bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Gear Tooth Stresses by Finite Element Method
Authors: Filiz I. Huseyin , Eyercioglu O.
Published: February 2008

Stresses developed in the root fillet of the spur gear tooth due to static load are evaluated by using the finite element method. The method is automated with a computer program with which the effects of module, contact ratio, fillet radius, pressure angle and teeth numbers of driving and driven gears are evaluated. The results are compared with previous studies. The formula which gives the closest results to this study is presented.
Mating of Rigid Parts by a Manipulator With Its Own Compliance
Authors: Leu M. C. , Jia Y. L.
Published: February 2008

In most assembly tasks involving mating of parts, industrial robots are not equipped with special compliant devices such as a remote center compliant hand. It is useful to know how the mating force and part movement are affected by assembly compliance, which depends upon robot configuration, and by other assembly parameters such as initial position errors, clearance between mating parts, etc. Such knowledge is helpful to the design of the layout of an assembly cell, specification of robot accuracy, specification of manufacturing tolerance, and so on. This paper derives the mating force and part movement in the mating of rigid cylindrical parts by an industrial manipulator with its own compliance, using a planar peg-in-hole insertion model. The derived mathematical relations are experimentally verified by performing insertion tests with a SCARA-type robot.
Evaluation of Drilled Hole Quality in Printed Circuit Boards
Authors: Srinivasan M. N. , Hough C. L. , Bolton R. W. , Davis F. M.
Published: February 2008

The effect of drilling speed and the chip load on the hole quality in a printed circuit board was investigated. The hole defects considered were smear, burr, nail heading and void. Holes drilled with different combinations of the speed and chip load were sectioned and examined using a scanning electron microscope to identify and quantify the defects. Each defect was related to the drilling variables in order to explain the reason for its formation and discuss the broad trends in the relationships.
A Slip-Line Field Model for the Determination of Chip Curl Radius
Authors: Liu X. D. , Lee L. C. , Lam K. Y.
Published: February 2008

A slip-line field model is presented for the determination of the chip curl radius when cutting with a grooved restricted contact tool. The calculated values are found to provide a good approximation, especially for larger uncut chip thicknesses. The calculated results are consistently lower than the measured ones due to the elastic recovery of the chip after leaving the groove.
Automatic Runner Balancing of Injection Molds Using Flow Simulation
Authors: Kim B. H. , Ramesh M. C.
Published: February 2008

The objective of this paper is to present a methodology for automatically balancing multi-cavity injection molds with the aid of flow simulation. After the runner and cavity layout has been designed, the methodology adjusts runner and gate sizes iteratively based on the outputs of flow analysis. This methodology also ensures that the runner sizes in the final design are machinable. To illustrate this methodology, two examples are used wherein a 20-cavity mold and a 3-cavity mold are modeled and filling of all the cavities at the same time in both cases is achieved. In the case of the 20-cavity mold, the effect of changes in the processing conditions on the balance of the flow is also studied using a 33-factorial test. The examples indicate that the described methodology can be used effectively to balance runner systems for multi-cavity molds.
Characteristics of Abrasive Waterjet Generated Surfaces and Effects of Cutting Parameters and Structure Vibration
Authors: Chao J. , Zhou G. , Leu M. C. , Geskin E.
Published: February 2008

We use three-dimensional surface topography analysis for evaluating waterjet generated surfaces. The waterjet generated surface is separated into smooth and striation zones, where striation influence is negligible in the smooth zone. It is found that the smooth zone has a random, moderately isotropic texture, with the height distribution nearly Gaussian. The effects of cutting speed, depth of cut, and abrasive size on the surface roughness are studied for the smooth zone and striation zone separately. This provides useful information for controlling process parameters to obtain smooth finished surfaces. Spectral analysis is used to investigate the surface striation and machine structure vibration. It is found that forced vibration of the mechanical structure strongly influences striations generated in the waterjet machining system.
A Dual-Mechanism Approach to the Prediction of Machining Forces, Part 1: Model Development
Authors: Endres W. J. , DeVor R. E. , Kapoor S. G.
Published: February 2008

A cutting-process model addressing the chip removal and edge ploughing mechanisms separately yet simultaneously is presented. The model is developed such that it is readily applicable in an industrial setting, its coefficients have physical meaning, and it can be calibrated with a concise quantity of orthogonal cutting data. The total cutting and thrust forces are each the summation of its individual components acting on the rake face and clearance face. These components are calculated using the rake and effective clearance angles from the normal and friction forces acting on each of these tool surfaces. These normal and friction forces are calculated by the chip removal and edge ploughing portions of the model, respectively, using four empirical coefficients. To calculate the clearance face forces, the interference volume is required, the calculation of which is based on a geometrical representation of the clearance face interference region. This representation is characterized in part by the depth of tool penetration, which is influenced by thermal energy generation and is therefore determined using a fifth empirical model.
A Dual-Mechanism Approach to the Prediction of Machining Forces, Part 2: Calibration and Validation
Authors: Endres W. J. , DeVor R. E. , Kapoor S. G.
Published: February 2008

The Dual-Mechanism Machining Force Model (DMMFM) developed in Part 1 of this paper is calibrated through a specially developed algorithm, then validated. The calibration results are used to study the total machining force predictive capabilities of both the traditional lumped shearing model and the DMMFM. It is shown that the Dual-Mechanism Approach contributes greatly to our ability to both physically explain the trends in the machining force data and to understand their implications. This is achieved through an interpretation of the individual rake face and clearance face forces that are predicted using the DMMFM. The interpretation is based on the relations of these rake face and clearance face forces to the process inputs resulting from their effects on the DMMFM coefficients through thermal energy generation and temperature, shear-strain level and shear-strain rate. Some implications of the knowledge of the individual rake face and clearance face forces, as predicted by the DMMFM, are also discussed.
Analysis of Transient Temperatures in Grinding
Authors: Guo C. , Malkin S.
Published: February 2008

Temperatures generated in the workpiece during straight surface plunge grinding follow a transient behavior as the grinding wheel engages with and disengages from the workpiece, and throughout the entire grinding pass for workpieces which are shorter than needed to reach a quasi-steady state condition. In the present paper, a thermal model is developed for the transient temperature distribution under regular and creep-feed grinding conditions. Numerical results obtained using a finite difference method indicate that the workpiece temperature rises rapidly during initial wheel-workpiece engagement (cut in), subsequently reaches a quasi-steady state value if the workpiece is sufficiently long, and increases still further during final wheel-workpiece disengagement (cut out) as workpiece material is suddenly unavailable to dissipate heat. Cooling by a nozzle directed at the end face of the workpiece should significantly reduce the temperature rise during cut out.
Material Properties in Abrasive-Waterjet Machining
Authors: Hashish M.
Published: February 2008

The abrasive-waterjet (AWJ) machining process is a controlled erosive wear process where the abrasive cutting agents are focused in a narrow beam. The beam-material interaction process constitutes more than one mode, the most dominant of which are the cutting wear mode and the deformation wear mode. The cutting wear mode occurs at the top of the kerf due to shallow angles of impact and results in a steady-state interface. The material hardness (H) or Vicker’s hardness number is the most relevant material property to this mode of interaction. The deformation wear mode occurs below the cutting wear mode due to large angles of impact and results in an unsteady penetration process. The modulus of elasticity (E) was found to correlate well with the deformation wear material removal. A prediction model was used to express the depth of cut (h) as a function of material properties: h=A/H+B/(E+C) where A, B, and C are process constants.
An Adaptive Error Correction Method Using Feature-Based Analysis Techniques for Machine Performance Improvement, Part 1: Theory Derivation
Authors: Mou J. , Donmez M. A. , Cetinkunt S.
Published: February 2008

An adaptive error correction method using a feature-based analysis technique for improving the accuracy of CNC machine tools is presented. The method described in this paper emphasizes the integration of the process-intermittent gauging and analysis techniques with information from pre-process characterization and post-process inspection. The proposed method utilizes the information from pre-process characterization, process-intermittent gauging, and post-process inspection to improve machine performance automatically. Algorithms are derived for analyzing the post-process and process-intermittent inspection data to decouple process-related errors from machine errors and for identifying the residual systematic errors. A feature-based analysis technique is developed to relate the dimensional and form errors of manufactured features to the systematic machine tool errors. Inverse kinematics and statistical methods are used to identify and characterize the contribution of each residual error component on imperfect features. Also a recursive tuning algorithm is developed for fine tuning the geometric-thermal model.
An Optimization Strategy for Maximizing Coordinate Measuring Machine Productivity, Part 1: Quantifying the Effects of Operating Speed on Measurement Quality
Authors: Jones S. D. , Ulsoy A. Galip
Published: February 2008

The ability to quickly obtain precise dimensional information about manufactured parts is vital for any successful mass production operation. Coordinate Measuring Machines (CMMs) can be used to obtain dimensional measurements, but the effects of structural vibrations often limit the speed at which measurements can be obtained. In this, the first of two papers, the effects of operating speed on CMM measurement quality are illustrated, and the factors affecting measurement speed are then analyzed through an Analysis of Variance (ANOVA) study. Results of the illustration and ANOVA show that as operating speed increases, the quality of the measurements obtained decreases, and that the individual axes of the prismatic CMM structure experimentally evaluated react differently to measuring speeds. Also given are results that show the trade-off between measurement time and quality and indicate the existence of optimal operating speeds for certain values of measurement quality. A model is then developed that describes the relationship between measurement speed and measurement quality for use in the optimization strategy presented in Part 2 of this paper.
Development of a Microscopic Laser Interferometry System for Precision Surface Measurement
Authors: Salisbury E. J. , Moon K. S. , Sutherland J. W.
Published: February 2008

A new technique for the evaluation of precision surfaces using laser interferometry is presented. Laser interferometry creates a fringe pattern which contains information about the surface texture of the specimen. The technique presented compares the ideal fringe pattern to the actual fringe pattern to determine the height deviation on the specimen. In this paper, a simulation model is used to predict the fringe pattern for a given surface. The surface topography of a groove on a computer hard disk is then reconstructed from an experimentally obtained fringe pattern. The reconstruction process is verified by comparing the reconstructed surface to a photograph of the actual surface.
An Experimental Investigation of the Crack Growth Phenomenon for Drilling of Fiber-Reinforced Composite Materials
Authors: DiPaolo G. , Kapoor S. G. , DeVor R. E.
Published: February 2008

An experimental study has been conducted to study the crack growth phenomenon that occurs while drilling fiber-reinforced composite materials (FRCM), specifically unidirectional (UD) carbon fiber/epoxy resin. It uses an experimental setup that exploits the technology of video to understand the complete crack growth phenomenon as the drill emerges from the exit side of the workpiece. Significant damage mechanisms are observed and defined, and correlations between the average exit drill forces and the crack tip position are shown. Instantaneous forces as they vary along the orientation of the cutting edges are identified in terms of their contribution to the crack propagation.
Supervisory Control of Drilling
Authors: Furness R. J. , Ulsoy A. Galip , Wu C. L.
Published: February 2008

A supervisory process control approach to machining is presented in this paper, and demonstrated by application to a drilling operation. The supervisory process control concept incorporates optimization and control functions in a hierarchical structure. This approach utilizes feedback measurements to parameterize the constraints of a process optimization problem whose solution determines both strategies and references for process control. For this particular drilling operation, a three-phase strategy (utilizing a combination of feed, speed, and torque control) evolved due to inherent variation in constraint activity as a function of hole depth. A controller comparison study was conducted which demonstrates the advantages of this approach compared to (1) uncontrolled “conventional” drilling, (2) feed and speed controlled drilling, and (3) torque and speed controlled drilling. Benefits of reduced machining time, improved hole quality, and the elimination of tool breakage are demonstrated, and the potential economic impact is highlighted for an example production application.
PVD Film Method for Measuring the Temperature Distribution in Cutting Tools
Authors: Kato T. , Fujii H.
Published: February 2008

A new method to measure the temperature distribution in cutting tools is reported. In this method, a thin PVD (physically vapor deposited) film deposited on a cutting tool is used as a thermal sensor. Various films of different materials are deposited to determine the location of a multiplicity of isotherms at different temperatures. Cemented carbide tools and alumina ceramic tools are used for tests. It is confirmed that the boundary between the melted film zone and the unmelted film zone shows the isotherm directly and clearly. The method is also found to be very sensitive and applicable to any tool material as well as to a very small area.
Inverse Heat Transfer Analysis of Grinding, Part 1: Methods
Authors: Guo C. , Malkin S.
Published: February 2008

Thermal analyses of the grinding process generally require assumptions concerning the distributions of the heat flux to the workpiece within the grinding zone and convective cooling outside the grinding zone. The present work is concerned with the use of inverse heat transfer methods to estimate the heat flux and convection heat transfer coefficient distributions on the workpiece surface during straight surface grinding from temperature measurements within the workpiece. In the present paper, three inverse heat transfer methods are developed: temperature matching, integral, and sequential methods. Each method is evaluated for accuracy and stability using simulated temperature data. The selection of the sampling frequency of the temperature measurements and location of the temperature sensor are found to be critical for both estimation accuracy and stability. In a second paper, these inverse heat transfer methods are applied to estimate the distributions of the heat flux and convection heat transfer coefficients on the workpiece surface for grinding of steels with aluminum oxide and CBN abrasive wheels.
Can Design for Nonisothermal Pancake Forging of Gamma Titanium Aluminide Alloys
Authors: Jain V. K. , Goetz R. L. , Semiatin S. L.
Published: February 2008

The design of cans to produce uniform, defect-free gamma titanium aluminide alloy pancakes via conventional, nonisothermal forging, was established using finite element modeling (FEM) and laboratory validation trials. The specific problem addressed was ingot breakdown via pancake forging, a process typically comprising a high reduction ratio (∼6:1) and a moderately high deformation rate (∼1 s−1) to minimize the effects of die chilling. Can and process variables investigated in the FEM simulations included can end cap shape and thickness, ram speed, and preheat temperature. The FEM results demonstrated that there is an optimal end cap thickness and ram speed to obtain moderately uniform flow between the can and titanium aluminide workpiece. These results were validated through trials on the near-gamma titanium aluminide alloy Ti-45.5Al-2Cr-2Nb forged in AlSl type 304 stainless steel cans.
Measurement of Pressure Distribution Between Contact Surfaces by Light Reflection
Authors: Yamaguchi K. , Uchida M. , Mondori F.
Published: February 2008

In the present study, the authors propose a method to determine the pressure distribution acting on contact surfaces and detail the development of a measuring device. The principle of pressure measurement is based on the scattered reflection of light from the surface after contact. The device developed measures the pressure distribution and displays it in three dimensions. Pressure distributions measured on various contact surfaces are shown.
Robust Tolerance Design for Quality
Authors: Kusiak A. , Feng Chang-Xue
Published: February 2008

Design of a product (process) includes system design, parameter design, and tolerance design. Robust design is closely applicable to parameter design and tolerance design. The current literature on robust design has focused on parameter design while the problem of tolerance design has not been adequately covered. The tolerance design literature emphasizes the use of optimization to minimize cost while little attention has been paid to minimizing the sensitivity of tolerances to the variation of manufacturing processes. This paper discusses the application of the design of experiments (DOE) approach to tolerance synthesis to minimize manufacturing variations in a probabilistic case. The DOE approach is illustrated with an example.
Efficient Tool-Path Planning for Machining Free-Form Surfaces
Authors: Lin Rong-Shine , Koren Y.
Published: February 2008

This paper presents an analytical method for planning an efficient tool-path in machining free-form surfaces on 3-axis milling machines. This new approach uses a nonconstant offset of the previous tool-path, which guarantees the cutter moving in an unmachined area of the part surface and without redundant machining. The method comprises three steps: (1) the calculation of the tool-path interval, (2) the conversion from the path interval to the parametric interval, and (3) the synthesis of efficient tool-path planning.
Spread Sheet Model of Continuous Casting
Authors: Thomas B. G. , Ho B.
Published: February 2008

Spreadsheet programs, such as Microsoft Excel, Informix WINGZ, and Lotus 123, provide a framework for very fast and easy development of simple engineering models. The present paper describes a model of the continuous casting process that has been developed using a spreadsheet program, Microsoft Excel, running on a Macintosh II personal computer. The model consists of two-dimensional (2-D) steady-state finite-difference heat conduction calculations within a continuous casting mold coupled to a one-dimensional (1-D) transient solidification heat transfer model of the solidifying shell. The model structure and equations are described and the model predictions are compared with previous solutions. Practical examples using the model are discussed and sample results are provided. Spreadsheet programs running on personal computers are capable of relatively complex calculations that would require extensive effort using conventional programming languages.
An Integrated Lattice Filter Adaptive Control System for Time-Varying CMM Structural Vibration Control, Part 2: Experimental Implementation
Authors: Lu E. , Ni J. , Huang Z. G. , Wu S. M.
Published: February 2008

The integrated fast lattice filter adaptive control algorithm developed in Part 1 of this paper will be implemented for the control of the structural vibration of a coordinate measuring machine (CMM). The structural vibration of a CMM exhibits time-varying dynamic characteristics. For auxiliary control, the probe head acceleration was measured to compute the voltage input to the servo motor of the CMM. The developed algorithm uses directly the lattice filter parameters to track and control the CMM structural dynamics and is implemented on a Sheffield horizontal arm Coordinate Measuring Machine using a floating point Digital Signal Processor TMS320C30. Through experiments, significant reduction of the CMM settling time has been achieved by suppressing the structural vibration. In certain configurations, the reduction was 95 percent.
Static and Dynamic Characteristics of Spot Welded Sheet Metal Beams
Authors: Pal K. , Cronin D. L.
Published: February 2008

Although widely employed as structural components in the auto industry, spot welded sheet metal beams manifest static and dynamic behavior that is not well characterized. For the present study, sample beams of three representative cross-sections—hat, box and box with partition—were fabricated of sheet steel. The spacing between the spot welds that hold these sections together was varied from 25.4 mm (1 in.) to 203.2 mm (8 in.) using a 25.4 mm (1 in.) increment. The beams were subjected to static bending and static torsion tests, and bending and torsional stiffnesses were determined as functions of spot weld spacing. The beams were then vibrated, and significant lower natural frequencies were determined as functions of spot weld spacing. Mode shapes were also observed for these frequencies. Pains were taken throughout the testing to ensure that the results obtained were of good statistical quality. Work was also done to distinguish the effect on results of beam length and end conditions from that of spot weld spacing. As part of the study finite element models of the beams were constructed. The results of finite element analysis (FEA) and experiment are compared and insights are offered concerning the appropriate modeling of such structures.
Infrared Sensing for On-Line Weld Geometry Monitoring and Control
Authors: Banerjee P. , Govardhan S. , Wikle H. C. , Liu J. Y. , Chin B. A.
Published: February 2008

This paper describes a method for on-line weld geometry monitoring and control using a single front-side infrared sensor. Variations in plate thickness, shielding gas composition and minor element content are known to cause weld geometry changes. These changes in the weld geometry can be distinctly detected from an analysis of temperature gradients computed from infrared data. Deviations in temperature gradients were used to control the bead width and depth of penetration during the welding process. The analytical techniques described in this paper have been used to control gas tungsten arc and gas metal arc welding processes.
Improving Milling Performance with High Pressure Waterjet Assisted Cooling / Lubrication
Authors: Kovacevic R. , Cherukuthota C. , Mohan R.
Published: February 2008

During machining, due to relative motion between tool and workpiece, severe thermal/frictional conditions exist at the tool-chip interface. Metal machining processes can be more efficient in terms of increasing the metal removal rate and lengthening tool life, if the thermal/frictional conditions are controlled effectively. A high pressure waterjet assisted coolant/lubricant system that can be used in conjunction with rotary tools (e.g., face milling) is developed here. The performance of this system is evaluated in terms of cutting force, surface quality, tool wear, and chip shape. The improvement in the effectiveness of the developed system with increase in water pressure and orifice diameter is also investigated. Stochastic modeling of the surface profile is performed to obtain more information about the role of waterjet in the machining process.
New Method for Estimating Residual Stresses in Pipe Made by Surfacing Weld
Authors: Terasaki T. , Akiyama T. , Ishimura T.
Published: February 2008

A new method is presented for estimating residual stresses produced in a pipe made by surfacing weld. By focusing on the concept and the feature of inherent strain causing the residual stress, the proposed method has both the convenience of the Sachs method and the accuracy of the inherent strain method. The experiment for residual stress of a steel with brass cladding was done by both the Sachs and proposed method. The equation of the Sachs method for composite pipe was derived. The equation for the new method was obtained on the basis of the theory of inherent strain. It is found that the proposed method is useful for estimating residual stresses of pipe with cladding.
A BEM/FEM Framework for Simulation of a Plastic Workpiece Deformed by an Elastic Tool
Authors: Beaudoin A. J. , Dawson P. R. , Mukherjee S.
Published: February 2008

A solution methodology is developed for the simulation of a plastic workpiece deformed by a compliant tool. The solution for elastic tool displacements is based on the Boundary Element Method (BEM); the viscoplastic response of the workpiece is computed using the Finite Element Method (FEM). At each time increment, tool deflections are recomputed from the elastic solution based on surface tractions developed in the previous converged solution for the viscoplastic response of the workpiece material. Tool stresses may be recovered at any point in the simulation using the BEM solution. The updated tool geometry and motion correspondingly modify the kinematic contact constraint applied in the viscoplastic solution over the subsequent time step. Application of this methodology is demonstrated for simulation of a plane strain forging operation.
Integrating Optimal Experimental Design into the Design of a Multi-Axis Load Transducer
Authors: Wickham M. J. , Riley D. R. , Nachtsheim C. J.
Published: February 2008

The determination of loads applied to a structure is often necessary in the design process. In some situations it is not feasible to insert a load cell in the system to measure these applied loads. In these cases, it would be expedient to utilize the structure itself as a load transducer. This can be accomplished by measuring strains at a number of locations on the structure. The precision with which the applied loads can be estimated from measured structural responses depends on the number of strain gages utilized and their placement on the structure. This paper presents a computational methodology which utilizes optimal experimental design techniques to select the number, locations and angular orientations of the strain gages which will provide the most precise load estimates based on the generalized load vector. Selection is made from a candidate set created using a finite element analysis. The application of this method is illustrated with an example.
Simultaneous In-Process Inspection of Surface Form and Roughness of Machined Sculptured Surfaces
Authors: Philpott M. L. , Mitchell S. E. , Tobolski J. F. , Green P. A.
Published: February 2008

A noncontact measuring system for the simultaneous in-process inspection of surface form and surface roughness of sculptured machined surfaces is described. Previous presented work demonstrated successful algorithms for open-loop and closed-loop convergence to a specified, or desired, surface form. In this paper, results of implementing these algorithms with the new measuring system are briefly described. A new methodology is presented which extends the concept to enable convergence to both the desired surface form and the desired surface roughness. Two scanning procedures for simultaneous form and roughness inspection are presented. Software modules for surface roughness planning and control have been developed and incorporated into an Integrated Mold Production System (or IMPS).
Effects of
Plasmodium falciparum
Parasite Population Size and Patient Age on Early and Late Parasitological Outcomes of Antimalarial Treatment in Children
Authors: Borrmann Steffen , Matsiegui Pierre-Blaise , Missinou Michel Anoumou , Kremsner Peter G.
Published: February 2008

The design and interpretation of trials assessing the chemotherapeutic effects of antimalarial drugs depend on our understanding of how different selection criteria affect treatment outcomes. In this study, we analyzed the effects of baseline parameters on the initial parasite elimination rate and the risk of subsequent recrudescence as a marker for incompletely eliminated asexual blood-stage parasites in pediatric patients with uncomplicated
Plasmodium falciparum
infection treated with amodiaquine in a high-transmission area. We found that (i) parasite population size and patient age independently determine early and late parasitological treatment outcome measurements; (ii) the rate of recrudescence is higher in patients 1 to 3 years of age than in patients aged <1 or >3 years; (iii) patients aged >5 years with parasite densities between 2,000 and 10,000/μl have a lower recrudescence rate (13%; 95% confidence interval [CI], 8% to 21%) than patients aged <5 years with parasite densities of >10,000/μl (40%; 95% CI, 30% to 50%); and (iv) the sensitivity of detecting recrudescences outside this high-risk group, i.e., in patients of >5 years of age or with parasite densities of <10,000/μl, is as low as 27% or 22%, respectively. In conclusion, these findings highlight the need to use adequate selection criteria and to report parasitological outcome results adjusted for the readily available determinants of chemotherapeutic failure, i.e., patient age and baseline parasitemia. The thresholds may vary by transmission intensity and drug regimen. A better understanding of the limitations of antimalarial regimens in high-risk subgroups of patients has important implications for setting policy recommendations.
Pharmacokinetic Determinants of the Window of Selection for Antimalarial Drug Resistance
Authors: Stepniewska K. , White N. J.
Published: February 2008

The selection and spread of antimalarial drug resistance pose enormous challenges to the health of people living in tropical countries. Most antimalarial drugs are slowly eliminated and so, following treatment in areas of endemicity, provide a gradient of concentrations to which newly acquired parasites are exposed. There is a variable period during which a new blood-stage infection with resistant malaria parasites can emerge from the liver and subsequently produce gametocyte densities sufficient for transmission while reinfection by sensitive parasites is still suppressed. This “window of selection” drives the spread of resistance. We have examined the factors which determine the duration of this window and, thus, the resistance selection pressure. The duration ranges from zero to several months and is dependent on the degree of parasite resistance, the slope of the concentration-effect relationship, and the elimination kinetics of the antimalarial drug. The time at which the window opens and the duration of opening are both linear functions of the terminal elimination half-life. Because of competition from sibling susceptible parasites, the greater risks of extinction with low starting numbers, and opening of the window only when blood concentrations have fallen below the MIC, the window of selection for de novo resistance is narrower than that for resistance acquired elsewhere. The windows were examined for the currently available antimalarials. Drugs with elimination half-lives of less than 1 day, such as the artemisinins and quinine, do not select for resistance during the elimination phase.
Carbapenem-Resistant
Acinetobacter baumannii
Isolates from Tunisia Producing the OXA-58-Like Carbapenem-Hydrolyzing Oxacillinase OXA-97
Authors: Poirel Laurent , Mansour Wejdene , Bouallegue Olfa , Nordmann Patrice
Published: February 2008

The basis of the β-lactam resistance of 39 multidrug-resistant
Acinetobacter baumannii
isolates recovered from hospitalized patients was studied. These isolates were collected from 2001 to 2005 at the Sahloul Hospital in Sousse, Tunisia. They belonged to two distinct clones. One clone that grouped 19 isolates produced a carbapenem-hydrolyzing oxacillinase, OXA-97, that differed from OXA-58 by a single amino acid substitution and conferred the same β-lactam resistance profile as OXA-58. The
bla
OXA-97
gene was located on plasmids that varied in size in 18 isolates and was chromosomally located in a single isolate. Cloning and sequencing identified genetic structures surrounding the
bla
OXA-97
gene similar to those reported to be adjacent to the
bla
OXA-58
gene. In addition, the novel IS
Aba8
element (which is of the IS
21
family) was identified. This is the first report of the nosocomial spread of carbapenemase producers in
A. baumannii
isolates in Africa.
Identification of an Antiparallel Coiled-Coil/Loop Domain Required for Ligand Binding by theBorrelia hermsiiFhbA Protein: Additional Evidence for the Role of FhbA in the Host-Pathogen Interaction
Authors: Hovis Kelley M. , Freedman John C. , Zhang Hongming , Forbes Jonathan L. , Marconi Richard T.
Published: February 2008

Borrelia hermsii, an etiological agent of tick-borne relapsing fever in North America, binds host-derived serum proteins including factor H (FH), plasminogen, and an unidentified 60-kDa protein via its FhbA protein. Two distinct phylogenetic types of FhbA have been delineated (FhbA1 and FhbA2). These orthologs share a conserved C-terminal domain that contains two alpha helices with a high predictive probability of coiled-coil formation that are separated by a 14-amino-acid loop domain. Through site-directed mutagenesis, we have identified residues within these domains that influence the binding of both mouse and human FH, plasminogen, and/or the 60-kDa protein. To further investigate the involvement of FhbA in the host-pathogen interaction, strains that are either FhbA+(isolate YOR) or FhbA−(isolate REN) were tested for serum sensitivity. Significant differences were observed, with YOR and REN being serum resistant and serum sensitive (intermediate), respectively. To test the abilities of these strains to infect and persist in mice, mice were needle inoculated, and infectivity and persistence were then assessed. While both strains REN and YOR infected mice, only the FhbA+YOR strain persisted beyond day 4. Survival of the YOR isolate in blood correlated with the upregulation of thefhbAgene, as demonstrated by real-time reverse transcriptase PCR. These data advance our understanding of the unique interactions of FhbA with individual serum proteins and provide support for the hypothesis that FhbA is an important contributor to the pathogenesis of the relapsing fever spirocheteB. hermsii.
Leishmania pifanoiProteoglycolipid Complex P8 Induces Macrophage Cytokine Production through Toll-Like Receptor 4
Authors: Whitaker Shanta M. , Colmenares Maria , Pestana Karen Goldsmith , McMahon-Pratt Diane
Published: February 2008

The P8 proteoglycolipid complex (P8 PGLC) is a glyconjugate expressed byLeishmania mexicanacomplex parasites. We previously have shown that vaccination with P8 PGLC provides protection against cutaneous leishmaniasis in susceptible BALB/c mice. However, the biological importance of this complex remains unknown. Here we show that P8 PGLC localizes to the surface ofLeishmania pifanoiamastigotes and that upon exposure to macrophages, P8 PGLC binds and induces inflammatory cytokine and chemokine mRNAs such as tumor necrosis factor alpha and RANTES early after stimulation. Our studies indicate that cytokine and chemokine induction is dependent upon Toll-like receptor 4 (TLR4). Interestingly, key inflammatory cytokines and chemokines (such as interleukin-6 [IL-6], macrophage inflammatory protein 1β, and beta interferon [IFN-β]) that can be induced through TLR4 activation were not induced or only slightly upregulated by P8 PGLC. Activation by P8 PGLC does not occur in the presence of TLR4 alone and requires both CD14 and myeloid differentiation protein 2 for signaling; this requirement may be responsible for the limited TLR4 response. This is the first characterization of a TLR4 ligand forLeishmania. In vitro experiments indicate thatL. pifanoiamastigotes induce lower levels of cytokines in macrophages in the absence of TLR4; however, notably higher IL-10/IFN-γ ratios were found for TLR4-deficient mice than for BALB/c mice. Further, increased levels of parasites persist in BALB/c mice deficient in TLR4. Taken together, these results suggest that TLR4 recognition ofLeishmania pifanoiamastigotes is important for the control of infection and that this is mediated, in part, through the P8 PGLC.
Tobacco industry targeting youth in Argentina
Authors: Braun S , Mejia R , Ling P M , Pérez-Stable E J
Published: February 2008

Background/aim:

Argentina has one of the highest cigarette smoking rates among both men and women in the Americas and no legislated restrictions on tobacco industry advertising. The tobacco industry has traditionally expanded markets by targeting adolescents and young adults. The objective of this study was to determine whether and how the tobacco industry promotes cigarettes to adolescents in Argentina.

Methods:

We conducted a systematic search of tobacco industry documents available through the internet dated between 1995 and 2004 using standard search terms to identify marketing strategies in Argentina. A selected review of the four leading newspapers and nine magazines with reported high readership among adolescents was completed. The selected print media were searched for tobacco images and these were classified as advertisements if associated with a commercial product or as a story if not.

Results:

The tobacco industry used market segmentation as a strategy to target Argentinean consumers. British American Tobacco (BAT) undertook a young adult psychographic study and classified them as “progressives”, “Jurassics” or “conservatives” and “crudos” or “spoiled brats”. BAT marketed Lucky Strike to the “progressives” using Hollywood movies as a vehicle. The tobacco industry also targeted their national brands to the conservatives and linked these brands with “nationalistic values” in advertising campaigns. Philip Morris promoted Marlboro by sponsoring activities directed at young people and they launched the 10 cigarettes packet as a starter vehicle.

Conclusions:

The tobacco industry used psychographic segmentation of the population and developed advertising strategies focused on youth. Tobacco control researchers and advocates must be able to address these strategies in counter-marketing interventions.
Differential thermal expansion and contraction: a mechanistic approach to adhesion in asphalt concrete
Authors: Hussein H. Mohamed El , Halim A. O. Abd El
Published: February 2008

The difficulties associated with developing reliable roadway failure prediction models are due to the lack of sound theoretical analyses to assess the true causes of pavement distress. Low-temperature cracking and stripping may be two of the causes of pavement distress that are difficult to predict. This paper introduces a simple mechanistic approach that describes the response of the asphalt–aggregate system to temperature changes. The concept recognizes the thermal incompatibility between asphalt cement and aggregate. Owing to the considerable difference in the coefficients of thermal expansion of aggregate and asphalt, the asphalt matrix will attempt to contract more than the aggregate during thermal cooling. An analytical model was derived to estimate the thermally induced stresses resulting from differential thermal contraction. The experimental investigation, which is part of a study investigating adhesion, verified the findings of the analytical approach. Findings from this study explained field and laboratory observations made earlier by other investigators. These observations were associated with asphalt concrete low-temperature performance and its resistance to stripping. Key words: differential thermal contraction, asphalt matrix, localized damage, stripping.
Energy dissipation by jet diffusion in stormwater drop shafts
Authors: Rajaratnam N. , Johnston G. A. , Barber M. A.
Published: February 2008

This paper considers energy dissipation by jet diffusion in drop shafts used in urban stormwater systems, using the theory of circular turbulent jets. It presents experimental results on the decay of the maximum velocity in the jet for D/d in the range of 5 to 15, where D is the diameter of the chamber and d is the diameter of the jet at the water surface in the diffusion chamber. It was found that when D/d is small [Formula: see text], the decay of the velocity in the jet is appreciably larger than that in a jet in a large stagnant ambient. Key words: jet diffusion, drop shafts, stormwater systems, turbulent flow.
Aspects of performance of truck weigh stations
Authors: Fekpe Edward S. K. , Clayton Alan M. , Alfa Attahiru Sule
Published: February 2008

The performance characteristics of truck weigh stations are presented. Seasonally operated scales and random inspection sites are found to be at least 3 and 8 times respectively as effective in detecting violations as continuously operated permanent scales with no alternative bypass routes. The availability of alternative bypass routes reduces truckers' perceived probability of detection at permanent weigh scales by at least 5%. Higher perceived probabilities are associated with high inspection rates.Queuing theory is employed to study the impact of two alternative manpower levels on the performance of con tinuously operated permanent weigh scales. For the level of truck traffic volume considered, it is found that, theoretically, there is no significant delay to truck traffic through such weigh scale stations irrespective of the manning strategy. It is concluded that it is feasible to maintain minimal staff at the scales and redirect human resources to increase inspection capacities of other methods.The queuing model for the permanent scale operations represents a rare practical example of a classic M/Ek/1 model where the k stages in the service time Erlang distribution are real and not necessarily imaginary. Key words: permanent scale, effectiveness, enforcement, violation, inspection, arrival time, service time.
Hazardous material loading to municipal landfills in resource-based communities
Authors: Zeiss Chris
Published: February 2008

Landfills in rural, resource-based communities are receiving unknown quantities of potentially hazardous materials, including household hazardous wastes (HHHW) and industrial, commercial, and institutional (ICI) wastes in self-hauled and collection vehicle loads. Rural generation and disposal rates are expected to be higher than in urban areas.The research program was conducted in a resource-based community consisting of a town of about 5500 residents and the surrounding rural area with an equal number of residents in Alberta. The research objective was to determine the weight fraction of hazardous materials in the refuse through physical sampling of the waste stream at the community landfill. Over a 1-year period (1991), large collection vehicle loads and self-hauled private and ICI loads from the town and the rural area were sampled during 1 week in each season using a two-staged systematic random sampling design to measure the average weight fraction and variation by season and by type of load. The results show the annual average weight fraction of hazardous materials to be 6.7% with a 95% confidence interval of 4.0% to 9.4%. Seasonal differences are apparent, but are not significant. Self-hauled ICI and rural wastes tend to contain higher percentages of potentially hazardous materials, but the variation is also higher so the values are not significantly different from those from the town. The detected materials consist mainly of oily wastes (debris, oil containers, and vehicle oil filters), other automotive products, and paints. As a result, the hazardous material content of rural community refuse appears to be substantially higher than the 0.3% to 1.0% reported for HHHW in urban refuse streams. While the rural composition suggests that vehicle and home maintenance contribute some of the difference, this study also shows that ICI wastes and self-hauled loads contribute noticeable quantities of potentially hazardous materials. The results suggest that it is essential for rural communities to consider waste management alternatives for potentially hazardous materials because rural waste streams contain significantly higher percentages and because rural landfills are often not designed to as high a standard as large urban facilities. Key words: household hazardous waste, ICI waste, waste stream analysis, rural landfills, refuse waste stream.
Work-zone traffic management with transportation planning software
Authors: Islam M. Nazrul , Seneviratne Prianka N.
Published: February 2008

In this paper, the pros and cons of applying transportation planning software (TPS) in work-zone traffic management are investigated. The overall objective is to provide potential users, particularly small municipalities, with a basis for selecting the TPS best suited for evaluating traffic management alternatives for work zones. Four TPSs (TRANPLAN, MINUTP, SYSTEM II, and QRS II) were examined and rated with respect to eleven characteristics, SYSTEM II and QRS II, rated first and second, respectively, are used to assign traffic in a selected network. Alternate routes during road work are identified to minimize total delay and noise impact. The performance of the two TPSs is assessed in relation to predictive accuracy, post-processing requirements, and compatibility with other software. It is found that, while concerns about predictive accuracy and training needs can be overcome at a price, some special features are required within the present generation of TPS for them to be truly beneficial in the routine analysis of work-zone traffic plans. The significance of these features is discussed in reference to the assignment case study. Key words: traffic assignment, work zone, traffic management, planning, software, SYSTEM II, QRS II.