bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical roles of Leu99 and Leu115 at the heme distal side in auto‐oxidation and the redox potential of a heme‐regulated phosphodiesterase from Escherichia coli
Authors: Yokota Nao , Araki Yasuyuki , Kurokawa Hirofumi , Ito Osamu , Igarashi Jotaro , Shimizu Toru
Published: February 2006

The heme‐regulated phosphodiesterase from Escherichia coli (Ec DOS), which is a heme redox‐dependent enzyme, is active with a ferrous heme but inactive with a ferric heme. Global structural changes including axial ligand switching and a change in the rigidity of the FG loop accompanying the heme redox change may be related to the dependence of Ec DOS activity on the redox state. Axial ligands such as CO, NO, and O2 act as inhibitors of Ec DOS because they interact with the ferrous heme complex. The X‐ray crystal structure of the isolated heme‐bound domain (Ec DosH) shows that Leu99, Phe113 and Leu115 indirectly and directly form a hydrophobic triad on the heme plane and that they should be located at or near the ligand access channel of the heme iron. We generated L99T, L99F, L115T, and L115F mutants of Ec DosH and examined their physicochemical characteristics, including auto‐oxidation rates, O2 and CO binding kinetics, and redox potentials. The Fe(III) complex of the L115F mutant was unstable and had a Soret absorption spectrum located 5 nm lower than those of the wild‐type and other mutants. Auto‐oxidation rates of the mutants (0.049–0.33 min−1) were much higher than that of the wild‐type (0.0063 min−1). Furthermore, the redox potentials of the former three mutants (23.1–34.6 mV versus SHE) were also significantly lower than that of the wild‐type (63.9 mV versus SHE). Interaction between O2 and the L99F mutant was different from that in the wild‐type, whereas CO binding rates of the mutants were similar to those of the wild‐type. Thus, it appears that Leu99 and Leu115 are critical for determining the characteristics of heme iron. Finally, we discuss the roles of these amino‐acid residues in the heme electronic states.
Chromophore attachment in phycocyanin
Authors: Zhao Kai‐Hong , Wu Dong , Zhang Ling , Zhou Ming , Böhm Stephan , Bubenzer Claudia , Scheer Hugo
Published: February 2006

Covalent attachment of phycocyanobilin (PCB) to the α‐subunit of C‐phycocyanin, CpcA, is catalysed by the heterodimeric PCB : CpcA lyase, CpcE/F [Fairchild CD, Zhao J, Zhou J, Colson SE, Bryant DA & Glazer AN (1992) Proc Natl Acad Sci USA89, 7017–7021]. CpcE and CpcF of the cyanobacterium, Mastigocladus laminosus PCC 7603, form a 1 : 1 complex. Lyase‐mutants were constructed to probe functional domains. When in CpcE (276 residues) the N terminus was truncated beyond the R33YYAAWWL motif, or the C terminus beyond amino acid 237, the enzyme became inactive. Activity decreases to 20% when C‐terminal truncations went beyond L275, which is a key residue: the Km of CpcE(L275D) and (L276D) increased by 61% and 700%, kcat/Km decreased 3‐ and 83‐fold, respectively. The enzyme also lost activity when in CpcF (213 residues) the 20 N‐terminal amino acids were truncated; truncation of 53 C‐terminal amino acids inhibited complex formation with CpcE, possibly due to misfolding. According to chemical modifications, one accessible arginine and one accessible tryptophan are essential for CpcE activity, and one carboxylate for CpcF. Both subunits bind PCB, as assayed by Ni2+ affinity chromatography, SDS/PAGE and Zn2+‐induced fluorescence. The bound PCB could be transferred to CpcA to yield α‐CPC. The PCB transfer capacity correlates with the activity of the lyase, indicating that PCB bound to CpcE/F is an intermediate of the enzymatic reaction. A catalytic mechanism is proposed, in which a CpcE/F complex binds PCB and adjusts via a salt bridge the conformation of PCB, which is then transferred to CpcA.
Synthesis and structural characterization of a mimetic membrane‐anchored prion protein
Authors: Hicks Matthew R. , Gill Andrew C. , Bath Imanpreet K. , Rullay Atvinder K. , Sylvester Ian D. , Crout David H. , Pinheiro Teresa J. T.
Published: February 2006

During pathogenesis of transmissible spongiform encephalopathies (TSEs) an abnormal form (PrPSc) of the host encoded prion protein (PrPC) accumulates in insoluble fibrils and plaques. The two forms of PrP appear to have identical covalent structures, but differ in secondary and tertiary structure. Both PrPC and PrPSc have glycosylphospatidylinositol (GPI) anchors through which the protein is tethered to cell membranes. Membrane attachment has been suggested to play a role in the conversion of PrPC to PrPSc, but the majority of in vitro studies of the function, structure, folding and stability of PrP use recombinant protein lacking the GPI anchor. In order to study the effects of membranes on the structure of PrP, we synthesized a GPI anchor mimetic (GPIm), which we have covalently coupled to a genetically engineered cysteine residue at the C‐terminus of recombinant PrP. The lipid anchor places the protein at the same distance from the membrane as does the naturally occurring GPI anchor. We demonstrate that PrP coupled to GPIm (PrP–GPIm) inserts into model lipid membranes and that structural information can be obtained from this membrane‐anchored PrP. We show that the structure of PrP–GPIm reconstituted in phosphatidylcholine and raft membranes resembles that of PrP, without a GPI anchor, in solution. The results provide experimental evidence in support of previous suggestions that NMR structures of soluble, anchor‐free forms of PrP represent the structure of cellular, membrane‐anchored PrP. The availability of a lipid‐anchored construct of PrP provides a unique model to investigate the effects of different lipid environments on the structure and conversion mechanisms of PrP.
Palmitoylcarnitine modulates interaction between protein kinase C βII and its receptor RACK1
Authors: Sobiesiak‐Mirska Joanna , A. Nałęcz Katarzyna
Published: February 2006

Palmitoylcarnitine, known to promote differentiation of neuroblastoma NB‐2a cells as well as to inhibit protein kinase C (PKC) activity and to decrease phorbol ester binding, was shown previously to diminish the amount of complex formed between PKCδ and its substrate GAP‐43. In the present work we studied the effect of palmitoylcarnitine on the interaction between PKCβII and its receptor RACK1. Palmitoylcarnitine was found to decrease autophosphorylation of PKCβII on serine in a concentration‐dependent manner and to decrease the amount of PKCβII/RACK1 complex. The effect of palmitoylcarnitine on cellular localization was found to be dependent on the presence of ATP; palmitoylcarnitine lowered the amount of PKCβII in cytosol and decreased the amount of PKCβII–RACK1 complex in membrane in the absence of ATP. Palmitoylcarnitine also reversed the effect of phorbol ester on the increase in the amount of PKCβII in membrane. Palmitoylcarnitine binds to PKCβII through hydrophobic interactions, although acylation of PKCβII by the palmitate moiety has been excluded. The presence of palmitoylcarnitine did not have any additive effect on the diminution of PKCβII–RACK1 complex formation in the presence of a RACK1‐binding peptide from within the C2 region of PKCβII. These results rather exclude a possibility of interaction of palmitoylcarnitine with the C2 domain and suggest a possible interaction with the V5 domain and a conformational change affecting the C1 region.
Nipple/Breast Stimulation and Sexual Arousal in Young Men and Women
Authors: Levin Roy , Meston Cindy
Published: February 2006

Introduction

The role of nipple/breast stimulation in influencing sexual arousal in men and women during lovemaking has only been the subject of opinion-based comment rather than evidence-based study. No attempt to question people about such sexual behavior has ever been undertaken.

Aim

The study was designed to ascertain the effects of nipple/breast manipulation in young men and women on their sexual arousal.

Methods

A short questionnaire about nipple/breast stimulation during sexual activity was administered to 301 (148 men; 153 women) sexually experienced undergraduates (age range 17–29 years, 95% between 18 and 22).

Main Outcome Measures

Replies to questions in questionnaire.

Results

The major findings in regard to the women were that 81.5% reported that stimulation of their nipples/breasts caused or enhanced their sexual arousal, 78.2% agreed that when sexually aroused such manipulation increased their arousal, 59.1% had asked to have their nipples stimulated during lovemaking, and only 7.2% found that the manipulation decreased their arousal. In regard to the men, 51.7% reported that nipple stimulation caused or enhanced their sexual arousal, 39% agreed that when sexually aroused such manipulation increased their arousal, only 17.1% had asked to have their nipples stimulated, and only 7.5% found that such stimulation decreased their arousal.

Conclusion

Manipulation of the nipples/breasts causes or enhances sexual arousal in approximately 82% of young women and 52% of young men with only 7–8% reporting that it decreased their arousal.
The Minority of Young Adult Men with Sexual Disorders Seek Medical Treatment
Authors: Heruti Rafi J. , Swartzon Michael , Shochat Tzipi , Ashkenazi Isaac , Galor Shay , Justo Dan
Published: February 2006

Introduction

The Israel Defense Force (IDF) conducts screening examinations of military personnel aimed at early detection of morbidities, including erectile dysfunction (ED) and other sexual disorders (SDs). Men with SDs are referred to the IDF’s sex clinic for consultation.

Aim

We present the long-term compliance of military men with SDs to the screening program.

Main Outcome Measures

We investigated how many men screened for ED and other SDs turned to the IDF’s sex clinic for consultation.

Methods

Subjects 25–50 years old performed screening examinations at the Staff Periodic Examination Center. The Sexual Health Inventory for Men (SHIM) questionnaire was used to categorize ED. The IDF’s sex clinic records were investigated.

Results

During 2001–2003, 5,836 men completed the SHIM questionnaire. Overall, 1,570 (26.9%) men had low SHIM scores suggesting ED and other SDs. Although only 76 (4.8%) of these men turned to the IDF’s sex clinic over these years, more men conferred with the IDF’s sexologist every year, and more men were referred by their primary-care physicians to the IDF’s sex clinic regardless of their SHIM score.

Conclusions

Screening for SDs in young adult men is not enough; encouraging young adult men screened for SDs to turn to a sex clinic for evaluation is the true challenge. Nevertheless, adding a sexual questionnaire to screening examinations may raise the awareness of sexual issues in both the patients and their primary-care physicians.
Is Sex Only for the Healthy and Wealthy?
Authors: Ströberg Peter , Hedelin Hans , Bergström AnnBritt
Published: February 2006

Objective

To study reasons for Sildenafil (a phosphodiesterase type 5 inhibitor) treatment abortion in erectile dysfunction (ED), with special regard to the relation between cost and use.

Methods

Men (N=132) with ED, where treatment with Sildenafil was instituted between 1998 and 2000, were mailed a questionnaire in February 2003, regarding their current ED treatment, including frequency of use, reasons for change or discontinuation, effect on partner relations, and total income of the household.

Results

The response rate was 69%. Nearly every second man (47%) still used Sildenafil at least twice per month. The remaining 53% had aborted oral ED treatment: 10% due to return of normal erections, 43% due to (either alone or in combination): cost of treatment, impaired health, loss of efficacy, change to another ED treatment, or side-effects. Cost was the most common cause (48%) for discontinuation. In low-income households, rationing of treatment or abortion due to the cost was reported significantly (P <0001) more often (86%) than in high-income households (35%).

Conclusion

Just under half of all the patients (47%) used Sildenafil for more than 2 years after initiation of treatment. The cost of the treatment is an important factor for patient compliance in households with a low income, despite the fact that the treatment is highly effective and improves the partner relationship.
Sildenafil Citrate Improves Self-Esteem, Confidence, and Relationships in Men with Erectile Dysfunction: Results from an International, Multi-Center, Double-Blind, Placebo-Controlled Trial
Authors: Althof Stanley E. , O'Leary Michael P. , Cappelleri Joseph C. , Hvidsten Kyle , Stecher Vera J. , Glina Sidney , King Rosie , Siegel Richard L.
Published: February 2006

Introduction

Erectile dysfunction (ED) can significantly impact a man's relationships and well-being.

Aim

We assessed changes in self-esteem, confidence, sexual relationship satisfaction, and overall relationship satisfaction in men with ED using the validated Self-Esteem And Relationship questionnaire (SEAR).

Methods

This was a 12-week, double-blind, placebo-controlled, flexible-dose (25, 50, 100 mg, as needed) international study of sildenafil in men ≥18 years of age in Mexico, Brazil, Australia, and Japan.

Main Outcome Measures

The primary study outcome was change in self-esteem from baseline to the end of treatment. Secondary study measures were changes in other SEAR components, International Index of Erectile Function (IIEF) domains, percentage of intercourse attempts that were successful, and the response to a global efficacy question at the end of treatment.

Results

Patients were well balanced for age and duration of ED (placebo = 149 and sildenafil = 151). Compared with placebo, sildenafil significantly improved self-esteem, confidence, sexual relationship satisfaction, and overall relationship satisfaction (P < 0.0001). The psychosocial measures of well-being assessed with the SEAR were positively correlated (range 0.60–0.86, P < 0.0001) with erectile function, the frequency of achieving erections that allowed satisfactory sexual intercourse, the percentage of successful sexual intercourse attempts, and global treatment efficacy.

Conclusions

Significant improvements in self-esteem, confidence, sexual relationship satisfaction, and overall relationship satisfaction after treatment of ED with sildenafil were consistent among countries. These data suggest a substantial cross-cultural improvement in well-being after successful treatment of ED with sildenafil.
The synergistic effects of the IL‐9 gene and environmental exposures on asthmatic Taiwanese families as determined by the transmission/disequilibrium test
Authors: Wang T‐N. , Chen W‐Y. , Huang Y‐F. , Shih N‐H. , Feng W‐W. , Tseng H‐I. , Lee C‐H. , Ko Y‐C.
Published: February 2006

Asthma occurs in genetically susceptible individuals in the presence of environmental factors. The interleukin‐9 (IL‐9) gene, one of the cytokine genes located on chromosome 5q31, plays an important role in the development of asthmatic syndrome by enhancing both T‐cell and mast‐cell function. This study investigated GT repeat polymorphism of the IL‐9 gene and the gene–environment interactions, which may predispose individuals to asthma and atopy pathogenesis. In this study, we used the transmission/disequilibrium test (TDT) to investigate the relationship between asthma and the IL‐9 gene by studying 123 parent–offspring trios and 91 siblings. For allele‐specific TDT chi‐squared test, allele 122 of the IL‐9 gene showed significant association with asthmatics with specific IgE against house dust (HD) (P = 0.038). The additions of covariates to TDT to conduct the synergistic effects between the IL‐9 gene and environmental factors into account were estimated by conditional logistic regression models. The odds ratio for transmission of allele 122 of the IL‐9 gene was 1.23 (P = 0.28) for all asthmatic probands. There was slight increased interaction effect on asthma between transmission of allele 122 of IL‐9 gene to offspring and who were exposed to the fur of pets (OR = 3.33, P = 0.047). We also detected elevated odds of transmission of allele 122 to atopic asthmatic probands (OR = 2.08, P = 0.03) and offspring with very high levels of serum IgE (≥ 800 IU mL−1). In conclusion, this study has found that the IL‐9 gene was slightly associated with asthmatics who have positive specific IgE against Der p (or Der f) and house dust, when information on environmental factors was incorporated as effect modifiers.
Reduced coronary reserve in response to short‐term ischaemia and vasoactive drugs in ex vivo hearts from diabetic mice
Authors: Bratkovsky S. V. , Aasum E. , Riemersma R. A. , Myhre E. S. P. , Larsen T. S.
Published: February 2006

Aim:  The aim of the present study was to compare the coronary flow (CF) reserve of ex vivo perfused hearts from type 2 diabetic (db/db) and non‐diabetic (db/+) mice.

Methods:  The hearts were perfused in the Langendorff mode with Krebs–Henseleit bicarbonate buffer (37 °C, pH 7.4) containing 11 mmol L−1 glucose as energy substrate. The coronary reserve was measured in response to three different interventions: (1) administration of nitroprusside (a nitric oxide donor), (2) administration of adenosine and (3) production of reactive hyperaemia by short‐term ischaemia.

Results:  Basal CF was approximately 15% lower in diabetic when compared with non‐diabetic hearts (2.1 ± 0.1 vs. 2.6 ± 0.2 mL min−1). The maximum increase in CF rate in response to sodium nitroprusside and adenosine was significantly lower in diabetic (0.6 ± 0.1 and 0.9 ± 0.1 mL min−1 respectively) than in non‐diabetic hearts (1.2 ± 0.1 and 1.4 ± 0.1 mL min−1 respectively). Also, there was a clear difference in the rate of return to basal CF following short‐term ischaemia between diabetic and non‐diabetic hearts. Thus, basal tone was restored 1–2 min after the peak hyperaemic response in non‐diabetic hearts, whereas it took approximately 5 min in diabetic hearts.

Conclusion:  These results show that basal CF, as well as the CF reserve, is impaired in hearts from type 2 diabetic mice. As diabetic and non‐diabetic hearts were exposed to the same (maximum) concentrations of NO or adenosine, it is suggested that the lower coronary reserve in type 2 diabetic hearts is, in part, because of a defect in the intracellular pathways mediating smooth muscle relaxation.
Genotypic variation in induced resistance and induced susceptibility in the peach‐Myzus persicae aphid system
Authors: Sauge Marie‐Hélène , Mus Florence , Lacroze Jean‐Philippe , Pascal Thierry , Kervella Jocelyne , Poëssel Jean‐Luc
Published: February 2006

In response to herbivore damage or stress, plants may express physiological or morphological changes known as induced responses. We tested whether previous herbivory by the aphid Myzus persicae differentially altered the expression of resistance and susceptibility among five genotypes of peach that differ in their resistance phenotype (avoidance resistance, antibiosis resistance or susceptibility). We measured behavioural and performance parameters of aphid success on plants previously infested by conspecifics as compared to uninfested controls. Significant variation was found both among genotypes and among resistance phenotype, including between genotypes showing a same resistance phenotype. Genotypes with avoidance resistance showed either induced resistance to aphid settling or no response. Genotypes with antibiosis resistance showed induced susceptibility to aphid settling, but the effects of previous herbivory on aphid development were either positive or negative depending on the genotype. In the susceptible genotype, most parameters of aphid settlement and performance, including reproduction, were positively influenced by previous herbivory. Using electronic recording, the aphid probing behaviour was examined to tentatively identify host plant tissues most likely to play a role in induced defenses. Probing behaviour was significantly affected by plant genotype, previous herbivory, and their interaction, indicating complex relations between the two factors. In the genotypes with avoidance resistance, aphids were deterred before they reach the phloem. In the genotypes expressing susceptibility or antibiosis resistance, previous herbivory triggered instead the induction of a phloem‐mediated response, that however diverged depending on the resistance status (facilitation or reduction of phloem sap uptake respectively). Genotypic variation in induction found in the peach‐M. persicae system establishes a useful framework to improve our knowledge of the ecological role of induced plant responses to aphids.
Population fluctuations, regulation and limitation in stream‐living brown trout
Authors: Daufresne Martin , Renault Olivier
Published: February 2006

Determining causes of variation in population size and identifying factors responsible for fluctuations in species abundance are crucial questions both in theoretical and applied ecology. Based on the analysis of abundance time series, many studies have concluded that population dynamics of the stream‐living brown trout (Salmo truttaL.) are mainly driven by year‐to‐year variation in the discharge level during emergence. Endogenous regulatory processes have often been considered as weak explanations for these fluctuations. This led some authors to consider that brown trout was able to persist in time with no operation of density‐dependent processes. Using a model of population dynamics, we studied the influence of both discharge level during emergence and density‐dependent regulatory processes on population limitation and fluctuations. We show that density‐dependent and density‐independent processes can act together on population density and stability at equilibrium (limitation process). We also show that the effects of internal feedbacks regulating population may often be invisible when analyzing abundance fluctuations at the interannual scale. Our results question the accuracy of studies based on the analysis of interannual fluctuations in abundance to identify processes driving population density at equilibrium.
Fish foraging effects on benthic assemblages along a warm‐temperate stream: differences among drift feeders, benthic predators and grazers
Authors: Inoue Mikio , Miyayoshi Masanobu
Published: February 2006

In streams, physical and biotic conditions change from the headwaters to the mouth, shaping longitudinal patterns in community structure. We examined how fish foraging effects on periphyton and benthic invertebrates changed along a longitudinal gradient of a warm‐temperate stream in southwestern Japan. We established three study sites according to changes in the composition of fish feeding guilds (upper site characterized by drifting‐invertebrate feeders, Oncorhynchus masou; middle site by benthic invertebrate feeders, Rhinogobius spp.; lower site by the presence of periphyton grazers, Sicyopterus japonicus), and performed two manipulative experiments to examine effects of different fish assemblages on periphyton and benthic invertebrate abundances. Results of an exclosure experiment suggested that fishes had no effect on the benthic assemblages at the upper and middle sites whereas fishes reduced the abundances of both periphyton and invertebrates on stone surfaces at the lower site, where both benthic invertebrate feeders and grazers inhabited. A subsequent enclosure experiment showed that the reduction of invertebrate densities at the lower site was caused by the grazers rather than benthic invertebrate feeders. These experimental results suggested that effects of fishes on benthic assemblages are intensified downstream, owing to the occurrence of the grazing fish. Furthermore, observational data based on field sampling suggested that such grazing effects were reflected in longitudinal patterns in periphyton and invertebrate abundances. Overall results emphasize an important role of the grazing fish (S. japonicus) in shaping longitudinal patterns in benthic assemblage structure.
Entropy and diversity
Authors: Jost Lou
Published: February 2006

Entropies such as the Shannon–Wiener and Gini–Simpson indices are not themselves diversities. Conversion of these to effective number of species is the key to a unified and intuitive interpretation of diversity. Effective numbers of species derived from standard diversity indices share a common set of intuitive mathematical properties and behave as one would expect of a diversity, while raw indices do not. Contrary to Keylock, the lack of concavity of effective numbers of species is irrelevant as long as they are used as transformations of concave alpha, beta, and gamma entropies. The practical importance of this transformation is demonstrated by applying it to a popular community similarity measure based on raw diversity indices or entropies. The standard similarity measure based on untransformed indices is shown to give misleading results, but transforming the indices or entropies to effective numbers of species produces a stable, easily interpreted, sensitive general similarity measure. General overlap measures derived from this transformed similarity measure yield the Jaccard index, Sørensen index, Horn index of overlap, and the Morisita–Horn index as special cases.
Abundance and co‐occurrence patterns of core and satellite species of ground beetles on small lake islands
Authors: Ulrich Werner , Zalewski Marcin
Published: February 2006

15 lake islands and two mainland sites of Mamry lake in Poland were sampled to investigate community structures and patterns of co‐occurrences of ground beetles (Carabidae). The total ground beetle metacommunity of 71 species was divided into a group of core species occupying at least half of all study sites and of satellite species, which occurred at two sites or less. This division is mirrored by reduced dispersal abilities and non‐random patterns of site occupancy. Core and satellite species also differed in patterns of relative abundance. The core group followed a lognormal distribution, the satellite group a power function as predicted by the self‐similarity model of occurrence. We conclude that the division into core and satellite species is not a sample artefact but reflects different life history strategies. We also conclude that current models of niche division and co‐occurrence might miss important aspects of community structure if they do not refer to patterns of dispersal.

From these findings we infer that the regional distribution of core species might be shaped by species interactions and processes of niche divisions whereas the spatial distribution of satellite species are best interpreted as stemming from random dispersal.
Edaphic niche differentiation among Polybotrya ferns in western Amazonia: implications for coexistence and speciation
Authors: Tuomisto Hanna
Published: February 2006

To study the degree of edaphic specialization in Amazonian plants, the distribution patterns of seven species of Polybotrya ferns were studied in 109 sites in a climatically uniform area of northwestern Amazonia (Colombia, Ecuador and northern Peru). The two most abundant species of Polybotrya were found in about two‐thirds of the sites with almost 7000 individuals each, the rarest species occurred in just one site with 40 individuals. Each of the seven species appeared to have a unique realised niche, when niche dimensions were defined by gradients in soil texture, soil cation content, and inundation. The species also differed in how broadly or narrowly they were distributed along each gradient. Some species were practically never found in the same sites, whereas others co‐occurred with a high frequency, in spite of showing clearly different abundance patterns among sites. A single site only contains a small part of the edaphic variation present in the landscape, and a small proportion of any species’ niche space, so broad‐scale studies are needed to adequately describe and compare species’ niches and to assess to what degree niche differences promote species coexistence. The distribution patterns in Polybotrya are consistent with, but do not prove, that ecological speciation may have been important in the radiation of the genus. If such a pattern is found to be common in other Amazonian plants, this would indicate that each evolutionary lineage has adapted to the available habitats largely independently of the others.
Determination of the Link Lengths for a Spatial 3-DOF Parallel Manipulator
Authors: Liu Xin-Jun , Wang Jinsong , Kim Jongwon
Published: February 2006

This paper addresses the issue of determining the optimal geometric parameters of a 3-DOF parallel manipulator. One of the advantages of the manipulator is that the moving platform exhibits high tilting capabilities, e.g., as much as ±50deg. The first step of the new optimal methodology proposed in this paper to achieve the optimum design involves developing a design space that includes all possible basic similarity manipulators. The next step deals with the graphical representation of atlases that can illustrate relationships between performance criteria and design parameters. With such atlases, the designer can identify an optimum region with respect to the specification on performances. The region contains the optimum candidates, from which we can select one directly. Finally, the geometric parameters of the manipulator can be reached by comparing the desired workspace and the good-conditioning workspace. The design methodology discussed in this paper has no process to establish the objective function and does not involve any optimization algorithm, which is normally used in traditional optimization. We expect that since each manipulator in the developed design space represents all of its similarity manipulators in terms of performances, this method will guarantee an optimum design result.
Geometric Design of Three-Phalanx Underactuated Fingers
Authors: Birglen Lionel , Gosselin Clément M.
Published: February 2006

This paper studies the grasp stability of two classes of three-phalanx underactuated fingers with transmission mechanisms based on either linkages or tendons and pulleys. The concept of underactuation in robotic fingers—with fewer actuators than degrees of freedom—allows the hand to adjust itself to an irregularly shaped object without complex control strategy and sensors. With a n-phalanx finger, n contacts (one for each phalanx) are normally required to statically constrain the finger. However, some contact forces may be lacking due to either the transmission mechanism, or simply the object size and position. Thus, one may define an ith order equilibrium, when the finger is in static equilibrium with i missing contacts. In this paper, the case for which n=3 is studied with a particular emphasis on the cases for which i=1 and i=2. The fact that some contact forces do not appear or are negative, can lead in some cases to the ejection of the object from the hand, when no equilibrium configuration is achieved.
Hierarchical Role-Based Viewing for Multilevel Information Security in Collaborative CAD
Authors: Cera Christopher D. , Braude Ilya , Kim Taeseong , Han JungHyun , Regli William C.
Published: February 2006

Information security and assurance are new frontiers for collaborative design. In this context, information assurance (IA) refers to methodologies to protect engineering information by ensuring its availability, confidentiality, integrity, nonrepudiation, authentication, access control, etc. In collaborative design, IA techniques are needed to protect intellectual property, establish security privileges and create “need to know” protections on critical features. This paper provides a framework for information assurance within collaborative design based on a technique we call Role-Based Viewing. We extend upon prior work to present Hierarchical Role-Based Viewing as a more flexible and practical approach since role hierarchies naturally reflect an organization’s lines of authority and responsibility. We establish a direct correspondence between multilevel security and multiresolution surfaces where a hierarchy is represented as a weighted directed acyclic graph. The permission discovery process is formalized as a graph reachability problem and the path-cost can be used as input to a multiresolution function. By incorporating security with collaborative design, the costs and risks incurred by multiorganizational collaboration can be reduced. The authors believe that this work is the first of its kind to unite multilevel security and information clouded with geometric data, including multiresolution surfaces, in the fields of computer-aided design and collaborative engineering.
Framework of a Product Lifecycle Costing System
Authors: Xu X. , Chen J. L.-Q. , Xie S. Q.
Published: February 2006

Today’s competitive business environment imposes new challenges to manufacturing companies. For these companies to survive in this environment, implementing product lifecycle management (PLM) technologies with an emphasis on cost control is one valid approach. PLM is a strategic business approach that applies a consistent set of business solutions to help manufacturing companies manage all the activities related to a product in an integrated way across the lifecycle from customer need to product recycling and disposal. Product lifecycle cost is an important measure for PLM implementation. It can help track and analyze the financial information of activities associated with each phase of a product’s lifecycle. The paper presents a framework of the product lifecycle costing system for supporting decision making, especially the decision making at very early stages of a product lifecycle. It can be used as a design support tool to help new product development. A number of methodologies and tools are developed in the system. The case based reasoning method is used to quickly build a new product model. The costs of product development processes related to the new product are calculated using activity based costing methods. Dynamic programming is then used to obtain an optimal set of product development processes with the objective of optimizing the overall product development cost. This system is built using object oriented modeling methods.
Tool Sequence Selection for 2.5D Pockets with Uneven Stock
Authors: D’Souza Roshan M.
Published: February 2006

This paper describes an algorithm to select the cheapest tool sequence for machining 2.5D pockets using the milling process when the stock is uneven (noncylindrical). Uneven stock is generated when multiple setups are used to machine a prismatic part. Even though the pockets have flat bottom faces, the amount of material to be removed will vary along the depth of the pocket. This research has developed algorithms for finding accessible areas for tools, and pocket decomposition when the stock is uneven. Finally, it is shown that tool sequence selection problem can be formulated as the shortest path problem in a single-source, single-sink directed acyclic graph.
CAFixD: A Case-Based Reasoning Fixture Design Method. Framework and Indexing Mechanisms
Authors: Boyle Iain M. , Rong Kevin , Brown David C.
Published: February 2006

Fixtures accurately locate and secure a part during machining operations. Various computer-aided fixture design (CAFD) methods have been developed to reduce design costs associated with fixturing. One approach uses a case-based reasoning (CBR) method where relevant design experience is retrieved from a design library and adapted to provide a new design solution. Indexing design cases is a critical issue in CBR, and CBR systems can suffer from an inability to distinguish between cases if indexing is inadequate. This paper presents CAFixD, a CAFD methodology that adopts a rigorous approach to defining indexing attributes based upon axiomatic design functional requirement decomposition. A design requirement is decomposed in terms of functional requirements, physical solutions are retrieved and adapted for each individual requirement, and the design is then reconstituted to form a complete fixture design. This paper presents the CAFixD framework and operation, and discusses in detail the indexing mechanisms used.
Web-Based Interactive Analysis and Animation of Mechanisms
Authors: Cheng Harry H. , Trang Dung T.
Published: February 2006

A Web-based mechanism analysis and animation system is presented in this article. The system is developed in Ch, an embeddable C/C++ interpreter, and Ch Mechanism Toolkit. It allows users to solve complicated planar mechanism problems conveniently on-line. Users can input the required data to define a mechanism in a Web browser and then click a button for kinematic and dynamic analysis, graphical plotting, and animation for fourbar, crank-slider, geared fivebar, sixbar linkages and cam-follower systems. Examples are provided to illustrate its ease of use as well as its suitability for distance learning. The Web-based system for mechanism analysis and animation is available on the Web at http://www.softintegration/webservices/mechanism/
Elements of an Interface Standard for Knowledge Sources in Knowledge-Based Engineering
Authors: Poenisch Volker , Clark Andrew
Published: February 2006

Software architectures for knowledge-based engineering often separate applications from their knowledge sources. We propose elements for a new standard for the resulting interface. The fully automatic transfer of knowledge would require a shared engineering ontology. We suggest something less ambitious, namely to make only part of the knowledge machine-intelligible, such as a number embedded in a rule. This proposal still requires a human to code the knowledge from the source into the application. However, it would allow the application to automatically handle some updates to the knowledge sources. We discuss the details of a formalism to describe the machine-intelligible part of the knowledge; we suggest some meta-data; and we clarify the relationship of the proposal to existing standards.
Finding Undercut-Free Parting Directions for Polygons with Curved Edges
Authors: McMains Sara , Chen Xiaorui
Published: February 2006

We consider the problem of whether a given geometry can be molded in a two-part, rigid, reusable mold with opposite removal directions. We describe an efficient algorithm for solving the opposite direction moldability problem for a 2D “polygon” bounded by edges that may be either straight or curved. We introduce a structure, the normal graph of the polygon, that represents the range of normals of the polygon’s edges, along with their connectivity. We prove that the normal graph captures the directions of all lines corresponding to feasible parting directions. Rather than building the full normal graph, which could take time O(nlogn) for a polygon bounded by n possibly curved edges, we build a summary structure in O(n) time and space, from which we can determine all feasible parting directions in time O(n).
A Model for Capturing Product Assembly Information
Authors: Rachuri Sudarsan , Han Young-Hyun , Foufou Sebti , Feng Shaw C. , Roy Utpal , Wang Fujun , Sriram Ram D. , Lyons Kevin W.
Published: February 2006

The important issue of mechanical assemblies has been a subject of intense research over the past several years. Most electromechanical products are assemblies of several components, for various technical as well as economic reasons. This paper provides an object-oriented definition of an assembly model called the Open Assembly Model (OAM) and defines an extension to the NIST Core Product Model (NIST-CPM). The assembly model represents the function, form, and behavior of the assembly and defines both a system level conceptual model and associated hierarchical relationships. The model provides a way for tolerance representation and propagation, kinematics representation, and engineering analysis at the system level. The assembly model is open so as to enable plug-and-play with various applications, such as analysis (FEM, tolerance, assembly), process planning, and virtual assembly (using VR techniques). With the advent of the Internet more and more products are designed and manufactured globally in a distributed and collaborative environment. The class structure defined in OAM can be used by designers to collaborate in such an environment. The proposed model includes both assembly as a concept and assembly as a data structure. For the latter it uses STEP. The OAM together with CPM can be used to capture the assembly evolution from the conceptual to the detailed design stages. It is expected that the proposed OAM will enhance the assembly information content in the STEP standard. A case study example is discussed to explain the Usecase analysis of the assembly model.
On Generating a Class of Foldable Six-Bar Spatial Linkages
Authors: Baker J. Eddie
Published: February 2006

Recently isolated through fortuity and subsequent inference, a family of six-revolute spatial linkages is distinguished by dimensional properties which allow the individual loops to be folded, hence making them of possible interest in the field of deployable structures. The purpose of this paper is to demonstrate a novel method for generating each of the linkages from planar and Bennett chains. Alternative compositions are discussed, along with the family's potential for being fashioned into nests of linkages.
Topological Representations and Characteristics of Variable Kinematic Joints
Authors: Yan Hong-Sen , Kuo Chin-Hsing
Published: February 2006

There exist some mechanisms with variable topologies that have interesting applications, for examples, legged walking machines, mechanical push-button stopper locks, and various toys. A variable kinematic joint is a kinematic joint that is capable of topological variation in a mechanism with variable topology. This work aims at the topological representations and characteristic analysis of variable kinematic joints. During the operation process of a mechanism, the topology states of a variable kinematic joint can be expressed symbolically as the joint sequences, graphically the digraphs, and mathematically the matrices. With the applications of graph theory, it proves that the topological characteristics of variable kinematic joints appeared with the abilities of reversibility, continuity, variability of degrees of freedom, joint homomorphism, contractibility, and expansibility. Two examples are provided for illustrating how the proposed concepts can be used to analyze and synthesize the variable joints. The results of this work provide a logical foundation for the systematic structural synthesis regarding the kinematic joints and mechanisms with variable topologies.
Helical Gears, Effects of Tooth Deviations and Tooth Modifications on Load Sharing and Fillet Stresses
Authors: Guilbault Raynald , Gosselin Claude , Cloutier Louis
Published: February 2006

Based on a few specific cases, this paper presents a comparative investigation of the effect of helix slope and form deviation tolerances as specified by grades 5 and 7 of the ANSI/AGMA ISO 1328-1 Standard for Cylindrical Gears. In addition, the consequences of longitudinal flank crowning and radial tip relief modifications are investigated, as applied on a misaligned helical gear set. For all simulations, the express model (Guilbault et al., 2005, ASME J. Mech. Des., 127(6), pp. 1161–1172) is employed. The bending deflection and fillet stresses are obtained from a combination of finite strip and finite difference meshes. The rolling-sliding motion of mating gear teeth is modeled with a cell discretization of the contact area, which offers fast and accurate results. Similar contact conditions arise from a helix slope deviation or a misalignment of the gear set: the first contact point is driven to a theoretical contact line endpoint. Such a condition produces a localized, and clearly impaired, contact area subject to overloading. Consequently, flank crowning and tip relief corrections must be carefully regarded in the design process. The presented results highlight that, if improperly combined, profile modifications can amplify the overloading condition.
Symmetrical Coupler Curve and Singular Point Classification in Planar and Spherical Swinging-Block Linkages
Authors: Shirazi Kourosh H.
Published: February 2006

The purpose of the present paper is coupler curve synthesis and classification in planar and spherical swinging block linkages for path generation problem. It is shown that the swinging block mechanism, which is an inversion of the slider crank mechanism, can be classified into two types. The first type generates Lemniscate coupler curves consisting one or two loops. In this case, two double points, namely cusp and crunode, occur depending on the mechanism's dimension. The second type generates Cardioid and Limaçon type coupler-curves consisting of one, two, three, and four loops. In this case, three kinds of double points, namely cusp, crunode, and tacnode, occur. For the spherical swinging-block linkages, a parametric coupler curve equation is derived. Using a trigonometric similitude between the planar and spherical linkages, a symmetrical coupler curve and singular point classification is accomplished.
The Design of a Chain of Spherical Stephenson Mechanisms for a Gearless Robotic Pitch-Roll Wrist
Authors: Hernandez S. , Bai S. , Angeles J.
Published: February 2006

Although bevel-gear robotic wrists are widely used in industrial manipulators due to their simple kinematics and low manufacturing cost, their gear trains function under rolling and sliding, the latter bringing about noise and vibration. Sliding is inherent to the straight teeth of the bevel gears of these trains. Moreover, unavoidable backlash introduces unmodeled dynamics, which mars robot performance. To alleviate these drawbacks, a gearless pitch-roll wrist is currently under development for low backlash and high stiffness. The wrist consists of spherical cam-rollers and spherical Stephenson linkages, besides two roller-carrying disks that drive a combination of cams and Stephenson mechanisms, the whole system rotating as a differential mechanism. The paper focuses on the design of the chain of spherical Stephenson mechanisms. The problem of the dimensional synthesis is addressed, and interference avoidance is discussed. An embodiment of the concept is also included.
Development of Analytical Model of Cantilever Hook Performance
Authors: Suri Gaurav , Luscher Anthony F.
Published: February 2006

With an increase in the use of polymeric materials in commercial products, snap-fits are attracting increased attention as alternatives to other, more traditional, joining methods. The field of snap-fit design is receiving greater attention as an engineering and research activity. Research in this area has focused on the development of performance models for individual features and heuristics for the design of snap-fit assemblies. An improved analytical model for cantilever hook snap-fit features is developed in this study. The modeling approach is a significant improvement over currently available analytical design equations. The model captures the effect of a snap-fit’s catch in causing contact forces to be offset from the beam’s neutral axis. Beam rotation, influence of axial force, and moment components on beam deformation are also incorporated by formulating a set of equations that model the system in its deformed configuration. The equation system is iteratively solved for several such configurations to model insertion and retention processes for snap-fits. The axial force component, which has been hitherto ignored in analytical design equations, is found to have significant effect on predicted snap-fit performance. The design space of cantilever hook features is explored by varying input design parameters. The model shows excellent agreement with experimental results, especially for low and medium retention angle snap-fit features. However, for high retention angle snap-fits, more accurate governing equations are required. Suggestions for possible improvements and future research directions are provided.