bluuebunny/crossref_metadata_2025 huggingface dataset:
Arteriolar Remodeling Following Ischemic Injury Extends from Capillary to Large Arteriole in the Microcirculation
Authors: Bailey Alexander M. , O'Neill Thomas J. , Morris Cassandra E. , Peirce Shayn M.
Published: June 2008

Objective: Skeletal muscle vasculature undergoes arteriogenesis to restore tissue perfusion and function following loss of blood flow. This process has been shown to occur in large vessels following ischemia, although recent studies suggest this may occur in the microcirculation as well. We tested the hypothesis that ischemia induces microvascular remodeling in the skeletal muscle microcirculation on the scale of capillary to sub‐35 μm diameter arterioles.

Methods: Ligations of a feeding arteriole to the caudal‐half of the spinotrapezius muscle were performed on C57BL/6 mice. At 5 days, microvascular remodeling responses were quantified using intravital and whole‐mount confocal microscopy. Immunohistochemistry was performed to visualize vessels, incorporated leukocytes, and regions of hypoxia.

Results: Ischemic tissue underwent localized microvascular remodeling characteristic of arteriogenesis, including pronounced vessel tortuosity. In patent microvessels (diameters 15–35 μm), we observed increases in vascular density (38%), branching (90%) and collateral development (36.5%). The formation of new arterioles (diameters 6–35 μm) increased by 24.3%, while chronic hypoxia was absent from all tissues.

Conclusions: Ischemic injury induces arteriogenesis in skeletal muscle microcirculation. Furthermore, this surgical model enables en face analysis of microcirculatory adaptations with single‐cell resolution and can provide investigators with morphometric data on a microscale that is difficult to achieve using other models.
Regulation of ROS signal transduction by NADPH oxidase 4 localization
Authors: Chen Kai , Kirber Michael T. , Xiao Hui , Yang Yu , Keaney John F.
Published: June 2008

Reactive oxygen species (ROS) function as intracellular signaling molecules in a diverse range of biological processes. However, it is unclear how freely diffusible ROS dictate specific cellular responses. In this study, we demonstrate that nicotinamide adenine dinucleotide phosphate reduced oxidase 4 (Nox4), a major Nox isoform expressed in nonphagocytic cells, including vascular endothelium, is localized to the endoplasmic reticulum (ER). ER localization of Nox4 is critical for the regulation of protein tyrosine phosphatase (PTP) 1B, also an ER resident, through redox-mediated signaling. Nox4-mediated oxidation and inactivation of PTP1B in the ER serves as a regulatory switch for epidermal growth factor (EGF) receptor trafficking and specifically acts to terminate EGF signaling. Consistent with this notion, PTP1B oxidation could also be modulated by ER targeting of antioxidant enzymes but not their untargeted counterparts. These data indicate that the specificity of intracellular ROS-mediated signal transduction may be modulated by the localization of Nox isoforms within specific subcellular compartments.
Chibby cooperates with 14-3-3 to regulate β-catenin subcellular distribution and signaling activity
Authors: Li Feng-Qian , Mofunanya Adaobi , Harris Kimberley , Takemaru Ken-Ichi
Published: June 2008

β-Catenin functions in both cell–cell adhesion and as a transcriptional coactivator in the canonical Wnt pathway. Nuclear accumulation of β-catenin is the hallmark of active Wnt signaling and is frequently observed in human cancers. Although β-catenin shuttles in and out of the nucleus, the molecular mechanisms underlying its translocation remain poorly understood. Chibby (Cby) is an evolutionarily conserved molecule that inhibits β-catenin–mediated transcriptional activation. Here, we identified 14-3-3ε and 14-3-3ζ as Cby-binding partners using affinity purification/mass spectrometry. 14-3-3 proteins specifically recognize serine 20 within the 14-3-3–binding motif of Cby when phosphorylated by Akt kinase. Notably, 14-3-3 binding results in sequestration of Cby into the cytoplasm. Moreover, Cby and 14-3-3 form a stable tripartite complex with β-catenin, causing β-catenin to partition into the cytoplasm. Our results therefore suggest a novel paradigm through which Cby acts in concert with 14-3-3 proteins to facilitate nuclear export of β-catenin, thereby antagonizing β-catenin signaling.
Glial and neuronal isoforms of Neurofascin have distinct roles in the assembly of nodes of Ranvier in the central nervous system
Authors: Zonta Barbara , Tait Steven , Melrose Shona , Anderson Heather , Harroch Sheila , Higginson Jennifer , Sherman Diane L. , Brophy Peter J.
Published: June 2008

Rapid nerve impulse conduction in myelinated axons requires the concentration of voltage-gated sodium channels at nodes of Ranvier. Myelin-forming oligodendrocytes in the central nervous system (CNS) induce the clustering of sodium channels into nodal complexes flanked by paranodal axoglial junctions. However, the molecular mechanisms for nodal complex assembly in the CNS are unknown. Two isoforms of Neurofascin, neuronal Nfasc186 and glial Nfasc155, are components of the nodal and paranodal complexes, respectively. Neurofascin-null mice have disrupted nodal and paranodal complexes. We show that transgenic Nfasc186 can rescue the nodal complex when expressed in Nfasc−/− mice in the absence of the Nfasc155–Caspr–Contactin adhesion complex. Reconstitution of the axoglial adhesion complex by expressing transgenic Nfasc155 in oligodendrocytes also rescues the nodal complex independently of Nfasc186. Furthermore, the Nfasc155 adhesion complex has an additional function in promoting the migration of myelinating processes along CNS axons. We propose that glial and neuronal Neurofascins have distinct functions in the assembly of the CNS node of Ranvier.
ERK5 promotes Src-induced podosome formation by limiting Rho activation
Authors: Schramp Mark , Ying Olivia , Kim Tai Young , Martin G. Steven
Published: June 2008

Increased Src activity, often associated with tumorigenesis, leads to the formation of invasive adhesions termed podosomes. Podosome formation requires the function of Rho family guanosine triphosphatases and reorganization of the actin cytoskeleton. In addition, Src induces changes in gene expression required for transformation, in part by activating mitogen-activated protein kinase (MAPK) signaling pathways. We sought to determine whether MAPK signaling regulates podosome formation. Unlike extracellular signal–regulated kinase 1/2 (ERK1/2), ERK5 is constitutively activated in Src-transformed fibroblasts. ERK5-deficient cells expressing v-Src exhibited increased RhoA activation and signaling, which lead to cellular retraction and an inability to form podosomes or induce invasion. Addition of the Rho-kinase inhibitor Y27632 to ERK5-deficient cells expressing v-Src led to cellular extension and restored podosome formation. In Src-transformed cells, ERK5 induced the expression of a Rho GTPase-activating protein (RhoGAP), RhoGAP7/DLC-1, via activation of the transcription factor myocyte enhancing factor 2C, and RhoGAP7 expression restored podosome formation in ERK5-deficient cells. We conclude that ERK5 promotes Src-induced podosome formation by inducing RhoGAP7 and thereby limiting Rho activation.
Mechanisms and consequences of agonist-induced talin recruitment to platelet integrin αIIbβ3
Authors: Watanabe Naohide , Bodin Laurent , Pandey Manjula , Krause Matthias , Coughlin Shaun , Boussiotis Vassiliki A. , Ginsberg Mark H. , Shattil Sanford J.
Published: June 2008

Platelet aggregation requires agonist-induced αIIbβ3 activation, a process mediated by Rap1 and talin. To study mechanisms, we engineered αIIbβ3 Chinese hamster ovary (CHO) cells to conditionally express talin and protease-activated receptor (PAR) thrombin receptors. Human PAR1 or murine PAR4 stimulation activates αIIbβ3, which was measured with antibody PAC-1, indicating complete pathway reconstitution. Knockdown of Rap1–guanosine triphosphate–interacting adaptor molecule (RIAM), a Rap1 effector, blocks this response. In living cells, RIAM overexpression stimulates and RIAM knockdown blocks talin recruitment to αIIbβ3, which is monitored by bimolecular fluorescence complementation. Mutations in talin or β3 that disrupt their mutual interaction block both talin recruitment and αIIbβ3 activation. However, one talin mutant (L325R) is recruited to αIIbβ3 but cannot activate it. In platelets, RIAM localizes to filopodia and lamellipodia, and, in megakaryocytes, RIAM knockdown blocks PAR4-mediated αIIbβ3 activation. The RIAM-related protein lamellipodin promotes talin recruitment and αIIbβ3 activity in CHO cells but is not expressed in megakaryocytes or platelets. Thus, talin recruitment to αIIbβ3 by RIAM mediates agonist-induced αIIbβ3 activation, with implications for hemostasis and thrombosis.
Administration of rhIL-7 in humans increases in vivo TCR repertoire diversity by preferential expansion of naive T cell subsets
Authors: Sportès Claude , Hakim Frances T. , Memon Sarfraz A. , Zhang Hua , Chua Kevin S. , Brown Margaret R. , Fleisher Thomas A. , Krumlauf Michael C. , Babb Rebecca R. , Chow Catherine K. , Fry Terry J. , Engels Julie , Buffet Renaud , Morre Michel , Amato Robert J. , Venzon David J. , Korngold Robert , Pecora Andrew , Gress Ronald E. , Mackall Crystal L.
Published: June 2008

Interleukin-7 (IL-7) is a homeostatic cytokine for resting T cells with increasing serum and tissue levels during T cell depletion. In preclinical studies, IL-7 therapy exerts marked stimulating effects on T cell immune reconstitution in mice and primates. First-in-human clinical studies of recombinant human IL-7 (rhIL-7) provided the opportunity to investigate the effects of IL-7 therapy on lymphocytes in vivo. rhIL-7 induced in vivo T cell cycling, bcl-2 up-regulation, and a sustained increase in peripheral blood CD4+ and CD8+ T cells. This T cell expansion caused a significant broadening of circulating T cell receptor (TCR) repertoire diversity independent of the subjects' age as naive T cells, including recent thymic emigrants (RTEs), expanded preferentially, whereas the proportions of regulatory T (T reg) cells and senescent CD8+ effectors diminished. The resulting composition of the circulating T cell pool more closely resembled that seen earlier in life. This profile, distinctive among cytokines under clinical development, suggests that rhIL-7 therapy could enhance and broaden immune responses, particularly in individuals with limited naive T cells and diminished TCR repertoire diversity, as occurs after physiological (age), pathological (human immunodeficiency virus), or iatrogenic (chemotherapy) lymphocyte depletion.
Immunogenicity of premalignant lesions is the primary cause of general cytotoxic T lymphocyte unresponsiveness
Authors: Willimsky Gerald , Czéh Melinda , Loddenkemper Christoph , Gellermann Johanna , Schmidt Karin , Wust Peter , Stein Harald , Blankenstein Thomas
Published: June 2008

Cancer is sporadic in nature, characterized by an initial clonal oncogenic event and usually a long latency. When and how it subverts the immune system is unknown. We show, in a model of sporadic immunogenic cancer, that tumor-specific tolerance closely coincides with the first tumor antigen recognition by B cells. During the subsequent latency period until tumors progress, the mice acquire general cytotoxic T lymphocyte (CTL) unresponsiveness, which is associated with high transforming growth factor (TGF) β1 levels and expansion of immature myeloid cells (iMCs). In mice with large nonimmunogenic tumors, iMCs expand but TGF-β1 serum levels are normal, and unrelated CTL responses are undiminished. We conclude that (a) tolerance to the tumor antigen occurs at the premalignant stage, (b) tumor latency is unlikely caused by CTL control, and (c) a persistent immunogenic tumor antigen causes general CTL unresponsiveness but tumor burden and iMCs per se do not.
Foxp3+ regulatory T cells maintain immune homeostasis in the skin
Authors: Dudda Jan C. , Perdue Nikole , Bachtanian Eva , Campbell Daniel J.
Published: June 2008

Cutaneous immune responses must be tightly controlled to prevent unwanted inflammation in response to innocuous antigens, while maintaining the ability to combat skin-tropic pathogens. Foxp3+ regulatory T (T reg) cells are potent immune regulators and are found at high frequency in both human and mouse skin. Although T reg cells migrate to the skin and can dampen immune responses during experimentally induced inflammation or infection, the importance of cutaneous T reg cells for maintaining normal immune homeostasis in the skin has not been addressed. To selectively block T reg cell function in the skin, we restored the T reg cell compartment in Foxp3-deficient scurfy mice with cells whose ability to migrate to the skin was impaired because of targeted mutation of α-1,3-fucosyltransferase VII (Fut7). Although Fut7-deficient T reg cells were present at normal frequency and could function in all other tissues examined, these animals rapidly developed severe cutaneous inflammation. Thus, skin-resident T reg cell are essential for maintaining normal immune homeostasis at this site.
IL-12– and IL-23–modulated T cells induce distinct types of EAE based on histology, CNS chemokine profile, and response to cytokine inhibition
Authors: Kroenke Mark A. , Carlson Thaddeus J. , Andjelkovic Anuska V. , Segal Benjamin M.
Published: June 2008

The interleukin (IL)-12p40 family of cytokines plays a critical role in the development of experimental autoimmune encephalomyelitis (EAE). However, the relative contributions of IL-12 and IL-23 to the pathogenic process remain to be elucidated. Here, we show that activation of uncommitted myelin-reactive T cells in the presence of either IL-12p70 or IL-23 confers encephalogenicity. Adoptive transfer of either IL-12p70– or IL-23–polarized T cells into naive syngeneic hosts resulted in an ascending paralysis that was clinically indistinguishable between the two groups. However, histological and reverse transcription–polymerase chain reaction analysis of central nervous system (CNS) tissues revealed distinct histopathological features and immune profiles. IL-12p70–driven disease was characterized by macrophage-rich infiltrates and prominent NOS2 up-regulation, whereas neutrophils and granulocyte–colony-stimulating factor (CSF) were prominent in IL-23–driven lesions. The monocyte-attracting chemokines CXCL9, 10, and 11 were preferentially expressed in the CNS of mice injected with IL-12p70–modulated T cells, whereas the neutrophil-attracting chemokines CXCL1 and CXCL2 were up-regulated in the CNS of mice given IL-23–modulated T cells. Treatment with anti–IL-17 or anti–granulocyte/macrophage-CSF inhibited EAE induced by transfer of IL-23–polarized, but not IL-12p70–polarized, cells. These findings indicate that autoimmunity can be mediated by distinct effector populations that use disparate immunological pathways to achieve a similar clinical outcome.
TAK1 is required for the survival of hematopoietic cells and hepatocytes in mice
Authors: Tang Minghui , Wei Xudong , Guo Yinshi , Breslin Peter , Zhang Shubin , Zhang Shanshan , Wei Wei , Xia Zhenbiao , Diaz Manuel , Akira Shizuo , Zhang Jiwang
Published: June 2008

Transforming growth factor β–activated kinase 1 (TAK1), a member of the MAPKKK family, is a key mediator of proinflammatory and stress signals. Activation of TAK1 by proinflammatory cytokines and T and B cell receptors induces the nuclear localization of nuclear factor κB (NF-κB) and the activation of c-Jun N-terminal kinase (JNK)/AP1 and P38, which play important roles in mediating inflammation, immune responses, T and B cell activation, and epithelial cell survival. Here, we report that TAK1 is critical for the survival of both hematopoietic cells and hepatocytes. Deletion of TAK1 results in bone marrow (BM) and liver failure in mice due to the massive apoptotic death of hematopoietic cells and hepatocytes. Hematopoietic stem cells and progenitors were among those hematopoietic cells affected by TAK1 deletion–induced cell death. This apoptotic cell death is autonomous, as demonstrated by reciprocal BM transplantation. Deletion of TAK1 resulted in the inactivation of both JNK and NF-κB signaling, as well as the down-regulation of expression of prosurvival genes.
The World Summit of Harmonization on Traditional, Alternative and Complementary Medicine (TACM) in Lima, Peru
Authors: Gonzales Gustavo F. , Aguilar José , Villar Martha
Published: June 2008

The World Summit of Harmonization on Traditional, Alternative and Complementary Medicine (TACM) was held in Lima, Peru, November 7–11, 2007, with almost 600 worldwide participants. This meeting was organized by Peruvian Medical College, the institution that affiliates and authorizes all physicians to practice medicine in Peru. The meeting included seven sections starting with an overview on the current status of the TACM. The second section included experiences from different countries on regulations and quality control in products and services used in the TACM. The worldwide experience of education and training in TACM was a very important part of the meeting in which speakers from Spain, Germany, Argentina, Italy, Brazil, Cuba and Peru shared their experience. The meeting included topics on homeopathy, acupuncture, mind–body medicine, neural therapy, chiropraxis, among others. Two final sessions were related to the ways of linking Traditional medicine to the national Health Systems in the Latin America countries and also the association between bio‐commerce and TACM including intellectual properties and bio‐piracy.
Engineering of halophilic enzymes: Two acidic amino acid residues at the carboxy‐terminal region confer halophilic characteristics to Halomonas and Pseudomonas nucleoside diphosphate kinases
Authors: Tokunaga Hiroko , Arakawa Tsutomu , Tokunaga Masao
Published: June 2008

Nucleoside diphosphate kinase from Halomonas sp. 593 (HaNDK) exhibits halophilic characteristics. Residues 134 and 135 in the carboxy‐terminal region of HaNDK are Glu–Glu, while those of its homologous counterpart of non‐halophilic Pseudomonas NDK (PaNDK) are Ala–Ala. The double mutation, E134A‐E135A, in HaNDK results in the loss of the halophilic characteristics, and, conversely, the double mutation of A134E‐A135E in PaNDK confers halophilic characters to this enzyme, indicating that the charged state of these two residues that are located in the C‐terminal region plays a critical role in determining halophilic characteristics. The importance of these two residues versus the net negative charges will be discussed in relation to the halophilicity of NDK.
Primary upper tract urothelial carcinoma with thyroid‐like features
Authors: Viprakasit Davis P , Turner Geoffrey , Goldschmidt Robert A , Keeler Thomas C
Published: June 2008

Abstract:  We present a unique case of primary urothelial carcinoma with both histological and immunohistochemical features similar to thyroid papillary carcinoma. Following surgical resection of the primary tumor and localized metastatic lymphadenectomy, the patient was treated with a course of adjuvant chemotherapy. No evidence of primary thyroid carcinoma was noted. The patient was without recurrence after a 6 month follow‐up.
Real Options, International Entry Mode Choice and Performance
Authors: Brouthers Keith D. , Brouthers Lance Eliot , Werner Steve
Published: June 2008

abstract  Recent scholarship suggests that combining insights from real option theory with transaction cost economics may improve decision‐making models. In response to this suggestion we develop and test a model of international entry mode choice that draws from both perspectives. Examining samples of Dutch and Greek firms entering Central and Eastern European markets, we found that adding real option variables to a transaction cost model significantly improved its explanatory power. Additionally, firms that used the combined real option/transaction cost predicted choices had significantly higher levels of subsidiary performance satisfaction than firms that did not. Our results suggest that effective managerial decision‐making may involve more than mere transaction cost minimization considerations; real option value creation insights also appear to influence the success of decision outcomes.
The Influence of Top Management Team International Exposure on International Alliance Formation
Authors: Lee Ho‐Uk , Park Jong‐Hun
Published: June 2008

abstract  This study examines the effect of top management team (TMT) international exposure on the formation of international alliances. We develop our arguments based on relational capital theory to suggest that top executives with international exposure are critical to firms’ international alliance formation. Supporting this view, we find that TMT international exposure is positively associated with the formation of international alliances. Moreover, we find evidence to suggest that the effect of TMT international exposure on international alliance formation is more positive as the level of environmental uncertainty increases. We discuss implications and directions for future research.
Senior Team Attributes and Organizational Ambidexterity: The Moderating Role of Transformational Leadership
Authors: Jansen Justin J. P. , George Gerard , Van den Bosch Frans A. J. , Volberda Henk W.
Published: June 2008

abstract  Organizations capable of pursuing exploration and exploitation simultaneously have been suggested to obtain superior performance. Combining both types of activities and achieving organizational ambidexterity, however, leads to the presence of multiple and often conflicting goals, and poses considerable challenges to senior teams in ambidextrous organizations. This study explores the role of senior team attributes and leadership behaviour in reconciling conflicting interests among senior team members and achieving organizational ambidexterity. Findings indicate that a senior team shared vision and contingency rewards are associated with a firm's ability to combine high levels of exploratory and exploitative innovations. In addition, our study shows that an executive director's transformational leadership increases the effectiveness of senior team attributes in ambidextrous organizations and moderates the effectiveness of senior team social integration and contingency rewards. Hence, our study clarifies how senior executives reconcile conflicting demands and facilitate the balancing of seemingly contradictory forces in ambidextrous organizations. Implications for literatures on senior team attributes, transformational leadership and organizational ambidexterity are discussed.
Blood culture isolates and antimicrobial sensitivities from 427 critically ill neonatal foals
Authors: Russell CM , Axon JE , Blishen A , Begg AP
Published: June 2008

Objective  To assist correct decision‐making about antimicrobial treatment of equine neonates with septicaemia.

Design  Retrospective study of microbial blood culture results obtained from foals less than 7 days of age.

Methods  Microbial blood culture results from foals less than 7 days of age admitted to an intensive care unit between July 1999 and December 2004 were reviewed. Antimicrobial sensitivity was assessed by the Kirby Bauer disc diffusion method. Antimicrobials were defined as an effective first‐line choice antimicrobial if greater than 70% of isolates were susceptible. Multiple drug resistance (MDR) was defined as resistance to at least three antimicrobials in different chemical classes or with different mechanisms of resistance.

Results  Of the 427 Thoroughbred foals included in the study, a positive blood culture was obtained in 110 foals and 124 microorganisms were isolated. Gram‐positive isolates, predominantly Streptococcus/Enterococcus spp, were obtained in 41% of foals. Gram‐negative isolates were predominantly of the Enterobacteriaceae family, in particular Escherichia coli. The overall antimicrobial sensitivity of the isolates was low. The Gram‐positive organisms had unpredictable sensitivity patterns. MDR was recorded in 32% of isolates. In total, 81% of foals were discharged from hospital and 74.5% of foals with a positive blood culture were discharged.

Conclusion  With the increasing prevalence of Gram‐positive microorganisms and their unpredictable sensitivity patterns, blood cultures remain important in the diagnosis and treatment of equine neonatal septicaemia.
Radiometric pooled faecal culture for the detection of Mycobacterium avium subsp paratuberculosis in low‐shedder cattle
Authors: Eamens GJ , Walker DM , Porter NS , Fell SA
Published: June 2008

Objective   To identify the optimum pooling rate for pooled faecal culture (PFC) as a diagnostic tool in bovine Johne's disease control, for detection of cattle shedding low concentrations of Mycobacterium avium subsp paratuberculosis (Map).

Method   Thirteen target animals were selected by delayed growth of Map from initial individual radiometric faecal cultures (first growth index at 5 weeks or later). A procedure based on radiometric culture and IS900 polymerase chain reaction and restriction endonuclease analysis confirmation was then used for PFC.

Results   Eight samples (stored for up to 17 months at −80°C) yielded Map on subsequent culture, either from undiluted faeces or those mixed with normal cattle faeces at dilution rates from 1 in 5 to 1 in 50. From a regression equation, culture‐positive animals were considered to be shedding relatively low levels of Map (< 6 × 104/g of faeces). Pooling dilutions of more than 1 in 5 reduced PFC sensitivity. A minimum incubation period of 10 weeks at a dilution of 1 in 5 is recommended to detect such infected cattle. This pooling rate in radiometric culture is probably capable of detecting cattle shedding ≤ 5 × 103 Map organisms/g of faeces, representing an estimated inoculum per culture vial of fewer than 20 viable organisms.

Conclusion   Map was detected in more than 50% of the stored faecal samples from cattle shedding low concentrations of the organism. A pooling rate of 5 samples per pool is required to reliably detect infected low‐shedder cattle using PFC based on radiometric culture.
Application of a Multiaxial Fatigue Criterion for the Evaluation of Life of Gears of Complex Geometry
Authors: Borgianni Leonardo , Forte Paola , Marchi Luigi
Published: June 2008

Gears can show significant biaxial stress state at tooth root fillet, due to the way they are loaded and their particular geometry. This biaxial stress state can show a significant variability in principal axes during meshing. Moreover loads may have non predictable components that can be evaluated with the aid of recorded data from complex spectra. In these conditions, commonly adopted approaches for fatigue evaluation may be unsuitable for a reliable fatigue life prediction. This work is aimed at discussing a computer implementation of a fatigue life prediction method suitable for multiaxial stress states and constant amplitude or random loading. For random loading a counting procedure to extract cycles from complex load histories is discussed. This method, proposed by Vidal et al., is based on the r.m.s. value of a damage indicator over all the planes through the point where the fatigue life calculation is made. Miner’s rule is used for the evaluation of the overall damage. The whole fatigue life of the component is evaluated in terms of the numbers of repetitions of the loading block. FEM data are used to evaluate stresses under load. The implementation was validated using test data found in the technical literature. Examples of applications to gears are finally discussed.
Application of Multiaxial Criteria to Contact Fatigue Assessment of Spur Gears
Authors: Davoli Piermaria , Bernasconi Andrea , Carnevali Luca
Published: June 2008

A new methodology for evaluating the effect of contact stresses generated during the meshing of two spur involute gears is hereby proposed. Taking into account modern multiaxial fatigue criteria (usually applied to other kinds of problems), the real load path on the teeth flank and the consequent evolution of the subsurface stresses, this method aims at the assessment of the pitting and spalling limits of gears. The method is proposed for a better comprehension of these phenomena and for the definition of effective surface fatigue limits of case hardened and nitrided gears. The applied multiaxial criteria include both integral and critical plane approaches.
Deformation Mechanism of Hot Finish Rolling of Plastic Gears: Analysis of Material Flow in Melted Layer
Authors: Moriwaki Ichiro , Oka Hidenori
Published: June 2008

Hot finish rolling has been proposed as a simple finishing process for injection-molded plastic gears. In this process, plastic work gears are finished by meshing with a heated die wheel under very low load. Heat applied by the die wheel yields a melted layer on a tooth flank of the plastic work gear, and sliding between tooth flanks of the die wheel and the work gear induces material flow in the melted layer. This material flow contributes to the change in the work tooth form. Therefore, in order to simulate the hot finish rolling process, the material flow must be analyzed. The present paper describes a simple model in which the material flow is considered as the flow of incompressive fluid with free surface. Then, the effects of the sliding velocity and the friction are discussed. As a result, calculated forms of free surfaces qualitatively agreed with measured forms of finished teeth.
Effects of Heating Conditions on Residual Stresses, Hardened Layers and Bending Fatigue Strength of Induction Hardened Gears
Authors: Miyachika Kouitsu , Mada Hidefumi , Oda Satoshi , Fujio Hiroshige , Tsuboi Hajime
Published: June 2008

This paper presents a study on effects of heating conditions on residual stresses, hardened layers and bending fatigue strengths of induction hardened gears. Residual stresses and hardened layers of gears induction hardened under various heating conditions were calculated by means of the induction-hardening simulator, which had been developed by authors. Measurements of hardened layers and bending fatigue tests of gears induction hardened under various heating conditions were carried out. Calculated hardened layers were compared with measured ones. The optimum heating condition for the bending fatigue strength of induction-hardened gears was examined.
Influence of Shot Peening on Surface Durability of Plasma Case-Hardened Sintered Powder Metal Gears
Authors: Yoshida Akira , Ohue Yuji , Seki Masanori
Published: June 2008

In order to investigate the influence of shot peening on the surface durability of sintered powder metal gears, the plasma case-hardened sintered powder metal rollers and gears shotpeened with different condition were fatigue-tested under a sliding-rolling contact condition. The hardness, the compressive residual stress and the surface roughness of the rollers and gears increased by the shot peening. The failure mode of the rollers and gears was mainly spalling. The main crack of the failed rollers and gears propagated through the pores below the roller and the tooth surfaces. The surface durabilities of the lightly shot-peened rollers and gears were higher than those of the other rollers and gears. While, the surface durabilities of the strongly shot-peened rollers are lower than that of the unpeened roller because of the increase of the surface roughness and the deformed sharp pore by the strong shot peening.
Side Tracking in Helical Synchronous Belt Drives Under Torque: Influence of Pulley Flange on Axial Belt Movement
Authors: Ueda Hiroyuki , Kagotani Masanori , Koyama Tomio
Published: June 2008

When helical synchronous belt drives operate under a torque, the belt experiences side tracking, which results in an offset between the position of the belt on the driving pulley and that on the driven pulley. Side tracking causes the belt from running off the pulley. The general countermeasure is to fit a flange either to the driving pulley, to both the driving and driven pulleys, or to one side of the driving pulley and the opposite side on the driven pulley. In this study, the axial movement of helical synchronous belts under torque was investigated when the pulley flange attaches to either the driving pulley or driven pulley. In addition, fatigue tests were conducted in order to ascertain the damage to the side face of the belt. It was found that the offset is effectively reduced when a flange is installed on the driving pulley, on the side that affects the direction of the moved belt, even if a flange is not fitted to the same side of the driven pulley. When a flange is fitted solely on the driven pulley, there is a large offset, but the force of the belt pushing against the flange is reduced. As a result, the damage to the side face of the belt is mitigated.
Experimental/Numerical Analysis of the Timing Belt Drive Behavior of a V6 Engine
Authors: Manin Lionel , Remond Didier , Gaborel Jean-Philippe
Published: June 2008

The timing belts used for automotive engine are asked to last more and more, and to be less noisy. In this way, it is necessary to simulate the behavior of the engine timing belt drives for optimization, but also to understand it from experimental analysis. The first objective of the work was to analyze experimentally the behavior of a V6 engine timing belt drive in terms of: pulley speeds, belt span tensions, transmission error. The second objective was to compare the measurements with simulations. The engine has four overhead camshafts and 4 valves per cylinder. The timing belt drive is composed of six pulleys, three idlers and an automatic tensioner. The crankshaft and the two first camshaft speeds are measured with optical encoders. Spans tensions are measured by means of strain gauges glued on the idler mounting axes. All the data are simultaneously recorded. Tests have been run from 800 rpm to 6000 rpm. Measured data are first analyzed in the time domain. Some phenomena like, nil span tensions, speeds acyclism and transmission error amplitude, are observed. Then, analyses of the harmonic content of the span tensions, pulley speeds and transmission errors between the crankshaft and the camshafts, are performed versus engine rotation speed. Finally, the tests have been simulated and comparisons are made between numerical and experimental results.
Meshing Stiffness and Tooth Root Stress for Internal Cylindrical Gears With Thin Rim
Authors: de Vaujany Jean-Pierre , Guingand Miche`le , Remond Didier
Published: June 2008

The main objective of this study is to quantify the influence of the deformation of the rim of an internal gear on the meshing stiffness and the stress distribution in tooth fillets. The 3D model used is based on a method derived from the Finite Prism Method. Tooth bending effects and contact deformations are processed simultaneously. Scientific use of the software has resulted in formulating an equation to calculate the maximal tension stress in the tooth root. This formula has been obtained by using the statistical design of experiment method.
Tooth Root Stress and Tooth Contact Stress of the Modified Cycloid Helical Gear
Authors: Tutulan Florin Gabriel , Nagamura Kazuteru , Ikejo Kiyotaka
Published: June 2008

This paper describes the relationship between tooth root and tooth contact stresses and the tooth profile of the modified cycloid helical gear, which was developed as a non-involute tooth profile gear based on cycloid tooth profile and which has a greater surface durability than the involute helical gear. The modified cycloid helical gear has some design parameters such as pressure angle and rolling circle, which define the modified cycloid tooth curve. The tooth bending and tooth contact strengths of the modified cycloid helical gear are directly affected by its tooth profile. In this study, we developed a method to calculate the load distribution, the tooth root stress and the tooth contact stress of the modified cycloid helical gear. Then we compared the tooth root stress calculated by this method with the experimentally measured data and the validity of the present calculation method was certified by the good agreement of the calculated values with the measured data. Furthermore, we discussed the effects of the design parameters on the tooth bending and tooth contact strengths of the modified cycloid helical gear considering the results of the tooth root and the tooth contact stresses calculated in the case of various values of the design parameters.
Systematic Investigations on the Influence of Case Depth on the Pitting and Bending Strength of Case Carburized Gears
Authors: Ho¨hn B.-R. , Oster P. , Tobie T.
Published: June 2008

The influence of case depth on the pitting and bending strength of case carburized gears was investigated. For this purpose an extensive test program on gears of different sizes, different gear geometry and with systematically varied case depth has been carried out. Residual stresses and further characteristics of the case hardened layer — that are influenced by the value of case depth as well — are examined. Based on the test results, rating formulas are derived to calculate the optimum case depth for maximum load capacity. Influence factors are defined, by which the influence of case depth on the load capacity regarding pitting and bending strength can be taken into consideration if rating a gear according to the standardized calculation method of DIN 3990/ISO 6336.
Fatigue Failure Mechanism of Steel Cords in Synchronous Belt
Authors: Takahashi Hideo , Iizuka Hiroshi
Published: June 2008

Synchronous belts are widely used as a power transmission element in many industrial equipments. The construction of the belts is a rubber and a helical cord as a tension member in the belts. The purpose of this study is to investigate the fatigue failure mechanism of the synchronous belts using steel cords. The steel cord focused here is 1*19 construction, that is made twisting nineteen steel wires. At first, the fatigue failure initiation site was found observing the failure morphology and measuring the belt deformation. Then, the fatigue failure mechanism was discussed with some fatigue tests of the steel cords and any mechanical and finite-element analysis. The belt failure was initiated near the tooth root, where the steel cords were fatigued. The belt curvature was measured by using the deformation of the marker lines that were put on the side surface of the belt. The belt was bent largely near the tooth root under high belt tension conditions. Namely, the belt was damaged by the bending fatigue near the tooth root. Then, the bending fatigue of the steel cord was tested and discussed the fatigue failure mechanism. The fatigue failure was firstly initiated in the outer layer wires. However, the bending stress was lower in the outer layer wires than in the core wire, according to a simple geometrical analysis. It is necessary to consider the initiation of another type of stresses based on the contact between the wires. Therefore, the finite-element was analyzed. We discussed the stress component that accelerated the fatigue failure in the outer layer wires. The friction force that was initiated between the wires well explained the acceleration of the fatigue failure in the outer layer wires.
Fatigue Failure Initiation Site in Synchronous Belts Under Constant and Fluctuating Torque Conditions
Authors: Iizuka Hiroshi , Ohta Yoshikatsu , Ueno Akihiro , Murakami Takeshi
Published: June 2008

Fatigue failure under fluctuating torque is important because the driving torque fluctuates in automotive engine camshaft drive-systems. The authors observed that the fatigue failure initiated at the tooth root on the opposite side of working flank under fluctuating torque conditions, while the failure initiated at the tooth root on the working flank side under constant torque conditions. In this study, the main factor that decides the failure initiation site is discussed, caring out some experiments and finite element analysis (FEA). According to the FEA results, the maximum stress initiation site is moved from the opposite side of working flank to the working flank side, increasing with the tooth load. The main factor that decides the failure initiation site is the distribution of tooth load on the working flank. The tooth load distributed near the tooth tip induces the high shearing stress at the tooth root on the opposite side of working flank, while the distributed load near the tooth root induces the high shearing stress at the tooth root on the working flank side.
Numerical Modelling of the Crack Propagation Path at Gear Tooth Root
Authors: Jelaska Damir T. , Glodez Srecko , Podrug Srdjan
Published: June 2008

A numerical model for determination of service life of gears in regard to bending fatigue in a gear tooth root is presented. The Coffin-Manson relationship is used to determine the number of stress cycles Ni required for the fatigue crack initiation, where it is assumed that the initial crack is located at the point of the largest stresses in a gear tooth root. The simply Paris equation is then used for the further simulation of the fatigue crack growth, where required material parameters have been determined previously by the appropriate test specimens. The functional relationship between the stress intensity factor and crack length K = f(a), which is needed for determination of the required number of loading cycles Np for a crack propagation from the initial to the critical length, is obtained numerically. The total number of stress cycles N for the final failure to occur is then a sum N = Ni + Np. Although some influences were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing.
Experimental Research on the Vibration and Noise Behavior of Helical Gearing System
Authors: Saiki Kohei , Watanabe Takeshi , Sato Terushige
Published: June 2008

Going with interior noise reduction in a vehicle, gear noise that is of pure frequency has been becoming a great influence on the comfortable driving. For decreasing the gear noise, it is important to predict precisely the gear noise behavior at the design stage before manufacturing. Therefore, it is necessary to clarify the physical mechanism of each resonance noise peak by actual measurement in the wide condition range of rotation speed and transmitting torque. In this research, a new 85kw oil-cooled motoring apparatus (Max speed: 6000rpm/135Nm, Max torque 400Nm/2000rpm) is developed for measuring the 3-dimensional (transverse, axial, rotational, and tilting) vibration of rotating gear blank. Also, the 3-directional (X, Y, and Z) vibration of the bearing’s holder, and the radiated gear noise are measured at the same time. As the result, the relationship between exciting vibration of rotating gear blank and the responding vibration of the bearing’s holder is carried out. The different effect upon the radiated gear noise of various vibration resonance modes is also investigated. Especially, some new interesting vibration modes, such as the drive and driven gears vibrate individually or synchronously, are found. Lastly, the mechanism of several resonance peaks which frequently causing the gear noise problems from slow city driving to fast highway operation, is conjectured concisely.
Utilization of Synchronous Averaging of Vibration for Diagnosis of Gear System to Estimate Tooth Error
Authors: Ratanasumawong Chanat , Houjoh Haruo , Matsumura Shigeki , Saitoh Michio , Ueda Yasushi
Published: June 2008

Generally, gear vibration behavior has base frequencies equal to meshing frequency and its harmonics. But it has become known that slight undulation even on ground gear surface sometimes generate peculiar vibration behavior that is non-integer order of meshing frequency, and it is called ‘ghost noise’. In the normal cases, the gear pair that is the source of vibration can be located by considering mesh frequencies of each gear pair and their harmonics. But if ghost noise components exist, it becomes difficult to detect which gear pair is the source. Therefore diagnosis method to detect ghost noise source with measuring vibration is required. In this study, we proposed the utilization of synchronous averaging to distinguish the source of ghost noise components. With this method, we could separate the effect of driving and driven gear from each other. The estimation results with synchronous averaging were verified with precise tooth surface measurements.
The Adaptation of CNC Helical Guide Technology to the Gear Shaping Process
Authors: Lange John M.
Published: June 2008

The Gear shaping process, like all gear manufacturing processes, has been enhanced by the application of CNC Technology. In the case of the gear shaping process the “partial” application of CNC Technology first occurred in 1982. While virtually all gear cutting and grinding machines have had their axes of motions converted to CNC, the development of a CNC electronic helical guide for the gear shaping process was delayed for technological reasons. The following questions will be discussed and answered: • Why is a helical guide necessary in the gear shaping process? • What had delayed CNC technology from being applied to the helical guide principle in the gear shaping process? • How has the addition of the electronic guide CNC Technology impacted the gear shaping process? • Have lead quality and productivity rates been aversely affected by the addition of the electronic guide feature? • How might this increase in flexibility, by using an electronic guide in the shaping process, be applied to real life applications?
Simulation of Plunge Shaving Operation for Spur and Helical Gear, and Tooth Contact Analysis of Finished Gear Drive
Authors: Kim David H.
Published: June 2008

A math model of the re-sharpening operation of shaving cutter by grinding disk, and the plunge shaving process for spur and helical gears has been developed. It has been achieved by three steps: a parametric representation of grinding disk surface, the derivation of shaving cutter surface as a function of grinding disk surface and re-sharpening motion parameters, and the derivation of the finished gear surface as a function of cutter surface and synchronized plunge shaving motion parameters. The study is complemented with a methodology of determining the bearing contact as a set of instantaneous contact ellipses and the transmission function for the finished gear drive by plunge shaving. It simulates meshing and contact of two mating gear tooth surfaces in point contact. The described methods will give manufacturers better insight on the interrelationship between the shaving cutter and the plunge-shaved gear tooth topologies, and a tool to enhance existing design and manufacturing practices.
Analysis and Optimization of the Loaded Meshing of a Face Gear
Authors: Guingand Miche`le , de Vaujany Jean-Pierre , Icard Yvan
Published: June 2008

This work deals with loaded face gear meshing. In the first part, the software developed is described briefly. This tool can simulate the loaded behavior of face gear meshing and provide results such as the instantaneous pressure distribution along the entire face width of the teeth in contact and loaded transmission error. In the second part of the paper, a comparison between the point or line contact is performed for loaded meshing. Further computations calculate assembling-error sensitivity for the two contact cases. To improve the case of line contact, a method for pinion crowning optimization is presented in the last part. The aim is to obtain the best loaded face gear meshing in order to avoid the sensitivity of the line contact case due to misalignment.