bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Influence of Injection Timing and Diesel Replacement on LPG-Diesel Dual-Fuel Engine
Authors: Sudhir C. V. , Desai Vijay , Suresh Kumar Y. , Mohanan P.
Published: January 2009

Reducing the emissions and fuel consumption for IC engines are no longer the future goals; instead they are the demands of today. People are concerned about rising fuel costs and effects of emissions on the environment. The major contributor for the increased levels of pollutants is the Diesel engines. Diesel engine finds application in almost in all fields, including transportation sector such as buses, trucks, railway engines, etc. and in industries as power generating units. In the present work an attempt is made for effective utilization of diesel engine aiming for reduction in fuel consumption and smoke density. This is achieved by some minor modifications in diesel engine, so as to run the existing diesel engine as a LPG-Diesel dual-fuel engine with LPG (Liquefied Petroleum Gas) induction at air intake. The important aspect of LPG-Diesel dual-fuel engine is that it shows significant reduction in smoke density and improved brake thermal efficiency with reduced energy consumption. An existing 4-S, single cylinder, naturally aspirated, water-cooled, direct injection, CI engine test rig was used for the experimental purpose. With proper instrumentation the tests were conducted under various LPG flow rates, loads, and injection timings. The influence of the diesel replacement by LPG on smoke density, brake specific energy consumption and brake thermal efficiency were studied. The optimal diesel replacement pertaining to the maximum allowable LPG gas flow limits could be assessed with these experiments. The influence of the injection timing variation on the engine performance and smoke density were analyzed form the experimental results. It was also observed that beyond half load operation of the dual-fuel engine, the brake thermal efficiency increases with diesel replacement, and at full load up to 4% improvement was observed compared to full diesel operation. At full load reduction in smoke density up to 25–36% was observed compared to full diesel operation. At advance injection timing of 30°btdc the performance was better with lower emissions compared to normal and retarded injection timings.
High Pressure Diesel Engine Modeling
Authors: Baudille Riccardo , Bella Gino , Rotondi Rossella
Published: January 2009

In multi hole Diesel injectors, cavitation can offer advantages in the development on the fuel spray, because the primary atomization of the liquid fuel jet can be improved due to the enhanced turbulence. Several multi dimensional models of cavitating nozzle flow have been developed in order to provide information about the flow at the exit of a cavitating orifice. In this paper an analytical one-dimensional model, by Sarre et al. [1], to predict the flow conditions at the exit of a cavitating nozzle, is analyzed. The results obtained are compared with the ones obtained using the multi dimensional code Fluent in order to investigate the predictive capability of the one-dimensional code. The model provides initial conditions for multidimensional spray modeling: the effective injection velocity and the initial drop or injected liquid ‘blob’ size. The simulations were performed using an improved version of the KIVA3V code, in which an hybrid break up model, developed by the authors, is used and the results in terms of penetrations and global SMD are compared with the experimental ones. The one dimensional model predicts reasonable discharge coefficient for sharp injector geometry. Where the r/d ratio increases and the cavitation effects appear not clearly marked there are same discrepancies between the one dimensional and the multidimensional approach.
Ignition System Designed to Extend the Plug Life, and the Lean Limit in a Natural Gas Engine
Authors: Chan A. K. , Waters S. H.
Published: January 2009

An ignition system that is based on the alternating (AC) rather than the traditional direct (DC) current in the spark plug discharge has been developed at the Caterpillar Technical Center. This system can generate a long duration discharge with controllable power. It is believed that such an ignition system can provide both a leaner operating limit and a longer spark plug life than a traditional DC system due to the long discharge duration and the low discharge power. The AC ignition system has successfully been tested on a Caterpillar single cylinder G3500 natural gas engine to determine the effects on the engine performance, combustion characteristics and emissions. The test results indicate that while the AC ignition system has only a small impact on engine performance (with respect to a traditional DC system), it does extend the lean limit with lower NOx emissions. Evidences also show the potential of reduce spark plug electrode erosions from the low breakdown and sustaining discharge powers from the AC ignition system. This paper summarizes the prototype design and engine demonstration results of the AC ignition system.
Instantaneous Engine Speed Analysis for Cylinder Isolation in Multiple Misfire Events
Authors: Ponti Fabrizio
Published: January 2009

Misfire detection is a subject that has been deep studied during the last years and many methodologies have been developed for this purpose. Affordably detecting the misfire event and isolating the cylinder where the missing combustion took place can be considered a solved problem for engines with a limited number of cylinders. Misfire detection and in particular cylinder isolation is still challenging for engine operating conditions at very low load and high engine speed, for engines with a high number of cylinders, or when more than one misfire event is present within the same engine cycle (multiple misfire). In particular this last malfunctioning condition is very challenging, and its detection is enforced by the international regulations without requiring cylinder isolation, but only the number of misfiring cylinders. Many methodologies have been developed in the past based on the analysis of the instantaneous engine speed. The missing combustion effect on this signal is anyway very low when the number of cylinders is high and for engine operating conditions at low engine speed, giving rise to misdetection or false alarms as already mentioned. In addition when a misfire event takes place a torsional vibration is excited and shows up in the instantaneous engine speed waveform. If a multiple misfire occurs this torsional vibration is excited more than once in a very short time interval. The interaction among these successive vibrations can further generate false alarms or misdetection, and an increased complexity when dealing with cylinder isolation is necessary. The approach here presented permits enhancing existing misfire detection methods through optimized algorithm that allows correctly isolating the multiple misfiring cylinders over the entire engine operating range. This has been obtained by proper identifying the effect of the torsional vibration over the instantaneous engine speed. The identified waveform has been then used to filter out the torsional vibration effects in order to enlighten the effects of the missing combustions. In addition a proper instantaneous engine speed windowing has been introduced in order to increase the detection signal to noise ratio over the whole engine operating range. The integration of these two signal processing techniques has proven to be very effective on the engine investigated in this study, and it is easily extendible to other engine architectures. Particular care has been devoted to satisfy on-board implementation requirements in terms of memory allocation and computational power. The tests have been conducted on an L4 1.2 liter spark ignition engine mounted in a test cell. In-cylinder pressure signals have been acquired in order to validate the methodology here developed.
A Modelling Approach to the Design Optimization of Catalytic Converters of I.C. Engines
Authors: Chen Ming , Schirmer Karen
Published: January 2009

In this paper, a modelling approach to the design optimization of catalytic converters is presented. The first step of the optimization is the model-assisted sizing of catalysts. For a given inlet exhaust condition, a semi-empirical, experimentally calibrated, 0-D steady state catalyst model is employed to sort through a data base of catalysts under given restraints, yielding few successful candidates. Following this screening process, a 1-D transient plug-flow catalyst model is used to analyze the species concentrations and the temperature variation across the catalyst. The second step deals with the flow optimization of the catalyst converter under the given geometric restraints. A commercially available CFD package is employed to simulate isothermal flow and to evaluate flow uniformity characteristics in the catalytic converter. The substrate is modelled as porous media, where viscous and initial resistances are specified via empirical formula. With the help of the CFD tool, the flow in the converter can be optimized using appropriate boundary layer control methods. In a specific example, the effects of perforated plate on the flow separation in a wide-angle diffuser are demonstrated. This paper also addresses the issue of flow resistance of perforated plates.
Controlling Vibration of the Entire Engine Rotating System
Authors: Knox Kevin J.
Published: January 2009

Aggressive goals for reliability improvement and noise reduction in compression ignition engines require treatment of all the rotating components as a system. The complex interaction of these components limits the practicality of simulations. Yet, at the same time, the large number of possible designs precludes testing every option. This paper presents a study where simulation is used to characterize rotating components and identify the proper application of solutions, and testing is used to integrate the possibilities in an optimal fashion. The study is done on a heavy-duty compression ignition engine, and includes a fresh look at traditional components (torsional viscoelastic dampers) as well as some novel technologies (pendulums and squeeze dampers).
The Geislinger Gesilco Advanced Composite Coupling With High Misalignment Compensation Capability and Low Weight
Authors: Sigle Christof
Published: January 2009

Misalignment couplings for ship drive lines are installed between engine and gear or between gear and waterjet and transmit torque from one shaft to another while accommodating misalignment between the two shafts. The development process, the analysis and the in-service-experience of a new membrane type flexible coupling entirely made of advanced composite material are presented in this paper. The concept of this new coupling promises low mass, high misalignment capacity and good sound insulation compared to conventional couplings.
Three-Dimensional Analysis of Tribological Performance and Heat Transfer in Piston and Cylinder Liner System
Authors: Ye Xiaoming , Chen Guohua , Luo Maji , Jiang Yankun
Published: January 2009

A three-dimensional, hydrodynamic mixed lubrication model has been developed to investigate the frictional performance of piston ring and cylinder liner contact. The model is based on the average Reynolds equation and asperity contact approach with the considerations of surface roughness, rupture location, blowby through the piston ring pack and nonaxisymmetry in circumferential direction of cylinder liner. The equation has been solved cyclically using the finite difference method in a fully flooded inlet boundary condition and a flow-continuity Reynolds boundary condition for cavitation outlet zone. The oil film thickness, hydrodynamic pressure distribution, friction force and friction heat generated at the piston ring/cylinder liner interface are determined as the function of crank angle position. The results show that the shape of the cylinder liner (out-of-roundness) significantly affects the lubrication performance of the piston ring pack. A heat transfer model has been presented to evaluate the effects of friction heat on the temperatures of piston and cylinder liner system. The friction heat is added on the piston ring/cylinder liner interface as the flux boundary condition. The temperature fields of piston and cylinder liner system are acquired by the FEM, which reveal the distribution of the friction heat in this system. The results show that the friction heat mainly affects the temperature on the region near the top ring groove of the piston ring pack. The effect decreases at the region away from the top ring groove, especially at the piston skirt. The effect of friction heat on the temperature of cylinder liner is smaller than that of piston ring pack.
Turbocharger Power for Future Railway Applications
Authors: Doetl Robert , Pesten David-Austin , Bernard Olivier , Phillipsen Bent
Published: January 2009

The design requirements of exhaust gas turbochargers for diesel locomotive applications are becoming more stringent. Some of the major drivers are meeting emission regulations and power demands, whilst maintaining the required levels of reliability and serviceability. These increasingly demanding requirements are significantly impacting the design of modern diesel-electric locomotives. In order to achieve these sometimes conflicting requirements, appropriate technology needs to be employed to both the engine and turbocharger design. Given that there are a number of possibilities one has with the engine design, including fuel injection timing and equipment, valve timing, compression ratio etc., this paper will focus on turbocharging and the development cycle of ABB Turbo Systems Ltd. new TPR61 locomotive turbocharger. Starting with the demanding operating environment for locomotive turbochargers and market and regulatory requirements (increasing power, efficiency and reliability — decreasing emissions and bsfc), the impact these have on turbocharger design will be shown. Based on proven ABB technology, the TPR61 is a special derivative, targeted for turbocharging locomotive diesel engines with ratings of up to 4000 hp per turbocharger or over 6000 hp locomotives with a twin turbocharger solution. For future requirements, the compressor stage development potential and also Variable Turbine Geometry (VTG) will be discussed, how it can be applied and the benefits it can bring to locomotive applications of the future.
Friction Teardown Data From Motored Engine Tests on Light Duty Automotive Diesel Engines at Low Temperatures and Speeds
Authors: Shayler Paul J. , Leong David K. W. , Murphy Michael
Published: January 2009

Friction data have been acquired from motored engine tests on four designs of light duty automotive diesel engines. The engines were all four-cylinder designs with a swept capacity around two litres (1.8l-2.2l). These are typically used in the small and medium car sectors of the European market. The test programme was aligned to cold start and warm-up conditions. The data cover temperatures at the start of motoring of −20°C and above, and motoring speeds covering 200 rev/min – 1000 rev/min. Most tests were carried out using 10W/30 oil. The breakdowns separated piston assembly, crankshaft assembly, valve train and auxiliary component contributions to friction mean effective pressure (fmep), from −20°C upwards, under quasi-steady thermal conditions. Under these conditions, during warm-up the variation of engine fmep exhibits a simple power law dependence on oil viscosity evaluated at the current bulk oil temperature. The dependence of component contributions on oil viscosity has been examined. The empirical coefficients and functions used in the engine friction model developed by Patton, Nitschke and Heywood (SAE 890836) have been modified to give an improved fit to the low speed, low temperature test data, whilst limiting the effect on predictions for fully-warm conditions. The quality of the predictions is illustrated. The degree to which the effect of design detail can be predicted and the scope to reduce friction levels through design are discussed.
Water Addition in Diesel Engine Intake for NOx Reduction: Comparison of Modeling and Experiments
Authors: Tamma Bhaskar , Alvarez Juan Carlos , Simon Aaron J.
Published: January 2009

Reduction in emissions, especially NOx has been the main study of various engine researchers in the light of stringent emission norms. To reduce the time and cost involved in testing these technologies, engine thermodynamic cycle predictive tools are used. The present work uses one such predictive tool (GT Power from Gamma Technologies) for predicting the influence of water addition in a turbocharged 6-cylinder diesel engine intake on engine performance and NOx emissions. The experiments for comparison with modeling included the introduction of liquid water in the engine intake stream, between the compressor and intercooler ranging from 0 to 100% of fuel flow rate. NOx emission reduced linearly with water addition with reduction of 63% with less than 1% penalty on fuel efficiency at 100% water addition. The GT Power model predicted the performance within 5% of experimental data and NOx emission within 10% of the experiments.
Design of a Compression Pressurized Air Blast Direct Injection System for Small Displacement Two-Stroke Engines
Authors: Gitano-Briggs Horizon , Kirkpatrick Allan , Wilson Bryan
Published: January 2009

In two-stroke engines replacement of carburetors with direct fuel injection systems greatly reduces engine emissions and fuel consumption by eliminating fuel short-circuiting. Air-blast direct fuel injection using a dedicated air pump has been successfully applied to both two- and four-stroke engines. In this study we re-examine the design of a low cost compression pressurized direct injection system. This system uses gases extracted from the combustion chamber during the compression stroke to supply pressure for the air blast injection, thus eliminating the air pump [1,2]. Gases, predominantly scavenging air, are transferred to a mixing cavity from the combustion chamber via a small (5mm diameter) solenoid poppet valve as the piston rises during the compression stroke. Proper functioning of the system requires careful optimization of the mixing cavity size and the blast valve timing to ensure adequate mixing cavity pressure and fuel atomization. To assist in the optimization of these design parameters a one-dimensional fluid dynamics model has been developed. Parameter sensitivity studies were carried out using the model to determine the optimum cavity size, blast valve timing, and fuel injection duration. These parameters were optimized over a wide range of engine speeds and throttle settings. Results show that a mixing cavity pressure of 500 kPa is attainable over the range of 1000 to 6000 rpm, from closed throttle to wide open throttle (WOT) without cavity pressurization encroaching into the ignition regime. Fuel maps and valve timings are presented and results are contrasted with the carbureted case, showing improved fuel efficiency and emissions for the direct injection system. These data will be used in the design of a physical demonstration engine.
Development and Commercialization of Large Stationary Engines Utilizing Low BTU Fuel Containing H2/CO
Authors: Toombs E. , Stowell T. , Austin N. , Danyluk P.
Published: January 2009

In 1996 Cabot Corporation begun development of engines capable of burning the off-gas from a pyrolysis process used to make carbon black. The fuel gas comes off the process at near atmospheric pressure, high temperature, and saturated with water. After de-watering the gas composition was approximately 16–20% Hydrogen, 16–20% Carbon Monoxide, 1–3% Sulfur compounds and the rest Nitrogen and water. Dewatered heating value of the fuel was around 3350–3720 kJ/nm3. Many engine configurations including both spark and oil ignited were evaluated to utilize this low energy fuel. The paper describes the development cycle and the early experience at commercialization at three sites.
Near Zero Emission Internal Combustion Engines
Authors: Wade W. R.
Published: January 2009

Near zero emission levels from an internal combustion engine were achieved to meet California’s Partial Zero Emission Vehicle (PZEV) requirement beginning with the 2003 model year. Using a systems approach, the tailpipe emission requirements for the PZEV standard were cascaded to the base engine design, control system and catalyst system to achieve the engine-out emissions and catalyst efficiency requirements. Major emphasis was on low emission cold starting and rapid catalyst light-off. Overall catalyst efficiencies of over 99.9% for hydrocarbon emissions, 98.8% for carbon monoxide emissions and 99.5% for oxides of nitrogen emissions were achieved over 150K miles. In addition to achieving near zero levels for tailpipe emissions, on-board diagnostics were developed to detect malfunctions in the near zero emission control systems. Likewise, a near zero evaporative emission system was developed. Future PZEV developments are described as more vehicles will be required to meet the PZEV requirements in the future.
Synthesis and Antimalarial Activities of Cyclen 4-Aminoquinoline Analogs
Authors: Khan M. O. Faruk , Levi Mark S. , Tekwani Babu L. , Khan Shabana I. , Kimura Eiichi , Borne Ronald F.
Published: January 2009

In an attempt to augment the efficacy of 7-chloro 4-aminoquinoline analogs and also to overcome resistance to antimalarial agents, we synthesized three cyclen (1,4,7,10-tetraazacyclododecane) analogs of chloroquine [a bisquinoline derivative, 7-chloro-4-(1,4,7,10-tetraaza-cyclododec-1-yl)-quinoline HBr, and a 7-chloro-4-(1,4,7,10-tetraaza-cyclododec-1-yl)-quinoline-Zn
2+
complex]. The bisquinoline displays the most potent in vitro and in vivo antimalarial activities. It displays 50% inhibitory concentrations (IC
50
s) of 7.5 nM against the D6 (chloroquine-sensitive) clone of
Plasmodium falciparum
and 19.2 nM against the W2 (chloroquine-resistant) clone, which are comparable to those of artemisinin (10.6 and 5.0 nM, respectively) and lower than those of chloroquine (10.7 and 87.2 nM, respectively), without any evidence of cytotoxicity to mammalian cells, indicating a high selectivity index (>1,333 against D6 clone and >521 against W2 clone). Potent antimalarial activities of the bisquinoline against chloroquine- and mefloquine-resistant strains of
P. falciparum
were also confirmed by in vitro [
3
H]hypoxanthine incorporation assay. The in vivo antimalarial activity of the bisquinoline, as determined in
P. berghei
-infected mice, is comparable to that of chloroquine (50% effective dose, ≤1.1 mg/kg when given orally); no apparent toxicity has been observed up to the highest dose tested (3 × 30 mg/kg). The bisquinoline inhibits in vitro hemozoin (β-hematin) formation with an IC
50
of 1.1 μM, which is about 10-fold more potent than chloroquine (IC
50
9.5 μM). Overall, this article describes the discovery of a new class of cyclen 4-aminoquinoline analogs as potent antimalarial drugs.
Relationship between Susceptibility to Daptomycin In Vitro and Activity In Vivo in a Rabbit Model of Aortic Valve Endocarditis
Authors: Chambers H. F. , Basuino L. , Diep B. A. , Steenbergen J. , Zhang S. , Tattevin P. , Alder J.
Published: January 2009

Daptomycin is approved for treatment of
Staphylococcus aureus
bacteremia and right-sided endocarditis. Increases in daptomycin MICs have been associated with failure. A rabbit model of aortic valve endocarditis was used to determine whether MIC correlates with activity in vivo and whether a higher daptomycin dose can improve efficacy. Two related clinical
S. aureus
strains, one with a daptomycin MIC of 0.5 μg/ml and the other with a MIC of 2 μg/ml, were used to establish aortic valve endocarditis in rabbits. Daptomycin was administered once a day for 4 days at 12 mg/kg of body weight or 18 mg/kg to simulate doses in humans of 6 mg/kg and 10 mg/kg, respectively. Endocardial vegetations, spleens, and kidneys were harvested and quantitatively cultured. The strain with a MIC of 2 μg/ml had a survival advantage over the strain with a MIC of 0.5 μg/ml with >100 times more organisms of the former in endocardial vegetations at the 12-mg/kg dose in a dual-infection model. Both the 12-mg/kg dose and the 18-mg/kg dose completely eradicated the strain with a MIC of 0.5 from vegetations, spleens, and kidneys. The 12-mg/kg dose was ineffective against the strain with a MIC of 2 in vegetations; the 18-mg/kg dose produced a reduction of 3 log
10
units in CFU in vegetations compared to the controls, although in no rabbit were organisms completely eliminated. Increasing the dose of daptomycin may improve its efficacy for infections caused by strains with reduced daptomycin susceptibility.
Activity of Posaconazole and Other Antifungal Agents against
Mucorales
Strains Identified by Sequencing of Internal Transcribed Spacers
Authors: Alastruey-Izquierdo Ana , Castelli Maria Victoria , Cuesta Isabel , Monzon Araceli , Cuenca-Estrella Manuel , Rodriguez-Tudela Juan Luis
Published: January 2009

The antifungal susceptibility profiles of 77 clinical strains of
Mucorales
species, identified by internal transcribed spacer sequencing, were analyzed. MICs obtained at 24 and 48 h were compared. Amphotericin B was the most active agent against all isolates, except for
Cunninghamella
and
Apophysomyces
isolates. Posaconazole also showed good activity for all species but
Cunninghamella bertholletiae
. Voriconazole had no activity against any of the fungi tested. Terbinafine showed good activity, except for
Rhizopus oryzae
,
Mucor circinelloides
, and
Rhizomucor variabilis
isolates.
Detection of Human Immunodeficiency Virus (HIV) Type 1 M184V and K103N Minority Variants in Patients with Primary HIV Infection
Authors: Toni Thomas A. , Asahchop Eugene L. , Moisi Daniela , Ntemgwa Michel , Oliveira Maureen , Masquelier Bernard , Brenner Bluma G. , Wainberg Mark A.
Published: January 2009

We used an allele-specific real-time PCR assay to explore the presence of K103N and M184V minority species among primary human immunodeficiency virus (HIV) infections and their potential influence in HIV transmission. Thirty randomly chosen antiretroviral drug-naive patients lacking both the K103N and the M184V mutations as determined by conventional sequencing methods were studied, and K103N and M184V viral minority species were found in three (10%) and four (11%) patients, respectively.
Mucor circinelloides
as a Cause of Invasive Maxillofacial Zygomycosis: an Emerging Dimorphic Pathogen with Reduced Susceptibility to Posaconazole
Authors: Khan Zia U. , Ahmad Suhail , Brazda Arnost , Chandy Rachel
Published: January 2009

A case of maxillofacial zygomycosis caused by
Mucor circinelloides
, identified by phenotypic and molecular methods and treated successfully with liposomal amphotericin B (AmBisome) and surgical debridement, is described. The isolate was resistant to posaconazole. This report underscores the importance of prior susceptibility testing of zygomycetes to guide therapy with the most effective antifungal agent for an improved prognosis.
Use of Sloppy Molecular Beacon Probes for Identification of Mycobacterial Species
Authors: El-Hajj Hiyam H. , Marras Salvatore A. E. , Tyagi Sanjay , Shashkina Elena , Kamboj Mini , Kiehn Timothy E. , Glickman Michael S. , Kramer Fred Russell , Alland David
Published: January 2009

We report here the use of novel “sloppy” molecular beacon probes in homogeneous PCR screening assays in which thermal denaturation of the resulting probe-amplicon hybrids provides a characteristic set of amplicon melting temperature (

T
m

) values that identify which species is present in a sample. Sloppy molecular beacons possess relatively long probe sequences, enabling them to form hybrids with amplicons from many different species despite the presence of mismatched base pairs. By using four sloppy molecular beacons, each possessing a different probe sequence and each labeled with a differently colored fluorophore, four different

T
m

values can be determined simultaneously. We tested this technique with 27 different species of mycobacteria and found that each species generates a unique, highly reproducible signature that is unaffected by the initial bacterial DNA concentration. Utilizing this general paradigm, screening assays can be designed for the identification of a wide range of species.
Impact of Blood Cultures Drawn by Phlebotomy on Contamination Rates and Health Care Costs in a Hospital Emergency Department
Authors: Gander Rita M. , Byrd Linda , DeCrescenzo Michael , Hirany Shaina , Bowen Michelle , Baughman Judy
Published: January 2009

We conducted a prospective comparison of blood culture contamination rates associated with dedicated phlebotomists and nonphlebotomy staff in the emergency department (ED) at Parkland Memorial Hospital in Dallas, TX. In addition, hospital charges and lengths of stay were determined for patients with negative, false-positive, and true-positive blood culture results. A total of 5,432 blood culture collections from two ED areas, the western wing of the ED (ED west) and the nonwestern wing of the ED (ED nonwest), were evaluated over a 13-month period. Phlebotomists drew 2,012 (55%) of the blood cultures in ED west while nonphlebotomy staff drew 1,650 (45%) in ED west and 1,770 (100%) in ED nonwest. The contamination rates of blood cultures collected by phlebotomists were significantly lower than those collected by nonphlebotomists in ED west (62/2,012 [3.1%] versus 122/1,650 [7.4%];
P
< 0.001). Similar results were observed when rates between phlebotomists in ED west and nonphlebotomy staff in ED nonwest were compared (62/2,012 [3.1%] versus 100/1,770 [5.6%];
P
< 0.001). Comparison of median patient charges between negative and false-positive episodes ($18,752 versus $27,472) showed $8,720 in additional charges per contamination event while the median length of stay increased marginally from 4 to 5 days. By utilizing phlebotomists to collect blood cultures in the ED, contamination rates were lowered to recommended levels, with projected reductions in patient charges of approximately $4.1 million per year.
ortho-Effect on the acid-catalyzed hydration of 2-substituted α-methylstyrenes
Authors: Prusek Ondřej , Bureš Filip , Pytela Oldřich
Published: January 2009

α-Methylstyrene and nine ortho-substituted analogs have been synthesized and the kinetics of their acid-catalyzed hydration in aqueous solutions of sulfuric acid at 25 °C have been investigated. The kinetic acidity function HS has been constructed from the dependence of the observed rate constants kobs on the sulfuric acid concentration. The catalytic rate constants of the acid-catalyzed hydration kortho have been calculated as well. The identical shape of the kinetic acidity functions for ortho- and para-derivatives confirms what the consistent mechanism A-SE2 of the acid-catalyzed hydration has already proved for the corresponding para-derivatives. The A-SE2 mechanism involves a rate-determining proton transfer of the hydrated proton to the substrate. From the dependence of the catalytic rate constants of the ortho-derivatives on the catalytic rate constants of the para-derivatives, it is seen that the logarithm of the catalytic rate constant for hydrogen as a substituent is markedly out of the range of the other substituents and, simultaneously, that the ortho-derivatives react significantly slower than the corresponding para-derivatives. In correlation with the substitent constants σp+, a reaction constant of ρ+ = –1.45 have been found. The constant is, in absolute value, considerably smaller than that for para-derivatives (ρ+ = –3.07). In parallel, the steric effects are enforced more significantly for the monoatomic substituents (slope of the Charton’s constants 3.92) than for substituents including more atoms (slope of the Charton’s constants 2.09). A small value of the reaction constant ρ+ has been elucidated due to the lower conjugation between the reaction centre and the benzene ring as a consequence of the geometric twist of the reaction centre out of the main aromatic plane accompanied by fading mesomeric interaction between the reaction centre and the substituents attached to the benzene ring. The isopropyl group in the carbocation is twisted less out of the aromatic plane for the monoatomic substituents and, therefore, also a small difference in the bulk of substituents has considerable steric influence on the conjugation between the carbocation and the benzene ring bearing substituents. On the contrary, the isopropyl group in the carbocations with polyatomic substituents is twisted to such a degree that changes in the bulk of substituents affect the resonant stabilization negligibly. Similar conclusions were also deduced from the correlations of the substitution constants σI and σR+.
HIV-1-mediated delivery of a short hairpin RNA targeting vascular endothelial growth factor in human retinal pigment epithelium cells
Authors: Lombardi G , Calistri A , Curtarello M , Giudice G L , Piermarocchi S , Prosdocimo G , Palù G , Parolin C
Published: January 2009

Background:

Vascular endothelial growth factor (VEGF) has been shown to play a major role in the pathological neovascularisation that occurs in degenerative retinal diseases like age-related macular degeneration (AMD). Although several approaches to attenuate VEGF show significant promise, repeated treatments are required to achieve therapeutic benefits. As lentiviruses efficiently and stably infect resting cells, a human immunodeficiency virus type 1 (HIV-1)-based vector was used for the delivery and long-term endogenous expression of a short hairpin RNA (shRNA) specific for VEGF in postmitotic human retinal pigment epithelium (RPE) cells.

Methods:

An HIV-1 vector expressing a shRNA targeting VEGF was developed and adopted to transduce RPE cell cultures, in both normoxic and hypoxic conditions in vitro. Intracellular VEGF expression was analysed by western blotting, and the release of VEGF in culture supernatants was determined by ELISA.

Results:

At least 90% of RPE cells were successfully transduced by HIV-1 virions. Inhibition of VEGF expression and reduction by 95% of VEGF release in transduced cells were achieved. Moreover, shRNA-VEGF effectively and specifically prevented hypoxia-induced VEGF upregulation.

Conclusion:

HIV-1-mediated delivery of a shRNA-VEGF leading to gene expression knockdown could represent a novel therapeutic strategy against neovascularisation-related eye diseases.
Temporal Shifts in Microbial Communities in Nonpregnant African-American Women with and without Bacterial Vaginosis
Authors: Wertz John , Isaacs-Cosgrove Natasha , Holzman Claudia , Marsh Terence L.
Published: January 2009

Bacterial vaginosis (BV) has been described as an increase in the number of anaerobic and facultatively anaerobic bacteria relative to lactobacilli in the vaginal tract. Several undesirable consequences of this community shift can include irritation, white discharge, an elevated pH, and increased susceptibility to sexually transmitted infections. While the etiology of the condition remains ill defined, BV has been associated with adverse reproductive and pregnancy outcomes. In order to describe the structure of vaginal communities over time we determined the phylogenetic composition of vaginal communities from seven women sampled at multiple points using 16S rRNA gene sequencing. We found that women with no evidence of BV had communities dominated by lactobacilli that appeared stable over our sampling periods while those with BV had greater diversity and decreased stability overtime. In addition, onlyLactobacillus inerswas found in BV positive communities.
Adhesion of Human ProbioticLactobacillus rhamnosusto Cervical and Vaginal Cells and Interaction with Vaginosis-Associated Pathogens
Authors: Coudeyras Sophie , Jugie Gwendoline , Vermerie Marion , Forestier Christiane
Published: January 2009

Objectives. The ability of a probioticLactobacillus rhamnosusstrain (Lcr35) to adhere to cervical and vaginal cells and to affect the viability of two main vaginosis-associated pathogens,Prevotella bivia, Gardnerella vaginalis, as well asCandida albicanswas investigated.Methods. Adhesion ability was determined in vitro with immortalized epithelial cells from the endocervix, ectocervix, and vagina. Coculture experiments were performed to count viable pathogens cells in the presence of Lcr35.Results. Lcr35 was able to specifically and rapidly adhere to the three cell lines. In coculture assays, a decrease in pathogen cell division rate was observed as from 4 hours of incubation and bactericidal activity after a longer period of incubation, mostly withP. bivia.Conclusion. The ability of Lcr35 to adhere to cervicovaginal cells and its antagonist activities against vaginosis-associated pathogens suggest that this probiotic strain is a promising candidate for use in therapy.
Analysis of a Delayed SIR Model with Nonlinear Incidence Rate
Authors: Zhang Jin-Zhu , Jin Zhen , Liu Quan-Xing , Zhang Zhi-Yu
Published: January 2009

An SIR epidemic model with incubation time and
saturated incidence rate is formulated, where the susceptibles are
assumed to satisfy the logistic equation and the incidence term is
of saturated form with the susceptible. The threshold value
ℜ0 determining whether the disease dies out is found. The
results obtained show that the global dynamics are completely
determined by the values of the threshold value ℜ0 and time
delay (i.e., incubation time length). If ℜ0 is less than one,
the disease‐free equilibrium is globally asymptotically stable and
the disease always dies out, while if it exceeds one there will be
an endemic. By using the time delay as a bifurcation parameter, the
local stability for the endemic equilibrium is investigated, and the
conditions with respect to the system to be absolutely stable and
conditionally stable are derived. Numerical results demonstrate that
the system with time delay exhibits rich complex dynamics, such as
quasiperiodic and chaotic patterns.
An Erlang Loss Queue with Time‐Phased Batch Arrivals as a Model for Traffic Control in Communication Networks
Authors: Lee Moon Ho , Dudin Sergey A.
Published: January 2009

A multiserver queueing model that does not have a buffer but has batch
arrival of customers is considered. In contrast to the standard batch arrival,
in which the entire batch arrives at the system during a single epoch, we
assume that the customers of a batch (flow) arrive individually in exponentially
distributed times. The service time is exponentially distributed.
Flows arrive according to a stationary Poisson arrival process. The flow size
distribution is geometric. The number of flows that can be simultaneously
admitted to the system is under control. The loss of any customer from
an admitted flow, with a fixed probability, implies termination of the flow
arrival. Analysis of the sojourn time and loss probability of an arbitrary
flow is performed.
The Role of PPARγReceptors and Leukotriene B4Receptors in Mediating the Effects of LY293111 in Pancreatic Cancer
Authors: Adrian Thomas E. , Hennig Rene , Friess Helmut , Ding Xianzhong
Published: January 2009

Pancreatic cancer is a devastating disease in which current therapies are inadequate. Separate lines of research have identified the 5‐lipoxygenase/leukotriene B4receptor pathway and the PPARγpathway as potential targets for prevention or treatment of this disease. LY293111 was originally designed as a potent leukotriene B4receptor antagonist for treatment of inflammatory conditions. LY293111 was also known to have inhibitory effects on 5‐lipoxygenase, which is upstream of the production of leukotrienes. LY293111 was shown to have potent anticancer effects in pancreatic cancer and several other solid malignancies, where it caused cell cycle arrest and marked apoptosis. Subsequently, it came to light that LY293111 exhibited PPARγagonist activity in addition to its effects on the 5‐lipoxygenase pathway. This raises the question of which of the two targets is of greatest importance with regard to the anticancer effects of this agent. The evidence to date is not conclusive, but suggests that the effects of LY293111 may be mediated by both LTB4receptors and PPARγ.
Infection with Hepatitis C Virus among HIV-Infected Pregnant Women in Thailand
Authors: Jamieson Denise J. , Skunodom Natapakwa , Chaowanachan Thanyanan , Roongpisuthipong Anuvat , Bower William A. , Chotpitayasunondh Tawee , Bhanich Supapol Wendy , Kuhnert Wendi L. , Siriwasin Wimol , Wiener Jeffrey , Chearskul Sanay , McConnell Michelle S. , Shaffer Nathan
Published: January 2009

Objective. The purpose of this study was to describe the epidemiology of coinfection with hepatitis C virus (HCV) and HIV among a cohort of pregnant Thai women.Methods. Samples from 1771 pregnant women enrolled in three vertical transmission of HIV studies in Bangkok, Thailand, were tested for HCV.Results. Among HIV-infected pregnant women, HCV seroprevelance was 3.8% and the active HCV infection rate was 3.0%. Among HIV-uninfected pregnant women, 0.3% were HCV-infected. Intravenous drug use by the woman was the factor most strongly associated with HCV seropositivity. Among 48 infants tested for HCV who were born to HIV/HCV coinfected women, two infants were HCV infected for an HCV transmission rate of 4.2% (95% 0.51–14.25%).Conclusions. HCV seroprevalence and perinatal transmission rates were low among this Thai cohort of HIV-infected pregnant women.
Morphological Changes of Gingiva in Streptozotocin Diabetic Rats
Authors: Tesseromatis C. , Kotsiou A. , Parara H. , Vairaktaris E. , Tsamouri M.
Published: January 2009

Gingivitis and periodontitis are chronic bacterial diseases of the underlying and surrounding tooth tissues. Diabetes mellitus is responsible for tooth deprivation both by decay and periodontal disease. The streptozotocin-induced diabetes results in a diabetic status in experimental animals similar to that observed in diabetes patients. The aim of the study was to investigate the relationship between the gingival lesions and the microangiopathy changes in streptozotocin-induced diabetes mellitus. Forty male Wistar rats were divided into two groups (control and experimental). Diabetes mellitus was induced by 45 mg/kg IV streptozotocin. The histological investigation of the marginal gingival and the relevant gingival papilla showed inflammation of the lamina propria and the squamous epithelium as well as marked thickness of the arteriole in the diabetic group, but no changes were observed in the control group. The results suggested a probable application of a routine gingival histological investigation in diabetic patients in order to control the progress of disease complications. It may be concluded that histological gingival investigation can be used as a routine assay for the control of the diabetic disease and prevention of its complications.
Impact of Mild Hypertension on Left Atrial Size and Function
Authors: Eshoo Suzanne , Ross David L. , Thomas Liza
Published: January 2009

Background—

Left atrial (LA) enlargement has been documented to occur in moderate and severe hypertension.

Methods and Results—

One hundred twelve mild hypertension patients were prospectively recruited and compared with 198 healthy volunteers. All recruits had a transthoracic echocardiogram. Maximum LA biplane volume, minimum LA biplane volume, and pre ‘p’-LA biplane volume were measured, and left atrial passive, active emptying, and conduit volumes were calculated at baseline and in a subgroup of patients after 12 months. After adjusting for age, gender, and body mass index, maximum LA biplane volume, pre ‘p’-LA biplane volume, and their indexed volumes were increased in the hypertension group. Active emptying volume and fraction were significantly increased in the hypertension group, with no change in conduit and passive volumes. Subgroup analysis comparing hypertensives with normal/mildly increased left ventricular mass (group 1) with those with moderate/severely increased left ventricular mass (group 2) at baseline demonstrated that maximum LA biplane volume (62.8�17.9 mL versus 45.4�13.7 mL;
P
<0.001) was significantly increased in group 2. Active emptying volume was also increased.

Conclusion—

Even mild hypertension seems to be associated with a reduction in early diastolic filling. This results in augmented late left ventricular diastolic filling due to active atrial contraction and may be the mechanism for the increase in left atrial size.
Apical Rotation Assessed by Speckle-Tracking Echocardiography as an Index of Global Left Ventricular Contractility
Authors: Kim Won-Jang , Lee Byeong Han , Kim Yun Jeong , Kang Jee Hye , Jung Yoo Jin , Song Jong-Min , Kang Duk-Hyun , Song Jae-Kwan
Published: January 2009

Background—

Left ventricular (LV) apical rotation and twist can be estimated noninvasively by speckle-tracking echocardiography (STE). In this study, we tested whether apical rotation is an accurate index of LV contractility.

Methods and Results—

We measured LV basal and apical rotation by STE in 11 open-chest anesthetized mongrel dogs under 8 different inotropic stages before and after ligation of either left anterior descending (n=6) or circumflex coronary artery (n=5). We measured LV pressure simultaneously with a high-fidelity pressure catheter and calculated LV ejection fraction (EF) with the biplane Simpson method and 2D echocardiography. Maximal positive dP/dt (dP/dt
max
) was used as the gold standard measurement of LV contractility. We compared LV twist and apical rotation and EF against dP/dt
max
by linear mixed model. LV apical rotation and twist showed dose-dependent increases and decreases after dobutamine and esmolol infusion, respectively. However, basal rotation did not change significantly during different inotropic conditions. There was a stronger association between dP/dt
max
and LV twist (
R
2
=0.747,
P
<0.001) and apical rotation (
R
2
=0.726,
P
<0.001) than between dP/dt
max
and EF (
R
2
=0.408,
P
<0.001), and this trend was more apparent with coronary ligation irrespective of the ligation site. There was also a high association between dP/dt
max
and apical rotation alone, both with (
R
2
=0.805,
P
<0.001) and without (
R
2
=0.748,
P
<0.001) coronary ligation. Apical rotation alone showed comparable accuracy to LV twist. Apical rotational velocity also showed a high association with dP/dt
max
(
R
2
=0.669,
P
<0.001) and LV twist (
R
2
=0.892,
P
<0.001).

Conclusions—

Apical rotation assessed by STE is an effective noninvasive index of global LV contractility and is more closely related to dP/dt
max
than LV EF.