bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Interaction Between Cadmium and Plumbum on Phytochelatins and Glutathione Production in Wheat (Triticum aestivum L.)
Authors: SUN Qin , WANG Xiao‐Rong , DING Shi‐Ming , YUAN Xin‐Fang
Published: April 2005

Abstract: Phytochelatins (PCs) may function as a potential biomarker for metal toxicity. However, less attention has been paid to the effects of metal interactions on the production of PCs and glutathione (GSH), the most prominent cellular thiol. In the present study, the effects of interactions between cadmium (Cd) and plumbum (Pb) on the production of PCs and GSH were monitored over a period of 14 d in wheat (Triticum aestivum L.) tissues. The results showed that combination of Cd and Pb led to synergistic growth inhibition in wheat. Exposure to Cd or Pb increased levels of PCs in a concentration‐, tissue‐, and time‐dependent manner. Cadmium was more effective that Pb in increasing PCs production. Compared with the effects of Cd or Pb alone on the production of PCs, the combination of Cd and Pb acted synergistically, resulting in an enhanced production of PCs. Cadmium also stimulated GSH production in a concentration‐, tissue‐, and time‐dependent manner. However, Pb had no obvious effects on GSH levels. The combination of Pb and Cd antagonized GSH production over the course of the growth period. The results of the present study suggest that metal interactions should be considered in the application of PCs and GSH as potential biomarkers for the evaluation of metal toxicity.

(Managing editor: Ping HE)
Effects of Exogenous Spermidine on Antioxidant System Responses of Typha latifolia L. Under Cd2+ Stress
Authors: TANG Chun‐Fang , LIU Yun‐Guo , ZENG Guang‐Ming , LI Xin , XU Wei‐Hua , LI Cheng‐Feng , YUAN Xing‐Zhong
Published: April 2005

Abstract: The effects of foliar spraying with spermidine (Spd), ranging in concentration from 0.25 to 0.50 mmol/L, on the antioxidant system under Cd2+ stress (range 0.1–0.2 mmol/L Cd2+) in Typha latifolia L. grown hydroponically were investigated in order to offer a referenced evidence for an understanding of the mechanism by which polyamines (PAs) relieve the damage to plants by heavy metal and improve the phytoremediation efficiency of heavy metal‐contaminated water. The results showed that Cd2+ stress induced oxidative injury, as evidenced by an increase in the generation of superoxide anion (O2‐), as well as the hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents in both leaves and caudices. With the exception of superoxide dismutase (SOD) activity in the leaves, an increase in the activities of catalase (CAT), guaiacol peroxidase (GPX), and glutathione reductase (GR) was observed in both leaves and caudices, SOD activity was increased in caudices, and ascorbate peroxidase (APX) activity was increased in leaves following Cd2+ treatment. The reduced glutathione (GSH) content in both leaves and caudices and the reductive ascorbate content in leaves was obviously increased, which were prompted by the application of exogenous Spd. Spraying with Spd increased the activity of GR and APX in both leaves and caudices, whereas the activity of SOD, CAT, and GPX was increased only in caudices following spraying with Spd. The generation of O2 ‐. and the H2O2 and MDA content in both leaves and caudices decreased after spraying with Spd. The decrease in MDA was more obvious following the application of 0.25 than 0.50 mmol/L Spd. It is supposed that exogenous Spd elevated the tolerance of T. latifolia under Cd2+ stress primarily by increasing GR activity and the GSH level.

(Managing editor: Ping HE)
Analysis of the Genetic Structure of Sclerotinia sclerotiorum (Lib.) de Bary Populations from Different Regions and Host Plants by Random Amplified Polymorphic DNA Markers
Authors: SUN Jun‐Ming , IRZYKOWSKI Witold , JEDRYCZKA Malgorzata , HAN Fen‐Xia
Published: April 2005

Abstract: The genetic diversity and genetic structure of a population of isolates of Sclerotinia sclerotiorum (Lib.) de Bary from different regions and host plants were investigated using the random amplified polymorphic DNA (RAPD) method with 20 random decamer primer pairs in order to provide some information on the phylogenetic taxa and breeding for resistance to sclerotinia stem rot. A minimum of three and a maximum of 15 unambiguously amplified bands were generated, furnishing a total of 170 bands ranging in size from 100 to 3 200 bp, corresponding to an average of 8.5 bands per primer pair. One hundred and four of these 170 bands (61.2%) were polymorphic, the percentage of polymorphic bands for each primer pair ranging from 0.0% to 86.7%. The genetic relationships among the isolates, based on the results of RAPD analysis, were examined. The genetic similarity of all selected isolates was quite high. At the species level, the genetic diversity estimated by Nei's gene diversity (h) was 0.197 and Shannon's index of diversity (I) was 0.300. The unweighted pair‐group mean analysis (UPGMA) cluster analysis showed that most isolates from the same regions were grouped in the same cluster or a close cluster. The population of isolates from Hefei (Anhui Province, China) was more uniform and relatively distant to other populations. The Canadian population collected from carrot (Daucus carota var. sativa DC.) was relatively close to the Polish population collected from oilseed rape (Brassica napus L.) plants. There was no relationship between isolates from the same host plants. An analysis of molecular variance (AMOVA) revealed that the percentage of variance attributable to variation among and within populations was 50.62% and 49.38%, respectively. When accessions from China, Europe, and Canada were treated as three separate groups, the variance components among groups, among populations within groups, and within populations were −0.96%, 51.48%, and 49.47%, respectively. The genetic differentiations among and within populations were highly significant (P < 0.001). Similarly, the coefficient of gene differentiation (Gst) in total populations calculated by population genetic analysis was 0.229 4, which indicated that the genetic variation among populations was 22.94%. The gene flow (Nm) was 1.68, which indicated that the gene permutation and interaction among populations was relatively high.

(Managing editor: Wei WANG)
Volatile Organic Compounds and Their Roles in Bacteriostasis in Five Conifer Species
Authors: GAO Yan , JIN You‐Ju , LI Hai‐Dong , CHEN Hua‐Jun
Published: April 2005

Abstract: In order to make clear the functions of plant volatile organic compounds (VOCs) on bacteriostasis and air decontamination, we analyzed the composition and content of VOCs in Pinus tabulaeformis Carr., P. bungeana Zucc., Sabina chinensis Antoine, Picea koraiensis Nakai, and Cedrus deodara G. Don under near‐natural conditions using the thermal‐desorption cold trap gas chromatography/mass spectrometer technique. The effects of the VOCs on airborne microorganisms were investigated using the method of natural sedimentation. Results showed that the major VOCs were as follows: limonene, β‐pinene, α‐pinene, and α‐caryophyllene in Pinus tabulaeformis and P. bungeana; limonene, borneol acetate, β‐pinene, myrcene, and tricylene in S. chinensis; limonene, α‐pinene, myrcene, camphene, and β‐pinene in Picea koraiensis; and limonene, 2, (10)‐pinene, α‐pinene, and myrcene in C. deodara. These VOCs and the corresponding foliar extracts inhibited the growth of bacteria and stimulated the growth of fungi. Experimental data using monomers of the VOCs demonstrated that limonene, β‐pinene, and three aldehydes could significantly inhibit bacterial growth, suggesting an inhibitory effect of VOCs on the growth of airborne microorganisms in the five conifer species. The bacteriostasis and air‐decontaminating effects of plant VOCs are further discussed in terms of their chemical composition.

(Managing editor: Wei WANG)
Vitamins A, C, and E and β‐Carotene Content in Seeds of Seven Species of Vicia L.
Authors: SAHIN Ahmet , KIRAN Yasar , KARATAS Fikret , SONMEZ Senem
Published: April 2005

Abstract: To determine the vitamins A, C, and E and β‐carotene content of Vicia species that can be used in animal feed, a high performance liquid chromatography (HPLC) method was used to investigate the vitamin and β‐carotene content in mature and immature seeds of seven Vicia species (Vicia anatolica Turrill., V. ervilia (L.) Willd., V. michauxii Sprengel, V. mollis Boiss. et Hausskn. ex Boiss., V. noeana Reuter ex Boiss., V. peregrina L., and V. sericocarpa Fenzl.), which are useful plants in animal feed in the eastern Anatolia region in Turkey. The vitamin content was found to differ between mature and immature seeds. The levels of vitamins A, C, and E and β‐carotene were higher in mature seeds than in immature seeds (P < 0.01).

(Managing editor: Wei WANG)
Dimethyl Sulfoxide Is Feasible for Plant Tubulin Assembly In vitro: A Comprehensive Analysis
Authors: XU Chun‐Hua , HUANG Shan‐Jin , YUAN Ming
Published: April 2005

Abstract: It is much more difficult for tubulin from plant sources to polymerize in vitro than tubulin from animal sources. Taxol, a most widely used reagent in microtubule studies, enhances plant microtubule assembly, but hinders microtubule dynamics. Dimethyl sulfoxide (DMSO), a widely used reagent in animal microtubule studies, is a good candidate for the investigation of plant microtubule assembly in vitro. However, proper investigation is lacking about the effects of DMSO on plant microtubule assembly in vitro. In the present study, DMSO was used to establish optimal conditions for the polymerization of plant tubulin. Tubulin, purified from lily pollen, polymerizes into microtubules at a critical concentration of 1.2 mg/mL in the presence of 10% DMSO. The polymers appear to have a normal microtubule structure, as revealed by electron microscopy. In the presence of 10% DMSO, microtubule polymerization decreases when the pH of the medium is increased from 6.5 to 7.4. Both the polymerization rate and the mass of the polymers increase as temperature increases from 25 to 40 °C. Tubulin polymerizes and depolymerizes along with cycling of temperature, from 37 to 4 °C, or following the addition to or the removal of Ca2+ from the medium. When incubated with nuclei isolated from tobacco BY‐2 suspension cells, tubulin assembles onto the nuclear surface in the presence of 10% DMSO. Labeling lily pollen tubulin with 5‐ (and 6‐) carboxytetramethyl‐rhodamine succinimidyl ester (NHS‐rhodamine) was performed successfully in the presence of 10% DMSO. Labeled tubulin assembles into a radial structure on the surface of BY‐2 nuclei. The polymerization of lily pollen tubulin is also enhanced by microtubule‐associated proteins from animal sources in the presence of 10% DMSO. All the experimental results indicate that plant tubulin functions normally in the presence of DMSO. Therefore, DMSO is an appropriate reagent for plant tubulin polymerization and investigation of plant microtubules in vitro.

(Managing editor: Li‐Hui ZHAO)
Starch Mobilization in Ultradried Seed of Maize (Zea mays L.) During Germination
Authors: WANG Xiao‐Feng , JING Xin‐Ming , LIN Jian
Published: April 2005

Abstract: The effects of ultradry storage on the starch mobilization in maize (Zea mays L.) seed after aging were investigated. The results indicated that there were no significant differences in the content of ATP, starch, and soluble sugar, as well as the activity of amylase, between ultradried seeds and seeds stored at −20 °C during germination. These results were consistent with the higher level of vigor of the ultradried seed. Sieve tube introduction of a fluorescence dye (carboxyl fluoresceindiacetate) and laser confocal microscopy were used to study the development of plasmodesmata in the ultradried seeds. The results indicated that plasmodesmata developed well in ultradried seeds. Fluorescence analysis also showed that the fluorescence intensity in the radicle of ultradried seeds was stronger than that in seeds with a higher moisture content. This suggests that ultradry treatment has no adverse effects on the seeds. After seed imbibition, cell orgaelles could be resumed. It is concluded that ultradry seed storage is beneficial for maintaining seed vigor and that starchy mobilization proceeds regularly during germination.

(Managing editor: Ping HE)
EVOLUTION OR EXTINCTION: WHERE ARE BANKS HEADED?
Authors: James Christopher , Houston Joel
Published: April 2005

The banking industry represents an interesting and important case study of how changes in technology and regulation influence business strategy and organizational design. A narrow focus on traditional bank products and performance measures would lead one to conclude that banking is a declining industry. Such a focus, however, would miss most of the innovations in banking–most notably, the move to “off‐balance‐sheet” activities–that have been taking place in recent years. A broader perspective shows banks evolving in ways that are enabling them to provide the same basic functions as before, but in new, more efficient ways.

In the past, most banks thought of themselves as delivering a set of specific, largely unrelated products to different sets of customers. Today many banks are pursuing strategies that aim to strengthen their ability to perform various functions–for example, financial planning for retail clients, or raising capital for middle market companies–that tend to cut across the old product boundaries. As a result, and in contrast to most industrial firms, many banks are offering a more diversified range of products and services than ever before with the aim of exploiting potential synergies among those products.

Such major changes in banks' strategies are in turn leading to fundamental changes in their “organizational architecture.” Some banking activities that were once controlled by a rigid management hierarchy are now being decentralized, whereas other functions that were largely decentralized are being subjected to more central coordination to help realize potential economies of scale and scope.

Along with these changes in decision‐making authority, banks are also being forced to rethink their internal performance evaluation and incentive compensation systems. As an ever larger portion of their activities continues to move off balance sheet, more and more banks are deciding that conventional accounting measures of bank operating performance such as ROA and ROE are inadequate, and that economic measures of performance like RAROC and EVA are needed to reflect the new reality of where banks are putting their capital at risk, and whether the rates of return they are earning on their different activities are high enough to reward their shareholders.
RAROC AT BANK OF AMERICA: FROM THEORY TO PRACTICE
Authors: Zaik Edward , Walter John , Retting Gabriela , James Christopher
Published: April 2005

In 1993, Bank of America's Risk and Capital Analysis Group was charged with the task of developing and instituting a single corporate‐wide system to allocate capital to all the bank's activities. Since 1994, that system has been providing quarterly reports of risk‐adjusted returns on capital (RAROC) for each of the bank's 37 major business units. By 1995, B of A had also developed the capability to calculate RAROC down to the level of individual products, transactions, and customer relationships.

RAROC systems allocate capital for two basic reasons: (1) risk management and (2) performance evaluation. For risk management purposes, the overriding goal of allocating capital to individual business units is to determine the bank's optimal capital structure–the proportion of equity to assets that minimizes the bank's overall cost of funding. This process involves estimating how much the risk (or volatility) of each business unit contributes to the total risk of the bank, and hence to the bank's overall capital requirements. For performance evaluation purposes, RAROC systems assign capital to business units as part of a process of determining the risk‐adjusted rate of return and, ultimately, the “economic profit” of each business unit. The objective in this case is to measure a business unit's contribution to shareholder value, and thus to provide a basis for effective planning, capital budgeting, and incentive compensation at the business unit level.

Concerns about capital adequacy, along with the Basel risk‐based capital requirements, have played some role in the growth of RAROC among commercial banks. But the most powerful impetus to bankers' use of more systematic risk measures is coming from increasingly activist institutional investors. Besides giving senior management an economic basis for evaluating the bank as a portfolio of businesses and for making resource allocation decisions that improve the bank's risk/reward profile, RAROC systems are also expected to produce better performance by holding managers accountable for the amount of investor capital they are putting at risk.
EXPRESS LANE OR TOLLBOOTH IN THE DESERT? THE SEC'S FRAMEWORK FOR SECURITY ISSUANCE
Authors: Bethel Jennifer E. , Sirri Erik R.
Published: April 2005

U.S. companies that need capital may choose between selling securities in the private and public markets. These venues differ in terms of direct issuance costs, the required information disclosed, the liability incurred, and the mechanics of the capital‐raising process itself. During the last two decades, the Securities and Exchange Commission (SEC) has deregulated private offerings by broadening their investor base and increasing secondary market liquidity. At the same time, SEC policy has bifurcated the offering process in the public market into two distinct segments based largely on company size and seasoning. Large public issuers have seen a gradual deregulation and acceleration of their capitalraising processes. Important changes for issuers include allowing them to incorporate information into registration statements by reference to Exchange Act reports, to use shelf registration to speed up offers, and to place securities offshore with less regulatory uncertainty. Though small issuers enjoy some of the benefits of these changes, deregulation of their offerings has been somewhat less pronounced. In a Commission report and a subsequent concept release, the SEC indicates it may restructure and unify these three disparate strands of capital raising through an innovative schema of registering companies rather than securities.
MIPS, QUIPS AND TOPrS: OLD WINE IN NEW BOTTLES
Authors: Khanna Arun , McConnell John J.
Published: April 2005

Monthly Income Preferred Stock (MIPS), Quarterly Income Preferred Stock (QUIPS), and Trust Originated Preferred Stock (TOPrS) all carry the title of preferred stock. As in the case of other forms of preferred stock, investors cannot force the issuer into bankruptcy if it fails to make a scheduled dividend payment. Unlike conventional preferred stock, however, the dividend payments on these new securities are deductible by the issuer for tax purposes.

Thus MIPS, QUIPS and TOPrS appear to provide issuers with in some respects the ideal security–one that offers the tax advantages of debt without the potential for financial distress and its associated costs. And since the first issue of this kind of security in 1993, nearly 300 corporate issuers have raised a total of close to $30 billion with this novel hybrid security.

But if these securities appear new, there is another security–namely, income bonds–that has offered these same advantages for at least the past 100 years. After discussing MIPS, QUIPS, and TOPrS in some detail, and the stock market's reaction issuing companies, the article explores the question: Why are tax‐deductible preferreds so popular today when income bonds have been shunned for the past 60 years?
THE BALANCED CAPITAL STRUCTURE
Authors: Patrick Steven C.
Published: April 2005

At leading companies, financial executives are becoming business partners rather than just scorekeepers. In this environment, capital structure can be a source of competitive advantage, and financial strategy issues are critical: Should your company buy back shares or issue stock, grow internally or join the M & A boom, issue fixed‐rate debt or stay floating? These decisions must be addressed one company at a time, balancing the competing priorities of cost, risk, and flexibility.

The most important issue, target leverage, depends on the company's desired risk profile, growth plans, and debt cost considerations. But market conditions are also very important: Can the company access the equity market? How will a repurchase announcement be interpreted? Market conditions also affect the raising of debt capital. Rather than maintaining a constant mix of fixed‐ to floating‐rate debt, companies should shift the mix during high‐ or low‐yield environments.

Many other financing issues will effectively be decided by market convention. For example, meeting a company's needs with respect to seniority, maturity structure, call flexibility, and financial covenants is often accomplished simply by choosing the market that most closely matches the firm's cost and risk preferences.
WHO WINS IN LARGE STOCK BUYBACKS – THOSE WHO SELL OR THOSE WHO HOLD?
Authors: McNally William
Published: April 2005

Both fixed‐price and dutch auction repurchases offer large premiums over current values to tendering shareholders. And, because announcements of such offers are generally accompanied by significant increases in stock prices, economists view selftender offers as mechanisms for signaling undervaluation.

Using samples of fixed‐price and dutch auction self‐tender offers from the 1980s, this study attempts to answer the following questions: Are non‐tendering shareholders fully compensated for the premium wealth transfer by the increase in the intrinsic value of their shares? Since fixed‐price offers feature larger premiums, are they accompanied by larger increases in intrinsic value (or do insiders have a tendency to “overpay” in fixed‐price offers)? Is the premium wealth transfer a big component of the returns to the two shareholder groups—and what percentage of firm value does the transfer represent?

The findings of this study, unlike those reported by earlier research, suggest that the two types of offers generate roughly the same total returns (about 10–11%, on average, during the offering period) to shareholders who do not tender. Fixed‐price offers involve considerably larger premiums (over the new, “full‐information” price) and wealth transfers than dutch auctions. Reflecting the higher premiums, shareholders tendering into fixed‐price offers receive higher returns than those tendering into dutch auctions (13.8% vs. 11.3% during the announcement period). But while fixed‐price offers involve a considerably larger wealth transfer from non‐tendering to tendering shareholders, fixed‐price repurchases compensate the non‐tendering shareholders for the larger wealth transfer with larger increases in “intrinsic value,” thus generating the same total return as dutch auctions. Moreover, despite the large premiums offered in both types of offers, the wealth transfer implicit in the premium represents a small cost (less than 1% in fixed‐price offers, and less than 0.1% in dutch auctions) to non‐tendering shareholders.
EVIDENCE ON HOW COMPANIES CHOOSE BETWEEN DIVIDENDS AND OPEN‐MARKET STOCK REPURCHASES
Authors: Bartov Eli , Krinsky Itzhak , Lee Jason
Published: April 2005

Dividends and open‐market stock repurchases are by far the two most common mechanisms for distributing excess cash to shareholders. This article identifies and then tests three potentially important factors for the corporate choice between increasing cash dividends and initiating openmarket stock repurchases. More specifically, the authors argue that companies are more likely to distribute cash to investors through open‐market repurchases than through dividend increases when (1) management believes its stock is undervalued, (2) management compensation packages include stock options, and (3) the company's stockholder base is dominated by institutional investors.

To test these three explanations, the authors use a matched‐pair design in which each company announcing an open market repurchase program in a given year is matched with a comparable‐size firm from the same industry that increased its cash dividends but did not initiate an open‐market repurchase program. As predicted, the results suggest that equity undervaluation, management compensation, and the level of institutional holdings are all important contributors to corporate choices between dividend increases and open‐market repurchases.
THE CHALLENGE OF MANAGING CREDIT SPREADS: NEW TOOLS ON THE HORIZON
Authors: Kalotay Andrew , Abreo Lesil , Darigan Michael
Published: April 2005

Broadly speaking, “credit spread” is the excess of a bond's yield over the appropriate Treasury rate that is necessary to compensate lenders for the perceived risk of default. In the primary market, credit spreads can significantly increase a corporation's borrowing cost. In the secondary market, the effect of fluctuating spreads is of material concern to investors and traders.

Credit spreads have exhibited considerable volatility in recent years, particularly during the fall of 1998. Although the absolute levels of spreads have ranged widely in recent years, from a few basis points to several hundred depending on rating category, their volatilities have been remarkably similar—about 25 to 39% on an annual basis. In spite of this high volatility, there are currently no cost‐effective means of hedging credit spreads.

The recently announced S&P Credit Indices presage a leap forward in credit derivatives. Computed from the prices of selected liquid bonds, these indices can serve as a basis for exchange‐traded futures contracts and options—tools that are in great demand for managing credit spread exposure.
THE CEO: A VISIBLE HAND IN WEALTH CREATION?
Authors: Prahalad C. K. , Doz Yves
Published: April 2005

Commensurate with the growth of their pay packages and public visibility, the role of the CEO in the corporate value creation process has increased significantly in recent years. This article argues that sustained wealth creation in a corporation has three distinct elements. The first and most basic is the selection of the lines of business in which to operate; this element is probably the most visible manifestation of CEO action in large corporations today. The second element is the value creation model, which answers the question: How is this particular set of businesses expected to add value over and above the sum of the values of each business or asset category standing alone? The third element is the internal governance system, which establishes the corporate structure and administrative processes of the firm and, perhaps even more important, defines the corporate values that drive the strategic and operational priorities of the different business units. The authors suggest that the essence of the work of the CEO is to develop and maintain a balanced relationship among these three elements of wealth creation and to ensure that the relationship evolves in the face of changing circumstances.

CEOs are inevitably faced with dilemmas in managing this process—in particular, the need to balance continuity and change and to maintain the integrity of short‐term performance disciplines while encouraging not only investment in growth opportunities (which can hurt near term performance), but also experimentation and collaboration among business units (which are difficult to measure and reward with most performance measurement and incentive schemes). Adding to the difficulties of managing such dilemmas, visibility and a strong public image are often thrust upon (if not sought by) CEOs, who must then determine how they can use that image to strengthen the commitment of their employees and investors.
JOINING THE NEW ECONOMY
Authors: Glassman David
Published: April 2005

The decline in the costs of communicating, coordinating, and collaborating across firms in the value chain has led to the emergence of new business models—virtually integrated companies, retail “bricks and clicks” organizations, and networks like AOL and eBay—that can be used by all kinds of companies to exploit new opportunities. With these new organizations comes a need for new governance practices—practices that permit swifter decisions, best practice sharing, and more focused operations.

The author argues that improvements in governance should focus on achieving the following:

 Organization structures that leverage external alliances while improving internal collaboration. This involves gaining acceptance of and support for a common aspiration across the company—the goal of deploying financial and human resources, complemented by technology, to build shareholder wealth.

 Performance measures that encourage managers to make longterm investments in capabilities even when accounting measures penalize earnings in the short term. This requires more than a change to internal measures that capitalize the spending; it also necessitates a more open dialogue with the investment community.

 Human resource policies that strengthen business literacy, reward collaboration, attract and retain entrepreneurs, and align objectives across the company's regions, functions, and product lines.

 Building a culture that embraces the opportunities brought by change, and accommodates the partnerships and collaborations required of a business ecosystem.
Analysis of the Size Effect in Partial-Slip Contact Fatigue
Authors: Iyer K.
Published: April 2005

A size effect has been observed in cylinder-on-flat partial slip contact fatigue experiments (Hills et al., 1988 and 1990). The size effect in this case is defined as a discontinuous drop in the fatigue life beyond some critical value of the width of the contact region. New analysis that directly accounts for the finite substrate thickness used in the original experiments shows that both the maximum local bulk stress and maximum local bulk cyclic stress range increased systematically with contact width in the original cylinder-on-flat experiments, rather than remaining approximately constant as intended in the original experimental design.
A Mechanics Approach to Static Friction of Elastic–Plastic Fractal Surfaces
Authors: Yang J. , Komvopoulos K.
Published: April 2005

A contact mechanics theory of static friction is presented for isotropic rough surfaces exhibiting fractal behavior. The analysis is based on a piecewise power-law size distribution and a normal slope distribution of the asperity contacts and elastic–fully plastic deformation models. Numerical integration yields solutions for the normal and friction forces in terms of fractal parameters, elastic–plastic material properties, and interfacial shear strength. The variation of the static coefficient of friction with normal load is related to the effect of the surface topography on the dominant deformation mode at the asperity contacts. Plastic deformation of the smaller asperity contacts dominates at low loads and elastic deformation of the larger asperity contacts dominates at high loads. The critical load signifying the transition from predominantly plastic to elastic deformation depends on the fractal parameters and material properties. In the low-load range, the static coefficient of friction decreases with the increase of the load, while in the high-load range it increases with the load. Numerical results for copper fractal surfaces illustrate the effects of normal load, surface topography, and interfacial shear strength on the static coefficient of friction.
Modal and Nodal EHD Analysis for Gas Journal Bearings
Authors: Boedo S. , Booker J. F.
Published: April 2005

This paper presents a novel finite element elastohydrodynamic lubrication analysis appropriate for gas journal bearings under dynamic conditions. The method employs gas pressure as a state variable, and structural sleeve deformation is represented by a linear combination of pre-selected mode shapes obtained from a related eigenvalue problem. The method takes into account temporal variation of journal position and velocity, and second-order slip flow boundary effects are included at no additional computational cost. The formulation is subsequently applied to a particular example (flexible large-aspect ratio, high-speed, MEMS-scale journal microbearing), where it is shown that a judicious choice of structural sleeve elasticity can significantly improve bearing performance (as measured by pressure distribution and load capacity) when compared with results obtained using rigid bearing surfaces.
An Extension to a Cohesive Zone Solution for Adhesive Cylinders
Authors: Morrow Clint A. , Lovell Michael R.
Published: April 2005

When adhesive forces are taken into consideration, contacting asperities can still interact after intimate contact is broken. Current theories that predict the contact behavior of adhesive cylindrical asperities fail to capture the forces in this regime. In the present investigation, prior solutions for adhesive cylindrical asperities will be extended to include the condition where the asperities are not in physical contact but are still interacting through adhesive forces. In the extended results, relationships between the adhesive contact radius and the applied normal load will be developed and discussed with respect to the design of micro-scale components.
Quantifying Multidirectional Sliding Motions in Total Knee Replacements
Authors: Hamilton M. A. , Sucec M. C. , Fregly B. J. , Banks S. A. , Sawyer W. G.
Published: April 2005

This manuscript describes a formulaic method to predict the severity of crossing motions experienced by ultra-high-molecular-weight polyethylene (UHMWPE) under sliding conditions across a bearing surface. A statistical model for evaluating the distribution of sliding about this orientation is described. This model compares favorably to published experimental data on UHMWPE under multidirectional pin-on-disk testing. These algorithms are applied to the tibial component of a total knee replacement using patient-specific kinematics for gait and stair-rise activities collected using fluoroscopy. A dynamic contact model is used to calculate contact pressures and slip velocities on individual surface elements from this kinematic data. The most significant degree of crossing motion intensity was observed in the lateral compartments for both gait and stair-rise activities. This coincided with the location of maximum tribological intensity. The maximum crossing motions are characteristic of 4 and 9 deg of bidirectional crossing motion for gait and stair, respectively.
Effects of Compressive Heating on Traction Force and Film Thickness in Point EHL Contacts
Authors: Kaneta M. , Shigeta T. , Yang P.
Published: April 2005

The effects of compressive and viscous heatings of lubricating fluid on the traction force and film thickness are investigated under low slide-roll ratios by thermal EHL analyses based on the Newtonian and Eyring fluid models. The effects of the thermal conductivity of contacting surfaces and oil viscosity on EHL performance are also studied using combinations of actual and virtual contacting materials. It is found that the film thickness is hardly influenced by fluid models but is influenced very much by the atmospheric oil viscosity and the thermal conductivity of contacting materials even under the same set of dimensionless parameters G, U and W. It is also found that the compressive heating as well as non-Newtonian fluid behavior plays a very important role for the traction force in EHL contacts under low slide-roll ratios depending on the thermal conductivity of contacting surfaces and atmospheric oil viscosity.
Application of Atomic Force Microscopy to the Study of Lubricant Additive Films
Authors: Topolovec Miklozˇicˇ K. , Spikes H. A.
Published: April 2005

Constant force mode atomic force microscopy is used to examine the films formed on steel surfaces by three different types of lubricant additive. Work on molybdenum dithiocarbamate friction modifier additive solutions shows that this additive forms tiny domains of low friction on the high spots of rubbed surfaces. Complementary Raman surface analysis suggests that these domains represent crystallites of MoS2. Study of the reaction films formed by zinc dialkyldithiophosphate additives confirms the formation of pad-like structures by these additives on rubbed surfaces. Primary and secondary forms of the additive are shown to form films of different morphology and properties. Colloid probe atomic force microscopy has also been applied to study the boundary film-forming properties of functionalized viscosity modifier polymers. It is shown that these polymers can form viscous boundary films on rubbed surfaces which produce much lower friction than the corresponding, nonfunctionalised polymers. Overall it is suggested that atomic force microscopy can provide valuable information concerning the nature and properties of boundary films formed by lubricant additives especially when used in parallel with macro-scale friction and film thickness measurements.
Experimental and Analytical Study of Bouncing Vibrations of a Flying Head Slider in a Near-Contact Regime
Authors: Ono Kyosuke , Yamane Masami , Yamaura Hiroshi
Published: April 2005

This paper presents an experimental and analytical study of bouncing vibrations of a flying head slider in near-contact and contact regimes. In our experiment we showed that, by reducing the ambient pressure, the slider begins to touch-down and exhibit bouncing vibrations, and by increasing the ambient pressure thereafter, the slider continues to vibrate until an ambient pressure higher than the touch-down pressure. In the analysis we used a two-degrees-of-freedom slider model with linear front and rear air-bearing springs and dashpots. In a numerical simulation of slider dynamics, we considered rough surface contact of the trailing air-bearing pad with a disk, including bulk deformation, adhesion force of lubricant and friction force. The disk is assumed to have no microwaviness. From the simulation of decreasing and increasing nominal flying height, we found that the slider exhibits a bouncing vibration and touch-down/take-off hysteresis as seen in the experiment. The frequency spectrum characteristics of the bouncing vibration agree well between numerical analysis and the experiment. From a parametric study of the bouncing vibration excited by initial spacing deviation, we found that the unstable flying height range can be decreased by increasing the air-bearing stiffness and can be completely eliminated if the lubricant adhesion force or the frictional coefficient is decreased to certain small values.
An Experimental Study of Bearing and Thread Friction in Fasteners
Authors: Nassar S. A. , El-Khiamy H. , Barber G. C. , Zou Q. , Sun T. S.
Published: April 2005

An experimental procedure is proposed for studying the underhead and thread friction in fasteners. The effective bearing friction radius, the underhead friction coefficient, and the thread friction coefficient are experimentally determined for fasteners with standard hexagonal heads and for flanged head fasteners. Hence, greater accuracy has been achieved in determining the value of the torque components that are consumed in overcoming friction in threaded fasteners. This would lead to a more reliable torque-tension correlation and would enhance the safety and quality of bolted assemblies. A design of experiment procedure is presented in order to investigate the effect of fastener material class, the thread pitch, and the fastener size on thread friction coefficient. For the underhead bearing friction, an experimental model is presented in order to determine the effect of the radii ratio of the contact area on the bearing friction radius.
Application of Optimization Approach to Static FE Analysis of Hard Disk Drive Slider
Authors: Hwang Pyung , Khan Polina V.
Published: April 2005

The objective of the present work is to present the numerical analysis of the computer hard disk slider. The air film pressure is calculated using the finite element method. The conjugate-gradient method and the perturbation method are employed in the static analysis of the slider. The steady state attitude of the femto slider is studied for various radial positions and skew angles. It is found that the perturbation method is an efficient method for gradient evaluation. Also, it is shown that optimization of the Hessian matrix form accelerates the search process.
Experimental Identification of Elastic, Damping and Adhesion Forces in Collision of Spherical Sliders With Stationary Magnetic Disks
Authors: Ono Kyosuke , Ohara Satoshi
Published: April 2005

This paper deals with the experimental identification of elastic, damping and adhesion forces in the dynamic collision of a spherical slider with a stationary magnetic disk. We used rough Al2O3TiC and smooth glass spherical sliders with a radius of 1 mm, and magnetic disks with four different lubricant film thicknesses of 0, 1, 2, and 3 nm. We found that the Al2O3TiC slider shows ordinary approach and rebound processes, whereas the glass slider showed a velocity drop at the end of the rebound process when the lubricant thickness was 1, 2, and 3 nm. We identified the elastic force factors in the approach and rebound processes, based on Herztian contact theory, and the damping force factors based on a damping force model that is proportional to slider velocity and penetration depth (contact area). From the drop in velocity when the slider and disk separated, we found that the dynamic adhesion force is almost equal to the static pull-off force except for with a 3 nm lubricant thickness. The dynamic adhesion force with a 3 nm lubricant thickness is significantly higher, probably because of squeeze damping effect.
Contact Analyses for Bodies With Frictional Heating and Plastic Behavior
Authors: Boucly Vincent , Ne´lias Daniel , Liu Shuangbiao , Wang Q. Jane , Keer Leon M.
Published: April 2005

The stress field within machine components is an important indicator for contact failures. Since both thermal stresses due to frictional heating and plasticity are significant in engineering application, it is critical to predict the total stress field. In this work, the steady-state thermal effect is considered and a thermo-elastic–plastic contact model is developed. The model is applicable for rolling and/or sliding contact problem, as far as small equivalent plastic strain hypothesis is respected. Influence coefficients for surface normal displacement, temperature, and strain and stress tensors are used with the discrete convolution and fast Fourier transform algorithm. The single-loop conjugate gradient iteration scheme is also applied to achieve fast convergence speed. Simulations are presented for several academic examples ranging from elastic to thermo-elastic–plastic. The thermo-elastic–plastic analyses show that the heat factor in a contact situation has significant effect not only on the critical Hertzian pressure and on the pressure distribution, but also on the magnitude and depth of the maximum von Mises stress during loading and the residual ones found after unloading.
Effects of Inclusions and Microstructures on Impact Energy of High Heat-Input Submerged-Arc-Weld Metals
Authors: Kim Beomjoo , Uhm Sangho , Lee Changhee , Lee Jongbong , An Youngho
Published: April 2005

Submerged-arc-weld metal made with variations of heat-input and consumables were examined to study the inclusions and their effects on the Charpy impact energy of the weld metal as a measure of the toughness. From the analysis, inclusions, of which diameters were smaller than 2 μm, seemed to be effective for acicular ferrite nucleation and the fraction of acicular ferrite was in proportion to the number density of inclusions <2 μm. However, as the heat input increased, the average size of inclusions increased but their number density decreased. It was also observed that the grain sizes of polygonal ferrite with increased heat input. Accordingly, the decrease of the Charpy impact energy with the heat input is inevitable due to these microstructural changes. But, this does not mean that the acicular ferrite cannot be nucleated.
Surface Characterization Using Wavelet Theory and Confocal Laser Scanning Microscopy
Authors: Yuan Chengqing , Peng Zhongxiao , Yan Xinping
Published: April 2005

Surface characterization, particularly roughness analysis, is very important for a wide range of applications including wear assessment. This paper proposes a set of methods and techniques to acquire appropriate images using confocal laser scanning microscopy, to separate roughness, waviness, and form using wavelet theory, and to characterize surface roughness for engineering surfaces and surfaces of small particles. Two application examples on engineering surfaces and wear particles have been presented in the paper to demonstrate that the method developed in this study can be used to measure surface roughness reliably and precisely. A guide on how to determine the iris size, step size, and objective lens has been scientifically provided according to theoretical analysis and experimental results.
An Anomalous Elastohydrodynamic Lubrication Film: Inlet Dimple
Authors: Guo F. , Wong P. L.
Published: April 2005

This paper presents a deliberately designed elastohydrodynamical lubrication (EHL) experiment for the study of the individual effect of the limiting shear stress and wall slippage. Very slow entrainment speeds were employed to avoid influential shear heating and oils of high viscosities were chosen to ensure that the conjunction was under typical EHL. An anomalous EHL film, characterized by a dimple at the inlet region, was obtained. Literature revealed that this inlet dimple was reported in some numerical studies taking into consideration the limiting-shear-stress characteristics of the lubricant and wall slippage. It was found that even under the same kinematic conditions, different types of film shape would be generated by simple disc sliding and simple ball sliding. Simple disc sliding produces an inlet dimple with a comparatively thick inlet film thickness, which droops rapidly toward the outlet region. For simple ball sliding, there is also an inlet dimple but the central film thickness is rather uniform. However, by prerunning the conjunction at a zero entrainment velocity (at the same linear speeds but in opposite directions) before the sliding experiment, the slope of the central film of simple disc sliding becomes smaller. It is probably due to the modification of solid-liquid interface, i.e., the slippage level, by the highly pressurized and stressed prerunning conditions. With a prescribed prerunning, which can produce very similar films at simple disc sliding and simple ball sliding, variation of film thickness was studied and it was found that the inlet dimple film has obvious dependence on entrainment speeds, but was not sensitive to loads. The present experimental results can be considered as direct evidence for those numerical findings of the inlet dimple. Tentatively, an effective viscosity wedge is proposed to account for the formation of the inlet dimple.