bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Space Transport in Noisy Hamiltonian Systems
Authors: KANDRUP HENRY E.
Published: February 2006

ABSTRACT: This paper analyses the effect of low amplitude friction and noise in accelerating phase space transport in time‐independent Hamiltonian systems that exhibit global stochasticy. Numerical experiments reveal that even very weak non‐Hamiltonian perturbations can dramatically increase the rate at which an ensemble of orbits penetrates obstructions like cantori or Arnold Webs, thus accelerating the approach toward an invariant measure, i.e., a microcanonical population of the accessible phase space region. An investigation of first passage times through cantori leads to three conclusions, namely: (i) that, at least for white noise, the detailed form of the perturbation is unimportant, (ii) that the presence or absence of friction is largely irrelevant, and (iii) that, overall, the amplitude of the response to weak noise scales logarithmically in the amplitude of the noise.
Empirical Model Decomposition Based Time-Frequency Analysis for the Effective Detection of Tool Breakage
Authors: Peng Yonghong
Published: February 2006

Extensive research has been performed to investigate effective techniques, including advanced sensors and new monitoring methods, to develop reliable condition monitoring systems for industrial applications. One promising approach to develop effective monitoring methods is the application of time-frequency analysis techniques to extract the crucial characteristics of the sensor signals. This paper investigates the effectiveness of a new time-frequency analysis method based on Empirical Model Decomposition and Hilbert transform for analyzing the nonstationary cutting force signal of the machining process. The advantage of EMD is its ability to adaptively decompose an arbitrary complicated time series into a set of components, called intrinsic mode functions (IMFs), which has particular physical meaning. By decomposing the time series into IMFs, it is flexible to perform the Hilbert transform to calculate the instantaneous frequencies and to generate effective time-frequency distributions called Hilbert spectra. Two effective approaches have been proposed in this paper for the effective detection of tool breakage. One approach is to identify the tool breakage in the Hilbert spectrum, and the other is to detect the tool breakage by means of the energies of the characteristic IMFs associated with characteristic frequencies of the milling process. The effectiveness of the proposed methods has been demonstrated by considerable experimental results. Experimental results show that (1) the relative significance of the energies associated with the characteristic frequencies of milling process in the Hilbert spectra indicates effectively the occurrence of tool breakage; (2) the IMFs are able to adaptively separate the characteristic frequencies. When tool breakage occurs the energies of the associated characteristic IMFs change in opposite directions, which is different from the effect of changes of the cutting conditions e.g. the depth of cut and spindle speed. Consequently, the proposed approach is not only able to effectively capture the significant information reflecting the tool condition, but also reduces the sensitivity to the effect of various uncertainties, and thus has good potential for industrial applications.
A Comprehensive Dynamic End Milling Simulation Model
Authors: Li Hongqi , Shin Yung C.
Published: February 2006

This paper presents a comprehensive time domain model that simulates end milling processes under general cutting conditions. Over an extensive range of axial depths of cut, the model can accurately predict regenerative forces and dynamic responses by considering varying dynamics along the cutting depth, three-dimensional forces, and cutting tool geometries. The prediction of stability limit is validated under cutting conditions of both large depths and very small radial immersions. In addition, three-dimensional surface profiles under both stable and chatter conditions are predicted and compared with measured ones. A new method to extract cutting pressure coefficients is also introduced and applied to the experimental validations.
Modeling the Progression of Flank Wear on Uncoated and Ceramic-Coated Polycrystalline Cubic Boron Nitride Tools in Hard Turning
Authors: Dawson Ty G. , Kurfess Thomas R.
Published: February 2006

Accurate wear modeling has always been desired, but has also been difficult and elusive. Most useful wear models have relied on experimental calibration because the physical wear mechanisms are not fully understood. This is particularly true in machining, where contact stresses and temperatures can be extremely high. In machining, the two wear modes most frequently discussed are crater wear and flank wear. Flank wear receives much more attention because it is easier to measure and the mechanism of material loss is thought to be better understood for most machining situations. This work focuses on flank wear for the same reasons. In hard turning, tool life is relatively short and both crater wear and flank wear influence the cutting process substantially. Understanding the progression of flank wear at various cutting conditions is beneficial in itself, but the ability to predict this progression will be extremely valuable. This work addresses both. Experimental flank wear progression is shown for uncoated and ceramic-coated polycrystalline cubic boron nitride (PCBN) tools at a range of cutting conditions. These data are used to calibrate a proposed mechanical wear model that predicts the progression of flank wear and tool failure points based on the cutting speed, feed, and cutting depth. The model was validated by additional experiments, which show good agreement with the predictions.
Effect of Oil Mist on Tool Temperature in Cutting
Authors: Ueda Takashi , Hosokawa Akira , Yamada Keiji
Published: February 2006

In this paper, the influence of oil mist on the tool temperature in cutting is investigated experimentally. The turning of a carbon steel with oil mist applied is performed, and the temperature of the alumina tool at the tool-chip interface is measured using a two-color pyrometer. The tool temperature in dry cutting at a cutting speed of 300 m/min is ∼1060°C, but it is ∼1000°C when oil mist is supplied. In intermittent turning, the oil mist has more effect on the tool temperature because it is supplied more efficiently to the tool-chip interface. In end milling with the oil mist applied, the tool temperature at the flank face is ∼580°C at a cutting speed of 400 m/min, though in dry cutting it is ∼660°C.
Magnetic Field Effects in Machining Processes and on Manufactured Part Mechanical Characteristics
Authors: Mansori Mohamed El , Klamecki Barney E.
Published: February 2006

A review of research results demonstrating that magnetic fields applied to machining processes and mechanically manufactured parts can have beneficial effects is presented, an explanatory mechanistic model is described, and the model is used to interpret some results. The magnetic field-material interaction model shows an exponential dependence of material behavior and mechanical property changes on applied field strength and material magnetostrictive characteristics. Implications for use of magnetic fields to manipulate tribological processes, control machining processes, and alter material properties are that low field strengths can be useful for treating materials that have large magnetostrictive stain and high magnetic saturation level.
Incorporating Adjustable Features in the Optimal Design of Polymer Sheet Extrusion Dies
Authors: Smith Douglas E. , Wang Qi
Published: February 2006

It is common for materials processing operations to have adjustable features that may be used to improve the quality of the final product when variability in operating conditions is encountered. This paper considers the polymer sheeting die design problem where variability in operating temperature or material properties, for example, requires that the die be designed to perform well under multiple operating conditions. An optimization procedure is presented where the design variables parametrize both stationary and adjustable model variables. In this approach, adjustable features of the die cavity are modified in an optimal manner consistent with the overall design objectives. The computational design approach incorporates finite element simulations based on the Generalized Hele-Shaw approximation to evaluate the die’s performance measures, and includes a gradient-based optimization algorithm and analytical design sensitivities to update the die’s geometry. Examples are provided to illustrate the design methodology where die cavities are designed to accommodate multiple materials, multiple flow rates, and various temperatures. This paper demonstrates that improved tooling designs may be computed with an optimization-based process design approach that incorporates the effect of adjustable features.
Effects of Scanning Schemes on Laser Tube Bending
Authors: Zhang Jie , Cheng Peng , Zhang Wenwu , Graham Michael , Jones Jerry , Jones Marshall , Yao Y. Lawrence
Published: February 2006

Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, and line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermomechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analyzed, along with the processing efficiency.
Corrugation and Buckling Defects in Wound Rolls
Authors: Lin P. M. , Wickert J. A.
Published: February 2006

Sheet metal, paper, and polymer webs are often stored and processed as large rolls comprising thousands of layers. Depending on the elastic properties of the web material, the roll’s dimensions, the type of core, and the winding tension, the stresses that develop within the roll can be sufficiently high to cause local or gross buckling defects to form. For instance, the cylindrical core onto which the web is wound can collapse, a failure mode that is termed “v-buckling.” In other cases, while the core might remain intact, a group of layers interior to the roll can wrinkle into a near-sinusoidal corrugated pattern around the circumference. This paper examines such “starring” defects analytically and experimentally. Measurements on a laboratory-scale web transport system are used to validate the model, and to identify conditions where no defects occur and the roll has acceptable quality, where starring patterns develop, and where v-buckling occurs. For particular core and web materials, the tension and diameter are the primary variables that influence the roll’s stability, and demarcations between stable and buckled configurations are identified in the tension-diameter design space. A model for the elastic stability of the roll-core system is developed, in which the corrugated layers are treated as multiple rings subjected to the resultant pressure generated by the roll’s internal stresses, and to the elastic support provided by the core and neighboring web layers. At the onset of corrugation, adjacent web layers couple through surface contact which is incorporated in the model as an elastic shear layer.
A Real-Time Method for Solving the Forward Kinematics of a Tripod With Fixed-Length Legs
Authors: Xu Younan , Xi Fengfeng
Published: February 2006

This paper presents a real-time method for solving the forward kinematics of a tripod with fixed-length legs. The basic idea is to model the problem at hand based on a spatial four-bar linkage through which three sliding legs can be interrelated by choosing one link as a driving variable and other two links as driven variables. As a result, the original multivariable nonlinear problem with three variables can be reduced to one variable problem. A complete approach is provided to solve the unitary nonlinear programing problem. This includes a method for solving the implicit functions in terms of the driving and driven variables, and an approximation method for selecting an initial value leading to a fast solution. The simulation results show that (i) the method is effective, (ii) can reach very accurate results within five iterations for an error bound of 10−10, and (iii) numerically very stable. The experiment results show that the proposed forward kinematic method is fast enough to be implemented in real time to provide an accurate prediction of the tool pose from the joint encoder measurement.
Multiple Attributes Utility Analysis in Setup Plan Evaluation
Authors: Xu Nuo , Huang Samuel H.
Published: February 2006

Setup planning is an intermediate phase of process planning, and automating setup planning constitutes a critical component of computer-aided process planning. The common absence of a clearly defined optimality of setup plans has been a major obstacle to converting automatic setup planning research progress into real advancement in practice. The optimality of a setup plan is a multiple attributes problem associated with uncertainties, and human interaction is vital in clarifying the optimality structure in a dynamic setup planning environment. In this paper, a quantitative setup plan evaluation system driven by multiple-attributes utility analysis coupled with manufacturing error simulation is proposed to serve three purposes: (1) to clarify what is optimality of setup plans, (2) to provide a systematic method of evaluating setup plan alternatives quantitatively, and (3) to incorporate in existing automatic setup planning systems a human interface to fulfill their potential values.
Robust Method of Multiple Variation Sources Identification in Manufacturing Processes For Quality Improvement
Authors: Li Zhiguo , Zhou Shiyu
Published: February 2006

Variation source identification is a critical step in the quality and productivity improvement of manufacturing processes and draws significant attention recently. In this article we present a robust pattern-matching technique for variation source identification. In this paper, a multiple variation sources identification technique is developed by adopting the linear relationship between variation sources and product quality characteristics, which is described by a coefficient matrix. The columns of the coefficient matrix are treated as the signatures of corresponding variation sources. The matching is conducted between the signature vectors and the eigenvectors of the sample covariance matrix of the product quality measurements. Multiple faults are allowed in the matching. Further, both the perturbation of unstructured noise and the sample uncertainties are considered in this matching method. A comprehensive case study illustrates the effectiveness of this method. This robust method can be used for root cause identification of manufacturing processes. The application of this method can significantly reduce the troubleshooting time and hence improve the quality and productivity of manufacturing processes.
Volumetric Error Compensation of Multi-Axis Laser Machining Center for Direct Patterning of Flat Panel Display
Authors: Jin Sang Y. , Lee Ki-Taek , Kim Kyuil
Published: February 2006

A new direct laser patterning system for improving the quality of the pattern on the glass substrate of large Flat Panel Displays (FPD) was developed, which consists of the laser machining center, the laser measurement system, and the adaptive rotational mirror system. The new system is distinguished from the existing system by its control mechanism which compensates for the laser beam error caused by the volumetric error of the multi-axis machine. The new system, in comparison with existing systems which control each stage of multi-axis, uses a fast steering mirror (FSM) and adaptive laser optics to compensate for the error of the laser beam on the substrate. Through this study, a mathematical model of the volumetric error of the multi-axis laser machining center was developed to quantify the geometric and the kinematic errors of each machine axis and their contributing effect on the substrate. The information contained in the mathematical model was expressed in a volumetric error matrix. Further, a mathematical model of the beam delivery was developed to measure the beam delivery on the substrate and its effect on the quality of the patterning. The patterning errors were corrected by using an FSM, which has two rotational angles. The viability of the proposed scheme was demonstrated through simulations and experiments.
Evaluation of Estimates of Roll Separating Force in Bar Rolling
Authors: Ragab A. R. , Samy S. N.
Published: February 2006

A systematic approach is presented to estimate the roll separating force in bar rolling. This force is the product of the contact area between the rolled material and the roll pass, the mean unit pressure on the roll and the average flow stress within the roll gap. The contact area is determined by a computerized scheme based on a descriptive geometry approach. Also an approximate model to determine the average strain, hence the strain rate and the rolling temperature within the roll gap is proposed to estimate the flow stress from available material characterizations. The mean unit pressure on the rolls uses models existing in the literature pertinent to three-dimensional analysis of bar rolling. These models are slightly modified to encompass the unifying Δ parameter expressing the geometry of the deformation zones, namely the ratio between the mean cross-sectional area and the contact area. The present approach is applied for a variety of common types of passes employed in bar rolling. Validation of the approach is realized through comparisons of predictions with a set of about 100 experimental and industrial data points for bar rolling in various passes. A fair agreement between the predictions and the measured data points is found. Reasons for the discrepancies are discussed. Furthermore a simplified analytical model to estimate the roll separating force which includes the least of adjusting empirical factors is suggested.
Analysis of the Laser Droplet Formation Process
Authors: Kokalj Tadej , Klemenčič Jure , Mužič Peter , Grabec Igor , Govekar Edvard
Published: February 2006

In this paper, a novel laser droplet formation process (LDFP) from a metal wire is investigated. The process consists of the formation of a molten pendant droplet and its detachment, which are both unstable and influenced by numerous process parameters. The goal of the investigation is to specify the main process parameters and the values that provide for stable and repeatable process. Based on theoretical and experimental consideration of LDFP, a methodology for estimation of process control parameters is proposed. Estimation of the parameters is demonstrated on examples of deposited droplets of nickel and tin-alloy wires. Experimental results on tin-alloy wire indicate that the problem of splashes on the substrate is still present, while those on nickel reveal an acceptable formation of droplets.
In-Process Diameter Measurement of Turned Workpiece With Curvatures
by Using Sensor Positioning
Authors: Shiraishi Masatake , Sumiya Hideyasu , Aoshima Shinichi
Published: February 2006

A modified triangular laser displacement sensor having a resolution of 1.0μm was used to measure the diameter of a turned workpiece with curvatures. This sensor was attached to a specially designed stage mounted on a precision slide unit and operated by three drive motors. In the measurement, the laser sensor was controlled by a θ motor depending on workpiece curvatures so that the illuminating laser beam is always normal to the part surface and can measure the workpiece diameter in an on-line fashion. This sensor positioning control was found to be effective for measuring the diameter of a curved workpiece with an accuracy of several micrometers.
Wear of Electroplated CBN Grinding Wheels
Authors: Shi Z. , Malkin S.
Published: February 2006

An investigation is reported on the wear of single-layer electroplated cubic boron nitride (CBN) grinding wheels and how the wear process affects the wheel topography and grinding behavior. Internal cylindrical and straight surface grinding experiments were conducted over a wide range of conditions on hardened bearing steel with wheels containing different abrasive grain sizes. The radial wheel wear was characterized in each case by an initial transient at a progressively decreasing rate to a steady-state wear regime at a nearly constant rate until the end of the wheel life. Wheel wear during the initial transient was found to be mainly due to pullout of the most protruding weakly held grains, and the radial wheel wear in the steady-state regime was dominated by grain fracture. The wear rate in the steady-state regime for various grinding conditions and grain sizes was found to be directly related to the undeformed chip thickness. Dulling of the grain tips by attrition and fragmentation caused an increase in the grinding power. Wheel wear was accompanied by a progressive increase in the active grain density and a corresponding decrease in surface roughness. The surface roughness was found to depend mainly on the active grain density and is insensitive to the operating parameters.
Analytic Wavelet-Based Ultrasonic Pulse Differentiation for Injection Mold Cavity Pressure Measurement
Authors: Zhang Li , Theurer Charles B. , Gao Robert X. , Kazmer David O.
Published: February 2006

A new signal-processing technique based on analytic wavelet transform has been developed for detecting and differentiating temporally overlapped ultrasonic pulse trains that carry spatially distributed pressure information across an injection mold cavity. Compared to conventional wavelets that have a constant relative bandwidth at all the scales, the analytic wavelets investigated in this paper feature variable relative bandwidth, making it possible to simultaneously match the frequency characteristics of the ultrasonic pulse trains transmitted from the mold-embedded pressure sensors. As a result, more accurate detection and differentiation of the temporal and spectral information embedded within the ultrasonic pulse trains could be achieved. Theoretical framework for the analytic wavelet transform was established, and a multichannel ultrasonic pulse detector based on the complex Morlet wavelet was designed and experimentally investigated. The results have confirmed the effectiveness of the new signal-processing technique for on-line pressure sensing for injection molding process monitoring.
A Finite-Differences Derivative-Descent Approach for Estimating Form Error in Precision-Manufactured Parts
Authors: Gosavi Abhijit , Phatakwala Shantanu
Published: February 2006

Background: Form-error measurement is mandatory for the quality assurance of manufactured parts and plays a critical role in precision engineering. There is now a significant literature on analytical methods of form-error measurement, which either use mathematical properties of the relevant objective function or develop a surrogate for the objective function that is more suitable in optimization. On the other hand, computational or numerical methods, which only require the numeric values of the objective function, are less studied in the literature on form-error metrology. Method of Approach: In this paper, we develop a methodology based on the theory of finite-differences derivative descent, which is of a computational nature, for measuring form error in a wide spectrum of features, including straightness, flatness, circularity, sphericity, and cylindricity. For measuring form-error in cylindricity, we also develop a mathematical model that can be used suitably in any computational technique. A goal of this research is to critically evaluate the performance of two computational methods, namely finite-differences and Nelder-Mead, in form-error metrology. Results: Empirically, we find encouraging evidence with the finite-differences approach. Many of the data sets used in experimentation are from the literature. We show that the finite-differences approach outperforms the Nelder-Mead technique in sphericity and cylindricity. Conclusions: Our encouraging empirical evidence with computational methods (like finite differences) indicates that these methods may require closer research attention in the future as the need for more accurate methods increases. A general conclusion from our work is that when analytical methods are unavailable, computational techniques form an efficient route for solving these problems.
Real-Time Weld Penetration Depth Monitoring With Laser Ultrasonic Sensing System
Authors: Mi Bao , Ume Charles
Published: February 2006

A real-time ultrasound-based system for controlling robotic weld quality by monitoring the weld pool is presented. The weld penetration depth is one of the most important geometric parameters that define weld quality, hence, remains a key control quantity. The sensing system is based on using a laser phased array technique to generate focused and steered ultrasound, and an electromagnetic acoustic transducer (EMAT) as a receiver. When a pulsed laser beam is incident on the surface of a condensed matter, either the thermoelastic expansion or ablation induces mechanical vibrations that propagate as ultrasound within the specimen. Both the ultrasound generation by the laser phased array and the reception by the EMAT are noncontact, which eliminates the need for a couplant medium. They are capable of operating at high temperatures involved in the welding process. The ultrasound generated by the laser phased array propagates through the weld pool and is picked up by the EMAT receiver. A signal-processing algorithm based on a cross-correlation technique has been developed to estimate the time-of-flight (TOF) of the ultrasound. The relationship between the TOF and the penetration depth of the weld has been established experimentally and analytically. The analytical relationship between the TOF and the penetration depth, which is obtained by the ray-tracing algorithm and geometric analysis, agrees well with the experimental measurements.
Identification of Spindle Integrated Force Sensor’s Transfer Function for Modular End Mills
Authors: Park Simon S.
Published: February 2006

A spindle integrated cutting force system where piezoelectric force sensors are embedded in the spindle housing is studied. The transfer function between the force experienced at the end mill and measured at the spindle integrated force sensor varies depending on the tool length sticking out. In the paper, a method is proposed to predict the transfer function of the overall system by coupling the receptances of the analytically modeled end mill and experimentally measured spindle structures. The experimentally proven method allows for the automated calibration of the spindle integrated force system whenever a tool change occurs to accurately measure high-frequency bandwidth cutting forces.
Tensile-Shear Forces and Fracture Modes in Single and Multiple Weld Specimens in Dual-Phase Steels
Authors: Marya Manuel , Wang Kathy , Hector Louis G. , Gayden Xiaohong
Published: February 2006

In this article, weld fracture criteria based upon low strain rate (i.e., ε̇∼10−3-10−2s−1) tensile-shear tests of spot welds in dual-phase (DP) steels DP600, DP780, and DP980 are developed. Three empirical equations are inferred from least-squares root-fitting analyses of tensile-shear testing data. Building upon existing results in the literature, the first equation relates the tensile-shear force to the weld diameter. The second and third equations relate, respectively, a critical weld diameter and a critical tensile-shear force for interfacial fracture to the sheet thickness and hardness extrema in the heat-affected zone. These idealized equations can serve as the basis for further development of fracture criteria resembling material flow laws that account for higher strain rates and more complicated deformation paths. The effect of spot-weld placement in specific patterns or arrays on deformation and fracture behavior was also investigated to explore underlying effects from deformation field interactions between adjacent spot welds.
Combination Exposure to Zidovudine plus Sulfamethoxazole-Trimethoprim Diminishes B-Lymphocyte Immune Responses toPneumocystis murinaInfection in Healthy Mice
Authors: Feola David J. , Garvy Beth A.
Published: February 2006

We have previously shown that zidovudine plus sulfamethoxazole-trimethoprim exposure decreases immune cell populations in the bone marrow of healthy mice by inducing apoptosis. The hypothesis of the current work was that this toxicity would have an adverse impact on the immune response. To determine this, BALB/c mice were treated with zidovudine, sulfamethoxazole-trimethoprim, the combination of both drugs, or vehicle only (control) via oral gavage for 21 days. On day 4 after dosing completion, the mice were infected intratracheally with 1 × 107Pneumocystis murinaorganisms. Immune cell populations (in lung digest, bronchoalveolar lavage fluid, tracheobronchial lymph node, and bone marrow samples), the lungPneumocystisburden, and serumPneumocystis-specific antibody titers were determined at days 6, 10, and 20 postinfection. While total bone marrow cellularity was recovered by day 6 postinfection in the combination exposure group, B-cell numbers did not recover until 10 days postinfection, primarily due to the persistent depletion of the late pre-B-cell phenotype. The numbers of CD4+and CD8+T cells, as well as the numbers of total B cells and activated B cells in tracheobronchial lymph nodes, were decreased at days 10 and 20 as a result of zidovudine plus sulfamethoxazole-trimethoprim exposure compared to the numbers in the control group. No significant differences in lung lavage or lung digest cell populations were observed. There was a trend of a delay inPneumocystisclearance in the combination treatment group, andPneumocystis-specific serum immunoglobulin G titers were reduced at day 20 postinfection. Together, these data indicate that the combination of zidovudine and sulfamethoxazole-trimethoprim adversely affects the humoral immune response toPneumocystis.
Influence of Exogenous Reproductive Hormones on Specific Antibody Production in Genital Secretions after Vaginal Vaccination with Recombinant Cholera Toxin B Subunit in Humans
Authors: Wassen Lotta , Jertborn Marianne
Published: February 2006

The objective of this study was to investigate the influence of exogenous reproductive hormones on the local and systemic production of specific immunoglobulin A (IgA) and IgG antibodies after vaginal vaccination with recombinant cholera toxin subunit B (CTB). Three groups of women using either progesterone-containing intrauterine devices (
n
= 9), oral contraceptives (
n
= 8), or no hormonal contraceptive methods (
n
= 9) were vaginally immunized twice, 2 weeks apart. Cervical secretions, vaginal fluids, and serum were collected before and after vaccination. Total and CTB-specific IgA and IgG antibodies in genital secretions and serum were analyzed by enzyme-linked immunosorbent assay. A majority of the women presented strong CTB-specific IgA and IgG antibody responses in cervicovaginal secretions after vaccination, whereas the antitoxin responses in serum were weaker. Exogenously administered steroid hormones did not seem to have any impact on the production of specific antibodies. Both the frequencies and the magnitudes of IgA and IgG antitoxin responses in genital secretions were comparable among the three immunization groups. An association, in particular for IgA, was found between the magnitudes of the CTB-specific antibody responses in cervical secretions and vaginal fluids after vaccination. The sensitivities and positive predictive values of vaginal antibody analyses to reflect responses in cervical secretions were also high, suggesting that vaginal fluids alone might be used for evaluation of genital immune responses in large-scale vaccination studies in the future.
Neutralizing Antibodies and Persistence of Immunity following Anthrax Vaccination
Authors: Hanson James F. , Taft Sarah C. , Weiss Alison A.
Published: February 2006

Anthrax toxin consists of protective antigen (PA) and two toxic components, lethal factor (LF) and edema factor (EF). PA binds to mammalian cellular receptors and delivers the toxic components to the cytoplasm. PA is the primary antigenic component of the current anthrax vaccine. Immunity is due to the generation of antibodies that prevent the PA-mediated internalization of LF and EF. In this study, we characterized sera obtained from vaccinated military personnel. Anthrax vaccine is administered in a series of six injections at 0, 2, and 4 weeks and 6, 12, and 18 months, followed by annual boosters. The vaccination histories of the subjects were highly varied; many subjects had not completed the entire series, and several had not received annual boosters. We developed a simple colorimetric assay using alamarBlue dye to assess the antibody-mediated neutralization of LF-mediated toxicity to the J774A.1 murine macrophage cell line. Recently vaccinated individuals had high antibody levels and neutralizing activity. One individual who had not been boosted for 5 years had low immunoglobulin G antibody levels but a detectable neutralization activity, suggesting that this individual produced low levels of very active antibodies.
Role of CYP2E1 Immunoglobulin G4 Subclass Antibodies and Complement in Pathogenesis of Idiosyncratic Drug-Induced Hepatitis
Authors: Njoku Dolores B. , Mellerson Jenelle L. , Talor Monica V. , Kerr Douglas R. , Faraday Nauder R. , Outschoorn Ingrid , Rose Noel R.
Published: February 2006

Idiosyncratic drug-induced hepatitis (IDDIH) is the third most common cause for acute liver failure in the United States. Previous studies have attempted to identify susceptible patients or early stages of disease with various degrees of success. To determine if total serum immunoglobulin subclasses, CYP2E1-specific subclass autoantibodies, complement components, or immune complexes could distinguish persons with IDDIH from others exposed to drugs, we studied persons exposed to halogenated volatile anesthetics, which have been associated with IDDIH and CYP2E1 autoantibodies. We found that patients with anesthetic-induced IDDIH had significantly elevated levels of CYP2E1-specific immunoglobulin G4 (IgG4) autoantibodies, while anesthetic-exposed healthy persons had significantly elevated levels of CYP2E1-specific IgG1 autoantibodies. Anesthetic IDDIH patients had significantly lower levels of C4a, C3a, and C5a compared to anesthetic-exposed healthy persons. C1q- and C3d-containing immune complexes were significantly elevated in anesthetic-exposed persons. In conclusion, our data suggest that anesthetic-exposed persons develop CYP2E1-specific IgG1 autoantibodies which may form detectable circulating immune complexes subsequently cleared by classical pathway activation of the complement system. Persons susceptible to anesthetic-induced IDDIH develop CYP2E1-specific IgG4 autoantibodies which form small, nonprecipitating immune complexes that escape clearance because of their size or by direct inhibition of complement activation.
The [
PSI
+
] Prion of
Saccharomyces cerevisiae
Can Be Propagated by an Hsp104 Orthologue from
Candida albicans
Authors: Zenthon Joanna F. , Ness Frederique , Cox Brian , Tuite Mick F.
Published: February 2006

The molecular chaperone Hsp104 is not only a key component of the cellular machinery induced to disassemble aggregated proteins in stressed cells of
Saccharomyces cerevisiae
but also plays an essential role in the propagation of the [
PSI
+
], [
URE3
], and [
RNQ/PIN
+
] prions in this organism. Here we demonstrate that the fungal pathogen
Candida albicans
carries an 899-residue stress-inducible orthologue of Hsp104 (CaHsp104) that shows a high degree of amino acid identity to
S. cerevisiae
Hsp104 (ScHsp104). This identity is significantly lower in the N- and C-terminal regions implicated in substrate recognition and cofactor binding, respectively. CaHsp104 is able to provide all known functions of ScHsp104 in an
S. cerevisiae hsp104
null mutant, i.e., tolerance to high-temperature stress, reactivation of heat-denatured proteins, and propagation of the [
PSI
+
] prion. As also observed for ScHsp104, overexpression of CaHsp104 leads to a loss of the [
PSI
+
] prion. However, unlike that of ScHsp104, CaHsp104 function is resistant to guanidine hydrochloride (GdnHCl), an inhibitor of the ATPase activity of this chaperone. These findings have implications both in terms of the mechanism of inhibition of Hsp104 by GdnHCl and in the evolution of the ability of fungal species to propagate prions.
Genome-Scale Analysis Reveals Sst2 as the Principal Regulator of Mating Pheromone Signaling in the Yeast
Saccharomyces cerevisiae
Authors: Chasse Scott A. , Flanary Paul , Parnell Stephen C. , Hao Nan , Cha Jiyoung Y. , Siderovski David P. , Dohlman Henrik G.
Published: February 2006

A common property of G protein-coupled receptors is that they become less responsive with prolonged stimulation. Regulators of G protein signaling (RGS proteins) are well known to accelerate G protein GTPase activity and do so by stabilizing the transition state conformation of the G protein α subunit. In the yeast
Saccharomyces cerevisiae
there are four RGS-homologous proteins (Sst2, Rgs2, Rax1, and Mdm1) and two Gα proteins (Gpa1 and Gpa2). We show that Sst2 is the only RGS protein that binds selectively to the transition state conformation of Gpa1. The other RGS proteins also bind Gpa1 and modulate pheromone signaling, but to a lesser extent and in a manner clearly distinct from Sst2. To identify other candidate pathway regulators, we compared pheromone responses in 4,349 gene deletion mutants representing nearly all nonessential genes in yeast. A number of mutants produced an increase (
sst2
,
bar1
,
asc1
, and
ygl024w
) or decrease (
cla4
) in pheromone sensitivity or resulted in pheromone-independent signaling (
sst2
,
pbs2
,
gas1
, and
ygl024w
). These findings suggest that Sst2 is the principal regulator of Gpa1-mediated signaling in vivo but that other proteins also contribute in distinct ways to pathway regulation.
Candida albicans VAC8
Is Required for Vacuolar Inheritance and Normal Hyphal Branching
Authors: Barelle Caroline J. , Richard Mathias L. , Gaillardin Claude , Gow Neil A. R. , Brown Alistair J. P.
Published: February 2006

Hyphal growth is prevalent during most
Candida albicans
infections. Current cell division models, which are based on cytological analyses of
C. albicans
, predict that hyphal branching is intimately linked with vacuolar inheritance in this fungus. Here we report the molecular validation of this model, showing that a specific mutation that disrupts vacuolar inheritance also affects hyphal division. The armadillo repeat-containing protein Vac8p plays an important role in vacuolar inheritance in
Saccharomyces cerevisiae
. The
VAC8
gene was identified in the
C. albicans
genome sequence and was resequenced. Homozygous
C. albicans vac8
Δ deletion mutants were generated, and their phenotypes were examined. Mutant
vac8
Δ cells contained fragmented vacuoles, and minimal vacuolar material was inherited by daughter cells in hyphal or budding forms. Normal rates of growth and hyphal extension were observed for the mutant hyphae on solid serum-containing medium. However, branching frequencies were significantly increased in the mutant hyphae. These observations are consistent with a causal relationship between vacuolar inheritance and the cell division cycle in the subapical compartments of
C. albicans
hyphae. The data support the hypothesis that cytoplasmic volume, rather than cell size, is critical for progression through G
1
.
Synthesis and Biological Evaluation of (E)-3-(Nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones
Authors: Opletalová Veronika , Pour Milan , Kuneš Jiří , Buchta Vladimír , Silva Luís , Kráľová Katarína , Chlupáčová Marta , Meltrová Dana , Peterka Milan , Posledníková Martina
Published: February 2006

The title (E)-(3-nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones were prepared by the Claisen- Schmidt condensation of acetylpyrazines and 2-nitro-, 3-nitro- and 4-nitrobenzaldehyde in pyridine using diethylamine as the catalyst. The compounds were bioassayed for in vitro antifungal, antimycobacterial and photosynthesis-inhibiting activity. The high potency of (E)-1-(5-tert-butylpyrazin-2-yl)-3-(4-nitrophenyl)prop-2-en-1-one againstMycobacterium tuberculosis(MIC 0.78 μg/ml) and moderate activities of several compounds againstTrichophyton mentagrophytesandCandidaspp. do not support the assumption that phenolic groups are essential for antimycobacterial and antifungal activity of chalcones and their analogues. In fact, the nitro-substituted compounds were superior to the previously described hydroxylated congeners with antimycobacterial activity (MIC ≥ 12.5 μg/ml). The compounds also reduced chlorophyll content in green algaChlorella vulgaris, and some of them inhibited photosynthetic electron transport in spinach chloroplasts as well. The photosynthesis-inhibiting activity of nitro derivatives was lower than that of the corresponding hydroxylated analogues.
Effect of all-transretinoic acid on tissue dynamics of choriocarcinoma cell lines: an organotypic model
Authors: Chiu P M , Feng H C , Benbrook D M , Ngan H Y S , Khoo U S , Xue W C , Tsao S W , Chan K W , Cheung A N Y
Published: February 2006

Background:All-transretinoic acid (ATRA) is a natural vitamin A derivative that has a profound effect on the regulation of cell growth, differentiation and death.

Aim:To investigate the tissue dynamic and cellular invasion effects of ATRA in choriocarcinoma (CCA), an aggressive trophoblastic tumour, by using a three-dimensional organotypic culture model system and cell invasion assay, respectively.

Methods:An organotypic culture model of two CCA cell lines, JAR and JEG, was established. The effects of 1 μM ATRA on proliferation, differentiation and apoptosis on this CCA model were assessed by morphological assessment of the mitotic and apoptotic figures as well as by Ki-67 and caspase-related M30 cytoDeath antibody immunohistochemistry and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay. The effect of ATRA on p53 and its regulated protein product, WAF1/Cip1, was also evaluated with DO7 and p21WAF1antibodies, respectively. Moreover, the effect of ATRA on cellular (CCA) invasion was also investigated with Cell Invasion Kit on the JEG cell line.

Results:ATRA was found to induce marked apoptosis in organotypic cultures of both cell lines, as evidenced by increased M30-positive cells (p<0.0001) and increased TUNEL-positive cells (p<0.0001) in treated cultures; to decrease proliferation, as evidenced by decreased Ki-67-positive cells (p<0.0001); and to decrease p53-DO7 immunoreactivity (p<0.0001) and increase p21WAF1(p<0.0001) immunoreactivity. 1.5 μM ATRA was found to effectively inhibit JEG cell invasion in the cell invasion assay.

Conclusion:ATRA treatment was found to inhibit invasion and proliferation and enhance apoptosis, probably by the activation of caspases and induction of differentiation. ATRA and synthetic retinoids may be alternative agents for the treatment of CCA.
Redox front formation in fractured crystalline rock: an analogue of matrix diffusion in an oxidizing front along water-conducting fractures
Authors: Akagawa Fuminori , Yoshida Hidekazu , Yogo Setsuo , Yamomoto Koshi
Published: February 2006

Redox fronts may be formed in the geological environment surrounding a shallow geological repository for radioactive waste due to oxidized pore water infiltration. Such oxidation fronts can exert an influence on contaminant retardation during matrix diffusion via redox changes and direct fixation by accumulated oxides. However, the process of matrix diffusion in oxidizing fractured crystalline rocks has rarely been described. This study focuses on a redox front in Cretaceous granitic rocks from central Japan. Detailed observations reveal that ferric iron has accumulated at grain boundaries and formed micro-spherical Fe-oxyhydroxide aggregations. Geochemical analyses with X-ray fluorescence, inductively coupled plasma–mass spectrometry and electron probe microanalysis examination show that rare earth elements, Cs and U have migrated to the front. Uranium, in particular, has been enriched at the front edge and probably retained by Fe-oxyhydroxides and this relationship persists in the oxidizing zone, presumably due to the strong adsorption capacity of the oxyhydroxides. These findings suggest that matrix diffusion in the oxidizing zone also can be an effective contaminant retardation.
PHYTOCHROME STRUCTURE AND SIGNALING MECHANISMS
Authors: Rockwell Nathan C. , Su Yi-Shin , Lagarias J. Clark
Published: February 2006

Phytochromes are a widespread family of red/far-red responsive photoreceptors first discovered in plants, where they constitute one of the three main classes of photomorphogenesis regulators. All phytochromes utilize covalently attached bilin chromophores that enable photoconversion between red-absorbing (Pr) and far-red-absorbing (Pfr) forms. Phytochromes are thus photoswitchable photosensors; canonical phytochromes have a conserved N-terminal photosensory core and a C-terminal regulatory region, which typically includes a histidine-kinase-related domain. The discovery of new bacterial and cyanobacterial members of the phytochrome family within the last decade has greatly aided biochemical and structural characterization of this family, with the first crystal structure of a bacteriophytochrome photosensory core appearing in 2005. This structure and other recent biochemical studies have provided exciting new insights into the structure of phytochrome, the photoconversion process that is central to light sensing, and the mechanism of signal transfer by this important family of photoreceptors.
PROTEIN DEGRADATION MACHINERIES IN PLASTIDS
Authors: Sakamoto Wataru
Published: February 2006

Plastids undergo drastic morphological and physiological changes under different developmental stages and in response to environmental conditions. A key to accomplishing these transitions and maintaining homeostasis is the quality and quantity control of many plastid proteins by proteases and chaperones. Although a limited number of plastid proteases have been identified by biochemical approaches, recent progress in genome information revealed various plant proteases that are of prokaryotic origin and that are localized in chloroplasts. Of these, ATP-dependent proteases such as Clp, FtsH, and Lon are considered the major enzymes involved in processive degradation (gradual degradation to oligopeptides and amino acids). The basic architecture of plant ATP-dependent proteases is very similar to the architechture of bacterial enzymes, such as those in Escherichia coli, but plastid enzymes apparently have extraordinary numbers of isomers. Recent molecular genetic characterization in Arabidopsis has identified differential roles of these isomers. This review covers what is currently known about the types and function of plastid proteases together with our new observations.