bluuebunny/crossref_metadata_2025 huggingface dataset:
Quadratic Programming to Optimize Energy Efficiency of Speed- and Displacement-Variable Pumps
Authors: Willkomm Johannes , Wahler Matthias , Weber Jürgen
Published: October 2014

Within the last years, speed-variable pump drives were investigated in numerous applications. In combination with a variable displacement pump, the volume flow and the drive speed can be decoupled. In this paper the resulting degree of freedom will be used to minimize the energy consumption of hydraulic processes by means of a novel model predictive control concept. A dynamic loss model of all drive components will be transformed to a mathematical quadratic optimization problem. The optimum use of the two control variables can achieve energy savings of up to 25% in comparison to known control strategies of speed-variable variable-displacement pumps. Especially in highly dynamic process cycles the proposed optimization guarantees optimum energy efficiency while known approaches become inefficient.
Investigation Into the Effects of Index Angle on Fluidborne Noise and Structureborne Noise of a Tandem Axial Piston Pump
Authors: Ye Shaogan , Xu Bing , Zhang Junhui
Published: October 2014

High noise level is one of the dominant drawbacks of axial piston pumps which are widely applied in industry, mobile and aircraft applications. Lots of early studies focused on the noise reduction of a single pump, while this study focuses on investigating the noise characteristics of a tandem axial piston pump. We develop a lumped parameters/finite element (LP/FE) model of an axial piston pump for fully capturing its fluidborne noise and structureborne noise characteristics. We consider fluid compressibility and main leakages in the LP model which is verified by a comparison of discharge flow rate with experimental tests built based on the secondary source method. The FE model was developed on the basis of actual pump with excitation forces obtained from the LP model. The effects of index angle in a tandem pump to the fluidborne noise and structureborne noise are analyzed with the LP/FE model, respectively. A sensitivity analysis is carried out in a wide range of discharge pressures and displacements at a fixed revolution speed, further. Results indicate that fluidborne noise is reduced by 52.1%, whilst structureborne noise is increased by 2 dB(A) with an index angle of 20° to zero, respectively.
Position Control of Direct Driven Hydraulic Drive
Authors: Bonato Carlo , Minav Tatiana A. , Sainio Panu , Pietola Matti
Published: October 2014

This paper investigates directly driven hydraulic setup for non-road mobile machinery (NRMM) application. The purpose of this research is to utilize the excellent control capabilities of modern electric drives in electro-hydraulic systems, create direct drive position control for the hydraulic cylinder and verify the results by measurements. The control is implemented directly with a motor drive without conventional control valves. Speed and position of the double-acting cylinder is determined by in-coming oil flow from the pump, out-coming flow of hydraulic motor and angular speed of the electric motor with a single feedback from motor rotor encoder. Empirical results proved that the control suits NRMM application. The achieved maximum final position error of 3.1 % of the position control for tested cycle is fulfilling required accuracy.
Tool for Studying Effects of Human Operators on Energy Consumption of Working Hydraulics of Off-Highway Working Vehicle
Authors: Luostarinen Lauri O. , Åman Rafael , Handroos Heikki
Published: October 2014

The improvement of the energy efficiency is an important topic for off-highway working vehicle developers and manufacturers. New energy efficient technologies, e.g. a hybrid power transmission with an energy recovery feature, have been introduced. However, currently most of the working vehicles are using more conventional technologies. Human operators have an effect on the overall efficiency of the vehicles. The research of the human effect is difficult and expensive using the conventional research methods. A real-time simulation and virtual reality (VR) technology have developed fast recently. A VR-based real-time simulator is a powerful low-cost tool and enables a several novel research methods. The aim of this study is to find the suitability of the VR-based simulator to find the effect of a human operator on the energy consumption of the working hydraulics of off-highway working vehicles. Experimental tests are carried out using human-in-the-loop simulation in an immersive VR-environment. The vehicle used for the case study is an underground mining loader. The results show that the proposed method is valid to find the values for the energy consumption and energy efficiency of a working hydraulics. A variation in the energy efficiency of the working hydraulics was found. The variation correlates with the operator’s driving style. With a larger group of operators the effect of a human operator on the energy consumption can be defined.
Experimental Analysis of Electro-Hydraulic Hybrid Actuator System for Off-Highway Working Vehicles
Authors: Åman Rafael , Ponomarev Pavel , Luostarinen Lauri O. , Handroos Heikki , Pyrhönen Juha , Lasse Laurila
Published: October 2014

Electro-hydraulic hybrid power transmission system can save energy and thus reduce the pollution while maintaining the same performance in comparison to the conventional fluid power system in off-highway working vehicles. This paper introduces experimental analysis of an electro-hydraulic hybrid actuator system specially developed for the recuperation of the potential and kinetic energy in off-highway working vehicles. In this compact assembly all the components are located near each other to save space. Proposed hybrid actuator system can be controlled directly by an electrical frequency converter which allows the replacement of long lossy fluid power transmission lines with electrical cables. Integrated electro-hydraulic energy converter (IEHEC) is the principal component of the proposed hybrid actuator system. The energy converter consists of a fixed-displacement hydraulic pump-motor and an integrated electrical permanent magnet synchronous motor-generator. IEHEC unit can be driven in four quadrants to produce the mechanical power required for the hydraulic actuator, or to recover the energy released by the actuator mechanism and supply it back to electrical circuit. Suitable places for this application are all actuators that carry out work cycle in which the kinetic and potential energy is available for recovery, e.g. lifting cylinders in cranes, fork lift trucks, etc.

The test rig allows the experimental analysis of behavior of real power transmission system in two modes while using simulated loads. The first mode is the work cycle mode using IEHEC as motor connected to the hydraulic pump. The other mode is the energy recovery mode while direction of operation is reversed. The real-time simulated loads, which are carried out by simulating typical work cycle of a mechanism, enable the loading in the work cycle and provide the recoverable energy in the recovery mode. The forces acting in actuator connection point are implemented in the test rig by a hydraulic cylinder which is controlled by bandwidth proportional cartridge valves and a dSpace Real-time Control system.

The electro-hydraulic hybrid actuator system was simulated in a certain loading case using virtual simulation and also hardware-in-the-loop (HIL) simulation in the test rig. The responses were compared. Experimental analysis of the dynamic behaviour of a real electro-hydraulic hybrid actuator system has been carried out by using HIL simulation.
Bond Graph Modelling and Energy Flow Analysis of a Reach Stacker
Authors: Schaep Thomas , Marquis-Favre Wilfrid , Bideaux Eric , Noppe Eric , Rodot Pierre , Bernigaud Jean-Christophe , Langlois Vincent
Published: October 2014

This study focuses on the global energy flow analysis along the three main energy lines of an off-highway vehicle used on port areas called a reach stacker. In order to characterize the energy consumption of the power train and the actuation system, a model of the machine has been established using the bond graph methodology. This language is suitable for representing multi domains energy transfers and allows the determination of the needed energy for an actuator to perform a given task. The simulation results are then compared with measurements carried out on a real reach stacker. Those data help to identify several parameters like friction coefficients and efficiencies. The energy flow analysis also gives detailed information on the main energy losses sources which prefigures coming evolutions.
Digital Hydraulic System Using Pumps and On/Off Valves Controlling the Actuator
Authors: Locateli Cristiano Cardoso , Teixeira Paulo Leonel , De Pieri Edson Roberto , Krus Petter , De Negri Victor Juliano
Published: October 2014

Hydraulic systems employed in several industrial and mobile applications present significant advantages, such as a high power-to-weight ratio and fast dynamic response. However, these systems have low efficiency due to high power dissipation. A recent concept called “digital hydraulics” comprises particularities that create opportunities for a reduction in load loss. This paper proposes a configuration and control method for actuator speed control based on the principles of digital hydraulics. In this context, several fixed displacement units and on/off valves are connected directly to the actuators without throttling valves. The system studied here presents three operation methods (pump mode, motor mode and idle mode), which allows discrete valves to replace continuous or flow control valves in order to control the actuator. Furthermore, a fixed or variable displacement pump with large displacement is replaced by several small, fixed displacement units. Simulations are performed with a co-simulation technique using AMESim and MATLAB. The actuator speed, inlet and outlet pressures on the fixed displacement units and flow rate in the circuit lines are analysed. Preliminary simulation results exhibit smooth transitions between speed levels, adequate dynamic performance, low power dissipation and high energy-storage capacity. A specific limitation of this technology is the obtained actuator discrete speed. The main contributions of this research are the development of a digital hydraulic system configuration and its control strategy, which allows speed control of hydraulic actuators and provides the capacity to store energy.
System Parameter Study for a Light-Weight Series Hydraulic Hybrid Vehicle
Authors: Baer Katharina , Ericson Liselott , Krus Petter
Published: October 2014

Amongst the hybrid vehicle propulsion solutions aiming to improve fuel efficiency, hybrid electric solutions currently receive most attention, especially on the market. However, hydraulic hybrids are an interesting alternative, especially for heavier vehicles due to higher power density which is beneficial if higher masses are moved. As a step towards a comprehensive design framework to compare several possible hydraulic hybrid architectures for a specified application and usage profile, the model of a series hydraulic hybrid vehicle was previously introduced and initially studied concerning component sizing for an exemplary light-duty vehicle in urban traffic. The vehicle is modeled in the Hopsan simulation tool. A comparably straight-forward engine management is used for the vehicle control; both pump and engine controls are based on the hydraulic accumulator’s state-of-charge. The model is developed further with respect to the accumulator component model. Based on that, the influence of several system and component parameters, such as maximum system pressure and engine characteristics, as well as controller parameters on the vehicle’s performance is analyzed. The goal is to allow for more understanding of the system’s characteristics to facilitate future optimization of the system.
The Finite Element Model of Vibroacoustical Characteristics of Pipe System Under Force Excitation by Oscillating Fluid Flow
Authors: Mironova Tatiana , Prokofiev Andrey , Sverbilov Victor
Published: October 2014

The finite element mathematical technique of vibroacoustical pipeline characteristics are developed. The technique allows calculations vibroacoustical characteristics of pipe with the axial line lying in one plane under force excitation by oscillating fluid flow. The technique is based on the solving differential equation system of interaction between solid and oscillating fluid in the pipeline. Solution was done for transient non-stationary nonlinear differential equation system. The weighted residual approximation with relations for a Galerkin finite element solutions were done. The boundary conditions for fluid is a parameter combination of complex pressure oscillation amplitude of pipeline inlet section, complex pressure oscillation amplitude of pipeline outlet section, complex velocity oscillation amplitude of pipeline inlet section, complex velocity oscillation amplitude of pipeline outlet section, load impedance, input impedance. The boundary conditions for solid is bonding of the pipeline. In this technique new seven node element were proposed. The new space-time single type elements based on Lagrange basis function. The single type of finite element are used for modeling vibroacoustical interaction between solid and oscillating fluid. Time response and amplitude spectrum of the pipeline vibration are resulted of these techniques. The mathematical technique computational coast is 3 orders less than available finite element techniques. The convergence estimate of experimental data and simulation results are made. The method is developed for pipeline diameter much smaller than acoustic wavelength in a fluid. It is actual for aircraft pipelines, pipes of power plants, mobile machines and pipes of stationary processing machines.
HIL Simulation of Elastomer Supported Machine Bed Dynamics
Authors: Saarikoski Tuomas , Pietola Matti
Published: October 2014

This paper presents a Hardware-in-the-Loop (HIL) test setup used for studying the dynamics of an elastomer supported machine bed. The setup uses real elastomer dampers and modeled machine dynamics (process model) connected together via real-time interface. The HIL approach was chosen since the elastomers are a critical part of the system, however, determining their properties for engineering needs can be a challenging task. Accurate elastomer models include many parameters that can only be determined by experimentally, and even then their implementation for real-life applications is not always practical.

Using real elastomers supports in the simulation removes uncertainties associated with classic elastomer models, while simulated process makes it possible to test different scenarios fast and with good repeatability. The process model includes a description of the machine body, a rotating unbalanced drive mechanism creating cyclic loading and external excitation forces acting on the machine. The method enables testing of machine bed supports in a realistic operating environment.

A test rig was built for housing the elastomers incorporating a hydraulic actuator for producing the process movement. The hydraulic circuit was designed for good dynamic performance with predictive control to minimize delays in the real-time interface. It was found that the HIL-setup can provide fast and accurate information about the plant model behavior in different operating scenarios using the elastomer supports.
Design Method for Fast Switching Seat Valves for Digital Displacement® Machines
Authors: Roemer Daniel B. , Johansen Per , Pedersen Henrik C. , Andersen Torben O.
Published: October 2014

Digital Displacement® (DD) machines are upcoming technology where the displacement of each pressure chamber is controlled electronically by use of two fast switching seat valves. The effective displacement and operation type (pumping/motoring) may be controlled by manipulating the seat valves corresponding to the piston movement, which has been shown to facilitate superior part load efficiency combined with high bandwidth compared to traditional displacement machines. However, DD machines need fast switching on-off valves with low pressure loss for efficient operation, especially in fast rotating operation, where switching times must be performed within a few milliseconds. These valve requirements make a simulation based design approach essential, where mechanical strength, thermal dissipation, fluid dynamics and electro-magnetic dynamics must be taken into account. In this paper a complete design method for DD seat valves are presented, taking into account the significant aspects related to obtaining efficient DD valves with basis in a given DD machine specifications. The seat area is minimized and the stroke length is minimized to obtain fast switching times while considering the pressure loss of the valves. A coupled optimization is finally conducted to optimize the electro-magnetic actuator, leading to a valve design based on the chosen valve topology. The design method is applied to an example DD machine and the resulting valve design fulfilling the requirements is presented.
Guided wrinkling with nanoimprinted SU-8 surfaces
Authors: Steinberg Christian , Blenskens Daniel , Dhima Khalid , Wang Si , Papenheim Marc , Scheer Hella-Christin , Zajadacz Joachim , Zimmer Klaus
Published: October 2014

The wrinkling of SU-8 may be useful for microelectromechanical systems and optical applications, but highly regular and periodic wrinkles are the most convenient for such applications. This paper reports wrinkles generated on SU-8 by exposure to 172 nm-wavelength ultraviolet under ozone. To identify the relevant processing parameters, the impact of the SU-8 layer thickness and the effects of the postexposure bake temperature and UV-ozone treatment time are investigated. With 5 μm-thick SU-8 layers, distinct wrinkles are obtained with an ultraviolet-ozone treatment of 3 min and at a postexposure bake temperature of at least 140 °C. To guide the wrinkling, topography is induced on the SU-8 surface via capillary force lithography. By using a stamp with equidistant cavities possessing different widths, the structure size dependence is investigated. Owing to local stress relaxation, single or double wrinkles form along the elevated lines depending upon the line width. Within the gaps between the lines, wrinkles oriented perpendicular to the lines develop induced by the nonrelaxed compressive stress. Wrinkling represents a simple alternative for covering the surface of SU-8 with largely self-forming regular structures that may act as transmissive optical elements.
Eccentric and Concentric Exercise of the Triceps Surae: An in Vivo Study of Dynamic Muscle and Tendon Biomechanical Parameters
Authors: Chaudhry Saira , Morrissey Dylan , Woledge Roger C. , Bader Dan L. , Screen Hazel R.C.
Published: October 2014

Triceps surae eccentric exercise is more effective than concentric exercise for treating Achilles tendinopathy, however the mechanisms underpinning these effects are unclear. This study compared the biomechanical characteristics of eccentric and concentric exercises to identify differences in the tendon load response. Eleven healthy volunteers performed eccentric and concentric exercises on a force plate, with ultrasonography, motion tracking, and EMG applied to measure Achilles tendon force, lower limb movement, and leg muscle activation. Tendon length was ultrasonographically tracked and quantified using a novel algorithm. The Fourier transform of the ground reaction force was also calculated to investigate for tremor, or perturbations. Tendon stiffness and extension did not vary between exercise types (P = .43). However, tendon perturbations were significantly higher during eccentric than concentric exercises (25%–40% higher, P = .02). Furthermore, perturbations during eccentric exercises were found to be negatively correlated with the tendon stiffness (R2 = .59). The particular efficacy of eccentric exercise does not appear to result from variation in tendon stiffness or extension within a given session. However, varied perturbation magnitude may have a role in mediating the observed clinical effects. This property is subject-specific, with the source and clinical timecourse of such perturbations requiring further research.
Emotional State Impacts Center of Pressure Displacement Before Forward Gait Initiation
Authors: Fawver Bradley , Beatty Garrett F. , Naugle Kelly M. , Hass Chris J. , Janelle Christopher M.
Published: October 2014

Emotional states influence whole-body movements during quiet standing, gait initiation, and steady state gait. A notable gap exists, however, in understanding how emotions affect postural changes during the period preceding the execution of planned whole-body movements. The impact of emotion-induced postural reactions on forthcoming posturomotor movements remains unknown. We sought to determine the influence of emotional reactions on center of pressure (COP) displacement before the initiation of forward gait. Participants (N = 23, 14 females) stood on a force plate and initiated forward gait at the offset of an emotional image (representing five discrete categories: attack, sad faces, erotica, happy faces, and neutral objects). COP displacement in the anteroposterior direction was quantified for a 2 second period during image presentation. Following picture onset, participants produced a posterior postural response to all image types. The greatest posterior displacement was occasioned in response to attack or threat stimuli compared with happy faces and erotica images. Results suggest the impact of emotional states on gait behavior begins during the motor planning period before the preparatory phase of gait initiation, and manifests in center of pressure displacement alterations.
HSF-1–mediated cytoskeletal integrity determines thermotolerance and life span
Authors: Baird Nathan A. , Douglas Peter M. , Simic Milos S. , Grant Ana R. , Moresco James J. , Wolff Suzanne C. , Yates John R. , Manning Gerard , Dillin Andrew
Published: October 2014

The conserved heat shock transcription factor–1 (HSF-1) is essential to cellular stress resistance and life-span determination. The canonical function of HSF-1 is to regulate a network of genes encoding molecular chaperones that protect proteins from damage caused by extrinsic environmental stress or intrinsic age-related deterioration. InCaenorhabditis elegans, we engineered a modified HSF-1 strain that increased stress resistance and longevity without enhanced chaperone induction. This health assurance acted through the regulation of the calcium-binding protein PAT-10. Loss ofpat-10caused a collapse of the actin cytoskeleton, stress resistance, and life span. Furthermore, overexpression ofpat-10increased actin filament stability, thermotolerance, and longevity, indicating that in addition to chaperone regulation, HSF-1 has a prominent role in cytoskeletal integrity, ensuring cellular function during stress and aging.
Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses
Authors: Calegari F. , Ayuso D. , Trabattoni A. , Belshaw L. , De Camillis S. , Anumula S. , Frassetto F. , Poletto L. , Palacios A. , Decleva P. , Greenwood J. B. , Martín F. , Nisoli M.
Published: October 2014

In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub–4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.
Ion permeation in K
+
channels occurs by direct Coulomb knock-on
Authors: Köpfer David A. , Song Chen , Gruene Tim , Sheldrick George M. , Zachariae Ulrich , de Groot Bert L.
Published: October 2014

Potassium channels selectively conduct K
+
ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K
+
concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K
+
ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K
+
conduction. Crystallographic data are consistent with directly neighboring K
+
ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K
+
channels.
Motor skill learning requires active central myelination
Authors: McKenzie Ian A. , Ohayon David , Li Huiliang , Paes de Faria Joana , Emery Ben , Tohyama Koujiro , Richardson William D.
Published: October 2014

Myelin-forming oligodendrocytes (OLs) are formed continuously in the healthy adult brain. In this work, we study the function of these late-forming cells and the myelin they produce. Learning a new motor skill (such as juggling) alters the structure of the brain’s white matter, which contains many OLs, suggesting that late-born OLs might contribute to motor learning. Consistent with this idea, we show that production of newly formed OLs is briefly accelerated in mice that learn a new skill (running on a “complex wheel” with irregularly spaced rungs). By genetically manipulating the transcription factor myelin regulatory factor in OL precursors, we blocked production of new OLs during adulthood without affecting preexisting OLs or myelin. This prevented the mice from mastering the complex wheel. Thus, generation of new OLs and myelin is important for learning motor skills.
The unresolved fine structure resolved: IRIS observations of the solar transition region
Authors: Hansteen V. , De Pontieu B. , Carlsson M. , Lemen J. , Title A. , Boerner P. , Hurlburt N. , Tarbell T. D. , Wuelser J. P. , Pereira T. M. D. , De Luca E. E. , Golub L. , McKillop S. , Reeves K. , Saar S. , Testa P. , Tian H. , Kankelborg C. , Jaeggli S. , Kleint L. , Martínez-Sykora J.
Published: October 2014

The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle.
Increased variability of tornado occurrence in the United States
Authors: Brooks Harold E. , Carbin Gregory W. , Marsh Patrick T.
Published: October 2014

Whether or not climate change has had an impact on the occurrence of tornadoes in the United States has become a question of high public and scientific interest, but changes in how tornadoes are reported have made it difficult to answer it convincingly. We show that, excluding the weakest tornadoes, the mean annual number of tornadoes has remained relatively constant, but their variability of occurrence has increased since the 1970s. This is due to a decrease in the number of days per year with tornadoes combined with an increase in days with many tornadoes, leading to greater variability on annual and monthly time scales and changes in the timing of the start of the tornado season.
Potassium ions line up
Authors: Hummer Gerhard
Published: October 2014

Do K
+
ions move in single file through potassium channels?
“Epicenters” of resilience
Authors: Zoback Mary Lou
Published: October 2014

The 25th anniversary of the magnitude (
M
) 6.9 Loma Prieta earthquake that struck the San Francisco Bay Area on 17 October 1989 is a fitting time to examine what progress has been made in increasing community resilience to minimize seismic risk. The regions affected by the 2010
M
7.0 earthquake that struck Port-au-Prince, Haiti, and the
M
8.8 event near Concepción, Chile, a few weeks later illustrate the extremes in earthquake resilience. In the zone of most intense shaking, 1 of every 10 Haitians was killed, compared to 1 of every 2500 Chileans, reflecting huge differences in construction quality and community resilience. The Loma Prieta event left 63 people dead, largely the result of the collapse of a bridge, an overpass, and homes built on unconsolidated fill. But beyond the loss of life, the Bay Area was affected by more than $10 billion in disruption of economic activity and damaged infrastructure. One challenge in implementing community resilience is to use science and engineering to find solutions that not only save lives but also get communities back to business as quickly as possible after a seismic event.
Employees thrive on innovative design
Authors: Gewin Virginia
Published: October 2014

First-in-class drugs and drought-resistant seeds may not seem to have much in common but the transformative technologies being developed to produce these game-changing products do. At the heart of those discoveries are the companies, identified by the 2014 Science Careers Top Employer Survey, that foster a spirit of innovation. These 20 biotechnology and pharmaceutical companies have their eyes on transformative prizes and invest in the intellectual capital needed to get there. From encouraging risky research to bolstering academic collaborations, keeping employees engaged and excited about their research is priority number one.
Multilocus Sequence Typing of Corynebacterium ulcerans Provides Evidence for Zoonotic Transmission and for Increased Prevalence of Certain Sequence Types among Toxigenic Strains
Authors: König Christina , Meinel Dominik M. , Margos Gabriele , Konrad Regina , Sing Andreas
Published: October 2014

Human-to-human-transmittedCorynebacterium diphtheriaewas historically the main pathogen causing diphtheria and has therefore been studied extensively in the past. More recently, diphtheria caused by toxigenicCorynebacterium ulceransis an emerging disease in several industrial countries, including the United Kingdom, the United States, France, and Germany. However, toxigenicC. ulceranshas so far been almost neglected in the development of epidemiologic tools. One of the most important tools in modern epidemiology to understand transmission pathways is sequence typing of pathogens. Here, we provide a protocol for multilocus sequence typing (MLST) to typeC. ulceransstrains rapidly and relatively cost-effectively. Applying MLST toC. ulceransfor the first time, we show that related sequence types (STs) might be associated with the presence of the diphtheria toxin gene, which encodes diphtheria toxin (DT), the most important diphtheria-causing virulence factor. Interestingly, we found only two very closely related STs in the isolates derived from six dogs. Additionally, our data show that all STs derived from animals which were at least twice present in our analysis were found in humans as well. This finding is congruent with zoonotic transmission ofC. ulcerans.
New Transport Medium for Cultural Recovery of Helicobacter pylori
Authors: Cellini Luigina , Di Campli Emanuela , Di Bartolomeo Soraya , Bessa Lucinda Janete , Baffoni Marina , Di Giulio Mara
Published: October 2014

We developed a new transport medium (GESA—
Helicobacter pylori
transport medium [publication no. WO/2014/019696, patent pending no. PCT/EP2013/002292; Liofilchem s.r.l., Roseto degli Abruzzi, Teramo, Italy]) for recovery of
Helicobacter pylori
from gastric biopsy samples. GESA transport medium, in a semisolid state, provides the optimal conditions for maintaining the viability of the microorganism over time. The efficacy of the transport medium was assessed through
in vitro
and
ex vivo
experiments. We were able to recover different suspensions of
H. pylori
ATCC 43629 and
H. pylori
13 A in GESA transport medium stored at 4°C for up to 10 days. In particular, with a starting inoculum of ∼10
5
CFU, after 7 days of storage, 150 ± 25 CFU and 40 ± 7 CFU of the reference and clinical strains were detected, respectively.
H. pylori
colonies were isolated from gastric specimens taken from both the antrum and the fundus in 68 (90.66%) of 75 urea breath test (UBT)-positive patients. Moreover, GESA transport medium allowed the recovery and isolation of
H. pylori
colonies from additional biopsy samples from 13 of the 75 detected subjects at up to 10 days of biopsy sample storage at 4°C. Finally, GESA transport medium preserved its characteristics when stored at 4°C for 1 year from its preparation, thus allowing good recovery of
H. pylori
. GESA transport medium can be considered a standardized transport medium with high performance that optimizes the recovery rate of
H. pylori
grown by culture.
Expression of Interferon Gamma by a Recombinant Rabies Virus Strongly Attenuates the Pathogenicity of the Virus via Induction of Type I Interferon
Authors: Barkhouse Darryll A. , Garcia Samantha A. , Bongiorno Emily K. , Lebrun Aurore , Faber Milosz , Hooper D. Craig
Published: October 2014

Previous animal model experiments have shown a correlation between interferon gamma (IFN-γ) expression and both survival from infection with attenuated rabies virus (RABV) and reduction of neurological sequelae. Therefore, we hypothesized that rapid production of murine IFN-γ by the rabies virus itself would induce a more robust antiviral response than would occur naturally in mice. To test this hypothesis, we used reverse engineering to clone the mouse IFN-γ gene into a pathogenic rabies virus backbone, SPBN, to produce the recombinant rabies virus designated SPBNγ. Morbidity and mortality were monitored in mice infected intranasally with SPBNγ or SPBN(−) control virus to determine the degree of attenuation caused by the expression of IFN-γ. Incorporation of IFN-γ into the rabies virus genome highly attenuated the virus. SPBNγ has a 50% lethal dose (LD
50)
more than 100-fold greater than SPBN(−).
In vitro
and
in vivo
mouse experiments show that SPBNγ infection enhances the production of type I interferons. Furthermore, knockout mice lacking the ability to signal through the type I interferon receptor (IFNAR
−/−
) cannot control the SPBNγ infection and rapidly die. These data suggest that IFN-γ production has antiviral effects in rabies, largely due to the induction of type I interferons.

IMPORTANCE
Survival from rabies is dependent upon the early control of virus replication and spread. Once the virus reaches the central nervous system (CNS), this becomes highly problematic. Studies of CNS immunity to RABV have shown that control of replication begins at the onset of T cell entry and IFN-γ production in the CNS prior to the appearance of virus-neutralizing antibodies. Moreover, antibody-deficient mice are able to control but not clear attenuated RABV from the CNS. We find here that IFN-γ triggers the early production of type I interferons with the expected antiviral effects. We also show that engineering a lethal rabies virus to express IFN-γ directly in the infected tissue reduces rabies virus replication and spread, limiting its pathogenicity in normal and immunocompromised mice. Therefore, vector delivery of IFN-γ to the brain may have the potential to treat individuals who would otherwise succumb to infection with rabies virus.
Nonstructural Protein 5A (NS5A) and Human Replication Protein A Increase the Processivity of Hepatitis C Virus NS5B Polymerase Activity
In Vitro
Authors: Mani Nagraj , Yuzhakov Alexander , Yuzhakov Olga , Coll Joyce T. , Black Jim , Saxena Kumkum , Fulghum John R. , Lippke Judith A. , Rao B. Govinda , Rijnbrand Rene , Kwong Ann D.
Published: October 2014

The precise role(s) and topological organization of different factors in the hepatitis C virus (HCV) RNA replication complex are not well understood. In order to elucidate the role of viral and host proteins in HCV replication, we have developed a novel
in vitro
replication system that utilizes a rolling-circle RNA template. Under close-to-physiological salt conditions, HCV NS5BΔ21, an RNA-dependent RNA polymerase, has poor affinity for the RNA template. Human replication protein A (RPA) and HCV NS5A recruit NS5BΔ21 to the template. Subsequently, NS3 is recruited to the replication complex by NS5BΔ21, resulting in RNA synthesis stimulation by helicase. Both RPA and NS5A
(S25-C447)
, but not NS5A
(S25-K215)
, enabled the NS5BΔ21-NS3 helicase complex to be stably associated with the template and synthesize RNA product in a highly processive manner
in vitro
. This new
in vitro
HCV replication system is a useful tool that may facilitate the study of other replication factors and aid in the discovery of novel inhibitors of HCV replication.

IMPORTANCE
The molecular mechanism of hepatitis C virus (HCV) replication is not fully understood, but viral and host proteins collaborate in this process. Using a rolling-circle RNA template, we have reconstituted an
in vitro
HCV replication system that allows us to interrogate the role of viral and host proteins in HCV replication and delineate the molecular interactions. We showed that HCV NS5A
(S25-C447)
and cellular replication protein A (RPA) functionally cooperate as a processivity factor to stimulate HCV replication by HCV NS5BΔ21 polymerase and NS3 helicase. This system paves the way to test other proteins and may be used as an assay for discovery of HCV inhibitors.
Complex T-Cell Receptor Repertoire Dynamics Underlie the CD8
+
T-Cell Response to HIV-1
Authors: Costa Ana I. , Koning Dan , Ladell Kristin , McLaren James E. , Grady Bart P. X. , Schellens Ingrid M. M. , van Ham Petra , Nijhuis Monique , Borghans José A. M. , Keşmir Can , Price David A. , van Baarle Debbie
Published: October 2014

Although CD8
+
T cells are important for the control of HIV-1
in vivo
, the precise correlates of immune efficacy remain unclear. In this study, we conducted a comprehensive analysis of viral sequence variation and T-cell receptor (TCR) repertoire composition across multiple epitope specificities in a group of antiretroviral treatment-naive individuals chronically infected with HIV-1. A negative correlation was detected between changes in antigen-specific TCR repertoire diversity and CD8
+
T-cell response magnitude, reflecting clonotypic expansions and contractions related to alterations in cognate viral epitope sequences. These patterns were independent of the individual, as evidenced by discordant clonotype-specific transitions directed against different epitopes in single subjects. Moreover, long-term asymptomatic HIV-1 infection was characterized by evolution of the TCR repertoire in parallel with viral replication. Collectively, these data suggest a continuous bidirectional process of adaptation between HIV-1 and virus-specific CD8
+
T-cell clonotypes orchestrated at the TCR-antigen interface.

IMPORTANCE
We describe a relation between viral epitope mutation, antigen-specific T-cell expansion, and the repertoire of responding clonotypes in chronic HIV-1 infection. This work provides insights into the process of coadaptation between the human immune system and a rapidly evolving lentivirus.
Insight into the Mechanism of Inhibition of Adeno-Associated Virus by the Mre11/Rad50/Nbs1 Complex
Authors: Lentz Thomas B. , Samulski R. Jude
Published: October 2014

Adeno-associated virus (AAV) is a dependent virus of the family
Parvoviridae
. The gene expression and replication of AAV and derived recombinant AAV (rAAV) vectors are severely limited (>10-fold) by the cellular DNA damage-sensing complex made up of Mre11, Rad50, and Nbs1 (MRN). The AAV genome does not encode the means to circumvent this block to productive infection but relies on coinfecting helper virus to do so. Using adenovirus helper proteins E1B55k and E4orf6, which enhance the transduction of AAV via degradation of MRN, we investigated the mechanism through which this DNA damage complex inhibits gene expression from rAAV. We tested the substrate specificity of inhibition and the contribution of different functions of the MRN complex. Our results demonstrate that both single- and double-stranded rAAV vectors are inhibited by MRN, which is in contrast to the predominant model that inhibition is the result of a block to second-strand synthesis. Exploring the contribution of known functions of MRN, we found that inhibition of rAAV does not require downstream DNA damage response factors, including signaling kinases ATM and ATR. The nuclease domain of Mre11 appears to play only a minor role in inhibition, while the DNA binding domain makes a greater contribution. Additionally, mutation of the inverted terminal repeat of the rAAV genome, which has been proposed to be the signal for interaction with MRN, is tolerated by the mechanism of inhibition. These results articulate a model of inhibition of gene expression in which physical interaction is more important than enzymatic activity and several key downstream damage repair factors are dispensable.

IMPORTANCE
Many viruses modulate the host DNA damage response (DDR) in order to create a cellular environment permissive for infection. The MRN complex is a primary sensor of damage in the cell but also responds to invading viral genomes, often posing a block to infection. AAV is greatly inhibited by MRN and dependent on coinfecting helper virus, such as adenovirus, to remove this factor. Currently, the mechanism through which MRN inhibits AAV and other viruses is poorly understood. Our results reform the predominant model that inhibition of rAAV by MRN is due to limiting second-strand DNA synthesis. Instead, a novel mechanism of inhibition of gene expression independent of a block in rAAV DNA synthesis or downstream damage factors is indicated. These findings have clear implications for understanding this restriction to transduction of AAV and rAAV vectors, which have high therapeutic relevance and likely translate to other viruses that must navigate the DDR.
Novel Mode of ISG15-Mediated Protection against Influenza A Virus and Sendai Virus in Mice
Authors: Morales David J. , Monte Kristen , Sun Lulu , Struckhoff Jessica J. , Agapov Eugene , Holtzman Michael J. , Stappenbeck Thaddeus S. , Lenschow Deborah J.
Published: October 2014

ISG15 is a diubiquitin-like modifier and one of the most rapidly induced genes upon type I interferon stimulation. Hundreds of host proteins and a number of viral proteins have been shown to be ISGylated, and understanding how these modifications affect the interferon response and virus replication has been of considerable interest. ISG15−/−mice exhibit increased susceptibility to viral infection, and in the case of influenza B virus and vaccinia virus, ISG15 conjugation has been shown to restrict virus replicationin vivo. A number of studies have also found that ISG15 is capable of antagonizing replication of some viruses in tissue culture. However, recent findings have demonstrated that ISG15 can protect mice from Chikungunya virus infection without affecting the virus burden. In order to better understand the function of ISG15in vivo, we characterized the pathogenesis of influenza A virus and Sendai virus in ISG15−/−mice. We found that ISG15 protects mice from virus induced lethality by a conjugation-dependent mechanism in both of these models. However, surprisingly, we found that ISG15 had minimal effect on virus replication and did not have an obvious role in the modulation of the acute immune response to infection. Instead, we observed an increase in the number of diseased small airways in mice lacking ISG15. This ability of ISG15 to protect mice in a conjugation-dependent, but nonantiviral, manner from respiratory virus infection represents a previously undescribed role for ISG15 and demonstrates the importance of further characterization of ISG15in vivo.

IMPORTANCEIt has previously been demonstrated that ISG15−/−mice are more susceptible to a number of viral infections. Since ISG15 is one of the most strongly induced genes after type I interferon stimulation, analysis of ISG15 function has largely focused on its role as an antiviral molecule during acute infection. Although a number of studies have shown that ISG15 does have a small effect on virus replication in tissue culture, few studies have confirmed this mechanism of protectionin vivo. In these studies we have found that while ISG15−/−mice are more susceptible to influenza A virus and Sendai virus infections, ISGylation does not appear to mediate this protection through the direct inhibition of virus replication or the modulation of the acute immune response. Thus, in addition to showing a novel mode of ISG15 mediated protection from virus infection, this study demonstrates the importance of studying the role of ISG15in vivo.