bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Step Design of Multicontact-Aided Cellular Compliant Mechanisms for Stress Relief
Authors: Mehta Vipul , Frecker Mary , Lesieutre George A.
Published: October 2012

A methodology for topology optimization to the design of compliant cellular mechanisms with and without internal contact is presented. A two-step procedure is pursued. First, a baseline noncontact mechanism is developed and optimized via an inverse homogenization method using the “solid isotropic material with penalization” approach. This compliant mechanism is optimized to yield specified elasticity coefficients, with the capability to sustain large effective strains by minimizing local linear elastic strain. In the second step, a system of internal contacts is designed. The initial continuum model of a noncontact mechanism is converted into a frame model, and possible contact links are defined. A computationally efficient algorithm is employed to eliminate those mechanisms having overlapping contact links. The remaining nonoverlapping designs are exhaustively investigated for stress relief. A differential evolution optimizer is used to maximize the stress relief. The results generated for a range of specified elasticity coefficients include a honeycomb-like cell, an auxetic cell, and a diamond-shaped cell. These various cell topologies have different effective properties corresponding to different structural requirements. For each such topology, a contact mechanism is devised that demonstrates stress relief. In one such case, the contact mechanism increases the strain magnification ratio by about 30%.
Multidisciplinary Design Optimization of Modular Industrial Robots by Utilizing High Level CAD Templates
Authors: Tarkian Mehdi , Persson Johan , Ölvander Johan , Feng Xiaolong
Published: October 2012

This paper presents a multidisciplinary design optimization (MDO) framework for automated design of a modular industrial robot. The developed design framework seamlessly integrates high level computer aided design (CAD) templates (HLCt) and physics based high fidelity models for automated geometry manipulation, dynamic simulation, and structural strength analysis. In the developed framework, methods such as surrogate models and multilevel optimization are employed in order to speed up the design optimization process. This work demonstrates how a parametric geometric model, based on the concept of HLCt, enables a multidisciplinary framework for multi-objective optimization of a modular industrial robot, which constitutes an example of a complex heterogeneous system.
Dynamic Analysis of Compliant Mechanisms
Authors: Li Zhe , Kota Sridhar
Published: October 2012

A systematic method for dynamic analysis of compliant mechanisms is presented including basic formulations for natural frequencies, modes, dynamic response, and frequency characteristics. Methods for design sensitivity analysis are developed to investigate the effect of various design parameters on the dynamic performance of compliant mechanisms. A micro compliant stroke amplifier mechanism, for MEMS actuator application, is presented as a design example to demonstrate significant differences between static and dynamic performance of compliant mechanisms.
A Novel Formulation for the Design of Distributed Compliant Mechanisms
Authors: Yin Luzhong , Ananthasuresh G. K.
Published: October 2012

The optimization problem formulations currently used to synthesize compliant topologies aim to maximize flexibility at the output point for desired motion while maximizing overall stiffness for satisfactorily bearing the applied loads. The best solution to this problem, as posed, is a linkage consisting of rigid members connected together with revolute joints. Current elastic mechanics-based formulations do generate compliant topologies that closely imitate a rigid-body linkage by means of lumped compliance as in flexures. Systematically generating such topology solutions could serve as a creative aide for subsequent modifications, especially when the force-deflection specifications are non-intuitive to human designers. However, flexure-based compliant designs are not useful in most applications when large displacements and/or high strength are desired. Ideally, compliant designs should distribute flexibility uniformly throughout the structure rather than limiting to a few flexures. In this paper we discuss why current formulations often do not provide distributed compliant designs, and present a novel formulation that guarantees distributed compliance. The method is explained in detail and is illustrated with examples.
A Novel Force Balancing Method for Real-Time Controllable Mechanisms
Authors: Ouyang P. R. , Zhang W. J.
Published: October 2012

A new force balancing method called adjusting kinematic parameters (AKP) method for real-time controllable (RTC) mechanisms is proposed in this paper. The principle and design equations to form force balanced mechanisms are described in detail, and the implementation of the AKP method is presented where two pivots on a link are adjustable. Simulation studies show that the AKP method is consistently better than the CW method for closed-loop RTC mechanisms.
Wheeled Omni-Directional Robot Dynamics Including Slip
Authors: Williams Robert L. , Carter Brian E. , Gallina Paolo , Rosati Giulio
Published: October 2012

A dynamic model is presented for omni-directional wheeled mobile robots, including wheel/motion surface slip. We derive the dynamics model, experimentally measure friction coefficients, and measure the force to cause slip (to validate our friction model). Dynamic simulation examples are then presented to demonstrate omni-directional motion with slip. After developing an improved friction model, compared to our initial model, the simulation results agree well with experimentally-measured trajectory data with slip. Initially we thought that only high robot velocity and acceleration governed the resulting slipping motion. However, we learned that the solid material existing in the discontinuities between omni-directional wheel rollers plays an equally important role in determining omni-directional mobile robot dynamic slip motion, even at low rates and accelerations.
Dynamic Simulation of a Metal Belt CVT Under Transient Conditions
Authors: Pennestri Ettore , Sferra Daniele , Valentini Pier Paolo , Baldascini Filippo
Published: October 2012

Most of the technical literature on CVT consider steady-state conditions. Very few analyze the behavior of CVT under transient conditions (Kanehara et al., 1999; Ide et al., 1995; Carbone et al., 2002) and none of them include the effects of pulley deformation. This paper is an attempt to fill the gap. It is herein presented a mathematical model of a V-belt metal CVT, valid also under transient conditions, where the pulley deformation has been included. The model, implemented in a numerical code, combines Gerbert’s theory of V belts and the contributions of (Sattler, 1999a; Sattler, 1999b) on pulley deformation. An innovative algorithm for the simulation of dynamic effects during shifting is proposed. Inertia effects as well as deformation of pulleys are taken into account. Two type of working conditions have been experimentally monitored and numerically simulated. Finally, the paper contains a description of the experimental apparatus used for the validation of the model herein presented.
Force Transmission Index Based Workspace Analysis of a Six DOF Wire-Driven Parallel Manipulator
Authors: Zheng Ya-Qing , Liu Xiong-Wei
Published: October 2012

This paper presents a novel six DOF wire-driven PKM. Its moving platform is supported by seven wires via spherical joints, and at the other end each wire is driven by a servo motor via a pulley mounted on a frame. The force transmission index (proposed by Takeda [15]) is adopted to analyze the relationship of the force transmissibility between the wires and the moving platform. Moreover, the workspace analysis of the moving platform is investigated by means of force transmission index. Finally, a case study is presented to demonstrate the application of the algorithm to determine the workspace of two manipulators with different design parameters using Monte-Carlo technique under the Matlab environment. The results show that the proposed algorithm can determine the workspace with different force transmissibility. The simulation results reveal that if more random points are selected, the practical workspace will be closer to the theoretical one.
Eigenvalue and Eigenvector Information of Graphs and Their Validity in Detection of Graph Isomorphism
Authors: He P. R. , Zhang W. J. , Li Q.
Published: October 2012

Detection of graph isomorphism (GI) has been widely used in many fields in science and engineering. Currently, a potential application of GI detection could be in molecular structure design for microelectromechanical systems and nano-systems. In this paper, we discuss the relationship between graphs and their eigenvalues as well as unique eigenvectors. We prove that the graphs having all distinct eigenvalues are isomorphic if and only if they have the same graph spectrum and the equivalent eigenvectors. The graphs having coincident eigenvalues might be isomorphic if they have the same graph spectrum and the equivalent unique eigenvectors. Further, a convergent recursive procedure is given to subdivide a group-to-group mapping once appeared in the graphs having coincident eigenvalues to seek potential one-to-one mappings so as to determining if the graphs are isomorphic.
Three-Dimensional Kinematic Analysis and Verification for a Flexible Robot Arm
Authors: Gu Min , Piedbœuf Jean-Claude
Published: October 2012

The main objective of the present paper is to derive an explicit expression for the endpoint position and orientation of a flexible robot arm and to verify its 3-dimensional nonlinear kinematics of deformation through experiment. In particular, we define a material rotation vector as the basic deformation parameter and assign to it a clear physical meaning. From this definition and the kinematic relation of deformation, we obtained the end-point position and orientation of a flexible robot arm via on-line strain measurement. The kinematic responses of the experimental robot arm were also obtained independently using a vision system. The coincident results between simulation, strain measurement and vision system convince us of our model.
On the Design of a Low-Force 5-DOF Force-Feedback Haptic Mechanism
Authors: Papadopoulos Evangelos , Vlachos Kostas , Mitropoulos Dionyssios
Published: October 2012

Virtual reality is becoming very important for training medical surgeons in various operations. Interfacing users with a virtual training environment, requires the existence of a properly designed haptic device. This paper presents the design of a new force feedback haptic mechanism with five active degrees of freedom (dof), which is used as part of a training simulator for urological operations. The mechanism consists of a two dof, 5-bar linkage and a three dof spherical joint, designed to present low friction, inertia and mass, to be statically balanced, and have a simple mass matrix. The device is suitable for the accurate application of small forces and moments. All five actuators of the haptic device are base-mounted DC motors and use a force transmission system based on capstan drives, pulleys and miniropes. The paper describes the chosen design, and its kinematics, dynamics, and control algorithm and hardware employed.
On the Bases of Wrench Spaces for the Kinematic and Dynamic Analyses of Mechanisms
Authors: Sugimoto Koichi
Published: October 2012

The aim of this paper is to find out a computational procedure for the kinematic and dynamic analysis of mechanisms with closed loops of sub-Lie-algebras, utilizing the theory that a basis of the wrench space having an influence on motion is automatically decided. It is shown that the analysis of a closed loop mechanism can be performed by selecting loop-cut-joints and colnputing wrenches of these joints from the condition that virtual works of passive joints are zero. The required number of parameters for wrenches of loop-cut-joints are automatically determined in this procedure. The wrenches acting on active joints can be expressed by the linear combinations of wrenches of loop-cut-joints and those expressing gravity forces and dynamic forces. The torques required for driving active joints can be computed from the condition of virtual works.
On the Synthesis of Reactionless Spatial 3-DOF Mechanisms Using Planar 4-Bar Linkages
Authors: Wu Yangnian , Gosselin Cle´ment M.
Published: October 2012

This paper presents the synthesis of a novel reactionless spatial 3-DOF mechanism using four-bar linkages without any counter-rotation. Based on the conditions of static and dynamic balancing of a single planar four-bar linkage developed elsewhere, the spatial problem is shown to be equivalent to verifying if the inertia tensor of reactionless four-bar linkages can be kept constant when the planar mechanism(s) is(are) moving. The reactionless conditions for planar four-bar linkages in space are first given. Then, reactionless spatial 3-DOF mechanisms using four-bar linkages are synthesized. A numerical example of the reactionless spatial 3-DOF mechanisms is given and, with the help of the dynamic simulation software ADAMS, it is shown that the mechanisms are reactionless for any trajectory and can be used to synthesize 6-DOF reactionless mechanisms.
Input Torque Balancing Using an Inverted Cam Mechanism
Authors: Demeulenaere Bram , Al-Bender Farid , De Schutter Joris
Published: October 2012

Input torque balancing is a well known way to reduce the fluctuation of the camshaft speed in high-speed cam-follower systems. This paper describes a methodology to design an inverted cam mechanism (ICM) that provides quasi perfect input torque balancing at any speed, provided that the cam-follower system is purely inertial. The ICM was introduced in the fifties, but the design methodologies proposed by Meyer zur Capellen (1964) and Michelin (1979) are respectively erroneous or too rough an approximation and are here corrected. The design methodology is based on a novel way to nondimensionalize the dynamic equation that governs the inverted cam design, in order to keep the theoretical results as generally valid as possible. It is applied to a design example, showing that there are two basic design parameters to be chosen. Based on a design chart, these parameters are determined in such a way that the ICM size is minimized, taking into account technological and dynamical mechanism constraints.
Planning for Kinematically Smooth Manipulator Trajectories
Authors: Mi Zan , Yang Jingzhou , Abdel-Malek Karim , Jay Laurent
Published: October 2012

This paper presents a general methodology and accompanying formulation for planning kinematically smooth path trajectories for serial robot manipulators. Starting from an initial point on the path, it is required to traverse a path trajectory without halting the motion (typically due to switch from one inverse solution to another). The problem focuses on determining a starting configuration at the initial point on the path. The problem is formulated in terms of a constraint function and characterized by a system of differential-algebraic equations (DAEs) of index 2. These DAEs are solved numerically by Runge-Kutta (RK) methods while a best starting configuration is chosen using a cost-function driven optimization method. The formulation is demonstrated through a planar 3 degree of freedom robot manipulator.
Simulation and Modelling for Inchworm Dynamics
Authors: Rinco´n Diana M. , Sotelo Jorge
Published: October 2012

Due to the great advances in computing tools, simulation has become an important component of most engineering disciplines. In this article, we simulate inchworm locomotion with friction only and variable mass. A theoretical model was developed and experimentally validated with a prototype. The results demonstrate a feasible innovative robot design for axial locomotion. The validated theoretical model can be later used to optimize the dynamic performance of this robot.
Robust Control of Coordinated Motion of Space-Based Robot System
Authors: Li Chen
Published: October 2012

In this paper, the coordinated control of the base’s attitude and its arms of space-based robot system is studied. With the momentum conservation of system, the kinematics and dynamics of system are analyzed. It is shown that the generalized Jacobi matrix and dynamic equations of the system can be linearly dependent on a group of inertial parameters. Based on the results proposed above, first a robust control scheme of coordinated motion in joint space is developed, then, a robust and adaptive composite control scheme of coordinated motion for both the base’s attitude and its arms to track the desired trajectory in inertia space is proposed. Both control schemes proposed above possess the advantages that needs no measuring the position, velocity and acceleration of the base with respect to the orbit, because of an effective exploitation of the particular property of the system dynamics. The first control scheme needs estimating less unknown parameters and possess stronger convergence as compared with the second control scheme. Therefore, it is suggested that the motion planning in joint space possess priority as the tasks of space-based robot system are specified. To show the feasibility of both control schemes proposed above, two simulation studies are present.
Control of a 3-DOF Over-Actuated Parallel Mechansim
Authors: Marquet Fre´de´ric , Company Olivier , Krut Se´bastian , Gascuel Olivier , Pierrot Franc¸ois
Published: October 2012

This paper presents the control of ARCHI, a 3-dof over-actuated parallel mechanism, designed as a subpart of a 5-axis hybrid machining robot. Control strategies of the parallel sub-mechanism (3 dof / 4 actuators) managing the internal constraint on the mechanism are proposed and experimental results are discussed.
The 3-RRS Wrist: A New, Very Simple and Not Over-Constrained Spherical Parallel Manipulator
Authors: Di Gregorio Raffaele
Published: October 2012

Orientating a rigid body without changing its position is required in many technical applications. This manipulation task is accomplished by manipulators (spherical manipulators) that are just able to make the end effector move according to controlled spherical motions. Spherical manipulators can be either serial or parallel. Parallel architectures are usually more stiff and precise than the serial ones, whereas their structures are more complex than the serial ones. This paper presents a new three-equal-legged spherical parallel manipulator, named 3-RRS wrist. The 3-RRS wrist is not overconstrained and exhibits a very simple architecture employing just three passive revolute pairs, three passive spherical pairs and three actuated revolute pairs adjacent to the frame. The kinematic analysis of the 3-RRS wrist is addressed and fully solved. Finally, its singularity conditions are written in explicit form and discussed. The results of this analysis lead to the conclusion that the new manipulator has only two types of singularities both easy to be identified with geometric reasoning.
Motion Generation for Groups of Robots: A Centralized Geometric Approach
Authors: Belta Calin , Kumar Vijay
Published: October 2012

We develop a method for generating smooth trajectories for a set of mobile robots satisfying constraints on relative positions. We show that, given two end configurations of the set of robots, by tuning one parameter, the user can choose an interpolating trajectory from a continuum of curves varying from the trajectory corresponding to maintaining a rigid formation to trajectories that allow the formation to change and the robots to reconfigure while moving.
A Motor-Integrated Parallel Hybrid Transmission
Authors: Tsai L. W. , Schultz G.
Published: October 2012

This paper presents a motor-integrated transmission mechanism for use in parallel hybrid electric vehicles. The transmission can provide five basic modes of operation that can be further classified into sixteen sub-modes: one electric motor mode, four engine modes, four engine/charge modes, three power modes, and four regenerative braking modes. Each of these sub-modes can be grouped into like clutching conditions, providing the functional appearance of a conventional 4-speed automatic transmission, with electric launch, engine-only, engine/charge, power-assist, and regeneration capability. CVT capability is provided with one of the engine/charge modes. The kinematics, static torque, and power flow relations for each mode are analyzed in detail. Finally, a clutching logic and a notional control strategy are developed. The transmission can be incorporated not only in front-wheel drive but also in rear-wheel drive vehicles. The compactness, mechanical simplicity, and operational flexibility of the transmission make it an excellent candidate for future hybrid electric vehicles.
A New Inchworm Mechanism With Hydrauilic Booster
Authors: Behjat Sara , Khajepour Amir , Morris Kirsten A.
Published: October 2012

Micro- and nanotechnology have been the cornerstones of many advanced products in recent years. Commercialization and mass production of these products require robots and positioning devices with nanometer precision and reasonable operational speed. High-speed nano-positioning devices can be used to increase productivity and reduce manufacturing cost in many areas including: optoelectronic fiber and lens assembly and positioning, biological cell manipulators, micro-machining, semiconductor manufacturing, and calibration of measurement instruments. In this paper, a new high-speed inchworm linear motor is introduced which employs a hydraulic booster to increase its operational speed without sacrificing the accuracy.
Errors and Corrections of Robotics Standard ANSI/RIA R15.05-1-1990: Industrial Robots and Robot Systems Point to Point and Static Performance Characteristics—Evaluation
Authors: Cui Hongliang , Zhu Zhenqi
Published: October 2012

The ANSI/RIA R15.05-1-1990 as an industrial robotics standard covers the point-to-point and static performance characteristics. This standard introduces many important concepts for carrying out performance test including standard test plane, standard test path, and working space center point. Working space center point plays a very important role in this standard. Defining a wrong working space center point will in turn define a wrong standard test plane, a wrong standard test path, and wrong test results. Eight mistakes related to working space center point and one conflict definition have been found and corrected in this standard. This will help to avoid the confusion existing in the existing standard that is not widely used. Efforts have been made to improve this standard by correcting certain errors and conflict definitions so that the standard can be used widely.
SAM: Simulation and Analysis of Mechanisms
Authors: Rankers Adrian M. , Schrama Herbert W.
Published: October 2012

SAM (Simulation and Analysis of Mechanisms) is an interactive PC-software package for the motion and force analysis of arbitrary planar mechanisms, which can be assembled from basic components including beams, sliders, gears, belts, springs, dampers and friction elements. SAM integrates pre-processing, numerical analysis and postprocessing, such as animation and xy-plots, in an easy to-use environment offering pull-down menus, mouse support and help facilities. The mathematical foundation of the program is based on the well-known finite element approach. Open loop, closed loop, multiple loop and even complex planetary mechanisms can equally well be analysed due to the finite element formulation. Over the past ten years, the program has proven its value and is appreciated by many users from industry and especially from educational institutes. Apart from the internal analysis engine its most apparent feature is the ease of use, which makes it an interesting tool for non-expert and occasional users.
LINCAGES 2000: Latest Developments and Case Study
Authors: Yu Ning , Erdman Arthur G. , Byers Brandon P.
Published: October 2012

This paper introduces the latest development of LINCAGES 2000, a mechanism design software package available on Windows 9x/NT and 2000. A case study of a motion generation mechanism design using LINCAGES 2000 is presented. Various design options are compared and their advantages and disadvantages are discussed. This software is proved to be a powerful tool for mechanism synthesis and analysis.
Nanoscale photon management in silicon solar cells
Authors: Jeong Sangmoo , Wang Shuang , Cui Yi
Published: October 2012

Light absorption in a photovoltaic device becomes critical as the thickness of an absorber layer is decreased to reduce cost. To enhance light absorption, photon management at the nanoscale has been studied because conventional methods, which are based on micrometer-sized structure, do not work well for thinner solar cells. This article reviews recent progress in photon management on the nanoscale for increasing light absorption in Si solar cells. The methodology for the absorption enhancement will be discussed, followed by advances in nanofabrication techniques that make the methodology a scalable and viable solution. The authors conclude with a discussion of the challenge of photon management schemes and future directions for light trapping in ultra-thin Si solar cells.
Graphical representation of the effects on tumor and OAR for determining the appropriate fractionation regimen in radiation therapy planning
Authors: Mizuta Masahiro , Date Hiroyuki , Takao Seishin , Kishimoto Naoki , Sutherland Kenneth L. , Onimaru Rikiya , Shirato Hiroki
Published: October 2012

Purpose:

The authors propose a graphical representation of the relation between the effect on the tumor and the damage effect on an organ at risk (OAR) against the irradiation dose, as an aid for choosing an appropriate fractionation regimen.

Methods:

The graphical relation is depicted by the radiation effect on the tumorE1 versus that on an OAR E0. By observing the features of the E1 vs E0 relation curve, i.e., convex or concave shape, one can judge whether multifractionation is better or not. This method is applied to the linear‐quadratic model (with α and β parameters) as an example. Further, the method is extended to the general case for nonuniform dose distribution to the OAR, which is frequently seen in clinical situations.

Results:

The criterion for selecting multi‐ or hypofractionation is based on the relation between the dose for the OAR and theα/β ratio of the OAR to the tumor. It is also shown that the graphical relation enables us to estimate the final effect after multifractionated treatment by plotting a tangent line on the curve.

Conclusions:

The graphical representation method is of use for improving planning in radiotherapy by determining the effective fractionation scheme.
Improving the homogeneity of tissue‐mimicking cryogel phantoms for medical imaging
Authors: Minton Joshua A. , Iravani Amin , Azizeh‐Mitra Yousefi
Published: October 2012

Purpose:

Tissue‐mimicking phantoms can help in uncovering potential weaknesses in medical imaging systems. This work presents a new approach to developing phantoms for magnetic resonance elastography (MRE). Elastography requires sufficiently large and well‐characterized phantoms to accurately validate motion estimation methods and to provide accurate stiffness measurements. Physically crosslinked polyvinyl alcohol hydrogels, prepared by the freeze‐thaw technique, have been extensively used as MRE phantoms. However, the large cryogels developed by this technique usually exhibit variations in properties due to the low thermal conductivity of the polymeric solution. This leads to variations in freezing‐thawing rates across the gels. Therefore, designing homogeneous large cryogels with tissue‐mimicking mechanical properties poses a challenge to medical imaging researchers.

Methods:

Unlike conventional freeze‐thaw techniques that use either sudden freezing or ramp freezing, the authors have developed a modified freeze‐thaw process featuring a combination of multiple ramps and isotherms within a single freeze‐thaw cycle. Aiming to develop brain‐mimicking phantoms, they have blended three different water‐soluble polymers (polyvinyl pyrrolidone, agarose, and polyacrylic acid) with polyvinyl alcohol and produced cryogels with a wide range of mechanical properties and swelling characteristics. The effect of the modified process on mechanical properties, swelling, and melting enthalpy of the produced gels has been investigated in this study.

Results:

It was demonstrated that imposing additional isotherms at the vicinity of phase change temperatures could effectively reduce the variations in properties within a typical large phantom (diameter vs height: 100 mm × 100 mm). While the conventional freeze‐thaw process resulted in ∼16% variation in the enthalpy of fusion across the produced gels, the modified process reduced this variation to below 8%. The homogeneity in mechanical properties was also improved by over 50% compared to the conventional process. Upon comparing the mechanical properties of the gels with those of brain white matter, the authors have shown that a blend of polyvinyl alcohol and polyvinyl pyrrolidone can provide brain‐mimicking properties, while leading to stable gels.

Conclusions:

The modified freeze‐thaw process enabled to minimize the temperature gradient within the large cryogel phantoms during the freeze‐thaw cycle. The results of this study can help to fill the gaps in the scientific literature with regard to developing homogeneous phantoms for medical imaging. This work also provides a solid foundation for future studies in this field and could facilitate formulating new hydrogels to replicate the viscoelastic properties of soft tissues.
An analytical method for computing voxel S values for electrons and photons
Authors: Amato Ernesto , Minutoli Fabio , Pacilio Massimiliano , Campennì Alfredo , Baldari Sergio
Published: October 2012

Purpose:

The use of voxel S values (VSVs) is perhaps the most common approach to radiation dosimetry for nonuniform distributions of activity within organs or tumors. However, VSVs are currently available only for a limited number of voxel sizes and radionuclides. The objective of this study was to develop a general method to evaluate them for any spectrum of electrons and photons in any cubic voxel dimension of practical interest for clinical dosimetry in targeted radionuclide therapy.

Methods:

The authors developed a Monte Carlo simulation in Geant4 in order to evaluate the energy deposited per disintegration (Edep) in a voxelized region of soft tissue from monoenergetic electrons (10–2000 keV) or photons (10–1000 keV) homogeneously distributed in the central voxel, considering voxel dimensions ranging from 3 mm to 10 mm. Edep was represented as a function of a dimensionless quantity termed the “normalized radius,” Rn = R/l, where l is the voxel size and R is the distance from the origin. The authors introduced two parametric functions in order to fit the electron and photon results, and they interpolated the parameters to derive VSVs for any energy and voxel side within the ranges mentioned above. In order to validate the results, the authors determined VSV for two radionuclides (131I and 89Sr) and two voxel dimensions and they compared them with reference data. A validation study in a simple sphere model, accounting for tissue inhomogeneities, is presented.

Results:

TheEdep(Rn) for both monoenergetic electrons and photons exhibit a smooth variation with energy and voxel size, implying that VSVs for monoenergetic electrons or photons may be derived by interpolation over the range of energies and dimensions considered. By integration, S values for continuous emission spectra from β− decay may be derived as well.

Conclusions:

The approach allows the determination of VSVs for monoenergetic (Auger or conversion) electrons and (x‐ray or gamma‐ray) photons by means of two functions whose parameters can be interpolated from tabular data provided. Through integration, it is possible to generalize the method to any continuous (beta) spectrum, allowing to calculate VSVs for any electron and photon emitter in a voxelized structure.
Toward Variable Funding for International Science
Authors: Edler Jakob
Published: October 2012

European ERA-NETs offer lessons for flexible international funding to better meet the needs of science and society.
Anticipating Critical Transitions
Authors: Scheffer Marten , Carpenter Stephen R. , Lenton Timothy M. , Bascompte Jordi , Brock William , Dakos Vasilis , van de Koppel Johan , van de Leemput Ingrid A. , Levin Simon A. , van Nes Egbert H. , Pascual Mercedes , Vandermeer John
Published: October 2012

All Change

Research on early warning signals for critical transitions in complex systems such as ecosystems, climate, and global finance systems recently has been gathering pace. At the same time, studies on complex networks are starting to reveal which architecture may cause systems to be vulnerable to systemic collapse.

Scheffer
et al.

(p.
344
) review how previously isolated lines of work can be connected, conclude that many critical transitions (such as escape from the poverty trap) can have positive outcomes, and highlight how the new approaches to sensing fragility can help to detect both risks and opportunities for desired change.
Direct Observation of Cotranscriptional Folding in an Adenine Riboswitch
Authors: Frieda Kirsten L. , Block Steven M.
Published: October 2012

Making a Riboswitch

During RNA synthesis by RNA polymerase (RNAP), nascent RNA will start to fold. This cotranscriptional folding can affect the final conformation and the function of the full-length RNA. Using single-molecule spectroscopy and optical tweezers,
Frieda and Block
(p.
397
) followed the cotranscriptional folding of the
pbuE
riboswitch from
Bacillus subtilis
directly in real time, observing the formation of the adenine-binding aptamer structure or the alternative transcription terminator hairpin structure. The structures formed within seconds of their sequences clearing the RNAP footprint, confirming that the
pbuE
riboswitch is kinetically controlled.
Comment on “Restoring Voluntary Control of Locomotion After Paralyzing Spinal Cord Injury”
Authors: Sławińska Urszula , Rossignol Serge , Bennett David J. , Schmidt Brian J. , Frigon Alain , Fouad Karim , Jordan Larry M.
Published: October 2012

Van den Brand
et al
. (Reports, 1 June 2012, p. 1182) claim to have restored voluntary control of locomotion after paralyzing spinal cord injury. They have not considered recent findings that their upright posture paradigm contributes to locomotor capability after such injuries. We propose that postural adjustments that activate the locomotor central pattern generator in the upright posture, rather than direct voluntary control of locomotion, account for their results.
Response to Comment on “Restoring Voluntary Control of Locomotion After Paralyzing Spinal Cord Injury”
Authors: Courtine Grégoire , Heutschi Janine , van den Brand Rubia
Published: October 2012

Sławińska
et al
. questioned the involvement of supraspinal centers in restoring locomotion after multisystem neuroprosthetic training in rats with paralyzing spinal cord injury. Here, we clarify misconceptions and present additional results illustrating the robust influence of brain input on electrochemically enabled spinal circuitries. We reassert that our intervention reestablished supraspinal control over hindlimb locomotion in paralyzed rats.
Integrated Compact Optical Vortex Beam Emitters
Authors: Cai Xinlun , Wang Jianwei , Strain Michael J. , Johnson-Morris Benjamin , Zhu Jiangbo , Sorel Marc , O’Brien Jeremy L. , Thompson Mark G. , Yu Siyuan
Published: October 2012

A Twist of Light

The angular momentum of photons can be used to encode and transmit information.

Cai
et al.

(p.
363
) developed a method for generating and emitting controllable orbital angular momentum states of light from a reconfigurable and scalable silicon photonic chip. Using micro-ring resonators embedded with angular gratings allowed the imprinting of optical angular momentum on the light propagating in the whispering gallery modes of the resonator. The method may enable large-scale integration of optical vortex emitters on complementary metal-oxide–semiconductor-compatible silicon chips.
Gene Duplication's Role in Evolution Gets Richer, More Complex
Authors: Pennisi Elizabeth
Published: October 2012

An experimental evolution study in bacteria in this week's issue shows that at least some genes take another route besides duplication to giving an organism new functions.
Looking for a Sugar Rush
Authors: Service Robert F.
Published: October 2012

The sugar molecules that stud cell surfaces and coat many proteins play critical roles, but they are poorly understood and researchers want new tools to study them.
Effect of Heat-Killed Escherichia coli, Lipopolysaccharide, and Muramyl Dipeptide Treatments on the Immune Response Phenotype and Allergy in Neonatal Pigs Sensitized to the Egg White Protein Ovomucoid
Authors: Schmied Julie , Rupa Prithy , Garvie Sarah , Wilkie Bruce
Published: October 2012

Predisposition to food allergies may reflect a type 2 immune response (IR) bias in neonates due to the intrauterine environment required to maintain pregnancy. The hygiene hypothesis states that lack of early environmental stimulus leading to inappropriate development and bias in IR may also contribute. Here, the ability of heat-killed
Escherichia coli
, lipopolysaccharide (LPS), or muramyl dipeptide (MDP) to alter IR bias and subsequent allergic response in neonatal pigs was investigated. Three groups of three litters of pigs (12 pigs/litter) were given intramuscular injections of
E. coli
, LPS, MDP, or phosphate-buffered saline (PBS) (control) and subsequently sensitized to the egg white allergen ovomucoid using an established protocol. To evaluate change in IR bias, immunoglobulin isotype-associated antibody activity (AbA), concentrations of type 1 and 2 and proinflammatory cytokines released from mitogen-stimulated blood mononuclear cells, and the percentage of T-regulatory cells (T-regs) in blood were measured. Clinical signs of allergy were assessed after oral challenge with egg white. The greatest effect on IR bias was observed in MDP-treated pigs, which had a type 2-biased phenotype by isotype-specific AbA, cytokine production, and a low proportion of T-regs. LPS-treated pigs had decreased type 1- and type 2-associated AbA.
E. coli
-treated pigs displayed increased response to Ovm as AbA and had more balanced cytokine profiles, as well as the highest proportion of T-regs. Accordingly, pigs treated with MDP were more susceptible to allergy than PBS controls, while pigs treated with LPS were less susceptible. Treatment with
E. coli
did not significantly alter the frequency of clinical signs.
The Genome Sequence of an Isolate of Indian Citrus Ringspot Virus Infecting the Sweet Orange in India
Authors: K Prabha , Baranwal V. K.
Published: October 2012

Whole-genome sequencing of an isolate of
Mandarivirus
infecting the sweet orange [
Citrus sinensis
(L) Blanco] in the western part of India (Pune) was done. The single-stranded positive-sense RNA genome of
Indian citrus ringspot virus
(ICRSV) Pune has 7,560 nucleotides (nt), excluding a poly(A) tail, comprised of 27.98% (2,115 nt) A, 32.12% (2,428 nt) C, 19.68% (1,488 nt) G, and 20.22% (1,529 nt) T residues. The genome, organized into six open reading frames (ORFs), shares 97.7% sequence identity with the complete genome of the ICRSV K1 isolate (AF406744.1) infecting the kinnow (
Citrus reticulate
Blanco, a hybrid between King and Willow mandarins) in north India. The ICRSV Pune genome formed a complex secondary structure with a large number of unpaired cytosine-rich regions, and recombination analysis highlighted potential recombination in the ICRSV genome.
Complete Genome Sequence of a Mammalian Species-Infectious and -Pathogenic H6N5 Avian Influenza Virus without Evidence of Adaptation
Authors: Park Seong-Jun , Park Bong-Kyun , Song Dae-Sub , Poo Haryoung
Published: October 2012

An H6N5 avian influenza virus (AIV) strain, designated A/aquatic bird/Korea/CN5/2009 (H6N5), was isolated from fecal swabs of aquatic birds in 2009, and surprisingly, it showed infectivity and pathogenicity in mammalian species without evidence of adaptation. In this study, we report the first complete genome sequence containing 3′ and 5′ noncoding regions (NCRs) of a mammalian species-infectious and pathogenic H6N5 AIV, which will help provide important insights into the molecular basis of pathogenesis, transmission, and evolution of AIV.
Complete Genome Sequence of a Newcastle Disease Virus Strain Isolated from Broiler Breeder Flocks in China
Authors: Chen Feng , Liu Jiajia , Liu Di , Yan Zhuanqiang , Ji Jun , Qin Jianping , Li Haiyan , Ma Jingyun , Bi Yingzuo , Xie Qingmei
Published: October 2012

In 2010 and 2011, several devastating Newcastle disease (ND) outbreaks occurred in China, affecting broilers, layers, and breeders. The CK-JSX1-201005 virus was isolated from broiler breeder flocks vaccinated with the classical ND virus (NDV) vaccine program, but laying rate decreased from 80% to 30 to 40% in the clinic. Here, we report the complete genome sequence and molecular characteristic of the CK-JSX1-201005 NDV. These findings provide additional insights into the genetic variation of NDV circulating in China and are useful for vaccine development for NDV.
Genome Sequence of a Natural Reassortant H5N2 Avian Influenza Virus from Domestic Mallard Ducks in Eastern China
Authors: Gu Min , Huang Junqing , Chen Yuxin , Chen Jian , Wang Xiaoquan , Liu Xiaowen , Liu Xiufan
Published: October 2012

Here, we report the genomic sequence of a Chinese reassortant H5N2 avian influenza virus which possessed the polybasic motif PLREKRRK-R/GL at the hemagglutinin cleavage site. Phylogenetic analysis showed that all eight genes were of the Eurasian lineage, five of which were highly homologous to the endemic clade 2.3.4 H5N1 viruses and their H5N5 reassortant descendants. These data suggested that novel multisubtypic NA reassortants bearing the H5N1 backbone could be generated through genetic reassortment in H5N1 circulating regions, which will help in understanding the evolution and segment reassortment mechanism of H5 subtype avian influenza viruses.
Complete Genome Sequence of a Reovirus Isolated from Grass Carp, Indicating Different Genotypes of GCRV in China
Authors: Wang Qing , Zeng Weiwei , Liu Chun , Zhang Chao , Wang Yingying , Shi Cunbin , Wu Shuqin
Published: October 2012

A widespread grass carp hemorrhagic disease (GCHD) caused by grass carp reovirus (GCRV) has been known in China since 1983. A virulent reovirus strain, HZ08, was isolated from diseased grass carp in Zhejiang Province, China. We sequenced and analyzed the complete genome of strain HZ08 and compared it with published GCRV genome sequences, contributing to the evidence of several genotypes of GCRV in China.
Genomic Sequence of
Heliothis virescens Ascovirus 3g
Isolated from Spodoptera exigua
Authors: Huang Guo-Hua , Wang Yun-Sheng , Wang Xing , Garretson Tyler A. , Dai Liang-Ying , Zhang Chuan-Xi , Cheng Xiao-Wen
Published: October 2012

Heliothis virescens ascovirus 3a
(HvAV-3a), a member of the family
Ascoviridae
, has the highest diversity among ascovirus species that have been reported in Australia, Indonesia, China, and the United States. To understand the diversity and origin of this important ascovirus, the complete genome of the HvAV Indonesia strain (HvAV-3g), isolated from
Spodoptera exigua
, was determined to be 199,721 bp, with a G+C content of 45.9%. Therefore, HvAV-3g has the largest genome among the reported ascovirus genomes to date. There are 194 predicted open reading frames (ORFs) encoding proteins of 50 or more amino acid residues. In comparison to HvAV-3e reported from Australia, HvAV-3g has all the ORFs in HvAV-3e with 6 additional ORFs unique to HvAV-3g, including 1 peptidase C26 gene with the highest identity to
Drosophila
spp. and 2 gas vesicle protein U (GvpU) genes with identities to
Bacillus megaterium
. The five unique homologous regions (hrs) and 25 baculovirus repeat ORFs (bro) of HvAV-3g are highly variable.
Significantly increasing hospital admissions for acute throat infections among children in England: is this related to tonsillectomy rates?
Authors: Koshy Elizabeth , Murray Joanna , Bottle Alex , Aylin Paul , Sharland Mike , Majeed Azeem , Saxena Sonia
Published: October 2012

Objective

To examine trends in hospital admissions for acute throat infection (ATI) and peritonsillar abscess (PTA) alongside tonsillectomy trends in children.

Design

We analysed Hospital Episode Statistics data to calculate annual age-standardised and age-sex specific rates for ATI, PTA and tonsillectomies in children aged 0–17 years who were admitted to hospital in England between 1 April 1999 and 31 March 2010.

Results

Age-standardised admission rates for ATI increased by 76% from 107.3 (95% CI 105.3 to 109.2) to 188.4 (95% CI 185.9 to 191.0) admissions per 100 000 children. Median length of stay for ATI admissions decreased from 1 to 0 days. Admission rates for PTA remained stable at between 9.6 (95% CI 9.0 to 10.2) and 8.7 (95% CI 8.1 to 9.2) per 100 000 children in 1999/2000 and 2009/2010, respectively. Age-standardised tonsillectomy rates declined from 367.4 (95% CI 363.8 to 371.0) to 278.0 (95% CI 274.9 to 281.1) per 100 000 children between 1999/2000 and 2000/2001, respectively, increased to 322.4 (95% CI 319.0 to 325.7) in 2002/2003 and then gradually declined again to 293.6 (95% CI 290.4 to 296.8) in 2009/2010.

Conclusions

ATI admission rates have increased substantially in the past decade, but the majority of children are discharged after a short stay. PTA admission rates have remained stable. This suggests the severity of throat infection has not increased. Tonsillectomy rates in England have been declining overall but do not appear to be associated with this increasing trend in ATI admissions. The increase most likely reflects changes in primary care and hospital service provision.
An unusual adverse effect of sildenafil citrate: Acute myocardial infarction in a nitrate-free patient
Authors: Cakmak Huseyin Altug , Ikitimur Baris , Karadag Bilgehan , Ongen Zeki
Published: October 2012

Myocardial infarction (MI) associated with sildenafil citrate is seen rarely in patients without any history of coronary artery disease. We report a nitrate-free patient with a history of cardiovascular risk factors who developed acute MI after taking sildenafil. A 44-year-old man diagnosed with acute anterior ST segment elevation MI 120 min after self-administration of 150 mg sildenafil was admitted before attempting any sexual intercourse. The coronary angiography revealed 99% occlusion of the left anterior descending artery (LAD) and a bare-metal stent was implanted. He was discharged after 5 days without any complication. Sildenafil may cause coronary steal or may lead to vasodilation causing hypotension in patient with pre-existing cardiovascular disease, especially in patients on nitrate therapy. Our patient was nitrate free, with normal blood pressure values. Emotional stimulation associated with anticipated sexual activity may have been a triggering factor for vulnerable coronary plaque rupture.
Surviving the storm: two cases of thyroid storm successfully treated with plasmapheresis
Authors: Carhill Aubrey , Gutierrez Absalon , Lakhia Ronak , Nalini Ramaswami
Published: October 2012

Thyroid storm is a rare, but critical, illness that can lead to multiorgan failure and carries a high death rate. The following case series describes two adult men with Graves’ disease who presented in thyroid storm and either failed or could not tolerate conventional medical management. However, both patients responded well to plasmapheresis, which resulted in clinical and biochemical stabilisation of their disease processes. The treatment option of plasmapheresis should be considered as a stabilising measure, especially when patients have failed or cannot tolerate conventional therapy. Plasmapheresis leads to amelioration of symptoms and a significant decline in thyroid hormone levels, providing a window to treat definitively with thyroidectomy.