bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Control Law for Pneumatic Artificial Muscles
Authors: Slightam Jonathon E. , Nagurka Mark L.
Published: December 2017

This paper presents a modified integral sliding surface, sliding mode control law for pneumatic artificial muscles. The cutoff frequency tuning parameter λ is squared to increase the gradient from absement (integral of position) to position and higher derivatives to reflect the more dominant terms in the actuator dynamics. The sliding mode controller is coupled with proportional and integral action compensation. The control system is sufficiently robust so that use of an observer and input-output feedback linearization are not required. Closed-loop control experiments are compared with traditional sliding mode controller designs presented in the literature for pneumatic artificial muscles. Experiments include the tracking of sinusoidal waves at 0.5 and 1 Hz, tracking of square-like waves with seventh-order trajectory transitions at a rate of 0.2 Hz without and with a steady-state period of 10 seconds, as well as a step input response. These experiments indicate that the control law provides similar bandwidth, tracking, and steady-state performance as approaches requiring nonlinear feedback and model observation for pneumatic artificial muscles. Experiments demonstrate an accuracy of 50 μm at steady-state with no overshoot and maximum tracking errors less than 0.4 mm for smooth square-like trajectories.
Influence of a New Hollow Piston Design on Volumetric Losses of a Common-Rail Pump
Authors: Rückert Marcel , Murrenhoff Hubertus , Heitzig Stefan
Published: December 2017

The cluster of excellence „Tailor-Made Fuels from Biomass“ at RWTH Aachen University develops and investigates new biofuel candidates, to reduce global emissions and create an alternative and sustainable diesel fuel. Biofuels pose a new challenge to existing common-rail injection pumps. Since fuels are used as lubricants for tribological contacts in these pumps, the deviating hydrodynamic properties in comparison to diesel can cause high leakage, wear, and a low overall-efficiency.

In order to ensure a reliable pump performance, especially for low-viscosity fuels or fuels with worse lubricity than diesel, an optimization of the tribological contacts is necessary. The most critical contact is the piston-cylinder contact. One possibility to reduce the leakage in this contact is the use of a hollow piston design. This design can reduce the gap between piston and cylinder by minor pressure-dependent elastic deformations of the piston.

In this paper, a first simulative look is taken at the compression behavior of the new piston design. The focus lies on the delayed pressure build-up due to the additional capacity caused by the shape of the piston. Based on the results, a new design approach is proposed subsequently in order to ensure a sufficient pressure build-up.

The manufactured contour of the new design is investigated in order to ensure the geometric properties and first measurement results are discussed. For the measurement, a low-viscosity fluid is used to compare leakage rates of the standard and the new hollow piston design. Based on the results, a conclusion is made, deriving further usage of the hollow piston.
A New Hydraulic Pump and Motor Test Bench for Extremely Low Operating Speeds
Authors: Achten Peter , Potma Jeroen , Eggenkamp Sjoerd
Published: December 2017

Most test benches for hydraulic pumps and motors are designed for operating speeds of 500 rpm or higher. Worldwide, there are only a few test benches which allow measurements at near zero operating speeds or startup conditions.

Low-speed testing is, however, of great importance for hydraulic motors, since the torque losses increase exponential at these conditions due to mixed lubrication and stick-slip effects. Low-speed operation is also important for hydraulic pumps which are used in electro-hydraulic actuators, in which the flow rate is controlled by the operating speed of the electric motors. Finally, measurements at low operating speeds can give detailed information about the pump or motor issues, since it is possible to measure the operation at many rotational positions of the rotating group, giving the ability to measure the losses of individual displacement volumes.

This paper describes the design and operation of a new test bench for testing hydraulic pumps and motors at extremely low operating speeds, below 1 rpm.
Investigation Into the Performance of the VL Seal Based on the 3D Model
Authors: Peng Chao , Ouyang Xiaoping , Gong Guofang , Yang Huayong , Zhou Qinghe
Published: December 2017

Reciprocating rod seals play an important role in the aviation hydraulic system. As a new type of the aerospace reciprocating seal, VL seal is gradually used in crucial and complicated working conditions. When the seal is installed in the groove, there is large deformation in the circumferential direction, which would cause the deviation while the traditional axisymmetric 2D model is used for analyzing its performance. Therefore the new 3D finite element model is developed in this paper to obtain more accurate results of the contact pressure and the stress of the VL seal. Furthermore a mixed lubrication model combined with the 3D model is implemented to obtain the friction and leakage characteristics of the VL seal, which is composed of the fluid lubrication model, the micro contact model and the deformation model. The performance of the seal in the outstroke and instroke is studied respectively and the effects of different working velocities on the seal are also discussed. The analysis results show that the 3D model can demonstrates more comprehensive performance than the traditional axisymmetric model when there is a tangential strain in the VL seal.
Dynamic Model of a Novel Alternating Flow (AF) Hydraulic Pump
Authors: Li Mengtang M. , Foss Ryan , Stelson Kim A. , Van de Ven James D. , Barth Eric J.
Published: December 2017

High power density and good controllability are the most appealing characteristics that make hydraulic systems the best choice for many applications. Current state of the art hydraulic variable displacement pumps show high efficiency at high displacement while they have poor efficiencies at low displacement. This paper proposes a novel alternating flow (AF) variable displacement hydraulic pump to 1) eliminate metering losses by acting as a high-bandwidth pump for displacement control, 2) achieve high efficiency across a wide range of operating conditions and displacements, and 3) allow multiple units to be easily common-shaft mounted for a compact multi-actuator displacement control system from a single prime-mover. A dynamic model using first principles describes the cylinder pressure, flows between pairs of cylinders, and net inlet and outlet flows as a function of the pump’s phase shift angle. The model captures hydraulic check valve dynamics, the effective bulk modulus, leakage flows, and viscous friction. Piston kinematics and dynamics are discussed and energy loss models are presented and used to guide the design for a first prototype of the AF hydraulic pump. The paper presents simulation results from the model that offer an initial evaluation of this novel pump concept and potential applications.
An Energy Efficient Hydraulic Winch Drive Concept Based on a Speed-Variable Switched Differential Pump
Authors: Schmidt Lasse , Andersen Torben O. , Pedersen Henrik C. , Hansen Anders H.
Published: December 2017

The application of valve driven hydraulic winch drives is related to substantial power losses, primarily due to throttle generated valve flows. More energy efficient solutions are also commonly applied in terms of conventional hydrostatic closed circuit drives as well as so-called secondary controls. Such solutions are typically constituted by many and rather expensive components, and are furthermore often suffering from low frequency dynamics. In this paper an alternative solution is proposed for winch drive operation, which is based on the so-called speed-variable switched differential pump, originally designed for direct drive of hydraulic differential cylinders. This concept utilizes three pumps, driven by a single electric servo drive. The concept is redesigned for usage in winch drives, driven by flow symmetric hydraulic motors and single directional loads as commonly seen in e.g. active heave compensation applications. A general drive configuration approach is presented, along with a proper control strategy and design. The resulting concept is evaluated when applied for active heave compensation. Results demonstrate control performance on level with conventional valve solutions in terms of motion tracking, however with improved efficiency, especially in the event that the electrical servo drive can realize four quadrant operation.
Energy and Control Characteristics of a Novel Meter Out Hydraulic System for Mobile Applications
Authors: Marani Pietro , Martelli Massimo
Published: December 2017

The metering out sensing system represents the latest, and most promising, architectural concept for improving the performance of mobile multiple actuation systems through hydraulic proportional components control.

The first part of the paper introduces the novel architecture of meter-out sensing control system, properly designed to distribute the flow rate directed to actuators according to the proportional control of the metering out element only. To do this, an innovative piloting subsystem controls the pump displacement, while a set of compensated proportional control valves applied to actuators outlet work to manage the load unbalance. The inlet doesn’t have any proportional throttle element thus reducing control losses with respect to state-of-the-art systems. In this way, the architecture is able to control both resisting and overrunning loads, and its design could easily include the automatic activation of the regenerative function to limit the requested hydraulic power.

Then, the paper highlights how the proposed architecture of meter-out sensing system, which does not require complex sensor networks or complex electronic controls, could overcome the most important limitations affecting other control technologies currently adopted in mobile hydraulics.

The third part of the paper depicts the main results obtained in the evaluation of the performance figures of merit for the metering out sensing system, performed through a Virtual Test Procedure applied to a lumped and distributed parameter numerical model.
Investigations on Condition Monitoring and Potential Energy Savings of Bi-Stable Process Valves Using Position Estimation
Authors: Kramer Thomas , Weber Jürgen , Pflug Günther , Harnisch Bodo
Published: December 2017

Bi-stable latching valves are an energy efficient alternative to mono-stable switching valves especially in applications of process technology requiring low switching frequencies. The bi-stability of such valves may be disadvantageous. Valve’s states may not only change by controlling the coil current, but also by undesired external forces. A sensorless position determination by detecting the armature position allows condition monitoring. Additionally, an appropriate power supply for switching the valve’s state increases the energy efficiency even further and can be realized by detecting the end stop with the basics of the position estimation method.

The paper deals with simulation-based investigations of a promising sensorless position determination of a novel bi-stable valve, which is partly manufactured from injection moldable magnetic material. The constraints and potentials of the estimation method are described, especially according to condition monitoring the valve’s state. Selected simulation results are validated by measurements. Furthermore, simulations of the magnetic behavior and the mechanical motion are performed demonstrating the potential for detection of the motion’s end stop to apply only the required switching energy to the actuator.
Cylinder Bore Micro-Surface Shaping for High Pressure Axial Piston Machine Operation Using Water as Hydraulic Fluid
Authors: Ernst Meike H. , Ivantysynova Monika
Published: December 2017

Water as a working fluid in hydraulic systems: the benefits of this particular hydraulic fluid are both numerous and consequential, but its implementation remains nontrivial for certain key applications. One of these key applications is the axial piston machine of swashplate type, which counts among its selling points efficiency, the possibility of variable displacement, and the ability to function in high-pressure systems [1]. Water as a working fluid tends to mar that last point with its extremely low viscosity — and the high leakages and low load support that stand as effects of that fluid property in the context of tribological interfaces. However, water’s environmentally friendly, fire resistant nature is coupled with a high thermal conductivity and high heat capacity favorable for keeping hydraulic systems cool, as well as a high bulk modulus that cuts slack in the exact execution of machine motions [2]. That makes it worth implementing in hydraulic systems, even in the face of the aforementioned troubles. This paper investigates the effects of a surface shape that can be applied to the cylinder bores of axial piston machines with the goal of improving load support while keeping down leakage in the critical piston cylinder tribological interface of axial piston machines operating at high pressures with water as their hydraulic fluid.
System and Thermal Modeling for a Novel On-Road Hydraulic Hybrid Vehicle by Comparison With Measurements in the Vehicle
Authors: Kwon Hyukjoon , Ivantysynova Monika
Published: December 2017

Hydraulic hybrid powertrains, which can be applied to many types of vehicles including cars, have several important advantages over electric hybrids, such as lower costs, higher power density, and more regenerative energy available from braking. There have been various investigations for hydraulic hybrid architectures and there always exists room for improvement in terms of performance and efficiency. In order to achieve improved performance and efficiency, a novel hydraulic hybrid transmission architecture has recently been suggested in Maha Fluid Power Research Center, which is implemented in the platform of 1999 Range Rover. Previous studies of the Maha hydraulic hybrid vehicle (HHV) mainly focused on the optimization of system components and controller. In order to further study and optimize hydraulic hybrid architectures, the thermal behavior has to be considered as well. A few existing thermal studies on other hydraulic systems have mostly focused on steady state characteristics due to the difficulty of simulating the unsteady state conditions. In this paper, a novel approach to thermal modeling of HHV for a novel HHV architecture is presented. The results have been validated with the measured data collected while driving the vehicle. The thermal model utilizes the flow rate and pressure obtained from the hydraulic system model and calculates the system temperature at different locations. In order to capture the rapid transition of the hydraulic system in HHV, a novel simulation scheme considering the flow direction for the control volume inputs is applied in the presented study. In addition, the presented model considers compressible flow in order to improve the accuracy of the model.
Active Vibration/Noise Control of Axial Piston Machine Using Swash Plate Control
Authors: Kim Taeho , Ivantysynova Monika
Published: December 2017

In this paper, active vibration control concept using the existing pump control system based on the multi-frequency two-weight notch LMS (Least Mean Square) filter was investigated and tested experimentally. This research also includes the direct swash plate acceleration measurement, the case acceleration measurement, and the simultaneous multi-position microphone measurement in the semi-anechoic chamber. A 75 cc/rev swash plate type axial pump was modified to implement swash plate active vibration control combining a high speed direct drive servovalve, an electronic swash plate angle sensor, a swash plate acceleration sensor, and a high speed real-time controller with the NI Labview FPGA. Vibration measurements utilizing a tri-axial swash plate acceleration sensor and two tri-axial case acceleration sensors, and noise measurements using three microphones were conducted in the semi-anechoic chamber to investigate the influence and effectiveness of the developed system and the proposed swash plate active vibration control.
Influence of Surface Roughness Effects on the Lubrication Performance of External Gear Machines
Authors: Thiagarajan Divya , Bratto Andrea , Vacca Andrea
Published: December 2017

In pressure compensated external gear machines (EGMs), lateral lubricating interfaces exist between floating lateral bushings and gears. These interfaces are primarily responsible for supporting the high pressure bearing loads in these gaps and promoting good operating efficiencies of these units. A fully coupled fluid-structure-thermal interaction lateral gap model has been developed previously in the authors’ research team which considers this highly coupled physical phenomena to predict the lubrication performance of the interface under full film as well as mixed film conditions. In the current work, capabilities of the lateral gap model are utilized in studying the impact of the variations in surface finishes on the performance of a commercially available EGM chosen for this study.

Lateral plate designs of varying surface roughness are chosen for the same EGM unit, to analyze their influence on the lubricating performance of the unit. Detailed surface profile measurements were carried out on these lateral plates under study to determine precise inputs to the lateral gap model. Resulting numerical simulations from the gap model over different operating conditions are used to examine the significant performance features associated with the lateral interface which are affected by such surface variations. Furthermore, the paper compares the simulated leakages obtained directly from the lateral gap model for each of the lateral plate designs, with corresponding experimental data over a wide range of operating conditions.
Design and Validation of Electro-Hydraulic Pressure-Control Valves for Closed-Loop Controller Implementation
Authors: Boza Jerry R. , Ro Kapseong
Published: December 2017

Electro-hydraulic pressure-control valves are used in many applications, such as manufacturing equipment, agricultural machinery, and aircrafts to name a few. A traditional electro-hydraulic pressure-control valve regulates an output pressure for a corresponding input current by balancing solenoid force, spring force, and regulated pressure force. This results in a repeatable steady-state pressure output that is nearly proportional to the input current. This is helpful in open loop applications when one wants to achieve a consistent output pressure for a corresponding input current. The transient pressure response, however, is highly sensitive to the component tolerances and manufacturing processes as well as the fluid properties in the regulated volume, such as bulk modulus, viscosity, density, and aeration. These properties are often unknown in a system and can vary significantly from system to system and also during use in a typical application, making controllability difficult. Since there is variation in the steady-state pressure output for a given valve population, these valves are often calibrated in the end system to better achieve the desired output. This helps, but there is variation in this process, and also variation within a single valve over life. So although various attempts are made to minimize steady-state error, it will always exist and therefore closed loop control is desirable. Unfortunately, attempts at closed loop control of a traditional pressure-control valve often yield unacceptable and inconsistent performance. This is due to the sensitivity of the transient response to system characteristics, primarily fluid and mechanical properties of the regulated control port volume. The transient performance sensitivity of the valve can be reduced by de-coupling the regulated pressure dynamics from the spool dynamics. This will conversely increase the sensitivity of the steady state performance; however this can be solved through the implementation of a closed loop controller. In this paper a dynamic model is developed for a traditional pressure-control valve and different pressure-control valves without the traditional pressure balancing force. The new valve models are validated experimentally and then used to compare the performance characteristics of the valves. Linear analysis is performed on the validated models to further illustrate the impact of the system properties. The objective of this work is to develop a pressure-control valve with more consistent transient performance characteristics that are less sensitive to the system parameters so that a closed loop controller can be developed for the valve.
On Peculiar Flow Characteristics in Hydraulic Orifices
Authors: Martelli Massimo , Gessi Silvia , Massarotti Giorgio P. , Marani Pietro , Zarotti Luca G.
Published: December 2017

A key component of hydraulic fluid power systems — the standard orifice and, consequently, all equivalent components — apparently has, to this day, some mysteries yet to be unveiled. Knowledge on cavitation-induced liquid flow choking or saturation, which is a well founded topic in some areas of the wide field of hydraulics, e.g. water distribution piping systems, is practically neglected when assessing the design of typical mineral-oil-based power generation and control systems, for both mobile and industrial applications. This conclusion holds true at every level of study, from the technical reference literature adopted by designers to the more popular textbooks and journal papers. Moreover, the rare works addressing the phenomenon are focused on the underlying physical mechanics, completely missing any kind of evaluation of the functional consequences, especially the need to “revise” the standard quadratic law of turbulent flow. Prompted by one of these works, a preliminary experimental activity has been carried out, aimed at determining the actual flow characteristic of standard screw-in orifices used in fluid power pilot circuits. The results confirmed the undoubted presence of flow saturation; based on that, a suitable theoretical description was developed, and some practical applications are outlined in the paper. Finally, few open questions are listed, which need to be answered.
Multi-Stage Modeling of a Stirling Thermocompressor
Authors: Thomas Seth , Barth Eric J.
Published: December 2017

Stirling engines are silent, high-efficiency power sources that generate work by shuttling a working fluid between hot and cold volumes while exploiting the working fluid’s change in pressure. Stirling engines are able to use multiple sources of heat to create this needed temperature difference, making them ideally suited for diverse waste heat recovery applications. A novel application of this technology would be to reuse waste heat from one industrial process to generate compressed air to power a second, pneumatic process, thus increasing a manufacturing facility’s overall energy efficiency. In this paper the authors explore the expected performance of using a modified Stirling engine, known as a Stirling thermocompressor, to intake air at standard atmospheric conditions and compress it into a storage container. Simulations were conducted with a multi-stage experimentally validated dynamic model, using input variables that match the author’s physical prototype. Models employing 5 or more thermocompressor stages predicted a 10-fold increase in compressed air pressure compared to ambient conditions. Future work will experimentally verify the paper’s conclusions.
Study of the Sloshing in a Fuel Tank Using CFD and EFD Approaches
Authors: Frosina Emma , Senatore Adolfo , Andreozzi Assunta , Marinaro Gianluca , Buono Dario , Bianco Gennaro , Auriemma Domenico , Fortunato Francesco , Damiano Fulvio , Giliberti Pino
Published: December 2017

This paper is focused on the study of the sloshing in the fuel tank of vehicles. As well known, fluid dynamic in an automotive fuel tank have to be studied and optimized to allow the correct fuel suction in all driving conditions, prevent undesired slosh noise and limit its influence on fuel vapor formation and management. Experimentation to predict the sloshing with a good accuracy depends on the ability to replace real working parameters and conditions like accelerations, decelerations, slope variations and rotations.

This paper shows results obtained studying the sloshing inside a reference tank with computational fluid-dynamic and experimental approaches.

The test bench for automotive fuel tank, employed in this analysis, has been designed by Moog Inc. on specification from Fiat Chrysler Automobiles and it is aimed at covering the wider possible range of dynamic conditions. It basically consists of a hexapod, which uses six independent actuators arranged in three triangles and connecting a base and a top platform, thus allowing all six DOFs. Above the top platform is mounted a tilt table with two additional actuators, to extend pitch and roll envelope, thus the name of “8-DOF bench”.

A dedicated CFD model has been built up using a CFD commercial code. The model has been integrated with the multiphase tool in order to correctly reply the real free surface.

Results, numerical and experimental, have been post-processed with Matlab® comparing percentage gaps of the free surfaces each other. The comparison has shown a good agreement.

This research is the result of a scientific collaboration between the Industrial Engineering Department of University of Naples Federico II and FCA Fiat Chrysler Automobiles.
Indirect Pressure Measurement on Hydraulic Components Through New MEMS Strain Sensors
Authors: Ruggeri Massimiliano , Massarotti Giorgio Paolo , Belsito Luca , Roncaglia Alberto
Published: December 2017

Sensors are playing a more important role in the modern hydraulic systems. Increasing needs for closed loop controls, high precision measurement, power control and energy monitoring, diagnosis and safety concerns, ask for both pressure and flow acquisition in both industrial and mobile applications.

Traditional pressure sensors need specific bored screw for mounting, and both pipes and components must be modified in order to apply pressure sensors. Traditional pressure sensors are related to mini-mess and to oil flow modification in the sensor area.

Sensors position in hydraulic circuits or components must be defined at design phase, in order to design the proper screw in desired circuit positions.

Most of times sensors result in a efficiency loss in the circuit.

Last but not least, the cost of traditional sensors, the need for proper connections for sensors installation and the work needed for sensor placement in machines production phase, could be avoided if sensors could be integrated in smart components.

Modern Silicon based technologies offer new solutions for a less invasive pressure measurement. Micro Electro-Mechanical Systems (MEMS) Technology is suitable to design new sensors for indirect pressure measurement. Also traditional technologies, coupled with modern electronics could offer solutions that were not enough precise 10 years ago, but presenting some tricks to be solved accurately.

The paper presents the first experimental results of the early stage of application of a MEMS strain gauge sensor application on components, where hydraulic pressure is measured through the component strain due to internal pressure force and component deformation.

New sensors called Double Ended Tuning Fork (DETF) MEMS Resonant Extensometer sensor, based on a silicon diapason made in void environment in a system on chip will be applied at components due to the sensor’s sensitivity and precision that can reach the 0,15 nε/ε.

At the same time the paper will show that pipes offer a deformation function of the mechanical characteristics and that the pressure effect is causing a deformation that can be even too high for the MEMS sensor.

The strain position sensor and component deformation are also proved by the FEM analysis in order to validate both pressure measurement and FEM analysis in respect to test bench results applied to the sensor strain acquisition.
Mitigating e-beam-induced hydrocarbon deposition on graphene for atomic-scale scanning transmission electron microscopy studies
Authors: Dyck Ondrej , Kim Songkil , Kalinin Sergei V. , Jesse Stephen
Published: December 2017

Chemical vapor deposition (CVD) grown graphene used in (scanning) transmission electron microscopy [(S)TEM] studies must undergo a careful transfer of the one-atom-thick membrane from the growth surface (typically a Cu foil) to the TEM grid. During this transfer process, the graphene invariably becomes contaminated with foreign materials. This contamination proves to be very problematic in the (S)TEM because often >95% of the graphene is obscured, and imaging of the pristine areas results in e-beam-induced hydrocarbon deposition which further acts to obscure the desired imaging area. In this article, the authors examine two cleaning techniques for CVD grown graphene that mitigate both aspects of the contamination problem: visible contamination covering the graphene, and “invisible” contamination that deposits onto the graphene under e-beam irradiation. The visible contamination may be removed quickly by a rapid thermal annealing to 1200 °C in situ and the invisible e-beam-deposited contamination may be removed through an Ar/O2 annealing procedure prior to imaging in the (S)TEM.
Tuning of material properties of ZnO thin films grown by plasma-enhanced atomic layer deposition at room temperature
Authors: Pilz Julian , Perrotta Alberto , Christian Paul , Tazreiter Martin , Resel Roland , Leising Günther , Griesser Thomas , Coclite Anna Maria
Published: December 2017

The ability to grow inorganic thin films with highly controllable structural and optical properties at low substrate temperature enables the manufacturing of functional devices on thermo-sensitive substrates without the need of material postprocessing. In this study, the authors report on the growth of zinc oxide films by direct plasma-enhanced atomic layer deposition at near room temperature. Diethyl zinc and oxygen plasma were used as the precursor and coreactant, respectively. The process was optimized with respect to the precursor and coreactant dosing as well as to the purging times, which ultimately resulted in saturated atomic layer deposition growth. The so-obtained films exhibit a polycrystalline pattern with a (100) texture and low amount of incorporated carbon. Furthermore, the possibility to tune crystallite size, refractive index, and bandgap of the films by adapting the plasma radio-frequency power is demonstrated.
Nanostructures formed by the surface self-assembly of 4-(chloromethyl)phenyltrichlorosilane studied with selected solvents and temperatures
Authors: Chambers Phillip C. , Garno Jayne C.
Published: December 2017

The self-assembly and growth of 4-(chloromethyl)-phenyltrichlorosilane (CMPS) nanostructures within nanoholes that were formed within a thin film of octadecyltrichlorosilane (OTS) was studied ex situ using atomic force microscopy (AFM). The effects of selected solvents and temperatures on the growth of the CMPS were investigated to gain insight into the mechanisms of the surface assembly and self-polymerization of CMPS. Surface platforms of nanoholes were generated within a thin film of OTS using particle lithography combined with immersion steps. The film of OTS provided a resist for preventing nonspecific adsorption of CMPS in areas surrounding the nanoholes. The uncovered areas of substrate within the nanoholes were used to direct the self-assembly of CMPS. Nanopatterns were imaged using AFM after key steps of the nanofabrication procedure. The samples were immersed in solutions of CMPS that were prepared with selected solvents that included toluene, bicyclohexyl, and dichloromethane. The size and morphology of CMPS nanostructures were influenced by the nature of the solvent, and nonpolar solvents were better suited for reproducibly growing regular nanostructures. For nanostructures of CMPS grown within nanoholes, the rate of CMPS self-assembly and growth exhibited differences at the molecular level for temperatures ranging from −4 to 20 °C. The analysis of the height and width of CMPS nanopatterns reveals that multiple layers formed with taller surface structures being formed at higher temperatures. Particle lithography provides a useful tool for studying chemical reactions at the nanometer scale since basic steps of sample preparation can used to make multiple nanopatterns for surface measurements under controlled environmental conditions.
The mechanism producing initial transients on the clarinet
Authors: Almeida A. , Li W. , Smith J. R. , Wolfe J.
Published: December 2017

In self-sustained instruments, starting transients are important timbral characteristics that help identify the instrument and the playing style. Often, the oscillation starts as a growing exponential. This study investigates the starting amplitude of this exponential for the clarinet. After a rapid tongue release, the reed quickly returns to its equilibrium position. The sudden change in aperture produces an abrupt change in both the airflow into the mouthpiece and the mouthpiece pressure. This perturbation travels along the bore and reflects at the open end. Returning to the mouthpiece with slight attenuation, the perturbation can be amplified by the reed acting as an active element—effectively a negative resistance. When the reed release time exceeds the time for sound to travel twice the bore length, the airflow and pressure wave into the bore via the aperture are superposed over their own returning reflection. Measurements of reed motion and mouthpiece pressures during reed release yield values that are used in a model to calculate waveforms showing similarities to those observed experimentally. The initial amplitude decreases with increasing reed release time, though not always monotonically. It can become very small in special cases due to synchronisation between the initial pulse and its reflection.
Concentrations of Cefuroxime in Brain Tissue of Neurointensive Care Patients
Authors: Hosmann A. , Ritscher L. C. , Burgmann H. , Oesterreicher Z. , Jäger W. , Poschner S. , Knosp E. , Reinprecht A. , Gruber A. , Zeitlinger M.
Published: December 2017

Effective concentrations of antibiotics in brain tissue are essential for antimicrobial therapy of brain infections. However, data concerning cerebral penetration properties of antibiotics for treatment or prophylaxis of central nervous system infections are rare. Six patients suffering subarachnoid hemorrhage and requiring cerebral microdialysis for neurochemical monitoring were included in this study. Free interstitial concentrations of cefuroxime after intravenous application of 1,500 mg were measured by microdialysis in brain tissue, as well as in plasma at steady-state (
n
= 6) or after single-dose administration (
n
= 1). At steady state, free area under the concentration-time curve from 0 to 24 h (AUC
0–24
) values of 389.0 ± 210.3 mg/liter·h and 131.4 ± 72.8 mg/liter·h were achieved for plasma and brain, respectively, resulting in a brain tissue penetration ratio (AUC
0–24 brain
/AUC
0–24 free plasma
) of 0.33 ± 0.1. Plasma and brain tissue concentrations at individual time points correlated well (
R
= 0.59,
P
= 0.001). At steady-state time over MIC (
t
>MIC) values of >40% of dosing interval were achieved up to an MIC of 16 mg/liter for plasma and 4 mg/liter for brain tissue. Although MIC
90
values could not be achieved in brain tissue for relevant bacteria, current dosing strategies of cefuroxime might be sufficient to treat pathogens with MIC values up to 4 mg/liter. The activity of cefuroxime in brain tissue might be overestimated when relying exclusively on plasma levels. Although currently insufficient data after single dose administration exist, lower brain-plasma ratios observed after the first dose might warrant a loading dose for treatment and perioperative prophylaxis.
Chemogenomic Profiling of the Fungal Pathogen Candida albicans
Authors: Chen Yaolin , Mallick Jaideep , Maqnas Alaa , Sun Yuan , Choudhury Baharul I. , Côte Pierre , Yan Lan , Ni Ting-jun-hong , Li Yan , Zhang Dazhi , Rodríguez-Ortiz Roberto , Lv Quan-zhen , Jiang Yuan-ying , Whiteway Malcolm
Published: December 2017

There is currently a small number of classes of antifungal drugs, and these drugs are known to target a very limited set of cellular functions. We derived a set of approximately 900 nonessential, transactivator-defective disruption strains from the tetracycline-regulated GRACE collection of strains of the fungal pathogen
Candida albicans
. This strain set was screened against classic antifungal drugs to identify gene inactivations that conferred either enhanced sensitivity or increased resistance to the compounds. We examined two azoles, fluconazole and posaconazole; two echinocandins, caspofungin and anidulafungin; and a polyene, amphotericin B. Overall, the chemogenomic profiles within drug classes were highly similar, but there was little overlap between classes, suggesting that the different drug classes interacted with discrete networks of genes in
C. albicans
. We also tested two pyridine amides, designated GPI-LY7 and GPI-C107; these drugs gave very similar profiles that were distinct from those of the echinocandins, azoles, or polyenes, supporting the idea that they target a distinct cellular function. Intriguingly, in cases where these gene sets can be compared to genetic disruptions conferring drug sensitivity in other fungi, we find very little correspondence in genes. Thus, even though the drug targets are the same in the different species, the specific genetic profiles that can lead to drug sensitivity are distinct. This implies that chemogenomic screens of one organism may be poorly predictive of the profiles found in other organisms and that drug sensitivity and resistance profiles can differ significantly among organisms even when the apparent target of the drug is the same.
Utilization of Host Polyamines in Alternatively Activated Macrophages Promotes Chronic Infection by Brucella abortus
Authors: Kerrinnes Tobias , Winter Maria G. , Young Briana M. , Diaz-Ochoa Vladimir E. , Winter Sebastian E. , Tsolis Renée M.
Published: December 2017

Treatment of intracellular bacterial pathogens with antibiotic therapy often requires a long course of multiple drugs. A barrier to developing strategies that enhance antibiotic efficacy against these pathogens is our poor understanding of the intracellular nutritional environment that maintains bacterial persistence. The intracellular pathogen
Brucella abortus
survives and replicates preferentially in alternatively activated macrophages (AAMs); however, knowledge of the metabolic adaptations promoting exploitation of this niche is limited. Here we show that one mechanism promoting enhanced survival in AAMs is a shift in macrophage arginine utilization from production of nitric oxide (NO) to biosynthesis of polyamines, induced by interleukin 4 (IL-4)/IL-13 treatment. Production of polyamines by infected AAMs promoted both intracellular survival of
B. abortus
and chronic infection in mice, as inhibition of macrophage polyamine synthesis or inactivation of the putative putrescine transporter encoded by
potIHGF
reduced both intracellular survival in AAMs and persistence in mice. These results demonstrate that increased intracellular availability of polyamines induced by arginase-1 expression in IL-4/IL-13-induced AAMs promotes chronic persistence of
B. abortus
within this niche and suggest that targeting of this pathway may aid in eradicating chronic infection.
NanI Sialidase Can Support the Growth and Survival of Clostridium perfringens Strain F4969 in the Presence of Sialyated Host Macromolecules (Mucin) or Caco-2 Cells
Authors: Li Jihong , McClane Bruce A.
Published: December 2017

Enterotoxin-producingClostridium perfringenstype A strains cause human gastrointestinal (GI) infections, including a very common food poisoning and 5 to 10% of all cases of antibiotic-associated diarrhea. This bacterium can utilize free sialic acid for growth, but most sialic acids in the GI tract are sequestered on macromolecules, such as the mucin proteins of mucus or glycoconjugates in host cells. However, manyC. perfringensstrains produce sialidases that might promote growth and survival by generating free sialic acid from those sialyated host macromolecules or by exposing underlying carbohydrates or proteins for digestion by other enzymes. The current study tested that possibility and found that theC. perfringensnonfoodborne human GI disease strain F4969 can use either a mucin preparation or Caco-2 cells, which are human enterocyte-like cells, to support its growth and survival. An isogenicnanInull mutant and complemented strain were used to show that this enhanced growth and survival using mucin or Caco-2 cells involved NanI, which is the major exosialidase of F4969 and many otherC. perfringensstrains. Experiments also suggested that, at least in part, this growth promotion involves utilization of NanI-generated sialic acid. In addition, a sialidase inhibitor named siastatin B reduced the growth and survival of F4969 growing with either the mucin preparation or Caco-2 cells. These findings suggest that, when produced, NanI may be a significant contributor toC. perfringenshuman GI infections by promoting the intestinal growth and survival of this bacterium. They also suggest the possibility that sialidase inhibitors might inhibitC. perfringensinfections.
Use of Proteins Identified through a Functional Genomic Screen To Develop a Protein Subunit Vaccine That Provides Significant Protection against Virulent Streptococcus suis in Pigs
Authors: Brockmeier Susan L. , Loving Crystal L. , Nicholson Tracy L. , Wang Jinhong , Peters Sarah E. , Weinert Lucy , Chaudhuri Roy , Seilly David J. , Langford Paul R. , Rycroft Andrew , Wren Brendan W. , Maskell Duncan J. , Tucker Alexander W.
Published: December 2017

Streptococcus suis
is a bacterium that is commonly carried in the respiratory tract and that is also one of the most important invasive pathogens of swine, commonly causing meningitis, arthritis, and septicemia. Due to the existence of many serotypes and a wide range of immune evasion capabilities, efficacious vaccines are not readily available. The selection of
S. suis
protein candidates for inclusion in a vaccine was accomplished by identifying fitness genes through a functional genomics screen and selecting conserved predicted surface-associated proteins. Five candidate proteins were selected for evaluation in a vaccine trial and administered both intranasally and intramuscularly with one of two different adjuvant formulations. Clinical protection was evaluated by subsequent intranasal challenge with virulent
S. suis
. While subunit vaccination with the
S. suis
proteins induced IgG antibodies to each individual protein and a cellular immune response to the pool of proteins and provided substantial protection from challenge with virulent
S. suis
, the immune response elicited and the degree of protection were dependent on the parenteral adjuvant given. Subunit vaccination induced IgG reactive against different
S. suis
serotypes, indicating a potential for cross protection.
Regulated Release of Cryptococcal Polysaccharide Drives Virulence and Suppresses Immune Cell Infiltration into the Central Nervous System
Authors: Denham Steven T. , Verma Surbhi , Reynolds Raymond C. , Worne Colleen L. , Daugherty Joshua M. , Lane Thomas E. , Brown Jessica C. S.
Published: December 2017

Cryptococcus neoformans
is a common environmental yeast and opportunistic pathogen responsible for 15% of AIDS-related deaths worldwide. Mortality primarily results from meningoencephalitis, which occurs when fungal cells disseminate to the brain from the initial pulmonary infection site. A key
C. neoformans
virulence trait is the polysaccharide capsule. Capsule shields
C. neoformans
from immune-mediated recognition and destruction. The main capsule component, glucuronoxylomannan (GXM), is found both attached to the cell surface and free in the extracellular space (as exo-GXM). Exo-GXM accumulates in patient serum and cerebrospinal fluid at microgram/milliliter concentrations, has well-documented immunosuppressive properties, and correlates with poor patient outcomes. However, it is poorly understood whether exo-GXM release is regulated or the result of shedding during normal capsule turnover. We demonstrate that exo-GXM release is regulated by environmental cues and inversely correlates with surface capsule levels. We identified genes specifically involved in exo-GXM release that do not alter surface capsule thickness. The first mutant, the
liv7
Δ strain, released less GXM than wild-type cells when capsule was not induced. The second mutant, the
cnag_00658
Δ strain, released more exo-GXM under capsule-inducing conditions. Exo-GXM release observed
in vitro
correlated with polystyrene adherence, virulence, and fungal burden during murine infection. Additionally, we found that exo-GXM reduced cell size and capsule thickness under capsule-inducing conditions, potentially influencing dissemination. Finally, we demonstrated that exo-GXM prevents immune cell infiltration into the brain during disseminated infection and highly inflammatory intracranial infection. Our data suggest that exo-GXM performs a distinct role from capsule GXM during infection, altering cell size and suppressing inflammation.
Toward Tuberculosis Vaccine Development: Recommendations for Nonhuman Primate Study Design
Authors: Laddy Dominick J. , Bonavia Aurelio , Hanekom Willem A. , Kaushal Deepak , Williams Ann , Roederer Mario , Seder Robert A. , Sharpe Sally , Verreck Frank A. W. , Darrah Patricia A.
Published: December 2017

Clinical trials of novel tuberculosis (TB) vaccines are expensive, while global resources for TB vaccine development are limited. Therefore, there is a need for robust and predictive preclinical data to support advancement of candidate vaccines into clinical trials. Here, we provide a rationale for using the nonhuman primate as an essential component of these efforts, as well as guidance to the TB community for standardizing experimental design and aligning endpoints to facilitate development of new TB vaccines.