bluuebunny/crossref_metadata_2025 huggingface dataset:
A Preliminary Study of the Spark Characteristics for Unconventional Cylinder Charge With Strong Air Movement
Authors: Yu Shui , Xie Kelvin , Han Xiaoye , Jeftic Marko , Gao Tongyang , Zheng Ming
Published: February 2012

Detailed fundamental understanding of spark discharge under strong air movement condition is crucial to optimize the ignition systems for stratified charge engines. In this paper, extensive bench tests of spark discharge under strong air movement condition are conducted by means of both optical and electrical diagnosis. Strong correlations between the physical structures of spark plasma channel and the gas velocity are found in this paper. The spark heat dissipation distance, the plasma stretched distance and the plasma area under various flow velocities are analyzed. The resistance between the electrode gaps is increased with the enhancement of flow velocity. As a result, the discharge voltage is enhanced, while the discharge duration is shortened. When the flow velocity is enhanced substantially, restrikes of spark discharge are observed. The increasing rate of the discharge voltage before the first restrike is found to be a 2-order polynomial relation to the gas velocity. With the enhancement of flow velocity, the delivered discharge energy increases linearly at the velocity below 25m/s, while it tends to be maintained at the higher flow velocities. Both the increase of the electrode gap size and the flow velocity shorten the spark discharge duration.
3-D Numerical Study of Turbulent Mixing of Intake Air and Exhaust Gas in a Low Pressure EGR System
Authors: Vithala Vishnu Teja , Hoard John , Assanis Dennis , Styles Daniel
Published: February 2012

A 3-D numerical study of turbulent mixing characteristics of air and exhaust gas in a low pressure EGR system (LP-EGR) has been performed under typical operating conditions. There are two objectives of this study. The first objective of the study is to understand and quantify the effects of following factors on mixing quality of exhaust gas and intake air: a) Rate of generation and dissipation of turbulence in the near mixing zone. b) Swirl induced due to formation of counter rotating vortex pairs (CVPs). c) Impingement of the EGR jet on the opposite wall of the intake manifold. The second objective of this study is to understand mixing quality with respect to pressure drop. Under typical conditions, on the low pressure side of the turbocharger, the pressure drop available to ensure required mass flow rate of EGR into the intake air is minimal. Hence, different EGR inlet configurations have been modeled to calculate the mixing quality along with the pressure drops. Some of configurations that have been studied are the effect of varying the diameter of EGR inlet tube, varying the insertion of EGR inlet tube into the intake air duct, angular injection, mixing elbow, multi-point EGR injection, EGR tube with multiple nozzles, venturi configuration, EGR flow control valve at EGR inlet etc. The above mixers have been compared by plotting respective mixing quality vs. EGR-side pressure drop and air-side pressure drop on a 3-D scatter plot at various operating conditions of the engine. One of the important conclusions of the study is that, in the range of operating conditions considered, a simple T-Junction like configuration, which generates maximum local turbulence and allows uninhibited formation and propagation of counter rotating vortex pairs, provides the best mixing quality with the least pressure drop.
Assessment of Novel In-Line Particulate Matter Sensor With Respect to OBD and Emissions Control Applications
Authors: Besch Marc C. , Thiruvengadam Arvind , Kappanna Hemanth K. , Cozzolini Alessandro , Carder Daniel K. , Gautam Mridul , Tikkanen Juha
Published: February 2012

Upcoming emissions legislations and On-Board-Diagnostics (OBD) system requirements, both in the US and Europe, impose new challenges for particulate matter (PM) control strategies, especially with regard to upcoming EURO-VI regulations that are expected to limit the particulate number (PN) emissions. Indeed, the US-EPA Heavy-Duty-OBD regulations already require monitoring of diesel particulate filters (DPF) in 2010 for at least one engine series, with extension to all engine series by 2013. Due to the current absence of reliable in-line PM sensors to monitor DPF filtration efficiencies, manufacturers adopted alternative methods based on pressure drop measurements and semi-empirical models that require extensive calibration efforts; hence, driving upward the development costs. In order to meet upcoming OBD requirements and reduce unnecessary DPF regeneration frequencies, so as to minimize fuel consumption penalties, reliable sensors need to be integrated into the aftertreatment control environment. These next-generation sensors must be capable of performing actual real-time PM concentration measurements on a continuous basis within the exhaust stream. The primary objective of this study was to assess the capabilities, limitations and sensitivity of a newly developed inline PM sensor, with regard to its future application for OBD monitoring or control strategies of PM filter systems. The operation of the so called Pegasor Particulate Sensor (PPS) [1] is based on the escaping current principle. The instrument is capable of performing continuous PM measurements, directly from the exhaust stack, while providing a real-time signal with a resolution of 100 Hz. The sensor’s output signal can be calibrated to either measure the concentration of mass, surface or number of exhaust particles. Designed as a flow-through device, the PPS has a tungsten corona wire imposing an equal charge on particles that is subsequently measured from the outflowing particles via a built-in electrometer. The system does not involve collection or contact with particles in the exhaust stream, which is especially advantageous for long-term stability and operation without frequent maintenance; hence, best suited for in-use application. A comprehensive test matrix was developed to gain a more pronounced understanding of the sensor’s measurement technology by comparing it to other proven aerosol instruments, namely the Ultrafine Condensation Particle Counter (UCPC), Engine Exhaust Particle Sizer (EEPS™) spectrometer, Tapered Element Oscillating Microbalance (TEOM), and gravimetric PM. Test results demonstrated a stable and repeatable response over consecutive European Transient Cycle (ETC) and Federal Test Procedure (FTP) cycles, as well as over idle and constant load operation with coefficients of variation below 2%, which is a prerequisite for OBD algorithm implementation.
Comparison of Soot Evolution Using High-Speed CMOS Color Camera and Two-Color Thermometry in an Optical Diesel Engine Fueled With B20 Biodiesel Blend and Ultra-Low Sulfur Diesel
Authors: Zha Kan , Florea Radu-Catalin , Jansons Marcis
Published: February 2012

Biodiesel is a desirable alternative fuel for the diesel engine due to its low engine-out soot emission tendency. When blended with petroleum-based diesel fuels, soot emissions generally decrease in proportion to the volume fraction of biodiesel in the mixture. While comparisons of engine-out soot measurements between biodiesel blends and petroleum-based diesel have been widely reported, in-cylinder soot evolution has not been experimentally explored to the same extent. To elucidate the soot emission reduction mechanism of biodiesel, a single-cylinder optically-accessible diesel engine was used to compare the in-cylinder soot evolution when fueled with ultra-low sulfur diesel (ULSD) to that using a B20 biodiesel blend (20% vol/vol biodiesel ASTM D6751-03A). Soot temperature and KL factors are simultaneously determined using a novel two-color optical thermometry technique implemented with a high-speed CMOS color camera having wide-band Bayer filters. The crank-angle resolved data allows quantitative comparison of the rate of in-cylinder soot formation. High-speed spray images show that B20 has more splashing during spray wall impingement than ULSD, distributing rebounding fuel droplets over a thicker annular ring interior to the piston bowl periphery. The subsequent soot luminescence is observed by high-speed combustion imaging and soot temperature and KL factor measurements. B20 forms soot both at low KL magnitudes over large areas between fuel jets, and at high values among remnants of the fuel spray, along its axis and away from the bowl edge. In contrast, ULSD soot luminescence is observed exclusively as pool burning on the piston bowl surfaces resulting from fuel wall impingement. The soot KL factor evolution during B20 combustion indicates earlier and significantly greater soot formation than with ULSD. B20 combustion is also observed to have a greater soot oxidation rate which results in lower engine-out soot emissions. Measured soot temperatures near 1875K were similar for the two fuels for the duration of combustion. For both fuels, higher fuel injection pressure led to lower late-cycle soot KL levels. The trends of soot natural luminosity correlated well with the trends of soot KL factor, suggesting that relatively simple measurements of combustion luminosity may provide somewhat quantitative information about in-cylinder soot formation and oxidation. The apparent rate of heat release (ARHR) analysis under steady skip-fire conditions indicates that B20 combustion is less sensitive to wall temperature than that observed with ULSD due to a lesser degree of pool burning. B20 was found to have both a shorter ignition delay and shorter combustion duration than ULSD.
Integration of a Dual-Mode SI-HCCI Engine Into Various Vehicle Architectures
Authors: Lawler Benjamin J. , Filipi Zoran S.
Published: February 2012

A simulation study was performed to evaluate the potential fuel economy benefits of integrating a dual-mode SI-HCCI engine into various vehicle architectures. The vehicle configurations that were considered include a conventional vehicle, a mild parallel hybrid, and a power-split hybrid. The three configurations were modeled and compared in detail for a given engine size (2.0 L for the conventional vehicle, 2.0 L for the mild parallel, and 1.5 L for the power-split) over the EPA UDDS (city) and Highway cycles. The results show that the dual-mode engine in the conventional vehicle offers a modest gain in vehicle fuel economy of approximately 5–7%. The gains were modest due to an advanced 6-speed transmission and a practically-based shift schedule, with which only 30% of the operating points were in the HCCI range for the city cycle and 56% for the highway cycle. The mild parallel hybrid achieved 32% better fuel economy than the conventional vehicle, both with SI engines. For the dual-mode engine in the mild parallel hybrid, a specific control strategy was used to manipulate engine operation in an attempt to minimize the number of engine mode transitions and maximize the time spent in HCCI. The parallel hybrid with the dual-mode engine and modified control strategy provides dramatic improvements of up to 48% in city driving, demonstrating that the addition of HCCI has a more significant effect with parallel hybrids than conventional vehicles. The power-split hybrid simulation showed that adding a dual-mode engine had an insignificant effect on vehicle fuel economy, mostly due to the ability of the planetary gear set to act as an e-CVT and keep the engine at relatively high loads. Finally, a systematic study of engine sizing provides guidelines for selecting the best option for a given vehicle application by characterizing the vehicle level interactions, and their effect on fuel economy, over an engine displacement sweep.
Dynamic Analysis of Electrical Power Grid Delivery: Using Prime Mover Engines to Balance Dynamic Wind Turbine Output
Authors: Grauer Diana K. , Reed Michael E.
Published: February 2012

This paper presents an investigation into integrated wind + combustion engine high penetration electrical generation systems. Renewable generation systems are now a reality of electrical transmission. Unfortunately, many of these renewable energy supplies are stochastic and highly dynamic. Conversely, the existing national grid has been designed for steady state operation. The research team has developed an algorithm to investigate the feasibility and relative capability of a reciprocating internal combustion engine to directly integrate with wind generation in a tightly coupled Hybrid Energy System. Utilizing the Idaho National Laboratory developed Phoenix Model Integration Platform, the research team has coupled demand data with wind turbine generation data and the Aspen Custom Modeler reciprocating engine electrical generator model to investigate the capability of reciprocating engine electrical generation to balance stochastic renewable energy.
Heating Value Sensor for Producer Gas
Authors: Jangale Vilas V. , Saveliev Alexei , Zelepouga Serguei , Gnatenko Vitaly , Pratapas John M.
Published: February 2012

Today, producer gas is being utilized as a fuel gas in boilers, internal combustion engines and turbines for heat and power generation. The composition of producer gas varies depending upon the gasification parameters. For improved process control and optimum utilization of these heat and power generating systems, it is desirable to monitor the producer gas composition in real-time. A new method and apparatus has been developed and lab-tested for quantitative characterization of producer gas. Spectroscopic and non-spectroscopic measurements are performed in order to detect both — spectrally active and inactive gases. Both methods are cross-sensitive to more than one gas. The measurements are then processed using multivariate statistical methods — principal components regression and partial least squares to fit a regression model which correlates the experimental measurements to the composition and heating value of producer gas. The fitted regression model is used to estimate the properties of unknown mixtures. The measurements and data processing are done in real time using a high speed hardware control and data acquisition system. A commercialized version of this sensor is expected to cost less than half the price of gas chromatographs, which are widely used in the gas industry today.
Exploring Strategies for Reducing High Intake Temperature Requirements and Allowing Optimal Operational Conditions in a Biogas Fueled HCCI Engine for Power Generation
Authors: Bedoya Iva´n D. , Saxena Samveg , Cadavid Francisco J. , Dibble Robert W.
Published: February 2012

This paper evaluates strategies for reducing the intake temperature requirement for igniting biogas in HCCI engines. HCCI combustion is a promising technology for stationary power generation using renewable fuels in combustion engines. Combustion of biogas in HCCI engines allows high thermal efficiency similar to Diesel engines, with low net CO2 and low NOx emissions. However, in order to ensure the occurrence of autoignition in purely biogas fueled HCCI engines, a high inlet temperature is needed. This paper presents experimental and numerical results. First, experimental analysis on a 4 cylinder, 1.9 L Volkswagen TDI Diesel engine running with biogas in HCCI mode shows high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and NOx emissions below the 2010 US limit (0.27g/kWh). Stable HCCI operation is experimentally demonstrated with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis, inlet pressures of 2–2.2 bar (absolute) and inlet temperatures of 200–210°C for equivalence ratios between 0.19–0.29. At lower equivalence ratios, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations while at higher equivalence ratios these same small pressure and temperature variations caused large changes to ringing intensity. Second, numerical simulations have been carried out to evaluate the effectiveness of high boost pressures and high compression ratios for reducing the inlet temperature requirements while attaining safe operation and high power output. The one zone model in Chemkin was used to evaluate the ignition timing and peak cylinder pressures with variations in temperatures at IVC from 373 to 473 K. In-cylinder temperature profiles between IVC and ignition were computed using Fluent 6.3 and fed into the multi-zone model in Chemkin to study combustion parameters. According to the numerical results, the use of both higher boost pressures and higher compression ratios permit lower inlet temperatures within the safe limits experimentally observed and allow higher power output. However, the range of inlet temperatures allowing safe and efficient operation using these strategies is very narrow, and precise inlet temperature control is needed to ensure the best results.
Improved Transient Control of a Two-Stroke Marine Diesel Engine With Variable Geometry Turbine
Authors: Xiros Nikolaos I. , Theotokatos Gerasimos
Published: February 2012

In this work, the cycle-mean-value approach to marine engine process simulation is considered. At first, a basic principles model is employed where the engine crankshaft and turbocharger shaft speeds are obtained by integration of the angular momentum conservation differential equations. Any other engine variable can then be obtained by solving a set of nonlinearly-coupled, algebraic equations, corresponding to energy and mass conservation through the engine. Nonlinear data analysis is then performed on this process model. By approximating the torque maps, generated by the thermodynamic basic principles model, with neural nets, explicit functional relationships are obtained. Identification of the power-plant operating regimes through linearization and decomposition is finally performed. In effect, a supervisory power-plant controller structure, applicable to real-time control and diagnostics, is proposed, incorporating the nonlinear state-space description of the plant.
Application of a Supercharger in a Two-Stage Boosting System for a Gasoline HCCI Engine: A Simulation Study
Authors: Shingne Prasad , Assanis Dennis , Babajimopoulos Aristotelis , Mond Alan , Yilmaz Hakan
Published: February 2012

Recently, a number of studies have demonstrated that boosting can extend the high load limit of HCCI. This paper compares two two-stage boosting systems for a 4-cylinder, 2.0 liter engine, within the framework of a 1D engine simulation. A series two-stage boosting system wherein both high and low pressure stages are turbochargers (TCTC) is compared with another series two-stage system, where the high pressure stage from TCTC is replaced with a small supercharger (TCSC). The engine model in these configurations is operated in steady state at high load boosted HCCI points (∼ 6.5 bar BMEP) over a range of engine speeds. The comparison has been carried out by two methods: in Method I the intake pressure to the engine has been matched for both TCTC and TCSC; and in Method II, the amount of fresh charge into the engine has been matched for both systems. A detailed energy balance shows that the performance in terms of BSFC for the TCSC system is worse for Method I. However, this changes for Method II, and the TCSC system is comparable or even better than the TCTC system. This is achieved by greatly reducing the pumping losses associated with the TCTC system, while the parasitic losses of the supercharger are minimized by having to boost to lower intake pressures due to lowered back pressures in the TCSC system.
A Novel Approach to Free-Piston Engine Control Using an FPGA Based Control System
Authors: Viele Matthew , Shorey Eric E. , Dase Carroll G. , Hoose Karl V. , Light Kendrick H.
Published: February 2012

The variable stroke length of the free-piston engine poses an interesting problem for the controls engineer. At a low level, the control system must be able to track piston position and address changes in top and bottom dead center positions. To accomplish this, a new FPGA (field programmable gate array) based engine position tracking software was developed, along with a simple method of mapping from a conventional engine control system to a free-piston control system. The tracking software was integrated into a complete rapid prototyping control system that was responsible for all control actions of the engine. The control system was laboratory tested on the HiPerTEC, an opposed, free-piston engine with a circular piston arrangement (as opposed to linear free-piston engines) developed by Applied Thermal Sciences, Inc (ATS). The control system has been demonstrated to run 8 cylinders up to an effective speed of 2,200rpm in spark ignition mode.
Drive Cycle Efficiency and Emissions Estimates for Reactivity Controlled Compression Ignition in a Multi-Cylinder Light-Duty Diesel Engine
Authors: Curran Scott J. , Cho Kukwon , Briggs Thomas E. , Wagner Robert M.
Published: February 2012

In-cylinder blending of gasoline and diesel to achieve Reactivity Controlled Compression Ignition (RCCI) has been shown to reduce NOx and PM emissions while maintaining or improving brake thermal efficiency (BTE) as compared to conventional diesel combustion (CDC). The RCCI concept has an advantage over many advanced combustion strategies in that by varying both the percent of premixed gasoline and EGR rate, stable combustion can be extended over more of the light-duty drive cycle load range. Changing the percent of premixed gasoline changes the fuel reactivity stratification in the cylinder providing further control of combustion phasing and cylinder pressure rise rate than the use of EGR alone. This paper examines the combustion and emissions performance of light-duty diesel engine using direct injected diesel fuel and port injected gasoline to enable RCCI for steady-state engine conditions which are consistent with a light-duty drive cycle. A GM 1.9L four-cylinder engine with the stock compression ratio of 17.5:1, common rail diesel injection system, high-pressure EGR system and variable geometry turbocharger was modified to allow for port fuel injection with gasoline. Engine-out emissions, engine performance and combustion behavior for RCCI operation is compared against both CDC and a premixed charge compression ignition (PCCI) strategy which relies on high levels of EGR dilution. The effect of percent of premixed gasoline, EGR rate, boost level, intake mixture temperature, combustion phasing, and cylinder pressure rise rate is investigated for RCCI combustion for the light-duty modal points. Engine-out emissions of NOx and PM were found to be considerably lower for RCCI operation as compared to CDC and PCCI, while HC and CO emissions were higher. BTE was similar or higher for many of the modal conditions for RCCI operation. The emissions results are used to estimate hot-start FTP-75 emissions levels with RCCI and are compared against CDC and PCCI modes.
Reactivity Controlled Compression Ignition (RCCI) Using Premixed Hydrated Ethanol and Direct Injection Diesel
Authors: Dempsey A. B. , Adhikary B. Das , Viswanathan S. , Reitz R. D.
Published: February 2012

Previous research has shown that a Homogeneous Charge Compression Ignition (HCCI) engine with efficient heat recovery can operate on a 35 to 65% volumetric mixture of ethanol-in-water while achieving high brake thermal efficiency (∼39%) and very low NOx emissions [4]. The major advantage of utilizing hydrated ethanol as a fuel is that the net energy gain improves from 21 to 55% of the heating value of ethanol and its co-products, since significant energy must be expended to remove water during production. This is required because wet ethanol is not suitable for conventional combustion engines. For example, spark ignition engines demand the use of pure ethanol because the dilution caused by water reduces the flame speed, resulting in misfire and problems due to condensation. The present study uses numerical simulations to explore the use of wet ethanol for Reactivity Controlled Compression Ignition (RCCI) operation in a heavy duty diesel engine. RCCI uses in-cylinder blending of a low reactivity fuel with a high reactivity fuel and has demonstrated significant fuel efficiency and emissions benefits using a variety of fuels, including gasoline and diesel. Combustion timing is controlled by the local blended fuel reactivity (i.e. octane number), and the combustion duration can be controlled by establishing optimized gradients in fuel reactivity in the combustion chamber. In the present study, the low reactivity fuel was hydrated ethanol while the higher reactivity fuel was diesel. First, the effect of water on ethanol/water/diesel HCCI was investigated using GT-Power and single-zone CHEMKIN simulations. The results showed that the main impact of the water in the ethanol is to reduce the IVC temperature due to vaporization cooling. Next, multidimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bar IMEP at 1300 rev/min with various grades of hydrated ethanol and a fixed diesel fraction of the total fuel. The results show that hydrated ethanol can be used in a RCCI engine with gross indicated thermal efficiencies up to 55% and very low emissions. A 70/30 ethanol/water mixture (by mass) was found to yield the best results across the entire load range without the need for EGR.
Commercialization of dye sensitized solar cells: Present status and future research needs to improve efficiency, stability, and manufacturing
Authors: Baxter Jason B.
Published: February 2012

Dye sensitized solar cells (DSSCs) have received a tremendous amount of attention since the first report of a 7% efficient cell in 1991. Confirmed record efficiencies are now 11.2% for small cells and 9.9% for submodules, and low-cost production methods are enabling manufacturing of DSSC products for a variety of markets. This review describes the present status of DSSC devices and manufacturing as well as research challenges that must be addressed to continue the rapid commercialization of DSSC technology. These challenges fall into the categories of improving efficiency, stability, and manufacturability. Efficiency improvements will hinge on the development of new combinations of dyes, redox couples, and photoanodes. Best-case lifetimes are determined by the kinetics of various molecular-level processes, and realization of these lifetimes will require improved encapsulation of cells and modules. Low-cost and sustainable manufacturing of DSSC modules depends on use of high-throughput roll-to-roll processing and inexpensive, abundant materials. Prospects for simultaneous improvement of efficiency, stability, and manufacturing are discussed.
PTEN Directly Activates the Actin Depolymerization Factor Cofilin-1 During PGE
2
-Mediated Inhibition of Phagocytosis of Fungi
Authors: Serezani C. Henrique , Kane Steve , Medeiros Alexandra I. , Cornett Ashley M. , Kim Sang-Hoon , Marques Mariana Morato , Lee Sang-Pyo , Lewis Casey , Bourdonnay Emilie , Ballinger Megan N. , White Eric S. , Peters-Golden Marc
Published: February 2012

By promoting actin depolymerization, the protein phosphatase activity of PTEN impairs macrophage phagocytosis of a fungal pathogen.
Protein Kinase CK2 Triggers Cytosolic Zinc Signaling Pathways by Phosphorylation of Zinc Channel ZIP7
Authors: Taylor Kathryn M. , Hiscox Stephen , Nicholson Robert I. , Hogstrand Christer , Kille Peter
Published: February 2012

Phosphorylation of the zinc channel ZIP7 releases zinc from the endoplasmic reticulum and promotes signals associated with proliferation and migration.
Natural Resistance
Authors: Zahn Laura
Published: February 2012

Resistance to avermectin, an antinematode drug, is conferred by a deletion in a glutamate-gated chloride channel.
Product Quality of Parenteral Vancomycin Products in the United States
Authors: Nambiar S. , Madurawe R. D. , Zuk S. M. , Khan S. R. , Ellison C. D. , Faustino P. J. , Mans D. J. , Trehy M. L. , Hadwiger M. E. , Boyne M. T. , Biswas K. , Cox E. M.
Published: February 2012

In response to concerns raised about the quality of parenteral vancomycin products, the U.S. Food and Drug Administration (FDA) is investigating the product quality of all FDA-approved parenteral vancomycin products available in the United States. Product quality was evaluated independently at two FDA Office of Testing and Research (FDA-OTR) sites. In the next phase of the investigation, being done in collaboration with the National Institute of Allergy and Infectious Diseases, the
in vivo
activity of these products will be evaluated in an appropriate animal model. This paper summarizes results of the FDA investigation completed thus far. One site used a validated ultrahigh-pressure liquid chromatography method (OTR-UPLC), and the second site used the high-performance liquid chromatography (HPLC) method for related substances provided in the British Pharmacopeia (BP) monograph for vancomycin intravenous infusion. Similar results were obtained by the two FDA-OTR laboratories using two different analytical methods. The products tested had 90 to 95% vancomycin B (active component of vancomycin) by the BP-HPLC method and 89 to 94% vancomycin by OTR-UPLC methods. Total impurities were 5 to 10% by BP-HPLC and 6 to 11% by OTR-UPLC methods. No single impurity was >2.0%, and the CDP-1 level was ≤2.0% across all products. Some variability in impurity profiles of the various products was observed. No adverse product quality issues were identified with the six U.S. vancomycin parenteral products. The quality parameters of all parenteral vancomycin products tested surpassed the United States Pharmacopeia acceptance criteria. Additional testing will characterize
in vivo
performance characteristics of these products.
The F423Y Mutation in the
pfmdr2
Gene and Mutations N51I, C59R, and S108N in the
pfdhfr
Gene Are Independently Associated with Pyrimethamine Resistance in Plasmodium falciparum Isolates
Authors: Briolant Sébastien , Bogreau Hervé , Gil Marine , Bouchiba Housem , Baret Eric , Amalvict Rémy , Rogier Christophe , Pradines Bruno
Published: February 2012

Screening for
in vitro
susceptibility to pyrimethamine and sequencing of the
pfmdr2
and
pfdhfr
genes were performed in 140
Plasmodium falciparum
isolates. The risk of
in vitro
resistance to pyrimethamine was analyzed with a logistic regression model. The mutation F423Y in
pfmdr2
(odds ratio [OR] = 2.12 [confidence interval {CI}, 1.02 to 4.59];
P
= 0.0489) and the mutation N51I, C59R, or S108N in
pfdhfr
(OR = 42.34 [CI, 5.52 to 324.61];
P
= 0.0003) were independently associated with
in vitro
resistance to pyrimethamine.
Antibiotic Exposure as a Risk Factor for Fluconazole-Resistant Candida Bloodstream Infection
Authors: Ben-Ami Ronen , Olshtain-Pops Keren , Krieger Michal , Oren Ilana , Bishara Jihad , Dan Michael , Wiener-Well Yonit , Weinberger Miriam , Zimhony Oren , Chowers Michal , Weber Gabriel , Potasman Israel , Chazan Bibiana , Kassis Imad , Shalit Itamar , Block Colin , Keller Nathan , Kontoyiannis Dimitrios P. , Giladi Michael ,   for the Israeli Candidemia Study Group
Published: February 2012

Recent exposure to azoles is an important risk factor for infection with fluconazole-resistant
Candida
spp., but little is known about the role of antibacterial drug exposure in the emergence of drug-resistant
Candida
. We did a prospective nationwide surveillance study of candidemia in Israel and analyzed the propensity score-adjusted association between antifungal and antibacterial drug exposure and bloodstream infection with
C. glabrata
and fluconazole-resistant
Candida
isolates. Four hundred forty-four episodes of candidemia (450
Candida
isolates, 69 [15%]
C. glabrata
isolates, and 38 [8.5%] fluconazole-resistant isolates) from 18 medical centers in Israel were included.
C. glabrata
bloodstream infection was strongly associated with recent metronidazole exposure (odds ratio [OR], 3.2;
P
< 0.001). Infection with a fluconazole-resistant isolate was associated with exposure to carbapenems, trimethoprim-sulfamethoxazole, clindamycin, and colistin (odds ratio, 2.8;
P
= 0.01). The inclusion of antibacterial drug exposure in a multivariable model significantly enhanced the model's predictive accuracy for fluconazole-resistant
Candida
bloodstream infection. Our findings may be relevant to the selection of empirical antifungal treatment and broaden the scope of antibiotic-associated collateral damage.
Induction of Oxidative Stress in Trypanosoma brucei by the Antitrypanosomal Dihydroquinoline OSU-40
Authors: He Shanshan , Dayton Alex , Kuppusamy Periannan , Werbovetz Karl A. , Drew Mark E.
Published: February 2012

Dihydroquinoline derivative OSU-40 (1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate) is selectively potent against
Trypanosma brucei rhodesiense in vitro
(50% inhibitory concentration [IC
50
], 14 nM; selectivity index, 1,700) and has been proposed to cause the formation of reactive oxygen species (ROS) in African trypanosomes (J. Fotie et al., J. Med. Chem. 53:966–982, 2010). In the present study, we sought to provide further support for the hypothesis that OSU-40 kills trypanosomes through oxidative stress. Inducible RNA interference (RNAi) was applied to downregulate key enzymes in parasite antioxidant defense, including
T. brucei
trypanothione synthetase (TbTryS) and superoxide dismutase B (TbSODB). Both TbTryS RNAi-induced and TbSODB RNAi-induced cells showed impaired growth and increased sensitivity toward OSU-40 by 2.4-fold and 3.4-fold, respectively. Decreased expression of key parasite antioxidant enzymes was thus associated with increased sensitivity to OSU-40, consistent with the hypothesis that OSU-40 acts through oxidative stress. Finally, the dose-dependent formation of free radicals was observed after incubation of
T. brucei
with OSU-40 utilizing electron spin resonance (ESR) spectroscopy. These data support the notion that the mode of antitrypanosomal action for this class of compounds is to induce oxidative stress.
Virulence of Escherichia coli Clinical Isolates in a Murine Sepsis Model in Relation to Sequence Type ST131 Status, Fluoroquinolone Resistance, and Virulence Genotype
Authors: Johnson James R. , Porter Stephen B. , Zhanel George , Kuskowski Michael A. , Denamur Erick
Published: February 2012

Escherichia coli
sequence type ST131 (O25b:H4) has emerged over the past decade as a globally disseminated, multidrug-resistant pathogen. Unlike traditional antimicrobial-resistant
E. coli
, ST131 derives from virulence-associated phylogenetic group B2 and exhibits extraintestinal virulence factors. This, plus preliminary evidence of virulence in experimental animals, has suggested that ST131's epidemic emergence may be due to high virulence potential, compared with other
E. coli
types. To test this hypothesis, we compared a large number of matched ST131 and non-ST131
E. coli
clinical isolates, both fluoroquinolone resistant and susceptible, plus isolates from classic extraintestinal pathogenic
E. coli
(ExPEC) sequence types (STs) and case report ST131 household transmission isolates, for virulence in a mouse subcutaneous sepsis model. Overall, in mice, the study isolates produced a wide range of lethality and clinical illness. However, neither ST131 status nor fluoroquinolone phenotype correlated with this diversity of illness severity, which occurred within each of the 6 study groups. In contrast, multiple known or suspected ExPEC virulence genes, including
pap
(P fimbriae),
vat
(vacuolating toxin),
kpsM
II (group 2 capsule),
ibeA
(invasion of brain endothelium), and
clbB/N
(colibactin synthesis), plus molecularly defined ExPEC status, were significantly associated with virulence. These findings point away from ST131 isolates as having higher virulence potential compared with other
E. coli
types in causing invasive extraintestinal infections and suggest instead that ST131's epidemiological success may reflect enhanced fitness for upstream steps in pathogenesis or in colonization and transmission. Additionally, the extensive within-ST virulence diversity suggests an opportunity to compare closely related strains to identify the responsible genetic determinants.
Baby knows best? The impact of weaning style on food preferences and body mass index in early childhood in a case–controlled sample
Authors: Townsend Ellen , Pitchford Nicola J
Published: February 2012

Objective

The impact of different weaning methods on food preferences and body mass index (BMI) in early childhood is not known. Here, we examine if weaning method—baby-led weaning versus traditional spoon feeding—influences food preferences and health-related outcomes.

Design, setting and participants

Parents (n=155) recruited through the Nottingham Toddler laboratory and relevant internet sites completed a questionnaire concerning (1) infant feeding and weaning style (baby-led=92, spoon-fed=63, age range 20–78 months), (2) their child's preference for 151 foods (analysed by common food categories, eg, carbohydrates, proteins, dairy) and (3) exposure (frequency of consumption). Food preference and exposure data were analysed using a case–controlled matched sample to account for the effect of age on food preference. All other analyses were conducted with the whole sample.

Main outcome measures

The primary outcome measures were food preferences, exposure and weaning style. The secondary outcome measures were BMI and picky eating.

Results

Compared to the spoon-fed group, the baby-led group demonstrated (1) significantly increased liking for carbohydrates (no other differences in preference were found) and (2) carbohydrates to be their most preferred foods (compared to sweet foods for the spoon-fed group). Preference and exposure ratings were not influenced by socially desirable responding or socioeconomic status, although an increased liking for vegetables was associated with higher social class. There was an increased incidence of (1) underweight in the baby-led group and (2) obesity in the spoon-fed group. No difference in picky eating was found between the two weaning groups.

Conclusions

Weaning style impacts on food preferences and health in early childhood. Our results suggest that infants weaned through the baby-led approach learn to regulate their food intake in a manner, which leads to a lower BMI and a preference for healthy foods like carbohydrates. This has implications for combating the well-documented rise of obesity in contemporary societies.
A CLASS OF INTERACTING PARTICLE SYSTEMS ON THE INFINITE CYLINDER WITH FLOCKING PHENOMENA
Authors: HA SEUNG-YEAL , KANG MOON-JIN , LATTANZIO CORRADO , RUBINO BRUNO
Published: February 2012

We present a class of extended Kuramoto models describing a flocking motion of particles on the infinite cylinder and provide sufficient conditions for the asymptotic formation of locked solutions where the distance between particles remains constant. Our proposed model includes the complex Kuramoto model for synchronization. We also provide several numerical simulation results and compare them with analytical results.
A CONTINUUM MODEL FOR ALIGNMENT OF SELF-PROPELLED PARTICLES WITH ANISOTROPY AND DENSITY-DEPENDENT PARAMETERS
Authors: FROUVELLE AMIC
Published: February 2012

We consider the macroscopic model derived by Degond and Motsch from a time-continuous version of the Vicsek model, describing the interaction orientation in a large number of self-propelled particles. In this paper, we study the influence of a slight modification at the individual level, letting the relaxation parameter depend on the local density and taking in account some anisotropy in the observation kernel (which can model an angle of vision).

The main result is a certain robustness of this macroscopic limit and of the methodology used to derive it. With some adaptations to the concept of generalized collisional invariants, we are able to derive the same system of partial differential equations, the only difference being in the definition of the coefficients, which depend on the density. This new feature may lead to the loss of hyperbolicity in some regimes.

We then provide a general method which enables us to get asymptotic expansions of these coefficients. These expansions shows, in some effective situations, that the system is not hyperbolic. This asymptotic study is also useful to measure the influence of the angle of vision in the final macroscopic model, when the noise is small.
OPTIMAL DECAY RATES TO CONSERVATION LAWS WITH DIFFUSION-TYPE TERMS OF REGULARITY-GAIN AND REGULARITY-LOSS
Authors: DUAN RENJUN , RUAN LIZHI , ZHU CHANGJIANG
Published: February 2012

We consider the Cauchy problem on nonlinear scalar conservation laws with a diffusion-type source term related to an index s ∈ ℝ over the whole space ℝn for any spatial dimension n ≥ 1. Here, the diffusion-type source term behaves as the usual diffusion term over the low frequency domain while it admits on the high frequency part a feature of regularity-gain and regularity-loss for s < 1 and s > 1, respectively. For all s ∈ ℝ, we not only obtain the Lp–Lq time-decay estimates on the linear solution semigroup but also establish the global existence and optimal time-decay rates of small-amplitude classical solutions to the nonlinear Cauchy problem. In the case of regularity-loss, the time-weighted energy method is introduced to overcome the weakly dissipative property of the equation. Moreover, the large-time behavior of solutions asymptotically tending to the heat diffusion waves is also studied. The current results have general applications to several concrete models arising from physics.
POLYMER-MODIFIED GADOLINIUM NANOPARTICLES FOR TARGETED MAGNETIC RESONANCE IMAGING AND THERAPY
Authors: BOYES STEPHEN G. , ROWE MISTY D. , SERKOVA NATALIE J. , KIM FERNANDO J. , LAMBERT JAMES R. , WERAHERA PRIYA N.
Published: February 2012

Functional imaging is a novel area in radiological sciences and allows for the non-invasive assessment and visualization of specific targets such as gene and protein expression, metabolic rates, and drug delivery in intact living subjects. As such, the field of molecular imaging has been defined as the non-invasive, quantitative, and repetitive imaging of biomolecules and biological processes in living organisms. For example, cancer cells may be genetically altered to attract molecules that alter the magnetic susceptibility, thereby permitting their identification by magnetic resonance imaging. These contrast agents and/or molecular reporters are seen as essential to the task of molecular medicine to increase both sensitivity and specificity of imaging. Therefore, there are five general principles which need to be fulfilled in order to conduct a successful in vivo molecular imaging study: (1) selection of appropriate cellular and subcellular targets; (2) development of suitable in vivo affinity ligands (molecular probes); (3) delivery of these probes to the target organ; (4) amplification strategies able to detect minimal target concentrations; and (5) development of imaging systems with high resolution. Although there has been a wide range of routes taken to incorporate both imaging agents and a disease-targeting moiety into diagnostic devices, arguably the most interesting of these routes employs the use of nanoparticles. Nanoscale diagnostic systems that incorporate molecular targeting agents and diagnostic imaging capabilities are emerging as the next-generation imaging agents and have the potential to dramatically improve the outcome of the imaging, diagnosis, and treatment of a wide range of diseases. The present review addresses chemical aspects in development of molecular probes based upon gadolinium nanoparticles and their potential role in translational clinical imaging and therapy.
The Value of Multiple Read/Write Streams for Approximating Frequency Moments
Authors: Beame Paul , Huynh Trinh
Published: February 2012

We consider the read/write streams model, an extension of the standard data stream model in which an algorithm can create and manipulate multiple read/write streams in addition to its input data stream. Like the data stream model, the most important parameter for this model is the amount of internal memory used by such an algorithm. The other key parameters are the number of streams the algorithm uses and the number of passes it makes on these streams. We consider how the addition of multiple streams impacts the ability of algorithms to approximate the frequency moments of the input stream.

We show that any randomized read/write stream algorithm with a fixed number of streams and a sublogarithmic number of passes that produces a constant factor approximation of the
k
-th frequency moment
F
k
of an input sequence of length of at most
N
from {1,...,
N
} requires space
Ω
(
N
1−4/k−δ
) for any
δ
 > 0. For comparison, it is known that with a single read-only one-pass data stream there is a randomized constant-factor approximation for
F
k
using
Õ
(
N
1−2/k
) space, and that by sorting, which can be done deterministically in
O
(log
N
) passes using 3 read/write streams,
F
k
can be computed exactly. Therefore, although the ability to manipulate multiple read/write streams can add substantial power to the data stream model, with a sublogarithmic number of passes this does not significantly improve the ability to approximate higher frequency moments efficiently. We obtain our results by showing a new connection between the read/write streams model and the multiparty number-in-hand communication model.
CS Ed week showcase at UNC Charlotte
Authors: Barnes Tiffany
Published: February 2012

UNC Charlotte celebrated CS Ed Week this year with a showcase to over 100 computing students and teachers from three local high schools. The program started with a panel on what it's like to be a Computer Science college student. Next, high schoolers toured our labs and got excited about our head-mounted virtual reality displays, student-created games, and visualizations. During lunch we played Snag'em and Table Tilt, two games we built to promote social networking and team building.
Home Bufferbloat Demonstration Videos
Authors: Gettys Jim
Published: February 2012

While bufferbloat is regularly present in computers and routers throughout the Internet, we frequently suffer its effects most directly at home--and it is at home where it can easily be investigated. The videos presented here demonstrate two instances of "typical" bufferbloat found in ordinary, modern broadband equipment and home routers. Under common loads, your real Internet "speed" can easily drop by a factor of ten due to bufferbloat.
Toll-Like Receptors in Ischaemia and Its Potential Role in the Pathophysiology of Muscle Damage in Critical Limb Ischaemia
Authors: Patel Hemanshu , Shaw Sidney G. , Shi-Wen Xu , Abraham David , Baker Daryll M. , Tsui Janice C. S.
Published: February 2012

Toll-like receptors (TLRs) are key receptors of the innate immune system which are expressed on immune and nonimmune cells. They are activated by both pathogen-associated molecular patterns and endogenous ligands. Activation of TLRs culminates in the release of proinflammatory cytokines, chemokines, and apoptosis. Ischaemia and ischaemia/reperfusion (I/R) injury are associated with significant inflammation and tissue damage. There is emerging evidence to suggest that TLRs are involved in mediating ischaemia-induced damage in several organs. Critical limb ischaemia (CLI) is the most severe form of peripheral arterial disease (PAD) and is associated with skeletal muscle damage and tissue loss; however its pathophysiology is poorly understood. This paper will underline the evidence implicating TLRs in the pathophysiology of cerebral, renal, hepatic, myocardial, and skeletal muscle ischaemia and I/R injury and discuss preliminary data that alludes to the potential role of TLRs in the pathophysiology of skeletal muscle damage in CLI.