bluuebunny/crossref_metadata_2025 huggingface dataset:
Process Optimization and Remanufacturability Analysis of Fuel Cell— Membrane Electrode Assembly With Process Simulation
Authors: Muruganantham R. , Annamalaisundaram S. , Sangeetha D. , Rajendra Boopathy S.
Published: October 2012

One of the most pressing environmental problems faced globally is waste management and landfill space. Remanufacturing is one of the green manufacturing techniques in which the geometrical form of the product is retained and the product is reused for the same purpose as during its original life cycle. This work analyzes the remanufacturability of membrane electrode assembly (MEA) which is the heart of the polymer-exchange membrane fuel cell (PEMFC). MEA was obtained by sandwiching the membrane (proton conducting membrane) between the anode and cathode of the fuel cell by hot pressing the anode and cathode onto the membrane at a desired temperature, pressure for a period of time. It is observed that 10% of MEAs are getting wasted while manufacturing it in the laboratory level. In order to utilize these waste MEAs, remanufacurability analysis is done. Wastages created in manufacturing (hot pressing) of MEA can be reduced by optimizing the manufacturing process parameters, such as temperature of the press, pressure applied, pressing time, and thickness of membrane. Using design of experiment and ANOVA contributing factors which influence the quality of MEA are identified with the help of DESIGN EXPERT software. Optimal values of process parameters are found out using desirability function in the software. The process parameter optimization will lead to reduction of wastage of MEA in hot pressing operation but these wastes cannot be avoided completely due to the presence of uncontrollable factors. So remanufacturability analysis will be useful for investigating the wastes. As a part of remanufacurability analysis design consideration for remanufacturing and recycling, the procedure for recovering the valuable materials from the retired membrane electrode assembly, reusing of electrodes are discussed. Two simulation models (current manufacturing system and manufacturing system with remanufacturing) have been created in WITNESS software in order to find the benefits of remanufacturing. The benefits are increase in MEA production and recovery of scrapped anode and cathode. Increase in MEA production due to remanufacturing has been found as 11.11%. Because of recovery process in remanufacturing, 10% of scrapped anode and cathode are utilized which leads to zero scrap of anode and cathode.
Issues in Polycrystalline Diamond Compact Cutter–Rock Interaction From a Metal Machining Point of View—Part I: Temperature, Stresses, and Forces
Authors: Che Demeng , Han Peidong , Guo Ping , Ehmann Kornel
Published: October 2012

This paper provides a comprehensive review of the literature that deals with issues surrounding the polycrystalline diamond compact (PDC) cutter–rock interface during rock cutting/drilling processes. The paper is separated into two parts addressing eight significant issues: Part I deals with fundamental issues associated with temperature/stress distribution and loading force prediction, while Part II focuses on issues related to PDC cutter/bit performance, wear and other failure phenomena, rock removal mechanism and cutting theory, rock properties, and numerical modeling of cutter–rock interaction. Experimental, analytical, and numerical methods are included into the investigation of the above-mentioned eight issues. Relevant concepts from metal cutting, micromachining, and other machining processes are also introduced to provide important insights and draw parallels between these interrelated fields.
Design of Compliant Parallel Kinematic Machines
Authors: Moon Yong-Mo , Kota Sridhar
Published: October 2012

Conventional Parallel Kinematic Machines (PKMs) suffer from poor repeatability due to backlash in various joints. Use of flexures to overcome this limitation has also been reported in the published literature. However, conventional flexures suffer from axis drift, limited range of motion and stress concentrations. We present a new method of design of Compliant PKMs (CPKMs) and using a new type of compliant joints. We employ large displacement compliant joints to construct PKMs, which exhibit sub-micron accuracy. The methodology presented in this paper allows us to synthesize a PKM for any desired number and type of kinematic degrees of freedom by employing modular construction elements. A library of constraining legs synthesized from compliant joints is used for construction of any CPKM. The paper presents a systematic approach to transforming an arbitrary 3D motions specification into a set of motions along orthogonal axes using dual vector. The method enables construction of any CPKM by using the library of standard constraining legs and active legs. The methodology is illustrated with a design example.
Dynamic Stability of Mobile Manipulators Considering Suspension Characteristics
Authors: Abo-Shanab R. F. , Sepehri N.
Published: October 2012

In this paper, the previously developed model for dynamic stability of mobile manipulators, by the authors [1], is extended. The extended model not only takes into account the dynamics of the base that can potentially rock back-and-forth but also, includes the flexibility of the contact between the base and the ground. The novel method of virtual links is used to facilitate the dynamic modelling of the mobile manipulator. The application of the study is directed at industrial machines that carry human-operated hydraulic manipulators. The model is therefore used to simulate planar movements of a Caterpillar 215B excavator-based log-loader. It is shown that the flexibility of the contact between the base and the ground reduces the manipulator’s stability. Assuming rigid contact between the base and the ground overestimates the stability of mobile manipulators. Therefore, the flexibility between the base and the ground should be considered in the dynamic model to accurately investigate the stability of the mobile manipulators.
Impulse Analysis and Its Applications to Dynamic Environment
Authors: So Byung Rok , Yi Byung-Ju , Kim Whee Kuk
Published: October 2012

Impact is inevitable when an object contacts with environment. In robot control problem dealing with impact, research focus is on minimizing the ill performance due to impact. On the other hand, in some applications interacting with dynamic environment the amount of impact has to be controlled in a desired fashion. This is the case specially when playing with a ball. At the instant of impact, both the external impulse exerted on the ball and the internal impulse experienced at the joints of the human body must be important properties. A modeling procedure of impulses, impulse geometry, and impulse measure will be briefly introduced and a new impulse measure for analysis of internal impulse is proposed. Based on these analytical tools, we initially analyze the external and internal impulses through a simple 3-linked planar robot, and extend to applications interacting with dynamic environment such as in landing on the ground, volleyball, and tennis. It is shown through simulation that the trend of the impulses calculated by the analytical model is coincident to the human experiences.
Kinematic Synthesis of Planar and Spatial Linkages Using Gradients and Superposition of Scalar Fields
Authors: Kebrle John , Adams W. T. , Shiakolas P. S. , Lawley T. J.
Published: October 2012

It is well known that the solutions to the three-position motion generation problem for the synthesis of the planar four-bar linkages results in a set of center-point and circle point circles. The four-position solution set yields a cubic curve, and the five-position solution yields a set of points. There are a variety of methods including graphical and algebraic, for generating center-point and circle-point circles for the 3-position, and Burmester curves for the 4-position planar motion generation problem. Dyads are synthesized based on these solution sets. In general, it is difficult or impossible to generalize these methods to 3D mechanisms. This paper begins by briefly reviewing the geometric constructions used in classical Burmester theory. Then, it presents a method using a scalar field to find the center-point and circle-point circles by finding the points where these fields are equal. The developed method uses Euclid’s chord angle principle to generate the solutions. This principle is then generalized to 3D to form the cone angle principle. This principle is used in a manner directly analogous to the planar case to synthesize the S-S dyad. Similar gradient and superposition methods using scalar fields based on the equations for the spherical R-R dyad, and the spatial C-C dyad are used to generate the spatial equivalent to the center-point circles and Burmester curves. Although these results have been known for some time, the method for generating these solution sets is new for spatial synthesis.
Estimation of Object Kinematics From Point Data
Authors: Vithani Anand R. , Gupta Krishna C.
Published: October 2012

One of the fundamental problems arising in kinematics is that of determining object position, velocity and acceleration from given point position, velocity and acceleration data. This type of problem is frequently encountered in robotics, biomechanics, real-time control of space structures, automatic guided vehicles, etc. Complications arise when redundant data are used and when the data have errors. Chutakanonta and Gupta proposed two simple and elegant methods for the estimation of object position from the given point position data. The present work is an extension of these methods for estimating the object velocity and acceleration states from the given point position, velocity and acceleration data. The method proposed herein uses Singular Value Decomposition (SVD) to effectively estimate the object velocity and acceleration states. Such matrix decompositions can be performed by using readily available matrix-oriented software like MATLAB and can be successfully used to simplify the solution of the over-determined system of equations encountered in these types of problems. Several hypothetical examples and examples that simulate practical situations are presented to determine the effectiveness, robustness and applicability of the proposed method. The method is found to be very effective in estimating the object velocity and acceleration states in the presence of imprecise and redundant data as well as for nearly co-planar point data.
The Comparison of Two Workspace-Density-Driven Inverse Kinematics Methods for Hyper Redundant Manipulators
Authors: Wang Yunfeng , Chirikjian Gregory S.
Published: October 2012

Motivated by the cascading of workspace densities, we have developed two new workspace-density-driven inverse kinematics methods for hyper-redundant manipulators in recent papers. One is based on the breadth-first search and the other is based on the divide-and-conquer search. Both methods do not involve a high dimensional Jacobian matrix and have their own favorable qualities. In this paper, we perform a detailed numerical comparison of these two methods. We focus on comparing the computation time, end-effector error and data storage requirements. This comparison will give users of these kinds of robots guidance as to when which method should be used.
Five Precision Points Synthesis of Spatial RRR Manipulators Using Interval Analysis
Authors: Lee Eric , Mavroidis Constantinos , Merlet Jean Pierre
Published: October 2012

In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints is solved for the first time using an interval analysis method. In this problem, five spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these pre-specified locations. Denavit and Hartenberg parameters and 4×4 homogeneous matrices are used to formulate the problem and obtain the design equations and an interval method is used to search for design solutions within a predetermined domain. At the time of writing this paper, six design solutions within the search domain and an additional twenty solutions outside the domain have been found.
Static Analysis of Prestressed Tensegrity Structures
Authors: Crane Carl D. , Duffy Joseph , Correa Julio C.
Published: October 2012

In this paper the mathematical model to perform the static analysis of a prestressed antiprism tensegrity structure subjected to an arbitrary reduction of its connecting ties is addressed. A virtual work approach is used to deduce the equilibrium equations and the numerical results are verified using a Newtonian approach. One example is provided to illustrate the mathematical model.
Conceptual Design of a Passive Arm Orthosis
Authors: Cardoso Luis F. , Toma´zio Se´rgio , Herder Just L.
Published: October 2012

For people suffering from neuromuscular diseases there is a need for a device to support the weight of their arm against gravity and allow either their residual muscle force or external power to position the arm in space. Many of the current assistive devices are externally powered, tend to be very bulky, and have poor aesthetics. The non-powered devices available suffer from limited range of motion and several other inconveniences. Home visits to patients suffering from SMA (spinal muscular atrophy) were made, and a literature search was performed to assess adequate design specifications, based mainly on range of motion, activities of daily living, and home environment. This paper presents a statically balanced, non-powered arm support design, which compensates the weight of the human arm against gravity in all of the four degrees of freedom of the human arm.
Design of a Robotic Stereotactic Device for Biopsy and Minimally Invasive Interventions in the Breast With Real Time MRI Guidance
Authors: Larson Blake T. , Tsekos Nikolaos V. , Erdman Arthur G. , Yacoub Essa , Tsekos Panagiotis V. , Koutlas Ioannis G.
Published: October 2012

The objective of this work was to develop a robotic device to perform biopsy and therapeutic interventions in the breast with real-time MRI guidance. This is the first US made surgical robotic device to perform real time MR-guided interventions in the breast. The device was designed to allow for (i) conditioning of the breast by compression, (ii) definition of the interventional probe trajectory, by setting the height and pitch of a probe insertion apparatus, and (iii) positioning of an interventional probe by setting the depth of insertion. The apparatus is fitted with five computer-controlled degrees of freedom for delivering an interventional procedure. The entire device is constructed of MR compatible materials, i.e. non-magnetic and non-conductive, to eliminate artifacts and distortion of the local magnetic field. The apparatus is remotely controlled by means of ultrasonic actuators and a graphical user interface, providing real-time MR-guided planning and monitoring of the operation.
Mechanical Design of a Haptic Interface for the Hand
Authors: Frisoli A. , Simoncini F. , Bergamasco M.
Published: October 2012

This paper presents an integrated approach to the mechanical design of a haptic interface for the hand. The presented approach evaluates the performance of the mechanism functionally to the task to be executed. A kinematics model of the hand is introduced in order to specifically characterize the influence of hand movements on the performance of the mechanism. After the identification of critical factors, the dimensions of the mechanism have been optimized as a function of them. A geometrical approach is presented to solve the Inverse Kinematic Problem and the singularity analysis.
Kinematic and Dynamic Analysis of a New Cylindrical 3-DOF Parallel Manipulator
Authors: Wang Qi-Ming , Wang Jinsong , Liu Xin-Jin , Zhang Hui
Published: October 2012

This article discusses the kinematic and dynamic modeling of a new cylindrical parallel manipulator with two translational degrees of freedom and one rotational degree of freedom. The model of dynamics is based on the Lagrange approach. Six generalized coordinates and three Lagrange multipliers are introduced in the modeling process, and they are released by the corresponding constraint functions. A case is presented to illustrate the advantages of this mechanism. The simulation results indicate that the actuator torques of this parallel manipulator possess of good properties. This model will be useful to improve the design of the mechanical components and the control algorithm of this manipulator.
Improving Indexing Accuracy of Grooved Globoidal Cam Mechanisms Using Asymmetrical Turret Motions
Authors: Tsay Der Min , Lin Bor Jeng , Chen Hsin Pao
Published: October 2012

A design procedure for increasing the indexing accuracy of intermittent grooved globoidal cam mechanisms is presented. It is based on the synthesis of asymmetrical dwell-rise-dwell (D-R-D) roller-follower turret motions to improve the kinematic and dynamic performance of the globoidal cam-turret devices for high-speed applications. Such asymmetrical turret motion curves are defined and tuned by nonparametric rational B-splines. Favorable results of kinematic characteristics, geometric properties including pressure angles and curvatures of cam surfaces, torques, and residual vibrations are revealed and compared to those obtained by traditional methods. Together with experimental results, a practical application example is given to demonstrate the usefulness and effectiveness.
Static Analysis of Spatial 7R Link Constant-Velocity Joints Extended Shaft Angle
Authors: Nango Jun , Watanabe Katsumi
Published: October 2012

The spatial 7R link constant-velocity joint is obtained when some of kinematic constants of spatial 7R 7-1ink mechanism are given suitably. This joint can transmit a rotational motion and a tor(tue with constant velocity between two intersecting shafts. It was verified experimentally that the shaft angle could be vary in the region of ±60°. The shaft angle limits the arrangement of rotating shafts which are used in several industrial equipments. If the shaft angle of the spatial 7R link constant-velocity joint is extended, this type of constant-velocity joint can be applied to the indirect driven type of articulated manipulator, for example. In this paper, it is investigated that the method of design of the spatial 7R link constant-velocity joint to actualize the constant-velocity joint which can transmit a rotational motion between two intersecting shafts at an angle of 90°. And when the shaft angle is greater, there is a fear that the motion transmissibility of constant-velocity joints become worse. So the motion transmissibility is examined by measuring the input torque of the constant-velocity joint. Also, it is examined that modifying the spatial 7R link constant-velocity joint to the multi-loop type is effective measure against increasing the output angle errors.
An Approach to Sequence Analysis of Carton Manipulation
Authors: Liu David H. , Dai Jian S.
Published: October 2012

This paper addresses the sequence-finding problem for a carton-folding task which requires the possibility that a feasible folding sequence of packaging cartons can be applied to a multi-fingered packaging unit. After reviewing the previous contributions to the related sequence task, this paper presents a solution to the folding sequence of cartons based on robotics and graph theory. Firstly a packaging carton is modelled as a virtual mechanism, whose links represented by panels of carton and joints by folds. Secondly the concept of a hereditary connectivity matrix (HCM) is introduced, which includes both the adjacency and configuration transformation of links of the virtual mechanism. Then a non-searching sequence-finding algorithm is produced to aim at giving a feasible packaging sequence of a foldable carton and giving a folding trajectory for providing the position and even orientation of a multi-fingered packaging unit in carton-folding manipulation. In the end, the simulation result for folding a particular carton is given.
Metric Based Dynamic Parameter Identification for Mobile Field Manipulator Systems
Authors: Sujan Vivek A. , Dubowsky Steven
Published: October 2012

High performance robot control algorithms often rely on system physical models. For field robots, the dynamic parameters of these physical models may not be well known. This paper presents a new information based performance metric for the on-line dynamic parameter identification of a multi-body system. The metric is used in an algorithm to optimally regulate the external excitation required by the dynamic system identification proceeding. This algorithm is applied to identify the vehicle and suspension parameters of a mobile field manipulator. Issues addressed include the development of appropriate vehicle models (compatible with the onboard sensors), Kalman observer estimation of optimal parameter values, mutual information based observability (or identification) metric, and formulation of the manipulator exciting trajectory. Simulations and experimental results show the effectiveness of this algorithm.
Mobile Robot for Uneven Terrain
Authors: Chin Kenneth , Breslawski Robert , Kientz Terry , Kumar Vijay
Published: October 2012

This paper outlines the details of the development of a mobile robot than can navigate uneven terrain. The robot incorporates a combination of wheels and legs. The legs are based on a parallel-drive 2-R linkage that allows the motors to be located on the robot frame. The legs are driven through servo motors while the wheels are powered through DC motors. A PIC microcontroller is used to control the system, while a novel IR-based communication module allows the user to remotely control the device. In the proof-of-concept prototype, a human operator can control the approximately 6×9×4 inches (15.24×22.86×10.16 cm) and approximately 8 lb. (3.63 kgs) robot (with onboard electronics and control systems) to climb and descend steps. Future versions can be expected to autonomous and equipped with cameras and ad hoc networking cards for field operations.
Mechanical Design of a Robotic System for Automatic Installation of Magnetic Markers on the Roadway
Authors: James Randy , Ozkan Basar , Ravani Bahram
Published: October 2012

Magnetic markers embedded into the roadway pavements are used in Intelligent Transportation Systems to provide the reference signals necessary for guiding and controlling vehicles. This technology has already been implemented in several locations in California to provide driver assistance for snowplow operators in harsh winter environments. Installation of these magnetic markers into the roadway pavement is a tedious manual operation. This paper presents a novel design of a robotic system developed for installation of these magnetic markers into the roadway pavement. It is shown how dynamic modeling and simulation can be used with simple experimentation to develop a mechanical design of a robotic system to overcome undesirable effects of vibrations due to drilling the roadway. In addition two new and innovative concepts are introduced in the design of a robotic system. One is the design of a roller type traction drive to achieve linear motion that can be used in a gantry robotic system and the second is a self alignment mechanism for proper insertion of magnetic markers that can be used for any insertion and assembly operations.
Nonlinear Control of a Single-Link Shape Memory Alloy Actuated Arm
Authors: Elahinia Mohammad H. , Ashrafiuon Hashem
Published: October 2012

This paper presents a nonlinear, robust control algorithm for accurate positioning of a single degree of freedom rotary manipulator actuated by Shape Memory Alloy (SMA). A model for an SMA actuated manipulator is presented. The model includes nonlinear dynamics of the manipulator, a constitutive model of Shape Memory Alloy, and electrical and heat transfer behavior of SMA wire. This model is used for open and closed loop motion simulations of the manipulator. Experiments are presented that show results similar to both closed and open loop simulation results. Due to modeling uncertainty and nonlinear behavior of the system, classic control methods such as Proportional-Integral-Derivative control are not able to present fast and accurate performance. Hence a nonlinear, robust control algorithm is presented based on Variable Structure Control. This algorithm is a control gain switching technique based on the weighted average of position and velocity feedbacks. This method has been designed through simulation and tested experimentally. Results show fast, accurate, and robust performance of the control system. Computer simulation and experimental results for different stabilization and tracking situations are also presented.
Study on breathing mode oscillation suppression of self-excited Hall thrusters
Authors: Liqiu Wei , Ke Han , Chunsheng Wang , Hong Li , ChaoHai Zhang , Daren Yu
Published: October 2012

It is found that the breathing mode oscillation of the discharge current is suppressed notably in a Hall thruster operating with the electromagnets driven in series by the discharge current. In order to study the physical mechanism of this suppression, the ionization distribution is measured experimentally and the spatiotemporal features of the ionization front motion are studied numerically with a one-dimensional quasineutrality hydrodynamic model. Results show that the ionization front motion is restricted in a small range due to the closed-loop feedback control of the magnetic field. The steady-state ionization distribution is narrow and condensed when the electromagnetic coils connect in series with the discharge circuit. The different magnetic field excitation accompanied by different ionization characteristics is the main reason for the suppression of the discharge-current low-frequency breathing mode oscillation.
High-density pattern transfer via roll-to-roll ultraviolet nanoimprint lithography using replica mold
Authors: Taniguchi Jun , Yoshikawa Hiroshi , Tazaki Go , Zento Toshiyuki
Published: October 2012

Roll-to-roll ultraviolet nanoimprint lithography (RTR UV-NIL) has attracted much attention as a high-throughput nanofabrication process. In particular, high-density nanoscale line-and-space (L&S) patterns are widely used for optical devices and printed circuits, such as wire-grid polarizers and transparent electrode films. To realize a simplified high-throughput RTR process, the authors developed a replica roll mold fabrication process and examined the feed speed of RTR UV-NIL. The replica mold was fabricated by applying parallel-plate UV-NIL using a silicon master mold with 100-nm L&S patterns and 200-nm groove depth. Replica molds were coated with 10-nm-thick tungsten and a fluorinated silane coupling agent to prevent the adhesion of UV-curable resin during RTR UV-NIL. The release-coated replica molds were wrapped around roll substrate having a diameter of 150 mm. Using the replica mold, RTR UV-NIL was carried out at different UV doses, which were determined as the product of the UV light intensity and feed speed. The results confirmed that a sufficient UV dose enabled successful pattern transfer, while an insufficient UV dose caused the pattern to break down. In this experiment, a rapid feed speed of 18 m/min was possible under conditions of high UV light intensity. In addition, the release agent was still active after 500 revolutions of the replica roll mold (235.5 m).
Large area nanofabrication of butterfly wing's three dimensional ultrastructures
Authors: Aryal Mukti , Ko Doo-Hyun , Tumbleston John R. , Gadisa Abay , Samulski Edward T. , Lopez Rene
Published: October 2012

The authors report a simple method for the artificial fabrication of the complex three-dimensional (3D) ultrastructures of butterfly wing scales. This method uses chemical vapor deposition, UV lithography, and chemical etching to create the ultrastructures over a large area surpassing previously used focused ion beam techniques that are limited to microscopic areas. Furthermore, this method shows flexibility to modify nanostructure types and can precisely control shapes and dimensions and periodicity. Fabricated 3D ultrastructures are also replicated using a nanoimprint method into soft polymer materials. Reflectivity measurements and simulations of the master and polymer replicas show selective UV reflection consistent with the length scales used in such butterfly-like nanostructures.
Three‐dimensional thermoacoustic imaging for early breast cancer detection
Authors: Ji Zhong , Lou Cunguang , Yang Sihua , Xing Da
Published: October 2012

Purpose:

Microwave‐induced thermoacoustic tomography (TAT) is a noninvasive modality based on the differences in microwave absorption of various biological tissues. In this paper, the feasibility of the early breast tumor detection by TAT system has been discussed and validated experimentally.

Methods:

A fast TAT system, which based on three 128‐elements transducers, a 384‐64ch switch and a parallel data acquisition system (DAS), was developed to reconstruct the three‐dimensional (3D) image of a breast model with similar microwave absorption coefficient to breast tissue. A novel method to explore the ability of TAT system to distinguish absorption coefficient was introduced and the minimum absorption coefficient difference that can be distinguished clearly by our TAT system is 12 m−1.

Results:

The potential applications of the TAT system were clearly demonstrated by successfully mapping breast model with mimicked tumors and microcalcification. An imaging experiment of human breast tumor embedding in the breast model was performed and the tumor was visualized by the 3D thermoacoustic volume.

Conclusions:

The thermoacoustic images match well with the samples and achieve penetration depth of 6 cm. The experimental results indicate that TAT has a great potential to be used for detecting early‐stage breast cancers with high contrast and high resolution.
Novel cases of diffraction of light from a grating: Theory and experiment
Authors: Jetty Ninad R. , Suman Akash , Khaparde Rajesh B.
Published: October 2012

A popular pedagogical approach for introducing diffraction is to assume normal incidence of light on a single slit or a plane transmission grating. Interesting cases of diffraction from a grating at orientations other than normal incidence remain largely unexplored. In this article, we report our study of these unexplored cases, which was taken up as an undergraduate student project. We define various cases of orientation of the grating and use the Fresnel–Kirchhoff formula to arrive at the diffracted intensity distribution. An experimental arrangement consisting of a laser, a grating mount, a digital camera, and a calibrated plane screen is employed to record our observations. We discuss for each case the theoretical and experimental results and establish the conformity between the two. Finally, we analyze the details of various cases and conclude that for an arbitrary orientation of the grating, the diffraction maxima fall along a second degree curve.
Real beads on virtual strings: Charged particles on magnetic field lines
Authors: Breizman Boris , Khudik Vladimir
Published: October 2012

We discuss a similarity between the drift of a charged particle inside a slowly moving solenoid and the motion of a fluid element in an ideal incompressible fluid. This similarity can serve as a useful instructional example to illustrate the concepts of magnetic field lines and magnetic confinement.
A simple experiment that demonstrates the “green flash”
Authors: Courtial Johannes
Published: October 2012

The green flash occurs when, under certain atmospheric conditions, the top segment of the low sun is visibly green. It is surrounded—in at least a few minds—by an air of mystery. I describe a simple experiment that demonstrates different aspects of the green flash. The experiment uses an odd-shaped, water-filled, fish tank to simulate the refractive properties of the atmosphere; milk powder added to the water mimicks the atmosphere’s scattering properties. A circular white-light source is viewed through the fish tank and the combination of refraction and scattering makes one end of the light source look green. The setup also allows experimentation with mirage effects, thereby drawing attention to their often neglected contribution to the green flash.
Trajectories of rolling marbles on various funnels
Authors: English L. Q. , Mareno A.
Published: October 2012

We investigate the trajectories of a small marble constrained to roll on frictionless surfaces, called funnels, of varying shapes. Actual coin funnels have a hyperbolic surface, and here we disprove the common claim that the orbits of the rolling marble or coin are the same as the Kepler orbits for planets revolving around the sun. In fact, it is straightforward to show that for no funnel surface can the Kepler orbits be recovered. Furthermore, we find that the types of trajectories that can arise depend heavily on the funnel shape.
What is the limit ℏ →  of quantum theory?
Authors: Klein U.
Published: October 2012

An analysis is made of the relation between quantum theory and classical mechanics, in the context of the limit ℏ→0. Several ways in which this limit may be performed are considered. It is shown that Schrödinger's equation for a single particle moving in an external potential V does not, except in special cases, lead, in this limit, to Newton's equation of motion for the particle. This shows that classical mechanics cannot be regarded as emerging from quantum mechanics—at least in this sense—upon straightforward application of the limit ℏ→0.
Ironing Out MYC in Prostate Cancer
Authors: Bettegowda Chetan
Published: October 2012

A new imaging approach may be able to better detect some prostate cancers.
Characterization of a New Clinical Yeast Species, Candida tunisiensis sp. nov., Isolated from a Strain Collection from Tunisian Hospitals
Authors: Eddouzi Jamel , Hofstetter Valérie , Groenewald Marizeth , Manai Mohamed , Sanglard Dominique
Published: October 2012

From a collection of yeast isolates isolated from patients in Tunisian hospitals between September 2006 and July 2010, the yeast strain JEY63 (CBS 12513), isolated from a 50-year-old male that suffered from oral thrush, could not be identified to the species level using conventional methods used in clinical laboratories. These methods include matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), germ tube formation, and the use of CHROMagar
Candida
and metabolic galleries. Sequence analysis of the nuclear rRNA (18S rRNA, 5.8S rRNA, and 26S rRNA) and internal transcribed spacer regions (ITS1 and ITS2) indicated that the ribosomal DNA sequences of this species were not yet reported. Multiple gene phylogenic analyses suggested that this isolate clustered at the base of the
Dipodascaceae
(
Saccharomycetales
,
Saccharomycetes
, and
Ascomycota
). JEY63 was named
Candida tunisiensis
sp. nov. according to several phenotypic criteria and its geographical origin.
C. tunisiensis
was able to grow at 42°C and does not form chlamydospores and hyphae but could grow as yeast and pseudohyphal forms.
C. tunisiensis
exhibited most probably a haploid genome with an estimated size of 10 Mb on at least three chromosomes. Using European Committee for Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI)
Candida albicans
susceptibility breakpoints as a reference,
C. tunisiensis
was resistant to fluconazole (MIC = 8 μg/ml), voriconazole (MIC = 0.5 μg/ml), itraconazole (MIC = 16 μg/ml), and amphotericin B (MIC = 4 μg/ml) but still susceptible to posaconazole (MIC = 0.008 μg/ml) and caspofungin (MIC = 0.5 μg/ml). In conclusion, MALDI-TOF MS permitted the early selection of an unusual isolate, which was still unreported in molecular databases but could not be unambiguously classified based on phylogenetic approaches.
Tailored HIV-1 Vectors for Genetic Modification of Primary Human Dendritic Cells and Monocytes
Authors: Durand Stéphanie , Nguyen Xuan-Nhi , Turpin Jocelyn , Cordeil Stephanie , Nazaret Nicolas , Croze Séverine , Mahieux Renaud , Lachuer Joël , Legras-Lachuer Catherine , Cimarelli Andrea
Published: October 2012

Monocyte-derived dendritic cells (MDDCs) play a key role in the regulation of the immune system and are the target of numerous gene therapy applications. The genetic modification of MDDCs is possible with human immunodeficiency virus type 1 (HIV-1)-derived lentiviral vectors (LVs) but requires high viral doses to bypass their natural resistance to viral infection, and this in turn affects their physiological properties. To date, a single viral protein is able to counter this restrictive phenotype, Vpx, a protein derived from members of the HIV-2/simian immunodeficiency virus SM lineage that counters at least two restriction factors present in myeloid cells. By tagging Vpx with a short heterologous membrane-targeting domain, we have obtained HIV-1 LVs incorporating high levels of this protein (HIV-1-Src-Vpx). These vectors efficiently transduce differentiated MDDCs and monocytes either as previously purified populations or as populations within unsorted peripheral blood mononuclear cells (PBMCs). In addition, these vectors can be efficiently pseudotyped with receptor-specific envelopes, further restricting their cellular tropism almost uniquely to MDDCs. Compared to conventional HIV-1 LVs, these novel vectors allow for an efficient genetic modification of MDDCs and, more importantly, do not cause their maturation or affect their survival, which are unwanted side effects of the transduction process. This study describes HIV-1-Src-Vpx LVs as a novel potent tool for the genetic modification of differentiated MDDCs and of circulating monocyte precursors with strong potential for a wide range of gene therapy applications.
mRNA Decay during Herpes Simplex Virus (HSV) Infections: Mutations That Affect Translation of an mRNA Influence the Sites at Which It Is Cleaved by the HSV Virion Host Shutoff (Vhs) Protein
Authors: Shiflett Lora A. , Read G. Sullivan
Published: October 2012

During lytic infections, the herpes simplex virus (HSV) virion host shutoff (Vhs) endoribonuclease degrades many host and viral mRNAs. Within infected cells it cuts mRNAs at preferred sites, including some in regions of translation initiation. Vhs binds the translation initiation factors eIF4H, eIF4AI, and eIF4AII, suggesting that its mRNA degradative function is somehow linked to translation. To explore how Vhs is targeted to preferred sites, we examined thein vitrodegradation of a target mRNA in rabbit reticulocyte lysates containingin vitro-translated Vhs. Vhs caused rapid degradation of mRNAs beginning with cleavages at sites in the first 250 nucleotides, including a number near the start codon and in the 5′ untranslated region. Ligation of the ends to form a circular mRNA inhibited Vhs cleavage at the same sites at which it cuts capped linear molecules. This was not due to an inability to cut any circular RNA, since Vhs cuts circular mRNAs containing an encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES) at the same sites as linear molecules with the IRES. Cutting linear mRNAs at preferred sites was augmented by the presence of a 5′ cap. Moreover, mutations that altered the 5′ proximal AUG abolished Vhs cleavage at nearby sites, while mutations that changed sequences surrounding the AUG to improve their match to the Kozak consensus sequence enhanced Vhs cutting near the start codon. The results indicate that mutations in an mRNA that affect its translation affect the sites at which it is cut by Vhs and suggest that Vhs is directed to its preferred cut sites during translation initiation.
Effect of Complement on HIV-2 Plasma Antiviral Activity Is Intratype Specific and Potent
Authors: Özkaya Şahin Gülşen , Holmgren Birgitta , Sheik-Khalil Enas , da Silva Zacarias , Nielsen Jens , Nowroozalizadeh Salma , Månsson Fredrik , Norrgren Hans , Aaby Peter , Fenyö Eva Maria , Jansson Marianne
Published: October 2012

Human immunodeficiency virus type 2 (HIV-2)-infected individuals develop immunodeficiency with a considerable delay and transmit the virus at rates lower than HIV-1-infected persons. Conceivably, comparative studies on the immune responsiveness of HIV-1- and HIV-2-infected hosts may help to explain the differences in pathogenesis and transmission between the two types of infection. Previous studies have shown that the neutralizing antibody response is more potent and broader in HIV-2 than in HIV-1 infection. In the present study, we have examined further the function of the humoral immune response and studied the effect of complement on the antiviral activity of plasma from singly HIV-1- or HIV-2-infected individuals, as well as HIV-1/HIV-2 dually infected individuals. The neutralization and antibody-dependent complement-mediated inactivation of HIV-1 and HIV-2 isolates were tested in a plaque reduction assay using U87.CD4.CCR5 cells. The results showed that the addition of complement increased intratype antiviral activities of both HIV-1 and HIV-2 plasma samples, although the complement effect was more pronounced with HIV-2 than HIV-1 plasma. Using an area-under-the-curve (AUC)-based readout, multivariate statistical analysis confirmed that the type of HIV infection was independently associated with the magnitude of the complement effect. The analyses carried out with purified IgG indicated that the complement effect was largely exerted through the classical complement pathway involving IgG in both HIV-1 and HIV-2 infections. In summary, these findings suggest that antibody binding to HIV-2 structures facilitates the efficient use of complement and thereby may be one factor contributing to a strong antiviral activity present in HIV-2 infection.
A Chimeric Vesiculo/Alphavirus Is an Effective Alphavirus Vaccine
Authors: Chattopadhyay Anasuya , Wang Eryu , Seymour Robert , Weaver Scott C. , Rose John K.
Published: October 2012

While a large number of mosquito-transmitted alphaviruses are known to cause serious human diseases, there are no licensed vaccines that protect against alphavirus infections. The alphavirus chikungunya virus (CHIKV) has caused multiple recent outbreaks of chikungunya fever. This virus has the potential to cause a worldwide epidemic and has generated strong interest in development of a prophylactic CHIKV vaccine. We report here on the development of a potent experimental vaccine for CHIKV based on a chimeric vesicular stomatitis virus (VSV) expressing the entire CHIKV envelope polyprotein (E3-E2-6K-E1) in place of the VSV glycoprotein (G). These VSVΔG-CHIKV chimeras incorporated functional CHIKV glycoproteins into the viral envelope in place of VSV G. The chimeric viruses were attenuated for growth in tissue culture but could be propagated to high titers without VSV G complementation. They also generated robust neutralizing antibody and cellular immune responses to CHIKV in mice after a single dose and protected mice against CHIKV infection. VSVΔG-alphavirus chimeras could have general applicability as alphavirus vaccines.
Attenuation of Semliki Forest Virus Neurovirulence by MicroRNA-Mediated Detargeting
Authors: Ylösmäki Erkko , Martikainen Miika , Hinkkanen Ari , Saksela Kalle
Published: October 2012

Artificial target sequences for tissue-specific miRNAs have recently been introduced as a new means for altering the tissue tropism of viral replication. This approach can be used to improve the safety of oncolytic viruses for cancer virotherapy by restricting their replication in unwanted tissues, such as the liver. Semliki Forest virus (SFV) is a positive-strand RNA virus and, similar to the related alphaviruses, like Sindbis virus, has potential as a gene therapy vector and an oncolytic virotherapy agent, but this potential is limited by the neurovirulence of these alphaviruses. Here, we have generated a replicative SFV4 carrying six tandem targets for the neuron-specific miR124 between the viral nonstructural protein 3 and 4 (nsp3 and nsp4) genes. When administered intraperitoneally into adult BALB/c mice, SFV4-miRT124 displayed an attenuated spread into the central nervous system (CNS) and greatly increased survival. Peripheral replication was not affected, indicating neuron-specific attenuation. Moreover, a strong protective SFV immunity was elicited in these animals. Intracranial infection of adult mice with SFV4-miRT124 showed greatly reduced infection of neurons in the brain but led to the infection of oligodendrocytes in the corpus callosum. Taken together, our data show that miR124-mediated attenuation of neurovirulence is a feasible and promising strategy for generating safer oncolytic alphavirus virotherapy agents.
Tsg101 Interacts with Herpes Simplex Virus 1 VP1/2 and Is a Substrate of VP1/2 Ubiquitin-Specific Protease Domain Activity
Authors: Caduco Martina , Comin Alessandra , Toffoletto Marta , Munegato Denis , Sartori Elena , Celestino Michele , Salata Cristiano , Parolin Cristina , Palù Giorgio , Calistri Arianna
Published: October 2012

Ubiquitination/deubiquitination of key factors represent crucial steps in the biogenesis of multivesicular body (MVB) and sorting of transmembrane proteins. We and others previously demonstrated that MVB is involved in herpes simplex virus 1 (HSV-1) envelopment and budding. Here, we report that the HSV-1 large tegument protein, VP1/2, interacts with and regulates the ubiquitination of Tsg101, a cellular protein essential in MVB formation, thus identifying the first cellular substrate of a herpesviral deubiquitinating enzyme.
Human Anti-Varicella-Zoster Virus (VZV) Recombinant Monoclonal Antibody Produced after Zostavax Immunization Recognizes the gH/gL Complex and Neutralizes VZV Infection
Authors: Birlea Marius , Owens Gregory P. , Eshleman Emily M. , Ritchie Alanna , Traktinskiy Igor , Bos Nathan , Seitz Scott , Azarkh Yevgeniy , Mahalingam Ravi , Gilden Don , Cohrs Randall J.
Published: October 2012

Varicella-zoster virus (VZV) is a ubiquitous, highly cell-associated, and exclusively human neurotropic alphaherpesvirus. VZV infection is initiated by membrane fusion, an event dependent in part on VZV glycoproteins gH and gL. Consistent with its location on the virus envelope, the gH/gL complex is a target of neutralizing antibodies produced after virus infection. One week after immunizing a 59-year-old VZV-seropositive man with Zostavax, we sorted his circulating blood plasma blasts and amplified expressed immunoglobulin variable domain sequences by single-cell PCR. Sequence analysis identified two plasma blast clones, one of which was used to construct a recombinant monoclonal antibody (rec-RC IgG). The rec-RC IgG colocalized with VZV gE on the membranes of VZV-infected cells and neutralized VZV infection in tissue culture. Mass spectrometric analysis of proteins immunoprecipitated by rec-RC IgG identified both VZV gH and gL. Transfection experiments showed that rec-RC IgG recognized a VZV gH/gL protein complex but not individual gH or gL proteins. Overall, our recombinant monoclonal anti-VZV antibody effectively neutralizes VZV and recognizes a conformational epitope within the VZV gH/L protein complex. An unlimited supply of this antibody provides the opportunity to analyze membrane fusion events that follow virus attachment and to identify multiple epitopes on VZV-specific proteins.