bluuebunny/crossref_metadata_2025 huggingface dataset:
Defect-Free Synthesis of Stephenson-II Function Generators
Authors: Hwang Wen-Miin , Chen Yi-Jie
Published: October 2010

This article presents a novel method for the dimensional synthesis of Stephenson-II function generators without order, circuit, and branch defects. The explicit equations relating the generated output and specified variables of Stephenson-II function generators are derived by eliminating and transforming angular variables on two five-bar loops and by using the specified values of input and output variables. Then, the deviation between the generated and required angular positions of the output link of the synthesized mechanism is obtained for the objective function. Using the characteristics of order, circuits, branches, and the geometric features of dead-center configurations for Stephenson-II function generators, the constraint equations for avoiding these defects are proposed for the optimal synthesis of Stephenson-II function generators. The synthesized mechanisms are shown to be defect-free and satisfy all functional requirements. An example is given to demonstrate the feasibility of the proposed method.
Variable Stiffness Spring Using Tensegrity Prisms
Authors: Azadi Mojtaba , Behzadipour Saeed , Faulkner Gary
Published: October 2010

A novel variable stiffness mechanism (i.e., variable spring) based on the concept of tensegrity structures is presented. Variable springs have extensive applications in noise and vibration control. The proposed method builds upon the prestress stiffness in tensegrities, which occurs along infinitesimal mechanisms and is fully controllable through force control in the members. A criterion is given to select a suitable tensegrity structure and an infinitesimal mechanism to develop a variable spring. Also, a mathematical model is developed for the stiffness components in an n-gon tensegrity prism. The variable components of the stiffness are then utilized to create a translational or rotational variable spring. In order to elaborate on the feasibility of the concept, a case study is presented on the engine mount of a vehicle. Parameters of a possible design of a variable stiffness mount are given, and the characteristics are compared with those of a conventional passive mount. This is followed by a detailed discussion on the properties of such a variable spring and the effects of various parameters.
Actuation Redundancy as a Way to Improve the Acceleration Capabilities of 3T and 3T1R Pick-and-Place Parallel Manipulators
Authors: Corbel David , Gouttefarde Marc , Company Olivier , Pierrot François
Published: October 2010

This paper analyzes the possible contribution of actuation redundancy in obtaining very high acceleration with parallel robot manipulators. This study is based on redundant and nonredundant Delta/Par4-like manipulators, which are frequently used for pick-and-place applications, and addresses the cases of translational manipulators (also called 3T manipulators) and manipulators with Schoenflies motions (also called 3T1R manipulators). A dynamic model, valid for both redundant and nonredundant manipulators, is used to analyze the moving platform’s acceleration capabilities: (i) at zero speed and in any direction and (ii) at zero speed in the “best” direction. The results show that actuation redundancy makes it possible to homogenize dynamic capabilities throughout the workspace and to increase the moving platform’s accelerations. Designs of redundant Delta/Par4-like manipulators capable of high acceleration pick-and-place trajectories are presented for both 3T and 3T1R manipulators.
Performance Characteristics of a 1 kW Scale Kite-Powered System
Authors: Olinger David J. , Goela Jitendra. S.
Published: October 2010

A 1 kW scale kite-powered system that uses kites to convert wind energy into electrical energy has been studied to determine its performance characteristics and establish feasibility of steady-state operation. In this kite-powered system, a kite is connected to a tether that transmits the generated aerodynamic forces on the kite to a power conversion system on the ground. The ground-based power conversion system consists of a rocking arm coupled to a Sprag clutch, flywheel, and electrical generator. Governing equations describing the dynamical motion of the kite, tether, and power conversion mechanism were developed assuming an inflexible, straight-line tether. A steady-state analysis of the kite aerodynamics was incorporated into the dynamical equations of the kite-powered system. The governing equations were solved numerically using a Runge–Kutta scheme to assess how performance parameters of the system such as output power, cycle time, and tether tension varied with wind speed, kite area, and aerodynamic characteristics of the kite. The results showed that a 1 kW scale system is feasible using the proposed design concept with a kite area of 25 m2 and wind speeds of 6 m/s. Preliminary efforts to build and test a working 1 kW scale kite-powered demonstrator are also reported.
Control Constraint Realization for Multibody Systems
Authors: Fumagalli Alessandro , Masarati Pierangelo , Morandini Marco , Mantegazza Paolo
Published: October 2010

This paper discusses the problem of control constraint realization applied to generic underactuated multibody systems. The conditions for the realization are presented. Focus is placed on the tangent realization of the control constraint. An alternative condition is formulated, based on the practical observation that differential-algebraic equations need to be integrated using implicit algorithms, thus naturally leading to the solution of the problem in form of matrix pencil. The analogy with the representation of linear systems in Laplace’s domain is also discussed. The formulation is applied to the solution of simple, yet illustrative problems, related to rigid and deformable bodies. Some implications of considering deformable continua are addressed.
Dynamics of Independently Rotating Wheel System in the Analysis of Multibody Railroad Vehicles
Authors: Sugiyama Hiroyuki , Matsumura Ryosuke , Suda Yoshihiro , Ezaki Hideaki
Published: October 2010

In this investigation, dynamic characteristics of independently rotating wheel systems are discussed. To this end, a multibody independently rotating wheelset (IRW) model is developed using the method of velocity transformation. The linear stability analysis of a two-axle IRW truck is performed, the hunting stability and vibration characteristics of IRW truck are investigated, and the results are compared with those obtained using the multibody dynamics model. Good agreement is obtained in hunting frequencies and critical speeds. It is shown using the linear IRW equations that since a constant forward speed is assumed for IRW, the longitudinal slip can occur due to the change in the wheel rolling radius. This leads to longitudinal creep forces even in the case of IRW and it contributes to a coupling of the lateral, yaw, and pitch motions of IRW. Furthermore, it is observed in several numerical examples that, due to small self-centering forces of IRW, continuous flange contact occurs on tangent track, while in curve negotiation, flange contacts on outer wheel of the front axle, as well as that on inner wheel of the rear axle, occur. Such an effect can be more significant when sharp curve negotiation is considered as encountered in light rail vehicle applications.
Concept Through Preliminary Bench Testing of a Powered Lower Limb Prosthetic Device
Authors: Bergelin Bryan J. , Mattos Javier O. , Wells Joseph G. , Voglewede Philip A.
Published: October 2010

This paper outlines the design and testing of a powered ankle prosthesis, which utilizes a four-bar mechanism in conjunction with a spring and motor that mimics nonamputee (normal) ankle moments. This approach would enable transtibial (below the knee) amputees to walk at a normal speed with minimal energy input. The design takes into account the energy supplied by the wearer required to achieve many of the desired characteristics of a normal gait. A proof-of-concept prototype prosthesis was designed, optimized, fabricated, and tested with the purpose of demonstrating its ability to match crucial ankle moments during the stance phase of gait. Testing of this prosthesis proved crucial in determining the prosthesis’ capabilities and in evaluating this approach.
A Coordinate Frame Useful for Rigid-Body Displacement Metrics
Authors: Venkataramanujam Venkatesh , Larochelle Pierre M.
Published: October 2010

This paper presents the definition of a coordinate frame, entitled the principal frame (PF), that is useful for metric calculations on spatial and planar rigid-body displacements. Given a set of displacements and using a point mass model for the moving rigid-body, the PF is determined from the associated centroid and principal axes. It is shown that the PF is invariant with respect to the choice of fixed coordinate frame as well as the system of units used. Hence, the PF is useful for left invariant metric computations. Three examples are presented to demonstrate the utility of the PF.
Spectral Reflectance Patterns of Photovoltaic Modules and Their Thermal Effects
Authors: Silva J. P. , Nofuentes G. , Muñoz J. V.
Published: October 2010

Determination of the working temperature of photovoltaic (PV) modules is an essential task in research and engineering projects. It acquires more relevance in the current environment, characterized by increasing figures of installed PV power, module efficiency, solar applications, and operational configurations. However, most of the current procedures for temperature determination of PV modules are simply based on empirical correlations, carried out at conditions defined by some specific standards, with the corresponding lack of accuracy when modules work under real conditions. Thus, the present work looks into a formal procedure for temperature determination by conducting a power balance between the dynamic incoming and outgoing power fluxes. Some additional parameters are included when compared with classic expressions. In particular, the spectral reflectance of the tandem glass-semiconductor is measured to determine the reflected fraction of solar irradiance. The relationship between reflectance and equilibrium temperature is determined for a representative group of PV modules, and the influence that the working point exerts on the module temperature has also been taken into account. Finally, the influence of spectral distribution on module temperature has been quantified by simulations carried out by using a spectral model. In this way, determination of absolute temperature is achieved within a ±2°C range, regardless of module characteristics and climatic or operational conditions. In addition, temperature differences between PV modules that work under the same external conditions can be predicted within ±0.5°C. To summarize, a thermal model suitable for different PV modules and working configurations is presented. Some new parameters are introduced in the calculus process, and the influence of the most relevant ones has been quantified. In this way, the present work is aimed at making a contribution to the study of PV module temperature.
Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing
Authors: Hoetmer Karin , Woo Geoffrey , Kim Charles , Herder Just
Published: October 2010

In some applications, nonconstant energy storage in the flexible segments of compliant mechanisms is undesired, particularly when high efficiency or high-fidelity force feedback is required. In these cases, the principle of static balancing can be applied, where a balancing segment with a negative stiffness is added to cancel the positive stiffness of the compliant mechanism. This paper presents a strategy for the design of statically balanced compliant mechanisms and validates it through the fabrication and testing of proof-of-concept prototypes. Three compliant mechanisms are statically balanced by the use of compressed plate springs. All three balanced mechanisms have approximately zero stiffness but suffer from a noticeable hysteresis loop and finite offset from zero force. Design considerations are given for the design and fabrication of statically balanced compliant mechanisms.
KdV and Kink-Antikink Solitons in an Extended Car-Following Model
Authors: Jin Yanfei , Xu Meng , Gao Ziyou
Published: October 2010

An extended car-following model is proposed in this paper by using the generalized optimal velocity function and considering the multivelocity differences. The stability condition of the model is derived by using the linear stability theory. From the reductive perturbation method and nonlinear analysis, the Korteweg–de Vries (KdV) and modified Korteweg–de Vries (mKdV) equations are derived to describe the traffic behaviors near the neutral stability line and around the critical point, respectively. The corresponding soliton wave and kink-antikink soliton solution are used to describe the different traffic jams. It is found that the generalized optimal velocity function and multivelocity differences consideration can further stabilize traffic flow and suppress traffic jams. The theoretical results are well verified through numerical simulations.
Subharmonic Orbits of a Strongly Nonlinear Oscillator Forced by Closely Spaced Harmonics
Authors: Sapsis Themistoklis P. , Vakakis Alexander F.
Published: October 2010

We study asymptotically the family of subharmonic responses of an essentially nonlinear oscillator forced by two closely spaced harmonics. By expressing the original oscillator in action-angle form, we reduce it to a dynamical system with three frequencies (two fast and one slow), which is amenable to a singular perturbation analysis. We then restrict the dynamics in neighborhoods of resonance manifolds and perform local bifurcation analysis of the forced subharmonic orbits. We find increased complexity in the dynamics as the frequency detuning between the forcing harmonics decreases or as the order of a secondary resonance condition increases. Moreover, we validate our asymptotic results by comparing them to direct numerical simulations of the original dynamical system. The method developed in this work can be applied to study the dynamics of strongly nonlinear (nonlinearizable) oscillators forced by multiple closely spaced harmonics; in addition, the formulation can be extended to the case of transient excitations.
A Parametric Study on the Baumgarte Stabilization Method for Forward Dynamics of Constrained Multibody Systems
Authors: Flores Paulo , Machado Margarida , Seabra Eurico , Tavares da Silva Miguel
Published: October 2010

This paper presents and discusses the results obtained from a parametric study on the Baumgarte stabilization method for forward dynamics of constrained multibody systems. The main purpose of this work is to analyze the influence of the variables that affect the violation of constraints, chiefly the values of the Baumgarte parameters, the integration method, the time step, and the quality of the initial conditions for the positions. In the sequel of this process, the formulation of the rigid multibody systems is reviewed. The generalized Cartesian coordinates are selected as the variables to describe the bodies’ degrees of freedom. The formulation of the equations of motion uses the Newton–Euler approach, augmented with the constraint equations that lead to a set of differential algebraic equations. Furthermore, the main issues related to the stabilization of the violation of constraints based on the Baumgarte approach are revised. Special attention is also given to some techniques that help in the selection process of the values of the Baumgarte parameters, namely, those based on the Taylor’s series and the Laplace transform technique. Finally, a slider-crank mechanism with eccentricity is considered as an example of application in order to illustrate how the violation of constraints can be affected by different factors.
On Superquadric Human Modeling and Risk Assessment for Safe Planning of Human-Safe Robotic Systems
Authors: Najmaei Nima , Kermani Mehrdad R.
Published: October 2010

This paper introduces a new superquadric-based human body modeling technique. The model is used as part of an on-line path planning scheme. The path planning scheme utilizes a previously proposed danger evaluation metric in which danger is characterized based on human and nonhuman factors. A new factor that accounts for the human body orientation is introduced and used along with other factors for danger evaluation. A superquadric model of the human is used to determine the values of the factors used for danger evaluation including body orientation. The resulting danger value is then used to direct the search for an alternative robot path in a direction that minimizes the danger. The use of superquadric-based human model for danger evaluation and subsequently path planning provides an accurate and computationally efficient solution. At the same time, the resulting solution guarantees a safe and danger-free path, given the factors used to characterize the danger. The approach exhibits adequate speed of decision making, rendering it potentially suitable for real-time applications involving human-robot interaction. The proposed method is evaluated using a CRS-F3 industrial manipulator through various case studies.
Iterative Learning Control With Switching Gain Feedback for Nonlinear Systems
Authors: Ouyang P. R. , Petz B. A. , Xi F. F.
Published: October 2010

Iterative learning control (ILC) is a simple and effective technique of tracking control aiming at improving system tracking performance from trial to trial in a repetitive mode. In this paper, we propose a new ILC called switching gain PD-PD (SPD-PD)-type ILC for trajectory tracking control of time-varying nonlinear systems with uncertainty and disturbance. In the developed control scheme, a PD feedback control with switching gains in the iteration domain and a PD-type ILC based on the previous iteration combine together into one updating law. The proposed SPD-PD ILC takes the advantages of feedback control and classical ILC and can also be viewed as online-offline ILC. It is theoretically proven that the boundednesses of the state error and the final tracking error are guaranteed in the presence of uncertainty, disturbance, and initialization error of the nonlinear systems. The convergence rate is adjustable by the adoption of the switching gains in the iteration domain. Simulation experiments are conducted for trajectory tracking control of a nonlinear system and a robotic system. The results show that fast convergence and small tracking error bounds can be observed by using the SPD-PD-type ILC.
An Entropic Method for Sequencing Discrete Design Decisions
Authors: Sen Chiradeep , Ameri Farhad , Summers Joshua D.
Published: October 2010

This paper presents a mathematical model for quantifying uncertainty of a discrete design solution and to monitor it through the design process. In the presented entropic view, uncertainty is highest at the beginning of the process as little information is known about the solution. As additional information is acquired or generated, the solution becomes increasingly well-defined and uncertainty reduces, finally diminishing to zero at the end of the process when the design is fully defined. In previous research, three components of design complexity—size, coupling, and solvability—were identified. In this research, these metrics are used to model solution uncertainty based on the search spaces of the variables (size) and the compatibility between variable values (coupling). Solvability of the variables is assumed uniform for simplicity. Design decisions are modeled as choosing a value, or a reduced set of values, from the existing search space of a variable, thus, reducing its uncertainty. Coupling is measured as the reduction of a variable’s search space as an effect of reducing the search space of another variable. This model is then used to monitor uncertainty reduction through a design process, leading to three strategies that prescribe deciding the variables in the order of their uncertainty, number of dependents, or the influence of on other variables. Comparison between these strategies shows how size and coupling of variables in a design can be used to determine task sequencing strategy for fast design convergence.
Time Delay Control for Two van der Pol Oscillators
Authors: Maccari Attilio
Published: October 2010

A method for time delay vibration control of the principal and fundamental resonances of two nonlinearly coupled van der Pol oscillators is investigated Using the asymptotic perturbation method, four slow-flow equations on the amplitude and phase of the oscillators are obtained. Their fixed points correspond to a two-period quasi-periodic phase-locked motion for the original system. In the system without control, stable periodic solutions (if any) exist only for fixed values of amplitude and phase and depend on the system parameters and excitation amplitude. In many cases, the amplitudes of these solutions do not correspond to the technical requirements. On the contrary, it is demonstrated that, if vibration control terms are added, stable two-period quasi-periodic solutions with arbitrarily chosen amplitudes can be accomplished. Therefore, an effective vibration control is possible if appropriate time delay and feedback gains are chosen.
Effect of Convex Tooth Flank Form Deviation on the Characteristics of Transmission Error of Gears Considering Elastic Deformation
Authors: Mohamad Edzrol Niza , Komori Masaharu , Murakami Hiroaki , Kubo Aizoh , Fang Suping
Published: October 2010

The transmission error of gears is an important factor for power transmissions, particularly automotive. Consequently, a lot of research has been conducted on the gear transmission. However, in contrast, there remains relatively little research clarifying the characteristics of gear transmission error and its relationship to the tooth flank form. The authors have proposed a general model for tooth meshing between gears. This expresses the transmission error theoretically from a quasi-infinite elastic model, which is composed of springs with stiffness specific to the gears. In this report, the influence of tooth flank form deviation on transmission error is further investigated by using this model. It is shown that the form of the ridge curve of the tooth flank form deviation greatly influences the actual contact ratio at the minimum point of peak-to-peak value of transmission error. The peak-to-peak value of transmission error is affected by the amplitude and the form of the ridge curve.
Scaling Effect of Direct Solar Hot Water Systems on Energy Efficiency
Authors: Arunachala U. C. , Bhatt M. Siddhartha , Sreepathi L. K.
Published: October 2010

Scale formation in risers and header of direct solar hot water systems is a problem in places where hard water is being used. In this paper, the effect of scaling on energy efficiency indices such as instantaneous efficiency, mass flow rate, and overall heat loss coefficient are quantified by Hottel–Whillier–Bliss equation in the case of thermosiphon and forced circulation systems. The effect of scaling on mass flow and heat transfer rate for both the systems are quantified with experimental validation. Experimentally found mass flow rate is 50% of the analytical mass flow rate for a clean riser and agrees 99% for the case of riser with 3.75 mm scale thickness. This is due to the extreme change in pressure gain in the narrow region. Scale mapping is done for the entire solar hot water system to study the nature of scale growth. The complete footer and nine risers for the length of 150 mm from footer are free from scaling in axial and radial direction. This is due to the low water temperature in the region. The major portion of header and risers for the length 180 mm from the header are completely blocked due to maximum temperature of water in that region. A scale prediction model is brought out based on the experimentally observed scaled water heaters in the field. It reveals that the major parameters to be considered for the correlation are water total hardness and calcium hardness. It is seen in the thermosiphon system that the mass flow rate decreased by scaling affects energy efficiency more than that caused by the heat transfer rate. The scaling effect is more predominant in thermosiphon systems than in forced circulation systems. The analytical study reveals a drop in instantaneous efficiency of 39.5% in thermosiphon system and 7.0% in the case of forced circulation system for the scale thickness of 3.75 mm. The difference between mass flow rate in scaled and unscaled condition is less in forced circulation but much higher in thermosiphon system.
A General Static Torque Constraint for Spatial Four-Bar Motion Generation With a Coupler Load
Authors: Russell Kevin , Shen Qiong
Published: October 2010

A general static torque constraint for spatial four-bar mechanisms with coupler forces is formulated in this work. With this constraint, the user can synthesize spatial four-bar motion generators that also support static coupler loads. This constraint is demonstrated in the synthesis of RRSS, SSRC, and 4R spherical motion generators to approximate prescribed coupler poses and do so within maximum specified driver torques for given coupler forces.
Pulsatile Flow Effects on the Hemodynamics of Intracranial Aneurysms
Authors: Le Trung B. , Borazjani Iman , Sotiropoulos Fotis
Published: October 2010

High-resolution numerical simulations are carried out to systematically investigate the effect of the incoming flow waveform on the hemodynamics and wall shear stress patterns of an anatomic sidewall intracranial aneurysm model. Various wave forms are constructed by appropriately scaling a typical human waveform such that the waveform maximum and time-averaged Reynolds numbers, the Womersley number (α), and the pulsatility index (PI) are systematically varied within the human physiologic range. We show that the waveform PI is the key parameter that governs the vortex dynamics across the aneurysm neck and the flow patterns within the dome. At low PI, the flow in the dome is similar to a driven cavity flow and is characterized by a quasi-stationary shear layer that delineates the parent artery flow from the recirculating flow within the dome. At high PI, on the other hand, the flow is dominated by vortex ring formation, transport across the neck, and impingement and breakdown at the distal wall of the aneurysm dome. We further show that the spatial and temporal characteristics of the wall shear stress field on the aneurysm dome are strongly correlated with the vortex dynamics across the neck. We finally argue that the ratio between the characteristic time scale of transport by the mean flow across the neck and the time scale of vortex ring formation can be used to predict for a given sidewall aneurysm model the critical value of the waveform PI for which the hemodynamics will transition from the cavity mode to the vortex ring mode.
Isolation of exchange- and spin-orbit-driven effects via manipulation of the axis of quantization
Authors: Komesu Takashi , Waddill G. D. , Yu S.-W. , Butterfield M. T. , Tobin J. G.
Published: October 2010

Double polarization photoelectron spectroscopy using circularly polarized x-rays and true spin detection has been performed using the 2p core levels of ultrathin films of Fe and Co. This includes both the separation into magnetization- and spin-specific spectra and an analysis of the polarization, asymmetry, and related quantities. It is shown how to selectively manipulate the manifestation of exchange- and spin-orbit effects simply by choosing different axes of quantization. Furthermore, the underlying simplicity of the results can be confirmed by comparison to a simple yet powerful single-electron picture.
UV ozone passivation of the metal/dielectric interface for HfO2-based organic thin film transistors
Authors: Tang W. M. , Ng W. T. , Helander M. G. , Greiner M. T. , Lu Z. H.
Published: October 2010

Ultraviolet (UV) ozone passivation of the metal/dielectric interface was investigated in HfO2-based devices. It is found that the passivation of Al gate reduces the gate leakage current by two orders of magnitude and increases the breakdown field strength by 14%. A thicker wide-band gap Al2O3 interlayer formed on the Al gate during UV ozone treatment improves the interface quality and suppresses the leakage associated with the high-k material. Copper phthalocyanine-based organic thin-film transistors with HfO2 as gate dielectric were fabricated on glass. UV ozone passivated devices exhibited a low threshold voltage of −0.29 V and a low subthreshold slope of 0.38 V/decade, demonstrating the advantage of UV ozone passivation.
Growth of size and density controlled GaAs/InxGa1−xAs/GaAs (x=0.10) nanowires on anodic alumina membrane-assisted etching of nanopatterned GaAs
Authors: Gunawan Aloysius A. , Jha S. , Kuech T. F.
Published: October 2010

Electrochemical anodization using anodic alumina membrane-assisted etching of GaAs(111)B produced nanopatterned GaAs surfaces, which served as substrates for the growth of GaAs/InxGa1−xAs/GaAs quantum well (QW) nanowires with controllable size and density. The nanodepressions created on the anodized GaAs surface minimize the migration of Au nanodots during thermal annealing. The Au nanodots were used in vapor-liquid-solid based growth of the nanostructures. The thickness of the evaporated Au islands, the anodization voltage, and the duration of the etching are the most important parameters used to tailor the size distribution and density of the Au catalysts and hence the diameter of nanowires. Transmission electron microscopy (TEM) reveals that the QW nanowires are single crystals with the ⟨111⟩ main axis direction, similar to nanowires synthesized using conventional methods on bare GaAs substrates and other patterning mechanisms. Z-contrast high-angle annular dark-field scanning TEM confirmed the presence of the InGaAs layer having widths of 70–100 nm. Photoluminescence spectroscopy on the QW nanowires showed consistent peaks at 1.375 eV indicative of the first electron–heavy hole recombination from the InGaAs QW layer. This transition energy corresponds to a 0.10 In composition, in disagreement with the value obtained from energy-dispersive x rays in scanning TEM (xEDX=0.05).
Surface and near-surface modifications of ultralow dielectric constant materials exposed to plasmas under sidewall-like conditions
Authors: Kuo Ming-Shu , Oehrlein G. S.
Published: October 2010

The authors describe the temporal evolution of the surface and near-surface regions of a porous SiCOH ultralow k (ULK) dielectric during exposure under sidewall-like exposure conditions to various plasma processing environments. The authors studied the exposure of the ULK material to Ar plasma, C4F8/Ar-based etching plasma, and O2 or CO2 ashing plasmas, as well as various sequences of these processes. Real-time monitoring of the ULK surfaces during plasma processing was performed by in situ ellipsometry employing a novel gap structure. Additionally, changes in ULK surface properties were characterized by x-ray photoelectron spectroscopy and selective dilute hydrofluoric acid wet etching in combination with ex situ ellipsometry measurements. Pristine ULK material exposed to O2 plasma without ion bombardment shows the formation of a near-surface porous layer. For exposure of the ULK to CO2 plasma operated at comparable plasma operation conditions, the modification depth for a given exposure time is reduced relative to O2, but otherwise an identical ellipsometric trajectory is followed. This is indicative of a similar ULK damage mechanism for the two discharges, although at different rates. Energetic (∼400 eV) ion bombardment on the surface of ULK with line-of-sight Ar plasma exposure introduced a ∼12 nm thick SiO2-like densified layer on the ULK surface meanwhile sputtering off the ULK material. The sidewall-like modifications of ULK due to metastable Ar, if present, were too subtle to be measurable in this article. For ULK exposed under sidewall-like geometry to C4F8/Ar-based etching plasma, fluorocarbon quickly permeated into the subsurface region and showed saturation at a mixed layer thickness of about 14 nm. For additional exposure to O2 or CO2 discharges, a strong decrease of the CO2 plasma induced ULK surface modifications with increasing fluorocarbon (FC) film thickness was found, indicative of surface protection by FC surface deposition along with pore-sealing by the FC material. Attempts to increase the protective nature of the FC film by additional plasma processing, e.g., by exposure to Ar or He plasma after FC plasma etching, did not reduce CO2 plasma induced ULK surface modifications further.
Atomic-Level Characterization of the Structural Dynamics of Proteins
Authors: Shaw David E. , Maragakis Paul , Lindorff-Larsen Kresten , Piana Stefano , Dror Ron O. , Eastwood Michael P. , Bank Joseph A. , Jumper John M. , Salmon John K. , Shan Yibing , Wriggers Willy
Published: October 2010

Following Folding Fast

Many protein functions involve conformational changes that occur on time-scales between tens of microseconds and milliseconds. This has limited the usefulness of all-atom molecular dynamics simulations, which are performed over shorter time-scales.

Shaw
et al.

(p.
341
) now report millisecond-scale, all-atom molecular dynamics simulations in an explicitly represented solvent environment. Simulation of the folding of a WW domain showed a well-defined folding pathway and simulation of the dynamics of bovine pancreatic trypsin inhibitor showed interconversion between distinct conformational states.
Cell Type–Specific Loss of BDNF Signaling Mimics Optogenetic Control of Cocaine Reward
Authors: Lobo Mary Kay , Covington Herbert E. , Chaudhury Dipesh , Friedman Allyson K. , Sun HaoSheng , Damez-Werno Diane , Dietz David M. , Zaman Samir , Koo Ja Wook , Kennedy Pamela J. , Mouzon Ezekiell , Mogri Murtaza , Neve Rachael L. , Deisseroth Karl , Han Ming-Hu , Nestler Eric J.
Published: October 2010

BDNF, Dopamine, and Cocaine Reward

The nucleus accumbens plays a crucial role in mediating the rewarding effects of drugs of abuse. Different subpopulations of nucleus accumbens projection neurons exhibit balanced but antagonistic influences on their downstream outputs and behaviors. However, their roles in regulating reward behaviors remains unclear.

Lobo
et al.

(p.
385
) evaluated the roles of the two subtypes of nucleus accumbens projection neurons, those expressing dopamine D1 versus D2 receptors, in cocaine reward. Deleting TrkB, the receptor for brain-derived neurotrophic factor, selectively in each cell type, and selectively controlling the firing of each cell type using optogenetic techniques allowed for confirmation that D1- and D2-containing neurons produced opposite effects on cocaine reward.
Crystal Growth Inhibitors for the Prevention of
l
-Cystine Kidney Stones Through Molecular Design
Authors: Rimer Jeffrey D. , An Zhihua , Zhu Zina , Lee Michael H. , Goldfarb David S. , Wesson Jeffrey A. , Ward Michael D.
Published: October 2010

Taking the Cystine

Kidney stones that form from
l
-cystine are much less common than those forming from calcium oxalate monohydrate, but are more likely to cause chronic kidney disease.

Rimer
et al.

(p.
337
; see the cover; see the Perspective by

Coe and Asplin

) designed two structural mimics for
l
-cystine. Atomic force microscopy showed that at low concentrations, the mimics could change the
l
-cystine crystal habit and inhibit overall crystal growth. These structural mimics may thus offer hope for treating cystinuria.
Response to Comments on “Narrow Primary Feather Rachises in
Confuciusornis
and
Archaeopteryx
Suggest Poor Flight Ability”
Authors: Nudds Robert L. , Dyke Gareth J.
Published: October 2010

Paul and Zheng
et al
. challenge our conclusions regarding the flight of
Confuciusornis
and
Archaeopteryx
, which derive from our method of assessing flight ability from estimated feather strength. They suggest that our mass and rachis data for these fossil birds are incorrect. Neither comment, however, invalidates our method nor alters conclusions of poor flight ability based upon our original data. We encourage researchers to use our method before critiquing our conclusions regarding early bird flight.
Painful Failure of Promising Genital Herpes Vaccine
Authors: Cohen Jon
Published: October 2010

A vaccine designed to ward off genital herpes has failed in a large clinical trial, abruptly ending the product's seemingly promising future.
Custom-Built Supercomputer Brings Protein Folding Into View
Authors: Service Robert F.
Published: October 2010

On page
341
of this week's issue of
Science
, computational biologists report that they ran a specially built supercomputer for about 3 weeks to simulate a relatively small protein going through 15 rounds of folding and unfolding over 200 microseconds.
Carbon-Linking Catalysts Get Nobel Nod
Authors: Service Robert F.
Published: October 2010

This year's Nobel Prize in chemistry went to Ei-ichi Negishi, Akira Suzuki, and Richard Heck for discovering catalysts used to tie the knot between carbon atoms on separate molecules.
A Defined Tuberculosis Vaccine Candidate Boosts BCG and Protects Against Multidrug-Resistant
Mycobacterium tuberculosis
Authors: Bertholet Sylvie , Ireton Gregory C. , Ordway Diane J. , Windish Hillarie Plessner , Pine Samuel O. , Kahn Maria , Phan Tony , Orme Ian M. , Vedvick Thomas S. , Baldwin Susan L. , Coler Rhea N. , Reed Steven G.
Published: October 2010

A vaccine with a four-protein fusion peptide from
Mycobacterium tuberculosis
effectively boosts the current childhood TB vaccine and protects against drug-resistant TB.
Fatty Eggs and Infertility
Authors: Bremer Andrew A.
Published: October 2010

Lipotoxicity in ovarian cells may account for the reduced fertility observed in obese women.
Mapping Human Disease Risk
Authors: Damani Samir
Published: October 2010

A third-generation human HapMap will help to decode the heritable component of human disease risk.
To Vaccinate or Not: Parents Decide
Authors: Hansel Donna E.
Published: October 2010

Although prophylactic human papillomavirus vaccines now are available, fewer than 20% of girls 9 to 26 years of age have completed the three-dose series.
Pneumococcal Nasopharyngeal Carriage following Reduced Doses of a 7-Valent Pneumococcal Conjugate Vaccine and a 23-Valent Pneumococcal Polysaccharide Vaccine Booster
Authors: Russell F. M. , Carapetis J. R. , Satzke C. , Tikoduadua L. , Waqatakirewa L. , Chandra R. , Seduadua A. , Oftadeh S. , Cheung Y. B. , Gilbert G. L. , Mulholland E. K.
Published: October 2010

This study was conducted to evaluate the effect of a reduced-dose 7-valent pneumococcal conjugate vaccine (PCV) primary series followed by a 23-valent pneumococcal polysaccharide vaccine (23vPPS) booster on nasopharyngeal (NP) pneumococcal carriage. For this purpose, Fijian infants aged 6 weeks were randomized to receive 0, 1, 2, or 3 PCV doses. Within each group, half received 23vPPS at 12 months. NP swabs were taken at 6, 9, 12, and 17 months and were cultured for
Streptococcus pneumoniae.
Isolates were serotyped by multiplex PCR and a reverse line blot assay. There were no significant differences in PCV vaccine type (VT) carriage between the 3- and 2-dose groups at 12 months. NP VT carriage was significantly higher (
P
, <0.01) in the unvaccinated group than in the 3-dose group at the age of 9 months. There appeared to be a PCV dose effect in the cumulative proportion of infants carrying the VT, with less VT carriage occurring with more doses of PCV. Non-PCV serotype (NVT) carriage rates were similar for all PCV groups. When groups were pooled by receipt or nonreceipt of 23vPPS at 12 months, there were no differences in pneumococcal, VT, or NVT carriage rates between the 2 groups at the age of 17 months. In conclusion, there appeared to be a PCV dose effect on VT carriage, with less VT carriage occurring with more doses of PCV. By the age of 17 months, NVT carriage rates were similar for all groups. 23vPPS had no impact on carriage, despite the substantial boosts in antibody levels.
Does Hepatitis B Virus Prenatal Transmission Result in Postnatal Immunoprophylaxis Failure?
Authors: Zhu Yi-Yang , Mao Ying-Zi , Wu Wei-Ling , Cai Qun-Xi , Lin Xian-Hua
Published: October 2010

The objective of this work was to evaluate whether postnatal hepatitis B immunization failure in children is caused by prenatal infections. A prospective study was conducted from October 2006 to September 2008. Fetal samples from HBsAg-positive mothers were retrieved by either amniocentesis or cordocentesis (percutaneous umbilical blood sampling [PUBS]). Hepatitis B virus (HBV) serologic markers (HBVM) and quantitative HBV DNA assays were performed to assess prenatal infection. All neonates were given combined HBV immunoprophylaxis after delivery. The newborns were followed up with HBV serologic testing at 1 year old. For the 252 pregnant women recruited, 16 fetuses were found to be HBV DNA positive, with all HBV DNA levels under 10
4
copies/ml. HBsAg and HBV DNA detected in the uterus were uncommon and were expressed at low levels. In contract to the case with prenatal statuses, neonatal serologies were more similar to their mothers'. The response rate of vaccination was 95%. Six children for whom immunoprophylaxis failed were born to HBeAg-positive mothers with high HBV DNA levels (>10
8
copies/ml), but only one of them was found to be positive for intrauterine HBV DNA (8.5 × 10
2
copies/ml). The presence of intrauterine hepatitis B antigen and DNA does not indicate postnatal HBV infection and vaccination failure.
Anaplasma marginaleInfection with Persistent High-Load Bacteremia Induces a Dysfunctional Memory CD4+T Lymphocyte Response but Sustained High IgG Titers
Authors: Han Sushan , Norimine Junzo , Brayton Kelly A. , Palmer Guy H. , Scoles Glen A. , Brown Wendy C.
Published: October 2010

Control of blood-borne infections is dependent on antigen-specific effector and memory T cells and high-affinity IgG responses. In chronic infections characterized by a high antigen load, it has been shown that antigen-specific T and B cells are vulnerable to downregulation and apoptosis.Anaplasma marginaleis a persistent infection of cattle characterized by acute and chronic high-load bacteremia. We previously showed that CD4+T cells primed by immunization with anA. marginaleouter membrane protein were rapidly deleted following infection. Furthermore, peripheral blood T cell responses to bacteria were not observed after acute infection was controlled, suggesting dysfunctional T cell priming to otherA. marginaleantigens. The current study more closely investigated the kinetics ofA. marginale-specific CD4+T cell responses primed during infection. Frequent sampling of peripheral blood and spleens revealed that antigen-specific CD4+T cell responses were first detected at 5 to 7 weeks, but the responses were sporadic and transient thereafter. A similar pattern was observed in animals sampled weekly for nearly 1 year. Paradoxically, by 2 weeks of infection, cattle had developed high titers ofA. marginale-specific IgG, which remained high throughout persistent infection. This dysfunctional CD4+T cell response to infection is consistent with continual downregulation or deletion of newly primed effector T cells, similar to what was observed for immunization-induced T cells followingA. marginaleinfection. The failure to establish a strong memory T cell response duringA. marginaleinfection likely contributes to bacterial persistence.
Immune Responses and Protection against ExperimentalBrucella suisBiovar 1 Challenge in Nonvaccinated orB. abortusStrain RB51-Vaccinated Cattle
Authors: Olsen S. C. , Hennager S. G.
Published: October 2010

Twenty Hereford heifers approximately 9 months of age were vaccinated with saline (control) or 2 × 1010CFU of theBrucella abortusstrain RB51 (RB51) vaccine. Immunologic responses after inoculation demonstrated significantly greater (P< 0.05) antibody and proliferative responses to RB51 antigens in cattle vaccinated with RB51 than in the controls. Pregnant cattle received a conjunctival challenge at approximately 6 months of gestation with 107CFU ofB. suisbv. 1 strains isolated from naturally infected cattle. The fluorescence polarization assay and the buffered acid plate agglutination test had the highest sensitivities in detectingB. suis-infected cattle between 2 and 12 weeks after experimental infection. Serologic responses and lymphocyte proliferative responses toB. suisantigens did not differ between control and RB51 vaccinees after experimental infection. No abortions occurred in cattle in either treatment group after challenge, although there appeared to be an increased incidence of retained placenta after parturition in both the control and the RB51 vaccination treatment groups. Our data suggest that the mammary gland is a preferred site forB. suislocalization in cattle. Vaccination with RB51 did not reduceB. suisinfection rates in maternal or fetal tissues. In conclusion, althoughB. suisis unlikely to cause abortions and fetal losses in cattle, our data suggest that RB51 vaccination will not protect cattle againstB. suisinfection after exposure.
Safety and Immunogenicity of a Novel
Staphylococcus aureus
Vaccine: Results from the First Study of the Vaccine Dose Range in Humans
Authors: Harro Clayton , Betts Robert , Orenstein Walter , Kwak Eun-Jeong , Greenberg Howard E. , Onorato Matthew T. , Hartzel Jon , Lipka Joy , DiNubile Mark J. , Kartsonis Nicholas
Published: October 2010

Merck V710 is a novel vaccine containing the conserved
Staphylococcus aureus
iron surface determinant B shown to be protective in animal models. A phase I, multicenter, double-blind study of the dose range was conducted to assess the immunogenicity and safety of an adjuvanted liquid formulation of V710. A total of 124 adults (18 to 55 years of age) were randomized 1:1:1:1 to receive one 0.5-ml intramuscular injection of V710 (5 μg, 30 μg, or 90 μg) or saline placebo. A positive immune response was defined as at least a 2-fold increase in IsdB-specific IgG levels from baseline levels. Local and systemic adverse events were assessed for 5 and 14 days, respectively, following vaccination. Positive immune responses were detected in 12 (67%) of the 18 subjects in the groups receiving 30 and 90 μg V710 tested at day 10. At day 14, a significantly greater proportion of subjects manifested a positive immune response with higher geometric mean concentrations in the V710 30-μg (86%; geometric mean concentration of 116 μg/ml) and 90-μg (87%; geometric mean concentration of 131 μg/ml) dose groups than in the V710 5-μg (29%; geometric mean concentration of 51 μg/ml) or placebo (4%; geometric mean concentration of 23 μg/ml) groups. Immune responses were durable through day 84. Subjects <40 and ≥40 years of age had comparable immune responses. The most common adverse events were injection-site pain, nausea, fatigue, and headache, usually of mild intensity. No immediate reactions or serious adverse events were reported. In this first study of V710 in humans, a single 30-μg or 90-μg dose was more immunogenic than the 5-μg dose or placebo. Immune responses were evident by 10 to 14 days after vaccination in most responders.