bluuebunny/crossref_metadata_2025 huggingface dataset:
Freeness and multirestriction of hyperplane arrangements
Authors: Schulze Mathias
Published: March 2012

Generalizing a result of Yoshinaga in dimension three, we show that a central hyperplane arrangement in 4-space is free exactly if its restriction with multiplicities to a fixed hyperplane of the arrangement is free and its reduced characteristic polynomial equals the characteristic polynomial of this restriction. We show that the same statement holds true in any dimension when imposing certain tameness hypotheses.
Modeling of On-Cell Reforming Reaction for Planar SOFC Stacks
Authors: Yang Choongmo , Lim Hyung-Tae , Hwang Soon Cheol , Kim Dohyung , Lai Kevin , Koeppel Brian J. , Recknagle Kurtis P. , Khaleel Moe A.
Published: March 2012

The planar Solid Oxide Fuel Cell (SOFC) stack is known to suffer thermal problems from high stack temperatures during operation to generate high current. On-Cell Reforming (OCR) phenomenon by the endothermic steam-methane reaction is often used to reduce stack temperature. Research Institute of Industrial Science & Technology (RIST) conducted single-cell experiments including temperature measurement to validate modeling tool simulations of OCR performance. 2D modeling is used to check the reforming rate during OCR using the temperature measurement data, and 3D modeling is used to check the overall thermal performance including furnace boundary conditions.
An Energy Balance Model for a Direct Methanol Fuel Cell
Authors: Chiu Yu-Jen , Lin Yen-Ling
Published: March 2012

Fuel cell is a kind of devices that generates electricity and heat via electrochemical reactions. Accompanying the development of relevant applications, the efficiency issue has received more and more interest. In the duration of electricity generation, a variety of polarization losses will disperse in the form of heat. Higher electricity efficiency leads to lower heat generation, and vice versa. The amount of the generated heat correlates with the temperature gradient of the fuel flow along the stack channel. For a direct methanol fuel cell (DMFC), both the fuel utilization efficiency and fuel concentration are essential indices for the system. However, it is much complicated to acquire them. As a result, it will be a feasible and valuable approach to correlate these indices with the temperature gradient. In this work, an energy balance model of a DMFC is established to investigate factors that contribute thermal influences on the system. Based on the model, the relationship between efficiency and temperature gradient is derived. The proposed model may serve as the basis of water and thermal management strategies, which are beneficial for enhancing the performance and reliability of such a power generation system.
The Role of Channel Plurality in Two-Phase Flow Instabilities in PEM Cathode Channels
Authors: Siefert Nicholas , O’Shea Colin , Litster Shawn
Published: March 2012

Water management is a critical issue in the development of proton exchange membrane (PEM) fuel cells with robust operation. Liquid water can accumulate and flood the gas delivery microchannels and the porous electrodes within PEM fuel cells and deteriorate performance. Since the liquid distribution fluctuates in time for two-phase flow, the rate of oxygen transport to the cathode catalyst layer also fluctuates, resulting in unstable power density and efficiency. In previous research into measuring the voltage loss and voltage fluctuation due to two-phase flow instabilities in the cathode channels of PEM fuel cells, we investigated the effect of the number of parallel channels covering the active area by studying flow fields with varying numbers of parallel channels (4 to 25) while keeping the active area constant at 5 cm2. The resulting voltage loss and fluctuation measurements were expressed as functions of two non-dimensional parameters: channel plurality and the air flow stoichiometric ratio. Channel plurality is a flow field design parameter that defines the number of channels per unit of active area, which is non-dimensionalized by the cross-sectional area of the channels. In this paper, we expand upon our prior studies by studying cathode flow field designs of varying active area, from 5 cm2 to 25 cm2, with a constant number of 25 channels. By increasing the active area with a constant number of channels, we are reducing the channel plurality value. The new results are mapped back to the non-dimensional parameters to extract empirical scaling rules for voltage loss and fluctuation. Furthermore, we compare this data to our prior work with constant active area and identify the significance of the fuel cell size in the scaling relationships. Finally, a refined scaling is presented for generalizing the results for fuel cells having different active area and number of channels.
Optimization of an Integrated SOFC-Fuel Processing System for Aircraft Propulsion
Authors: Brinson Thomas E. , Ordonez Juan C. , Luongo Cesar A.
Published: March 2012

As fuel cells continue to improve in performance and power densities levels rise, potential applications ensue. System-level performance modeling tools are needed to further the investigation of future applications. One such application is small-scale aircraft propulsion. Both piloted and unmanned fuel cell aircrafts have been successfully demonstrated suggesting the near-term viability of revolutionizing small-scale aviation. Nearly all of the flight demonstrations and modeling efforts are conducted with low temperature fuel cells; however, the solid oxide fuel cell (SOFC) should not be overlooked. Attributing to their durability and popularity in stationary applications, which require continuous operation, SOFCs are attractive options for long endurance flights. This study presents the optimization of an integrated solid oxide fuel cell-fuel processing system model for performance evaluation in aircraft propulsion. System parameters corresponding to maximum steady state thermal efficiencies for various flight phase power levels were obtained through implementation of the PSO algorithm (Particle Swarm Optimization). Optimal values for fuel utilization, air stoichiometric ratio, air bypass ratio, and burner ratio, a 4-dimensional optimization problem, were obtained while constraining the SOFC operating temperature to 650–1000 °C. The PSO swarm size was set to 35 particles and the number of iterations performed for each case flight power level was set at 40. Results indicate the maximum thermal efficiency of the integrated fuel cell-fuel processing system remains in the range of 44–46% throughout descend, loitering, and cruise conditions. This paper discusses a system-level model of an integrated fuel cell - fuel processing system, and presents a methodology for system optimization through the particle swarm algorithm.
Synthesis of Highly Dispersed Carbon Supported Platinum Nanocatalyst for Fuel Cells
Authors: Abbo Hanna S. , Green Ivan R. , Titinchi Salam J. J.
Published: March 2012

Pt/C and Pt/CNT catalysts were prepared by colloidal method using sodium citrate as a stabilizer, and ethylene glycol as the reducing agent and solvent. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results showed that the Pt particles were highly dispersed on the support and had a very narrow particle distribution with particle size range of 1.5–2.4 nm for both catalysts. Based on the electrochemical properties characterized by cyclic voltammetry, it was found that the as-synthesized electrocatalysts possessed a significantly higher catalytic activity than those of commercial Pt/C Johnson Matthey catalyst.
Analysis of a Passive Tubular Direct Methanol Fuel Cell
Authors: Ward Travis , Li Xianglin , Faghri Amir
Published: March 2012

In this work, it is shown that a novel tubular-shaped, passive Direct Methanol Fuel Cell (DMFC) can produce up to 2 times the instantaneous volumetric power density of a planar DMFC. First a numerical model was developed to determine the benefits of a tubular geometry and design characteristics for a passive tubular-shaped DMFC. Secondly, a tubular-shaped DMFC frame was designed, built, and tested to improve upon existing tubular DMFC literature and compare against an identical planar-shaped DMFC. From the numerical model, it was determined that increasing the ambient temperature from 20 to 40 °C increases the peak power density produced by the fuel cell during operation with 1 and 2 M methanol solutions. During operation with 3 M methanol the increased methanol crossover and oxygen depletion along the Cathode Transport Layer (CTL) reduce the power from the tubular DMFC. It was also determined that the thickness of the CTL must be greater than 1 mm for 1 M operation, greater than 5 mm for 2 M operation, and greater than 10 mm for 3 M methanol operation to prevent oxygen limitations along the CTL. From the experimental work, a tubular-shaped DMFC was built that presented an 870% improvement in power density from the previous best, passive, tubular-shaped DMFC found in the literature. The tubular DMFC produced 24.9 mW cm−2 while the planar DMFC produced 23.0 mW cm−2 with a Nafion® 115 membrane and 3 M methanol. The tubular DMFC experienced slightly higher methanol crossover than the planar DMFC, potentially due to a higher static fluid pressure in the Anode Fuel Reservoir (AFR), which is caused by the vertical orientation of the tubular fuel reservoir.
Bubbly, Two-Phase Flow in the Anode Channel of a Passive, Tubular Direct Methanol Fuel Cell
Authors: Bahrami Hafez , Faghri Amir
Published: March 2012

A numerical study is presented to investigate the turbulent, two-phase, steady state, isothermal, bubbly flow characteristic in the anode channel of a passive, tubular direct methanol fuel cell (DMFC) in order to accurately predict the gas volume fraction distribution along the channel. Accumulation of carbon dioxide gas bubbles at the channel’s wall hinders the diffusion of the fuel from the channel to the catalyst layer. The conservation governing equations of the mass and momentum for both the continuous (methanol and water solution) and dispersed (CO2 bubbles) phases in the bubbly regime are solved using the multi-fluid technique. Turbulence in the liquid phase is formulated by employing the classical, two-equation k–ε model. Due to the lack of experimental data regarding the gas volume fraction in the anode channel of DMFCs, the proposed model was initially applied to the bubble plum in a cylindrical liquid bath in which air is injected into the water from a nozzle located at the bottom-center of the bath. The results are compared with the existing experimental data in the literature for the gas volume fraction and the liquid velocity in the bath. Finally, the model is successfully extended to the anode channel of a tubular DMFC operating passively in the vertical orientation in which the CO2 gas bubbles are injected through the wall. The rate of gas injection depends on the cell current density which is assumed to be uniform along the anode catalyst layer and the channel’s wall. It is found that the gas volume fraction significantly changes along the channel from a large value at the bottom of the channel to a lower value at the top. The flow field inside the channel is also investigated for different cell current densities.
Manganese-Cobalt Spinel Coatings for SOFC Metallic Interconnects Manufactured by Conventional Plasma Spraying (PS) and Suspension Plasma Spraying (SPS)
Authors: Puranen Jouni , Hyva¨rinen Leo , Lagerbom Juha , Kylma¨lahti Mikko , Koivuluoto Heli , Vuoristo Petri
Published: March 2012

Protective coatings are used on ferritic stainless steel interconnects of solid oxide fuel cells (SOFCs) to prevent the oxidation and evaporation of volatile chromium compounds. Oxide scale is formed of chromium oxide (Cr2O3) which tends to react with the oxygen and water, forming chromium trioxide (CrO3) and chromium hydroxides (Cr2(OH)2). These compounds will migrate to the triple phase barrier (TPB) of a cathode and reduce back to Cr2O3. This reaction pathway is a notable reason for the degradation phenomena of the cell. Plasma spraying (PS) and suspension plasma spraying (SPS) were studied as possible manufacturing processes for thin Mn-Co-(Fe) spinel coatings. Powder for PS was manufactured by using a solid state reaction method from carbonates and oxide to form a MnCo1.8Fe0.2O4 and powder for SPS by co-precipitation process from nitrates to form a MnCo2O4 spinel structure. Using PS, coatings with thin and relatively dense structures were obtained. The composition of the coatings was homogeneous although, the decomposition of the spinel structure was noticed. The crystal structures of the PS coatings were partially restored by a separate annealing process. The spray parameters had a strong influence on the coating structure and the composition when SPS was used. The most homogenous coating structure was formed when low energy spraying parameters were used, whereas high energy parameters formed a columnar structure with larger cobalt rich areas. The decomposed spinel structure of the SPS coatings were fully restored by the annealing treatment. In SPS, more process optimization is needed to improve the coating quality and especially denseness.
Energy and Exergy Analysis of Gas Turbine – Fuel Cell Based Combined Cycle Power Plant
Authors: Sreeramulu M. , Gupta A. V. S. S. K. S. , Srinivas T.
Published: March 2012

The newer power generation systems are becoming more important for the society due to increase in demand for the electrical energy utilization and higher energy conversion efficiencies. Though it is not new, fuel cell technology is one of the promising systems for cleaner and competitive alternate power generation system. When the fuel cells are integrated with the gas turbines, the total thermal efficiency of the combined cycle can be obtained greater than 60%. This is appreciably better exergetic performance when compared to traditional gas turbine cycle. In this work, thermodynamic analysis of SOFC-GT combined system (2.898MW) has been carried out, to evaluate energy efficiency, exergy efficiency and exergy destruction of each component is calculated. The effect of compression ratio (rp), turbine inlet temperature (TIT), air fuel ratio and ambient temperature of air, on the performance of the system has been analyzed by adopting the different fuels. The outcome of the system modeling reveals that SOFC and combustion chamber are the main sources of exergy destruction. When the methane, natural gas and coal gas are used as fuels, at the optimum compression ratio 9, the total thermal efficiencies are found to be 63.3%, 62.12% and 61.02% respectively. The exergy efficiencies are obtained respectively as 60.85%, 59.16% and 60.06%.
Effect of the Microstructure of Porous Composite Electrodes on the Electric Power Density of Solid Oxide Fuel Cells
Authors: Farhad Siamak , Hamdullahpur Feridun
Published: March 2012

The electric power density generated in co-flow planar solid oxide fuel cells (SOFCs) with porous composite electrodes is predicted using the cell combined micro- macro-model; and the effect of the microstructural variables of the electrodes on the cell power generation is studied. In the combined micro- macro-model, the electrochemical performance of the porous composite electrodes is determined from the micro-model and the distributions of the temperature in solid structure of the cell and the temperature and species partial pressures of the bulk fuel and air streams are determined from the cell macro-model. As a case study, the effect of the microstructural variables of the porous composite electrodes of the Ni-YSZ/YSZ/LSM-YSZ cell operated at the given voltage, fuel utilization ratio, and excess air, on the average power density of the cell is investigated through computer simulation. The results reveal that there is an optimum value for each microstructural variables of the electrodes at which the cell power density is maximized.
Lattice Boltzmann Simulation of Solid Oxide Fuel Cell Performance
Authors: Xu Yousheng , Sun Pengtao , He Hui , Liu Yang
Published: March 2012

Based on models of a porous electrode, a more accurate lattice Boltzmann model for simulating the performance of a solid oxide fuel cell (SOFC) is proposed. The fuel is pure Carbon monoxide and the flow in the SOFC is steady. Results show good agreement between simulated and measured data. The accuracy of concentration overpotential prediction is crucial for low reactant concentrations. The addition of a small amount of air to the fuel yields fully stable performance without measurable carbon deposits detected on the catalyst layer or the fuel cell. Cell performance increases with the temperature. As a first test of the model, a benchmark problem regarding the performance of an internal reforming solid oxide fuel cell (IR-SOFC) is investigated. When the catalyst activity decreases, the rate of methane conversion decreases near the reactor entrance and thus the temperature profile is smoother. This phenomenon is termed methane slippage.
Quantification of Microstructural and Transport Properties of Solid Oxide Fuel Cells From Three-Dimensional Physically Realistic Network Structures
Authors: Gunda Naga Siva Kumar , Mitra Sushanta K.
Published: March 2012

The present work investigated a new method of calculating effective transport properties of solid oxide fuel cell (SOFC) electrodes from three-dimensional (3D) physically realistic network structures. These physically realistic network structures are topological equivalent representations of reconstructed microstructures in the form of spheres (nodes or bodies) and cylinders (segments or throats). Maximal ball algorithm is used to extract these physically realistic network structures from the series of two-dimensional (2D) cross-sectional images of SOFC electrodes. Dual-beam focused ion beam - scanning electron microscopy (FIB-SEM) is performed on SOFC electrodes to acquire series of 2D cross-sectional images. Finite element method is implemented to compute the effective transport properties from the network structures. As an example, we applied this method to calculate the effective gas diffusivity of lanthanum strontium manganite (LSM) of SOFC. The results obtained from physically realistic network structures are compared with reconstructed 3D microstructures.
Platinum Dissolution in Proton Exchange Membrane Fuel Cell Under Mechanical Vibrations
Authors: Diloyan Georgiy , Hutapea Parsaoran
Published: March 2012

One of the factors that affect the performance of proton exchange membrane fuel cells (PEMFC) is the loss of electrochemically active surface area of the Platinum (Pt) based electrocatalyst due to platinum dissolution and sintering. The intent of the current research is to understand the effect of mechanical vibrations on the Pt particles dissolution and overall PEMFC performance. This study is of great importance for the automotive application of fuel cells, since they operate under a vibrating environment. Carbon supported platinum plays an important role as an electrocatalyst in PEMFC. Pt particles, typically a few nanometers in size, are distributed on both cathode and anode sides. Pt particle dissolution and sintering is accelerated by a number of factors, one of which is potential cycling during fuel cell operation. To study the effect of mechanical vibrations on Pt dissolution and sintering, an electrocatalyst (from cathode side) was analyzed by SEM/EDS (Energy Dispersive Spectroscopy). The performance, dissolution and sintering of the Pt particles of 25 cm2 electrocatalyst coated membrane were studied during a series of tests. The experiment was conducted by running three accelerated tests. Each test duration was 300 hours, with different parameters of oscillations: one test without vibrations and remaining two tests under vibrations with frequencies of 20 Hz and 50 Hz (5g of magnitude) respectively. For each of the three tests a pristine membrane was used. The catalyst of each membrane was analyzed by ESEM/EDS in pristine state and in degraded state (after 300 hours of accelerated test). In order to specify the same area of observation on a catalyst before and after accelerated test, a relocation technique was used.
Linear Static, Real-Time Finite Element Computations Based on Element Masks
Authors: Graf Holger , Stork Andre´
Published: March 2012

This paper presents a new method for the manipulation of a given CAE domain in view of VR based explorations that enables engineers to interactively inspect and analyze a linear static domain. The interactions can ideally be performed in real-time in order to provide an intuitive impression of the changes to the underlying volumetric domain. We take the approach of element masking, i.e. the blending out of computations resulting from computational overhead for inner nodes, based on the inversion of the stiffness matrix. This allows us to optimize the re-simulation loop and to achieve real-time performance for strain and stress distributions with immediate visualization feedback caused by interactively changing boundary conditions. The novelty of the presented approach is a direct coupling of view dependent simulations and its close linkage to post-processing tasks. This allows engineers to also inspect the changes of the stress field inside of the volume during, e.g. cross sectioning.
A Semi-Automatic Modeling System for Quick Generation of Large Virtual Reality Models
Authors: Guidi Gabriele , Micoli Laura Loredana
Published: March 2012

In the last few years virtual reality applications have started to be introduced in the wide retail field, with immersive 3D models used as a tool for orienting strategic, logistic and marketing choices. However, in the aforementioned applications, the digitalization of the entire Point Of Sale (POS) has not yet been implemented as a standard process for the complexity related to the generation of thousands of texturized 3D models of single products. This work presents an original integrated system for the semi-automatic 3D modeling of simple 3D packages according to a pre-defined classification of shapes, and their management in a data base. Such approach allows to dramatically minimize the modeling time needed for each model and, therefore, of the whole shop, making economically sustainable the reverse modeling of commercial environments. A key advantage of the implemented process is that it can be used by operators non expert in 3D modeling and can be reapplied in several different fields.
Combining Product Information and Process Information to Build Virtual Assembly Situations for Knowledge Acquisition
Authors: Madhusudanan N. , Chakrabarti Amaresh
Published: March 2012

Assembly is an important part of the product development process. To avoid potential issues during assembly in specialized domains such as aircraft assembly, expert knowledge to predict such issues is helpful. Knowledge based systems can act as virtual experts to provide assistance. Knowledge acquisition for such systems however, is a challenge, and this paper describes one part of an ongoing research to acquire knowledge through a dialog between an expert and a knowledge acquisition system. In particular this paper discusses the use of a situation model for assemblies to present experts with a virtual assembly and help them locate the specific context of the knowledge they provide to the system.
Virtualization of Industrial Consumer Products for Haptic Interaction Design
Authors: Ferrise Francesco , Ambrogio Marco , Gatti Elia , Lizaranzu Joseba , Bordegoni Monica
Published: March 2012

The haptic feedback perceived during the interaction with consumer products is an important aspect since it concurs in creating, together with the aesthetic features and sonic feedback, the emotional response during the first contacts with a product. And this may be decisive for the user’s decision of purchasing a product instead of another one. So the design of the haptic behavior of interaction elements of products can be both a successful strategy for capturing consumers’ attention but even a need for avoiding problems during the use. The paper describes the process of virtualization of the interaction with an industrial consumer product by means of haptic, sound and visualization technologies in order to obtain a prototype (interactive Virtual Prototypes) useful to design and test the haptic feedback of interaction elements directly with end users.
Mobile 3D Representations for Device Troubleshooting
Authors: Castellani Stefania , Meunier Jean-Luc , Roulland Frederic
Published: March 2012

We are interested in supporting users in a real world application, that of troubleshooting malfunctioning office devices, such as printers or copiers. Basing upon findings from case studies of troubleshooting activities that we conducted, we are constructing a Mixed Reality troubleshooting system. The system allows end-users to try to solve the problem they are experiencing with the device by themselves, with online support available on the device, or by collaborating with a remote troubleshooter. The architecture of the system is centered on a 3D representation of the device augmented with status data of the actual device coming from its internal sensors. The 3D representation is provided to the end-users on the device screen and to the remote troubleshooters on their desktops and it offers a number of means to interact with it providing help for troubleshooting the device. The main purpose of this paper is to illustrate a new interaction mode with the virtual representation for the end-users that we are designing for our system and that is based on the use of a detachable device screen.
A Virtual Human for Lower Limb Prosthesis Set-Up
Authors: Colombo Giorgio , Facoetti Giancarlo , Movigliatti Daniele , Rizzi Caterina
Published: March 2012

This paper concerns the usage of virtual humans to validate lower limb prosthesis design. In particular, we are developing an innovative design framework centered on digital models of the whole patient or of his/her anatomical districts, which constitute the backbone of the design process. The framework integrates a set of virtual “assistants” to guide the technicians during each design task providing specific knowledge and design rules. In this paper, we focus the attention on the last step of the prosthesis deign process, i.e., the final set-up with the patient using a biomechanical model of the amputee. First, we describe the state of art on virtual humans and main features of the new design framework. Then, the application of virtual humans for the prosthesis set-up is presented as well as preliminary results.
A Tactile Simulation Approach to Enhance Virtual Prototypes Interaction
Authors: Mengoni Maura , Morichetti Paolo , Peruzzini Margherita , Germani Michele
Published: March 2012

Materials simulation in virtual prototyping is one of the most challenging issues as not completely fulfilled by current devices. It allows Virtual Reality-based interfaces to provide multisensory interaction and to enhance product experience by mainly stimulating user emotional response. In this context the paper presents a new tactile simulation approach based on material surface properties elaboration and processing to stimulate roughness and texture coarseness perception. The developed approach leads to the development of a tactile display and a software tool to manage the configuration of selective stimulating signals. The main problem the research aims at overcoming, regards with the nature of signals adopted by most electrotactile displays and the way to stimulate skin mechanoreceptors. The paper focuses on the description of the adopted approach and of the implemented software tool in order to control the tactile display.
Optimization of Manipulability in the Design of a Surgery Trainer Based on Virtual Reality
Authors: San Martin Jose , Trivino Gracian
Published: March 2012

In the field of Minimally Invasive Surgery, trainers based on virtual reality provide a very useful, non degradable, realistic training environment. The project of building this new type of trainers requires the development of new tools. In this paper, we describe a set of new measures that allow calculating the optimal position and orientation of haptic devices versus the virtual workspace of the application. We illustrate the use of these new tools applying them to a practical application.
Comparison of Single-Wall Versus Multi-Wall Immersive Environments to Support a Virtual Shopping Experience
Authors: Carlson Patrick , Kirpes Carl , Pavlik Ryan A. , Vance Judy M. , Yin Livien , Scott-Cooper Terrence , Lambert Troy
Published: March 2012

With the proliferation of large screen stereo display systems, major consumer product manufacturers are using this technology to test marketing ideas on consumers. One of the performance factors that is of interest to retailers or manufacturers of retail products is the ability of consumers to quickly and easily locate their products within a retail store. Virtual reality technology can be used to create a virtual store that is easily reconfigurable as a test environment for consumer feedback. The research presented in this paper involves a study that compares the use of a multi-wall immersive environment to a single-wall immersive environment. Users were given a list of products to find in the virtual store. A physical mockup of a shopping cart was created and instrumented in order to be used to navigate throughout the virtual store. The findings indicate that participants in the five-wall immersive environment were significantly faster in locating the objects than the participants using the one-wall immersive environment. In addition, participants in the five-wall condition reported that the shopping cart was easier to use than in the one-wall condition. This study indicates that the use of multiple walls to provide an increased sense of immersion improves the ability of consumers to locate items within a virtual shopping experience.
Automating tumor classification with pixel-by-pixel contrast-enhanced ultrasound perfusion kinetics
Authors: Ta Casey N. , Kono Yuko , Barback Christopher V. , Mattrey Robert F. , Kummel Andrew C.
Published: March 2012

Contrast-enhanced ultrasound (CEUS) enables highly specific time-resolved imaging of vasculature by intravenous injection of ∼2 μm gas filled microbubbles. To develop a quantitative automated diagnosis of breast tumors with CEUS, breast tumors were induced in rats by administration of N-ethyl-N-nitrosourea. A bolus injection of microbubbles was administered and CEUS videos of each tumor were acquired for at least 3 min. The time-intensity curve of each pixel within a region of interest (ROI) was analyzed to measure kinetic parameters associated with the wash-in, peak enhancement, and wash-out phases of microbubble bolus injections since it was expected that the aberrant vascularity of malignant tumors will result in faster and more diverse perfusion kinetics versus those of benign lesions. Parameters were classified using linear discriminant analysis to differentiate between benign and malignant tumors and improve diagnostic accuracy. Preliminary results with a small dataset (10 tumors, 19 videos) show 100% accuracy with fivefold cross-validation testing using as few as two choice variables for training and validation. Several of the parameters which provided the best differentiation between malignant and benign tumors employed comparative analysis of all the pixels in the ROI including enhancement coverage, fractional enhancement coverage times, and the standard deviation of the envelope curve difference normalized to the mean of the peak frame. Analysis of combinations of five variables demonstrated that pixel-by-pixel analysis produced the most robust information for tumor diagnostics and achieved 5 times greater separation of benign and malignant cases than ROI-based analysis.
Study on surface modification of silicon using CHF3/O2 plasma for nano-imprint lithography
Authors: Kim Youngkeun , Kang Sungchil , Ham Yong-Hyun , Kwon Kwang-Ho , Alexandrovich Shutov Dmitriy , Lee Hyun-Woo , Jong Lee Jae , Do Lee-Mi , Baek Kyu-Ha
Published: March 2012

In this article, we report the surface modification of silicon by an inductively coupled CHF3/O2 plasma treatment for demolding process in nano-imprint lithography. The effects of O2 addition to the CHF3 plasma on the surface polymer were investigated. The Si surface energy remained nearly constant at O2 gas fraction from 0% to 50%, but it increased up to ∼60 mN/m at O2 gas fraction of 60%. In order to examine the relationship between the plasma and surface energy of Si, we attempted to conduct a model-based analysis of the CHF3/O2 plasma. Plasma diagnostics were performed by using a double Langmuir probe. At the same time, the surface analysis of Si was carried out by contact angle measurements and x-ray photoelectron spectroscopy.
Visible light-induced photocatalytic properties of WO3 films deposited by dc reactive magnetron sputtering
Authors: Imai Masahiro , Kikuchi Maiko , Oka Nobuto , Shigesato Yuzo
Published: March 2012

The authors examined the photocatalytic activity of WO3 films (thickness 500–600 nm) deposited on a fused quartz substrate heated at 350–800 °C by dc reactive magnetron sputtering using a W metal target under the O2 gas pressure from 1.0 to 5.0 Pa. Films deposited at 800 °C under 5.0 Pa have excellent crystallinity of triclinic, P1(1) structure and a large surface area, as confirmed by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Exposure of acetaldehyde (CH3CHO) adsorbed onto the film surface to ultraviolet, visible, or standard fluorescence light induces oxidative photocatalytic decomposition indicated by a decrease in CH3CHO concentration and generation of CO2 gas. For all three types of irradiation, concentration ratio of decreased CH3CHO to increased CO2 is about 1:1, suggesting the possible presence of intermediates. The sputter-deposited WO3 film can be a good candidate as a visible light-responsive photocatalyst.
Presence detection under optimum fusion in an ultrasonic sensor system
Authors: Srinivasan Sriram , Pandharipande Ashish
Published: March 2012

Reliable presence detection is a requirement in energy-efficient occupancy-adaptive indoor lighting systems. A system of multiple ultrasonic sensors is considered for presence detection, and the performance gain from optimum fusion is studied. Two cases are considered wherein an individual sensor determines presence based on (i) local detection by processing echoes at its receiver, and (ii) the optimum Chair–Varshney fusion rule using multiple sensor detection results. The performance gains of using optimum fusion over local detection are characterized under different sensor system configurations and it is shown that improved detection sensitivity is obtained over a larger detection coverage region.
Bidirectional equalization for underwater acoustic communication
Authors: Song H. C.
Published: March 2012

The bidirectional decision feedback equalizer (BiDFE) that combines the outputs of a conventional decision feedback equalizer (DFE) and backward DFE can improve the performance of the conventional DFE by up to 1–2 dB based on simulations. In this letter, the BiDFE concept is extended to multichannel time reversal communications involving a DFE as a post-processor. Experimental data collected in shallow water (10–20 kHz) show that the performance can be enhanced by 0.4–1.8 dB in terms of output signal-to-noise ratio. In particular, a larger improvement (e.g., 1.8 dB) is achieved for time-varying channels where the channel diversity in opposite directions is more profound.
A Lineage of Myeloid Cells Independent of Myb and Hematopoietic Stem Cells
Authors: Schulz Christian , Perdiguero Elisa Gomez , Chorro Laurent , Szabo-Rogers Heather , Cagnard Nicolas , Kierdorf Katrin , Prinz Marco , Wu Bishan , Jacobsen Sten Eirik W. , Pollard Jeffrey W. , Frampton Jon , Liu Karen J. , Geissmann Frederic
Published: March 2012

Macrophage Development Rewritten

Macrophages provide protection against a wide variety of infections and critically shape the inflammatory environment in many tissues. These cells come in many flavors, as determined by differences in gene expression, cell surface phenotype and specific function.

Schulz
et al.

(p.
86
, published online 22 March) investigated whether adult macrophages all share a common developmental origin. Immune cells, including most macrophages, are widely thought to arise from hematopoietic stem cells (HSCs), which require the transcription factor Myb for their development. Analysis of Myb-deficient mice revealed that a population of yolk-sac–derived, tissue-resident macrophages was able to develop and persist in adult mice in the absence of HSCs. Importantly, yolk sac–derived macrophages also contributed substantially to the tissue macrophage pool even when HSCs were present.
Characterization of Circulating Endothelial Cells in Acute Myocardial Infarction
Authors: Damani Samir , Bacconi Andrea , Libiger Ondrej , Chourasia Aparajita H. , Serry Rod , Gollapudi Raghava , Goldberg Ron , Rapeport Kevin , Haaser Sharon , Topol Sarah , Knowlton Sharen , Bethel Kelly , Kuhn Peter , Wood Malcolm , Carragher Bridget , Schork Nicholas J. , Jiang John , Rao Chandra , Connelly Mark , Fowler Velia M. , Topol Eric J.
Published: March 2012

Features of endothelial cells in blood samples may eventually permit prediction of atherosclerotic plaque rupture events.
Restoring Methicillin-Resistant
Staphylococcus aureus
Susceptibility to β-Lactam Antibiotics
Authors: Tan Christopher M. , Therien Alex G. , Lu Jun , Lee Sang H. , Caron Alexandre , Gill Charles J. , Lebeau-Jacob Christian , Benton-Perdomo Liliana , Monteiro João M. , Pereira Pedro M. , Elsen Nathaniel L. , Wu Jin , Deschamps Kathleen , Petcu Mihai , Wong Simon , Daigneault Etienne , Kramer Susanne , Liang Lianzhu , Maxwell Eugene , Claveau David , Vaillancourt John , Skorey Kathryn , Tam John , Wang Hao , Meredith Timothy C. , Sillaots Susan , Wang-Jarantow Lisa , Ramtohul Yeeman , Langlois Eric , Landry France , Reid John C. , Parthasarathy Gopal , Sharma Sujata , Baryshnikova Anastasia , Lumb Kevin J. , Pinho Mariana G. , Soisson Stephen M. , Roemer Terry
Published: March 2012

Methicillin-resistant
Staphylococcus aureus
infection can be treated effectively by combining a β-lactam antibiotic with a drug that targets FtsZ.
Zoonotic Agents in Small Ruminants Kept on City Farms in Southern Germany
Authors: Schilling Anna-Katarina , Hotzel Helmut , Methner Ulrich , Sprague Lisa D. , Schmoock Gernot , El-Adawy Hosny , Ehricht Ralf , Wöhr Anna-Caroline , Erhard Michael , Geue Lutz
Published: March 2012

Sheep and goats are popular examples of livestock kept on city farms. In these settings, close contacts between humans and animals frequently occur. Although it is widely accepted that small ruminants can carry numerous zoonotic agents, it is unknown which of these agents actually occur in sheep and goats on city farms in Germany. We sampled feces and nasal liquid of 48 animals (28 goats, 20 sheep) distributed in 7 city farms and on one activity playground in southern Germany. We found that 100% of the sampled sheep and 89.3% of the goats carried Shiga toxin-producing
Escherichia coli
(STEC). The presence of
Staphylococcus
spp. in 75% of both sheep and goats could be demonstrated.
Campylobacter
spp. were detected in 25% and 14.3% of the sheep and goats, respectively. Neither
Salmonella
spp. nor
Coxiella burnetii
was found. On the basis of these data, we propose a reasonable hygiene scheme to prevent transmission of zoonotic agents during city farm visits.
Hepatitis C Virus-Multispecific T-Cell Responses without Viremia or Seroconversion among Egyptian Health Care Workers at High Risk of Infection
Authors: Abdelwahab Sayed F. , Zakaria Zainab , Sobhy Maha , Rewisha Eman , Mahmoud Mohamed A. , Amer Mahmoud A. , Del Sorbo Mariarosaria , Capone Stefania , Nicosia Alfredo , Folgori Antonella , Hashem Mohamed , El-Kamary Samer S.
Published: March 2012

Hepatitis C virus (HCV)-specific cell-mediated immunity (CMI) has been reported among exposed individuals without viremia or seroconversion. Limited data are available regarding CMI among at-risk, seronegative, aviremic Egyptian health care workers (HCW), where HCV genotype 4 predominates. We investigated CMI responses among HCW at the National Liver Institute, where over 85% of the patients are HCV infected. We quantified HCV-specific CMI in 52 seronegative aviremic Egyptian HCW using a gamma interferon (IFN-γ) enzyme-linked immunospot assay in response to 7 HCV genotype 4a overlapping 15-mer peptide pools covering most of the viral genome. A positive HCV-specific IFN-γ response was detected in 29 of 52 HCW (55.8%), where 21 (40.4%) had a positive response for two to seven HCV pools and 8 (15.4%) responded to only one pool. The average numbers of IFN-γ total spot-forming cells (SFC) per million peripheral blood mononuclear cells (PBMC) (± standard error of the mean [SEM]) in the 29 responding and 23 nonresponding HCW were 842 ± 141 and 64 ± 15, respectively (P< 0.001). Flow cytometry indicated that both CD4+and CD4−T cells produced IFN-γ. In summary, more than half of Egyptian HCW demonstrated strong HCV multispecific CMI without viremia or seroconversion, suggesting possible clearance of low HCV exposure(s). These data suggest that detecting anti-HCV and viremia to determine past exposure to HCV can lead to an underestimation of the true disease exposure and that CMI response may contribute to the low degree of chronic HCV infection in these HCW. These findings could have strong implications for planning vaccine studies among populations with a high HCV exposure rate. Further studies are needed to determine whether these responses are protective.
Cationic Liposomes Extend the Immunostimulatory Effect of CpG Oligodeoxynucleotide against Burkholderia pseudomallei Infection in BALB/c Mice
Authors: Puangpetch Apichaya , Anderson Robert , Huang Yan Y. , Sermswan Rasana W. , Chaicumpa Wanpen , Sirisinha Stitaya , Wongratanacheewin Surasakdi
Published: March 2012

Melioidosis is a severe disease caused by the Gram-negative bacteriumBurkholderia pseudomallei. Previously we showed that pretreatment of mice with CpG oligodeoxynucleotide (CpG ODN) 2 to 10 days prior toB. pseudomalleichallenge conferred as high as 90% protection, but this window of protection was rather short. In the present study, we therefore aimed to prolong this protective window and to gain further insight into the mechanisms underlying the protection induced by CpG ODN againstB. pseudomalleiinfection. It was found that the CpG ODN incorporated with cationic liposomes (DOTAP) but not zwitterionic liposomes (DOPC) provided complete protection against bacterial challenge. Although marked elevation of gamma interferon (IFN-γ) was found in the infected animals 2 days postinfection, it was significantly lowered by the DOTAP-plus-CpG ODN pretreatment. When appropriately activated, the phagocytic index and oxidative burst responses of neutrophils appeared not to be elevated. However, macrophages from stimulated mice showed higher levels of nitric oxide production and exhibited higher levels of antimicrobial activities, judging from lower numbers of viable intracellular bacteria. Taken together, our results demonstrate that DOTAP can enhance the protective window period of CpG ODN to at least 30 days and provide 100% protection againstB. pseudomalleiinfection. The protective effect of DOTAP plus CpG ODN could provide an alternative approach to preventing this lethal infection, for which no vaccine is yet available.
Analysis of Defined Combinations of Monoclonal Antibodies in Anthrax Toxin Neutralization Assays and Their Synergistic Action
Authors: Ngundi Miriam M. , Meade Bruce D. , Little Stephen F. , Quinn Conrad P. , Corbett Cindi R. , Brady Rebecca A. , Burns Drusilla L.
Published: March 2012

Antibodies against the protective antigen (PA) component of anthrax toxin play an important role in protection against disease caused byBacillus anthracis. In this study, we examined defined combinations of PA-specific monoclonal antibodies for their ability to neutralize anthrax toxin in cell culture assays. We observed additive, synergistic, and antagonistic effects of the antibodies depending on the specific antibody combination examined and the specific assay used. Synergistic toxin-neutralizing antibody interactions were examined in more detail. We found that one mechanism that can lead to antibody synergy is the bridging of PA monomers by one antibody, with resultant bivalent binding of the second antibody. These results may aid in optimal design of new vaccines and antibody therapies against anthrax.
Regulation of
ykrL
(
htpX
) by Rok and YkrK, a Novel Type of Regulator in Bacillus subtilis
Authors: Marciniak Bogumiła C. , Trip Hein , Fusetti Fabrizia , Kuipers Oscar P.
Published: March 2012

Expression of
ykrL
of
Bacillus subtilis
, encoding a close homologue of the
Escherichia coli
membrane protein quality control protease HtpX, was shown to be upregulated under membrane protein overproduction stress. Using DNA affinity chromatography, two proteins were found to bind to the promoter region of
ykrL
: Rok, known as a repressor of competence and genes for extracytoplasmic functions, and YkrK, a novel type of regulator encoded by the gene adjacent to
ykrL
but divergently transcribed. Electrophoretic mobility shift assays showed Rok and YkrK binding to the
ykrL
promoter region as well as YkrK binding to the
ykrK
promoter region. Comparative bioinformatic analysis of the
ykrL
promoter regions in related
Bacillus
species revealed a consensus motif, which was demonstrated to be the binding site of YkrK. Deletion of
rok
and
ykrK
in a P
ykrL
-
gfp
reporter strain showed that both proteins are repressors of
ykrL
expression. In addition, conditions which activated P
ykrL
(membrane protein overproduction, dissipation of the membrane potential, and salt and phenol stress) point to the involvement of YkrL in membrane protein quality control.
Computational Reconstruction of Bole1a, a Representative Synthetic Hepatitis C Virus Subtype 1a Genome
Authors: Munshaw Supriya , Bailey Justin R. , Liu Lin , Osburn William O. , Burke Kelly P. , Cox Andrea L. , Ray Stuart C.
Published: March 2012

Hepatitis C virus (HCV) research is hampered by the use of arbitrary representative isolates in cell culture and immunology. The most replicative isolatein vitrois a subtype 2a virus (JFH-1); however, genotype 1 is more prevalent worldwide and represents about 70% of infections in the United States, and genotypes differ from one another by 31% to 33% at the nucleotide level. For phylogenetic and immunologic analyses, viruses H77 and HCV-1 (both subtype 1a) are commonly used based on their historic importance. In an effort to rationally design a representative subtype 1a virus (Bole1a), we used Bayesian phylogenetics, ancestral sequence reconstruction, and covariance analysis on a curated set of 390 full-length human HCV 1a sequences from GenBank. By design, Bole1a contains variations present in widely circulating strains and matches more epitope-sized peptides in a full-genome comparison to subtype 1a isolates than any other sequence studied. Parallel analyses confirm that selected epitopes from the Bole1a genome were able to elicit a robust T cell response. In a proof of concept for infectivity, the envelope genes (E1 and E2) of Bole1a were expressed in an HIV pseudoparticle system containing HCV envelope genes and HIV nonenvelope genes with luciferase expression. The resulting Bole1a pseudoparticle robustly infected Hep3B cells. In this study, we demonstrate that a rationally designed, fully synthetic HCV genome contains representative epitopes and envelope genes that assemble properly and mediate entry into target cells.