in a single linear system. The coupling is resolved by solving the rigid body motion equations once per linear solver iteration of the pressure equation, where updated pressure field is used to calculate new forces acting on the body, and by introducing the updated rigid body boundary velocity in to the pressure equation. In this paper the monolithic coupling is validated on a simple 2D heave decay case. Additionally, the method is compared to the traditional partitioned approach (i.e. "strongly coupled" approach) in terms of computational efficiency and accuracy. The comparison is performed on a seakeeping case in regular head waves, and it shows that the monolithic approach achieves similar accuracy with fewer nonlinear correctors per time-step. Hence, significant savings in computational time can be achieved while retaining the same level of accuracy.
An improved cutoff rigidity model based on a modification of the Tyganenko 1989 magnetospheric model
Smart, Don
The Tyganenko (Planet. Space Sci., 37, 5-20, 1989) magnetospheric model is convenient to use and requires less computer recourses for the computation of geomagnetic cutoff rigidity models than the more sophisticated magnetospheric models. Its use by Smart et al. (Adv. Space Res., 37, 1206-1217, 2006) resulted in a useful set of world grids of geomagnetic cutoff rigidity values indexed by Kp and UT. Recent evaluation of these cutoff rigidity values by Rodgers et al. (J. Geophys. Res., 111, A04222, 2006) shows that for Kp values larger than 5, the equatorward latitude displacements of the cutoff rigidity contours were overestimated. A comparison of the Dst and Kp indices for the data interval used to construct the Tyganenko 1989 magnetospheric model shows that Dst increments of -50 nT are a good approximation of the effective Kp increment beyond the Kp 5 value. We present an improved set of cutoff rigidity world grids indexed by Kp and UT that are a better fit to the Rodgers et al. (2006) data than the original values by Smart et al. (2006).
Vertical velocity distribution in open-channel flow with rigid vegetation.
Zhu, Changjun; Hao, Wenlong; Chang, Xiangping
2014-01-01
In order to experimentally investigate the effects of rigid vegetation on the characteristics of flow, the vegetations were modeled by rigid cylindrical rod. Flow field is measured under the conditions of submerged rigid rod in flume with single layer and double layer vegetations. Experiments were performed for various spacings of the rigid rods. The vegetation models were aligned with the approaching flow in a rectangular channel. Vertical distributions of time-averaged velocity at various streamwise distances were evaluated using an acoustic Doppler velocimeter (ADV). The results indicate that, in submerged conditions, it is difficult to described velocity distribution along the entire depth using unified function. The characteristic of vertical distribution of longitudinal velocity is the presence of inflection. Under the inflection, the line is convex and groove above inflection. The interaction of high and low momentum fluids causes the flow to fold and creates strong vortices within each mixing layer. Understanding the flow phenomena in the area surrounding the tall vegetation, especially in the downstream region, is very important when modeling or studying the riparian environment. ADV measures of rigid vegetation distribution of the flow velocity field can give people a new understanding.
Allioux-Guérin, Myriam; Icard-Arcizet, Delphine; Durieux, Christiane; Hénon, Sylvie; Gallet, François; Mevel, Jean-Claude; Masse, Marie-Jo; Tramier, Marc; Coppey-Moisan, Maïté
2009-01-01
Abstract We investigate the dynamic response of single cells to weak and local rigidities, applied at controlled adhesion sites. Using multiple latex beads functionalized with fibronectin, and each trapped in its own optical trap, we study the reaction in real time of single 3T3 fibroblast cells to asymmetrical tensions in the tens of pN · μm−1 range. We show that the cell feels a rigidity gradient even at this low range of tension, and over time develops an adapted change in the force exerted on each adhesion site. The rate at which force increases is proportional to trap stiffness. Actomyosin recruitment is regulated in space and time along the rigidity gradient, resulting in a linear relationship between the amount of recruited actin and the force developed independently in trap stiffness. This time-regulated actomyosin behavior sustains a constant and rigidity-independent velocity of beads inside the traps. Our results show that the strengthening of extracellular matrix-cytoskeleton linkages along a rigidity gradient is regulated by controlling adhesion area and actomyosin recruitment, to maintain a constant deformation of the extracellular matrix. PMID:18931254
Otake, Y.; Murphy, R. J.; Kutzer, M. D.; Taylor, R. H.; Armand, M.
2014-03-01
Background: Snake-like dexterous manipulators may offer significant advantages in minimally-invasive surgery in areas not reachable with conventional tools. Precise control of a wire-driven manipulator is challenging due to factors such as cable deformation, unknown internal (cable friction) and external forces, thus requiring correcting the calibration intraoperatively by determining the actual pose of the manipulator. Method: A method for simultaneously estimating pose and kinematic configuration of a piecewise-rigid object such as a snake-like manipulator from a single x-ray projection is presented. The method parameterizes kinematics using a small number of variables (e.g., 5), and optimizes them simultaneously with the 6 degree-of-freedom pose parameter of the base link using an image similarity between digitally reconstructed radiographs (DRRs) of the manipulator's attenuation model and the real x-ray projection. Result: Simulation studies assumed various geometric magnifications (1.2-2.6) and out-of-plane angulations (0°-90°) in a scenario of hip osteolysis treatment, which demonstrated the median joint angle error was 0.04° (for 2.0 magnification, +/-10° out-of-plane rotation). Average computation time was 57.6 sec with 82,953 function evaluations on a mid-range GPU. The joint angle error remained lower than 0.07° while out-of-plane rotation was 0°-60°. An experiment using video images of a real manipulator demonstrated a similar trend as the simulation study except for slightly larger error around the tip attributed to accumulation of errors induced by deformation around each joint not modeled with a simple pin joint. Conclusions: The proposed approach enables high precision tracking of a piecewise-rigid object (i.e., a series of connected rigid structures) using a single projection image by incorporating prior knowledge about the shape and kinematic behavior of the object (e.g., each rigid structure connected by a pin joint parameterized by a
van der Laan, Mark J
2011-01-01
The statistics profession is at a unique point in history. The need for valid statistical tools is greater than ever; data sets are massive, often measuring hundreds of thousands of measurements for a single subject. The field is ready to move towards clear objective benchmarks under which tools can be evaluated. Targeted learning allows (1) the full generalization and utilization of cross-validation as an estimator selection tool so that the subjective choices made by humans are now made by the machine, and (2) targeting the fitting of the probability distribution of the data toward the targe
Interactive initialization of 2D/3D rigid registration
Energy Technology Data Exchange (ETDEWEB)
Gong, Ren Hui; Güler, Özgür [The Sheikh Zayed Institute for Pediatric Surgical Innovation, Children' s National Medical Center, Washington, DC 20010 (United States); Kürklüoglu, Mustafa [Department of Cardiac Surgery, Children' s National Medical Center, Washington, DC 20010 (United States); Lovejoy, John [Department of Orthopaedic Surgery and Sports Medicine, Children' s National Medical Center, Washington, DC 20010 (United States); Yaniv, Ziv, E-mail: ZYaniv@childrensnational.org [The Sheikh Zayed Institute for Pediatric Surgical Innovation, Children' s National Medical Center, Washington, DC 20010 and Departments of Pediatrics and Radiology, George Washington University, Washington, DC 20037 (United States)
2013-12-15
Purpose: Registration is one of the key technical components in an image-guided navigation system. A large number of 2D/3D registration algorithms have been previously proposed, but have not been able to transition into clinical practice. The authors identify the primary reason for the lack of adoption with the prerequisite for a sufficiently accurate initial transformation, mean target registration error of about 10 mm or less. In this paper, the authors present two interactive initialization approaches that provide the desired accuracy for x-ray/MR and x-ray/CT registration in the operating room setting. Methods: The authors have developed two interactive registration methods based on visual alignment of a preoperative image, MR, or CT to intraoperative x-rays. In the first approach, the operator uses a gesture based interface to align a volume rendering of the preoperative image to multiple x-rays. The second approach uses a tracked tool available as part of a navigation system. Preoperatively, a virtual replica of the tool is positioned next to the anatomical structures visible in the volumetric data. Intraoperatively, the physical tool is positioned in a similar manner and subsequently used to align a volume rendering to the x-ray images using an augmented reality (AR) approach. Both methods were assessed using three publicly available reference data sets for 2D/3D registration evaluation. Results: In the authors' experiments, the authors show that for x-ray/MR registration, the gesture based method resulted in a mean target registration error (mTRE) of 9.3 ± 5.0 mm with an average interaction time of 146.3 ± 73.0 s, and the AR-based method had mTREs of 7.2 ± 3.2 mm with interaction times of 44 ± 32 s. For x-ray/CT registration, the gesture based method resulted in a mTRE of 7.4 ± 5.0 mm with an average interaction time of 132.1 ± 66.4 s, and the AR-based method had mTREs of 8.3 ± 5.0 mm with interaction times of 58 ± 52 s. Conclusions: Based on
Interactive initialization of 2D/3D rigid registration.
Gong, Ren Hui; Güler, Özgür; Kürklüoglu, Mustafa; Lovejoy, John; Yaniv, Ziv
2013-12-01
Registration is one of the key technical components in an image-guided navigation system. A large number of 2D/3D registration algorithms have been previously proposed, but have not been able to transition into clinical practice. The authors identify the primary reason for the lack of adoption with the prerequisite for a sufficiently accurate initial transformation, mean target registration error of about 10 mm or less. In this paper, the authors present two interactive initialization approaches that provide the desired accuracy for x-ray/MR and x-ray/CT registration in the operating room setting. The authors have developed two interactive registration methods based on visual alignment of a preoperative image, MR, or CT to intraoperative x-rays. In the first approach, the operator uses a gesture based interface to align a volume rendering of the preoperative image to multiple x-rays. The second approach uses a tracked tool available as part of a navigation system. Preoperatively, a virtual replica of the tool is positioned next to the anatomical structures visible in the volumetric data. Intraoperatively, the physical tool is positioned in a similar manner and subsequently used to align a volume rendering to the x-ray images using an augmented reality (AR) approach. Both methods were assessed using three publicly available reference data sets for 2D/3D registration evaluation. In the authors' experiments, the authors show that for x-ray/MR registration, the gesture based method resulted in a mean target registration error (mTRE) of 9.3 ± 5.0 mm with an average interaction time of 146.3 ± 73.0 s, and the AR-based method had mTREs of 7.2 ± 3.2 mm with interaction times of 44 ± 32 s. For x-ray/CT registration, the gesture based method resulted in a mTRE of 7.4 ± 5.0 mm with an average interaction time of 132.1 ± 66.4 s, and the AR-based method had mTREs of 8.3 ± 5.0 mm with interaction times of 58 ± 52 s. Based on the authors' evaluation, the authors conclude
Aspects concerning verification methods and rigidity increment of complex technological systems
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.
Estimating the orientation of a rigid body moving in space using inertial sensors
Energy Technology Data Exchange (ETDEWEB)
He, Peng, E-mail: peng.he.1@ulaval.ca; Cardou, Philippe, E-mail: pcardou@gmc.ulaval.ca [Université Laval, Robotics Laboratory, Department of Mechanical Engineering (Canada); Desbiens, André, E-mail: andre.desbiens@gel.ulaval.ca [Université Laval, Department of Electrical and Computer Engineering (Canada); Gagnon, Eric, E-mail: Eric.Gagnon@drdc-rddc.gc.ca [RDDC Valcartier (Canada)
2015-09-15
This paper presents a novel method of estimating the orientation of a rigid body moving in space from inertial sensors, by discerning the gravitational and inertial components of the accelerations. In this method, both a rigid-body kinematics model and a stochastic model of the human-hand motion are formulated and combined in a nonlinear state-space system. The state equation represents the rigid body kinematics and stochastic model, and the output equation represents the inertial sensor measurements. It is necessary to mention that, since the output equation is a nonlinear function of the state, the extended Kalman filter (EKF) is applied. The absolute value of the error from the proposed method is shown to be less than 5 deg in simulation and in experiments. It is apparently stable, unlike the time-integration of gyroscope measurements, which is subjected to drift, and remains accurate under large accelerations, unlike the tilt-sensor method.
Compliant mechanism road bicycle brake: a rigid-body replacement case study
Energy Technology Data Exchange (ETDEWEB)
Olsen, Brian M [Los Alamos National Laboratory; Howell, Larry L [NON LANL; Magleby, Spencer P [NON LANL
2011-01-19
The design of high-performance bicycle brakes is complicated by the competing design objectives of increased performance and low weight. But this challenge also provides a good case study to demonstrate the design of compliant mechanisms to replace current rigid-link mechanisms. This paper briefly reviews current road brake designs, demonstrates the use of rigid-body replacement synthesis to design a compliant mechanism, and illustrates the combination of compliant mechanism design tools. The resulting concept was generated from the modified dual-pivot brake design and is a partially compliant mechanism where one pin has the dual role of a joint and a mounting pin. The pseudo-rigid-body model, finite element analysis, and optimization algorithms are used to generate design dimensions, and designs are considered for both titanium and E-glass flexures. The resulting design has the potential of reducing the part count and overall weight while maintaining a performance similar to the benchmark.
Adaptive rheology and ordering of cell cytoskeleton govern matrix rigidity sensing.
Gupta, Mukund; Sarangi, Bibhu Ranjan; Deschamps, Joran; Nematbakhsh, Yasaman; Callan-Jones, Andrew; Margadant, Felix; Mège, René-Marc; Lim, Chwee Teck; Voituriez, Raphaël; Ladoux, Benoît
2015-06-25
Matrix rigidity sensing regulates a large variety of cellular processes and has important implications for tissue development and disease. However, how cells probe matrix rigidity, and hence respond to it, remains unclear. Here, we show that rigidity sensing and adaptation emerge naturally from actin cytoskeleton remodelling. Our in vitro experiments and theoretical modelling demonstrate a biphasic rheology of the actin cytoskeleton, which transitions from fluid on soft substrates to solid on stiffer ones. Furthermore, we find that increasing substrate stiffness correlates with the emergence of an orientational order in actin stress fibres, which exhibit an isotropic to nematic transition that we characterize quantitatively in the framework of active matter theory. These findings imply mechanisms mediated by a large-scale reinforcement of actin structures under stress, which could be the mechanical drivers of substrate stiffness-dependent cell shape changes and cell polarity.
Technical characteristics of rigid sprayed PUR and PIR foams used in construction industry
Gravit, Marina; Kuleshin, Aleksey; Khametgalieva, Elina; Karakozova, Irina
2017-10-01
The article describes the distinctive properties of rigid polyurethane foam and polyisocyanurate (PUR and PIR). A brief review of the research was carried out on their modification with an objective to improve the thermal insulation properties and reducing the combustibility. A comparative analysis of the technical characteristics of rigid PUR and PIR foams of various manufacturers is presented. The problems of the state of the market for the production of polyurethane foam and polyisocyanurate in Russia have been marked. It is established that the further development of the fabrication technology of heat-insulating sprayed rigid PUR and PIR foams requires uniformity of technical characteristics of original components and finished products. Moreover, it requires the creation of unified information base for raw materials and auxiliary materials used in the production of PUR and PIR foam.
Rigid spine reinforced polymer microelectrode array probe and method of fabrication
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.
Modelling of Rigid Walled Enclosure Couple to a Flexible Wall using Matlab and Ansys APDL
Zaman, I.; Rozlan, S. A. M.; Azmir, N. A.; Ismon, M.; Madlan, M. A.; Yahya, M. N.; Zainulabidin, M. H.; Sani, M. S. M.; Noh, M. F. M.
2017-10-01
Generally, solutions to improve the noise problems in enclosure are to redesign or modifying the system such as increasing the thickness of the wall panels, enhancing the elasticity of the structure, and increase the damping mechanism of the wall structure. In this paper, the application of vibroacoustic modelling of enclosure coupled to a flexible wall was presented. The sound pressure characteristics of rigid walled enclosure, such as natural frequency and mode shape were determined using two approaches which are finite element simulation of Ansys® and mathematical model. The mathematical equations derived in Matlab® such as rigid walled enclosure and rigid walled enclosure coupled to flexible wall were used to validate finite element analysis (FEA). The result indicates that the theory and FEA display in a good agreement. Thus, proved that the FE model was accurate and can be applied in further research such as sound pressure and noise attenuation in enclosure.
Onofrey, John A; Staib, Lawrence H; Sarkar, Saradwata; Venkataraman, Rajesh; Nawaf, Cayce B; Sprenkle, Preston C; Papademetris, Xenophon
2017-07-01
Accurate and robust non-rigid registration of pre-procedure magnetic resonance (MR) imaging to intra-procedure trans-rectal ultrasound (TRUS) is critical for image-guided biopsies of prostate cancer. Prostate cancer is one of the most prevalent forms of cancer and the second leading cause of cancer-related death in men in the United States. TRUS-guided biopsy is the current clinical standard for prostate cancer diagnosis and assessment. State-of-the-art, clinical MR-TRUS image fusion relies upon semi-automated segmentations of the prostate in both the MR and the TRUS images to perform non-rigid surface-based registration of the gland. Segmentation of the prostate in TRUS imaging is itself a challenging task and prone to high variability. These segmentation errors can lead to poor registration and subsequently poor localization of biopsy targets, which may result in false-negative cancer detection. In this paper, we present a non-rigid surface registration approach to MR-TRUS fusion based on a statistical deformation model (SDM) of intra-procedural deformations derived from clinical training data. Synthetic validation experiments quantifying registration volume of interest overlaps of the PI-RADS parcellation standard and tests using clinical landmark data demonstrate that our use of an SDM for registration, with median target registration error of 2.98 mm, is significantly more accurate than the current clinical method. Furthermore, we show that the low-dimensional SDM registration results are robust to segmentation errors that are not uncommon in clinical TRUS data. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Abdulla Al Ansari
2013-09-01
Full Text Available Introduction: Penile prosthesis implantation is one of the treatment choices that is kept for patients who were not satisfied with other treatments. Although penile prosthesis satisfaction rates are higher, there are some dissatisfied patients. The patients’ reasons are mostly shortness and softness of implanted prosthesis. It was previously demonstrated that penile axial rigidity of more than 500 grams is enough for successful vaginal intromission. To our knowledge, there is no study comparing axial rigidity of penile prosthesis and satisfaction. Objectives: The aim of this study was to examine whether axial rigidity of penile prosthesis had impact on patient and partner satisfaction. Materials and Methods: We enrolled one hundred patients who were implanted penile prosthesis before to evaluate their penile axial rigidity. We used Rigidometry (by using the digital inflection rigidometer to assess the minimal axial pressure to bend the implanted penis. Results: We demonstrated that mean axial pressure to bend the implanted penis was 984.8 ± 268.7 grams. Overall satisfaction score with the penile prosthesis implant was 4.55 and 4.49 (out of 5 in patients and partners, respectively. In total, seven men were unsatisfied with their implant and reported a mean satisfaction score of 0.6 ± 0.48 (out of 5. All prostheses types showed good and more than 500 grams axial rigidity. The patients with Ambicor type, which were buckled at about 710.5 grams, showed worse satisfaction rates in comparison to other prostheses in two patients. Digital inflection rigidometer results of other penile prosthesis types in unsatisfied patient were 842.0, 872.0, 887.0 and 920 g. in CX700, Titan, Genesis and Titan OTR, respectively. Conclusion: We demonstrated that dissatisfaction rate was highest in Ambicor prosthesis implanted patients. Additionally, patients with 3-piece penile prosthesis were more satisfied than 2-piece or malleable ones, interestingly, although
Effect of Cyclooxygenase-2 inhibition on rigidity of animal model of Parkinson's disease
Directory of Open Access Journals (Sweden)
Fathi Moghaddam
2008-08-01
Full Text Available "nBackground: Parkinson's disease (PD is a degenerative neurodopaminergic disease in nigrostriatum pathway of animals and human, the resultant loss of nerve terminals accompanied by dopamine-glutamate and other related neurotransmitters-imbalances in this pathway are responsible for most of the movement abnormalities. Increasing evidence suggests that an inflammatory reaction accompanies the pathological processes caused by Cyclooxygenase-2 (COX-2 seen in many neurodegenerative disorders, including PD. These findings have not indicated any evidence based on the effect of selective and non selective COX-2 inhibitors on the rigidity of PD."n"nMethods: The rats left substantia nigra pars compacta (SNc was destroyed using the electrical lesion thus PD model was created. Then oral aspirin and celecoxib (200, 400 mg/kg were administrated to parkinsonian rats acutely and then the rigidity was evaluated using Murprogo's Method."n"nResults: Both compounds were able to decrease the rigidity of parkinsonian rats (p<0.05 respectively but selective cox-2 inhibitor (celecoxib was found more effective and potent than that of non selective cox-2 inhibitor (aspirin."n"nConclusion: The findings suggest that COX-2 inhibition decreases the rigidity of PD in the animal model. Therefore, as results of the study COX-2 inhibition was shown good evidence based on the use of aspirin and celecoxib and PD affiliated rigidity improvement that this can be beneficial and interest for neuroscientists. These findings are additional pharmacological and medicinal information to further assess of non steroidal anti inflammatory drugs (NSAIDs as alternative therapeutic agents for PD affiliated rigidity treatment. Further experiments seem to be necessary to complete this research such as investigation the effects of NSAIDs on the striatum neurotransmission pathway
Rigid Residue Scan Simulations Systematically Reveal Residue Entropic Roles in Protein Allostery.
Directory of Open Access Journals (Sweden)
Robert Kalescky
2016-04-01
Full Text Available 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.
Dimensional Metrology of Non-rigid Parts Without Specialized Inspection Fixtures =
Sabri, Vahid
Quality control is an important factor for manufacturing companies looking to prosper in an era of globalization, market pressures and technological advances. Functionality and product quality cannot be guaranteed without this important aspect. Manufactured parts have deviations from their nominal (CAD) shape caused by the manufacturing process. Thus, geometric inspection is a very important element in the quality control of mechanical parts. We will focus here on the geometric inspection of non-rigid (flexible) parts which are widely used in the aeronautic and automotive industries. Non-rigid parts can have different forms in a free-state condition compared with their nominal models due to residual stress and gravity loads. To solve this problem, dedicated inspection fixtures are generally used in industry to compensate for the displacement of such parts for simulating the use state in order to perform geometric inspections. These fixtures and the installation and inspection processes are expensive and time-consuming. Our aim in this thesis is therefore to develop an inspection method which eliminates the need for specialized fixtures. This is done by acquiring a point cloud from the part in a free-state condition using a contactless measuring device such as optical scanning and comparing it with the CAD model for the deviation identification. Using a non-rigid registration method and finite element analysis, we numerically inspect the profile of a non-rigid part. To do so, a simulated displacement is performed using an improved definition of displacement boundary conditions for simulating unfixed parts. In addition, we propose a numerical method for dimensional metrology of non-rigid parts in a free-state condition based on the arc length measurement by calculating the geodesic distance using the Fast Marching Method (FMM). In this thesis, we apply our developed methods on industrial non-rigid parts with free-form surfaces simulated with different types of
Steiner, Mark E; Smart, L Ryan
2012-06-01
This study evaluated the ability of flexible instruments compared with rigid instruments to place anatomic femoral tunnels in anterior cruciate ligament reconstructions by use of both transtibial drilling and anteromedial drilling without hyperflexion. Rigid and flexible pins were placed in 12 matched pairs of cadaveric knees with transtibial drilling (6 pairs) and anteromedial drilling (6 pairs) at 110° of flexion. Intraosseous pin lengths, femoral exit locations, and tunnel alignment were measured. Transtibial drilling with rigid pins placed relatively vertical femoral tunnels 5.8 ± 1.0 mm superior to the central anterior cruciate ligament insertion. Transtibial drilling with flexible pins placed tunnels in the center of the femoral attachment, but the tunnels were relatively close to the posterior femoral cortex, with a mean distance of 8.0 ± 5.9 mm (P Tunnel lengths with flexible pins were longer (42.0 ± 7.2 mm) compared with tunnel lengths with rigid pins (32.5 ± 7.1 mm) (P tunnels. Transtibial drilling with flexible pins produced anatomic tunnels, but the tunnels were close to the posterior femoral cortex. Anteromedial drilling without hyperflexion produced anatomic tunnels by use of rigid and flexible instruments, but with flexible instruments, the tunnels were longer and were farther from the posterior femoral cortex. Anteromedial drilling with flexible pins produced tunnels with good length and the best position. Flexible instruments compared with rigid instruments can facilitate the creation of anatomic femoral tunnels by use of anteromedial drilling without hyperflexion. Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
Computing the Free Energy along a Reaction Coordinate Using Rigid Body Dynamics.
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
Al Ansari, Abdulla; Talib, Raidh A; Canguven, Onder; Shamsodini, Ahmad
2013-09-26
Penile prosthesis implantation is one of the treatment choices that is kept for patients who were not satisfied with other treatments. Although penile prosthesis satisfaction rates are higher, there are some dissatisfied patients. The patients’ reasons are mostly shortness and softness of implanted prosthesis. It was previously demonstrated that penile axial rigidity of more than 500 grams is enough for successful vaginal intromission. To our knowledge, there is no study comparing axial rigidity of penile prosthesis and satisfaction. The aim of this study was to examine whether axial rigidity of penile prosthesis had impact on patient and partner satisfaction. We enrolled one hundred patients who were implanted penile prosthesis before to evaluate their penile axial rigidity. We used Rigidometry (by using the digital inflection rigidometer) to assess the minimal axial pressure to bend the implanted penis. We demonstrated that mean axial pressure to bend the implanted penis was 984.8 ± 268.7 grams. Overall satisfaction score with the penile prosthesis implant was 4.55 and 4.49 (out of 5) in patients and partners, respectively. In total, seven men were unsatisfied with their implant and reported a mean satisfaction score of 0.6 ± 0.48 (out of 5). All prostheses types showed good and more than 500 grams axial rigidity. The patients with Ambicor type, which were buckled at about 710.5 grams, showed worse satisfaction rates in comparison to other prostheses in two patients. Digital inflection rigidometer results of other penile prosthesis types in unsatisfied patient were 842.0, 872.0, 887.0 and 920 g. in CX700, Titan, Genesis and Titan OTR, respectively. We demonstrated that dissatisfaction rate was highest in Ambicor prosthesis implanted patients. Additionally, patients with 3-piece penile prosthesis were more satisfied than 2-piece or malleable ones, interestingly, although some cases had lower axial rigidity results.
Reichl, Michael; Kueny, Rebecca A; Danyali, Reza; Obid, Peter; Übeyli, Hüseyin; Püschel, Klaus; Morlock, Michael M; Huber, Gerd; Niemeyer, Thomas; Richter, Alexander
2017-05-01
Biomechanical ex vivo study. To determine if topping off instrumentation can reduce the hypermobility in the adjacent segments when compared with the classic rigid spinal instrumentation. Long rigid instrumentation might increase the mechanical load in the adjacent segments, the resulting hypermobility, and the risk for adjacent segment disease. Topping off instrumentation intends to reduce the hypermobility at the adjacent level by more evenly distributing segmental motion and, thereby, potentially mitigating adjacent level disease. Eight human spines (Th12-L5) were divided into 2 groups. In the rigid group, a 3-segment metal rod instrumentation (L2-L5) was performed. The hybrid group included a 2-segment metal rod instrumentation (L3-L5) with a dynamic topping off instrumentation (L2-L3). Each specimen was tested consecutively in 3 different configurations: native (N=8), 2-segment rod instrumentation (L3-L5, N=8), 3-segment instrumentation (rigid: N=4, hybrid: N=4). For each configuration the range of motion (ROM) of the whole spine and each level was measured by a motion capture system during 5 cycles of extension-flexion (angle controlled to ±5 degrees, 0.1 Hz frequency, no preload). In comparison with the intact spine, both the rigid 3-segment instrumentation and the hybrid instrumentation significantly reduced the ROM in the instrumented segments (L2-L5) while increasing the movement in the adjacent segment L1-L2 (P=0.002, η=0.82) and in Th12-L1 (Pinstrumentation in all segments. Introducing the dynamic topping off did not impart any significant difference in the segmental motion when compared with the rigid instrumentation. Therefore, the current biomechanical study could not show a benefit of using this specific topping off instrumentation to solve the problem of adjacent segment disease.
The Incidence and Evolution of Parkinsonian Rigidity in Rett Syndrome: A Pilot Study.
Humphreys, Peter; Barrowman, Nick
2016-07-01
Patients with Rett syndrome (RTT) may demonstrate parkinsonian features. Here, we report a preliminary cross-sectional and prospective evaluation of the evolution, regional distribution, and eventual incidence of rigid tone in a cohort of MECP2 mutation-positive patients. In 51 participants, muscle tone rigidity in extremity regions and neck plus hypomimia were quantified using an RTT rigidity distribution (RTTRD) score with a range of 0 to 15. RTTRD scores were correlated with age, ability to walk and speak, mutation type, and, in a small subgroup (n=9), cerebrospinal fluid (CSF) homovanillic acid (HVA) and 5-hydroxyindole-acetic acid levels. Participant ages ranged from 2 years and 5 months, to 54 years. Rigidity was found in 43/51 (84.3%); it appeared as early as age 3, increased in extent with age, and was present in all participants aged ≥13. Ankle region rigidity appeared first, followed by proximal legs, arms, neck, and face. Ambulatory participants (n=21) had lower RTTRD scores than nonambulatory (n=30; p=0.003). We found a trend to lower scores in participants with retained speech (n=13) versus those with none (n=38; p=0.074), and no difference in scores for those with truncating (n=25) versus missense mutations (n=22; p=0.387). RTTRD scores correlated negatively with CSF HVA levels (R=-0.83; p=0.005), but not with 5-hydroxyindole-acetic acid levels (R=-0.45; p=0.22). Although assessment of muscle tone is somewhat subjective and the RTTRD has not been validated, this study nevertheless suggests that parkinsonian rigidity in RTT is common and frequently increases in extent with age; its severity correlates directly with impaired ambulation and inversely with CSF HVA levels.
Levy, R.
1991-01-01
Post-processing algorithms are given to compute the vibratory elastic-rigid coupling matrices and the modal contributions to the rigid-body mass matrices and to the effective modal inertias and masses. Recomputation of the elastic-rigid coupling matrices for a change in origin is also described. A computational example is included. The algorithms can all be executed by using standard finite-element program eigenvalue analysis output with no changes to existing code or source programs.
Directory of Open Access Journals (Sweden)
Talat Körpınar
2012-01-01
Full Text Available In this paper, we study spacelike biharmonic slant helices according to Bishop frame in the Lorentzian group of rigid motions E(1,1. We characterize the spacelike biharmonic slant helices in terms of their curvatures in the Lorentzian group of rigid motions E(1,1. Finally, we obtain parametric equations of spacelike biharmonic slant helices according to Bishop frame in the Lorentzian group of rigid motions E(1,1.
An entropy model with variable target
K O Jörnsten; Larsson, T; J T Lundgren; Migdalas, A.
1990-01-01
In this paper an entropy model with variable target is presented, in which target values are assumed to belong to a specified convex set, so that multiple base-year information and forecasts of future trends can be handled without prior aggregation of such information into one fixed target. Three solution methods for such a model are presented -- one cutting-plane and two search methods -- all of which utilize the fact that entropy models with fixed targets can be solved efficiently. Some com...
Directory of Open Access Journals (Sweden)
Mihoko Sakurai
2012-12-01
Full Text Available A survey of the municipal government ICT divisions during and after the 2011 Great East Japan Earthquake and Tsunami crisis reveals the need for creative responses for “beyond assumed level” disasters. Complexity and diversity of the damage were simply too great for any plans to assume. Resident needs toward the municipal governments were also diverse and changed quickly as the time went by. The research also indicates that there would be ways to strengthen the capabilities to execute such spontaneous responses. Creative solutions executed during the 3.11 crisis were supported by the existence of open source software available on the net and skilled engineers that were capable of exploiting them. Frugal information system will be useful to improve preparedness for creative responses
Cosmic Rays In The Magnetosphere, 2. Apparent Cut-off Rigidities and Coupling Functions
Dorman, L. I.; Danilova, O. A.; Iucci, N.; Parisi, M.; Ptitsyna, N. G.; Tyasto, M. I.; Villoresi, G.
We calculate the apparent cut-off rigidities along the survey Italy-Antarctica-Italy** on the basis of results of Danilova et al. (2001) on trajectory calculations for inclined cut- off rigidities at eight azimuths (through 45?) and five zeniths angles (through 15?) along the survey. For calculations of apparent cut-off rigidities we use also the infor- mation on integral multiplicities of secondary neutrons in dependence of zenith angle of incident primary cosmic ray particles, as theoretically computed. This information is based on the theoretical calculations of meson-nuclear cascades for primary protons with different rigidities arriving to the EarthSs atmosphere at different zenith angles (Dorman and Pakhomov, 1979). These results have been checked and normalized by using coupling functions obtained in the same survey [Dorman et al. (2000)]. The determined apparent cut-off rigidities have been compared with results obtained by Clem et al. (1997) and with those used by Dorman et al. (2000) computed by using vertical cut-off rigidities, for trajectories especially calculated for the survey. On the basis of the apparent cut-off rigidities along the latitude survey, the coupling functions for neutron monitor and bare neutron counters found by Dorman et al. (2000) are now determined more accurately. **Survey realized with logistic and financial support of the Italian Antarctic Program (PNRA) and with the co-operation of IFSI-CNR. REFERENCES: Clem, J.M., et al. J. Geophys. Res., 102, 26,919 (1997). Danilova, O.A., et al., Latitude survey in December 1996-March 1997, 1. Cut-off rigidities for different azimuth and zenith angles, Paper ST13, This issue (2001) Dorman L.I. and Pakhomov N.I., "The dependence of the integral generation multiplicity of neutron component at various depths in the atmosphere on zenith angle on primary particle in- cidence". Proc. 16-th ICRC, Kyoto, 4, 416-420 (1979) Dorman, L.I., et al., J. Geophys. Res. 105 , 21,047 (2000).
Identification of the 3D Vibratory Motion of a Rigid Body by Accelerometer Measurements
Directory of Open Access Journals (Sweden)
Francesca Di Puccio
2004-01-01
Full Text Available The identification of the motion of a rigid body by means of linear accelerometers is a problem already investigated by many researchers, but still debated. The optimisation of the number and placement of accelerometers is also another important aspect of the problem. In this study, an experimental procedure is proposed and applied to identify the rigid-body vibratory motion of the steering wheel of a sporting car, by means of six linear accelerometers. Some numerical simulations for investigating possible errors are also presented.
Directory of Open Access Journals (Sweden)
Yakhlef O.
2017-06-01
Full Text Available A fixed point algorithmis proposed to solve a fluid-structure interaction problem with the supplementary constraint that the structure displacements are limited by a rigid obstacle. Fictitious domain approach with penalization is used for the fluid equations. The surface forces from the fluid acting on the structure are computed using the fluid solution in the structure domain. The continuity of the fluid and structure velocities is imposed through the penalization parameter. The constraint of non-penetration of the elastic structure into the rigid obstacle is treated weakly. A convex constrained optimization problem is solved in order to get the structure displacements. Numerical results are presented.
Directory of Open Access Journals (Sweden)
Zheyu Xu
2017-05-01
Full Text Available We present a case of 32-year-old male with profound mental retardation and autism spectrum disorder who had presented with seizures, rigidity and elevated creatine kinase and was initially diagnosed as neuroleptic malignant syndrome (NMS. The patient subsequently had a complicated clinical course, developing refractory status epilepticus, which lead to the eventual diagnosis of progressive encephalomyelitis with rigidity and myoclonus (PERM. We discuss the clinical similarities and differences between NMS and PERM, and highlight the need to consider alternative diagnoses when the clinical picture of NMS is atypical, particularly in this patient group where the history and clinical examination may be challenging.
A non-rigid map fusion-based direct SLAM method for endoscopic capsule robots.
Turan, Mehmet; Almalioglu, Yasin; Araujo, Helder; Konukoglu, Ender; Sitti, Metin
2017-01-01
Since the development of capsule endoscopy technology, medical device companies and research groups have made significant progress to turn passive capsule endoscopes into robotic active capsule endoscopes. However, the use of robotic capsules in endoscopy still has some challenges. One such challenge is the precise localization of the actively controlled robot in real-time. In this paper, we propose a non-rigid map fusion based direct simultaneous localization and mapping method for endoscopic capsule robots. The proposed method achieves high accuracy for extensive evaluations of pose estimation and map reconstruction performed on a non-rigid, realistic surgical EsophagoGastroDuodenoscopy Simulator and outperforms state-of-the art methods.
Interband B (E2) ratios in the rigid triaxial model, a review
Energy Technology Data Exchange (ETDEWEB)
Gupta, J.B.; Sharma, S.
1989-01-01
Uptodate accurate extensive data on /gamma/-g B(E2) ratios for even-even rare-earth nuclei is compared with the predictions of the rigid triaxial model of collective rotation to search for a correlation between the nuclear structure variation with Z, N and the /gamma//sub 0/ parameter of the model. The internal consistency in the predictions of the model is investigated and the spectral features vis-a-vis the /gamma/-soft and the /gamma/-rigid potential are discussed. (orig.).
Determination of Rigidity of Protein Bound Au(144) Clusters by Electron Cryomicroscopy.
Sexton, Jonathan Z; Ackerson, Christopher J
2010-09-30
A method for estimating the positional displacement of protein bound gold nanoparticles is presented and used to estimate the rigidity of linkage of Au(144) nanoparticles bound to a tetrameric model protein. We observe a distribution of displacement values where most Au(144) clusters are immobilized to within 3Å relative to the protein center of mass. The shape of the distribution suggests two physical processes of thermal motion and protein deformation. The application of this and similar rigid gold nanoparticle/protein conjugates in high resolution single particle electron cryo-microscopy is discussed.
Rigid registration of CT, MR and cryosection images using a GLCM framework
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Grimson, E.; Mosges, R.
1997-01-01
The majority of the available rigid registration measures are based on a 2-dimensional histogram of corresponding grey-values in the registered images. This paper shows that these features are similar to a family of texture measures based on grey level co-occurrence matrices (GLCM). Features from...... the GLCM literature are compared to the current range of measures using images from the visible human data set. The voxel-based rigid registration of cryosection and CT images have not been reported before. The tests show that mutual information is the best general measure, but some GLCM features...
Evolution of motions of a rigid body about its center of mass
Chernousko, Felix L; Leshchenko, Dmytro D
2017-01-01
The book presents a unified and well-developed approach to the dynamics of angular motions of rigid bodies subjected to perturbation torques of different physical nature. It contains both the basic foundations of the rigid body dynamics and of the asymptotic method of averaging. The rigorous approach based on the averaging procedure is applicable to bodies with arbitrary ellopsoids of inertia. Action of various perturbation torques, both external (gravitational, aerodynamical, solar pressure) and internal (due to viscous fluid in tanks, elastic and visco-elastic properties of a body) is considered in detail. The book can be used by researchers, engineers and students working in attitude dynamics of spacecraft.