bluuebunny/crossref_metadata_2025 huggingface dataset:
PP2A:B56ϵ is required for Wnt/β-catenin signaling during embryonic development
Authors: Yang Jing , Wu Jinling , Tan Change , Klein Peter S.
Published: October 2003

The Wnt/β-catenin pathway plays important roles during embryonic development and growth control. The B56 regulatory subunit of protein phosphatase 2A (PP2A) has been implicated as a regulator of this pathway. However, this has not been investigated by loss-of-function analyses. Here we report loss-of-function analysis of PP2A:B56ϵ during early Xenopus embryogenesis. We provide direct evidence that PP2A:B56ϵis required for Wnt/β-catenin signaling upstream of Dishevelled and downstream of the Wnt ligand. We show that maternal PP2A:B56ϵ function is required for dorsal development, and PP2A:B56ϵ function is required later for the expression of the Wnt target gene engrailed, for subsequent midbrain-hindbrain boundary formation, and for closure of the neural tube. These data demonstrate a positive role for PP2A:B56ϵ in the Wnt pathway.
The maternally expressed zebrafish T-box geneeomesoderminregulates organizer formation
Authors: Bruce Ashley E. E. , Howley Cristin , Zhou Yi , Vickers Sarah L. , Silver Lee M. , King Mary Lou , Ho Robert K.
Published: October 2003

Early embryonic development in many organisms relies upon maternal molecules deposited into the egg prior to fertilization. We have cloned and characterized a maternal T-box gene in the zebrafish, eomesodermin(eomes). During oogenesis, the eomes transcript becomes localized to the cortex of the oocyte. After fertilization during early cleavage stages, eomes is expressed in a vegetal to animal gradient in the embryo, whereas Eomesodermin protein (Eom) is distributed cytoplasmically throughout the blastoderm. Strikingly, following midblastula transition, nuclear-localized Eomesodermin is detected on the dorsal side of the embryo only. Overexpression of eomes results in Nodal-dependent and nieuwkoid/dharma (nwk/dhm) independent ectopic expression of the organizer markers goosecoid (gsc), chordin (chd) and floating head (flh) and in the formation of secondary axes. The same phenotypes are observed when a VP16-activator construct is injected into early embryos, indicating that eomes acts as a transcriptional activator. In addition, a dominant-negative construct and antisense morpholino oligonucleotides led to a reduction in gsc and flh expression. Together these data indicate that eomes plays a role in specifying the organizer.
Axolotl pronephric duct migration requires an epidermally derived,laminin 1-containing extracellular matrix and the integrin receptorα6β1
Authors: Morris Andrea R. , Drawbridge Julie , Steinberg Malcolm S.
Published: October 2003

The epidermis overlying the migrating axolotl pronephric duct is known to participate in duct guidance. This epidermis deposits an extracellular matrix onto the migrating duct and its pathway that is a potential source of directional guidance cues. The role of this matrix in pronephric duct guidance was assayed by presenting matrix deposited on microcarriers directly to migrating pronephric ducts in situ. We found that reorientation of extracellular-matrix-bearing carriers prior to their presentation to migrating ducts caused a corresponding reorientation of pronephric duct migration. Subepidermal microinjection of function-blocking antibodies against α6 integrin, β1 integrin or the laminin-1/E8 domain recognized byα6β1 integrin, all of which were detected and localized here,inhibited pronephric duct migration. Moreover, pre-exposure to anti-laminin-1/E8 function-blocking antibody prevented reoriented carriers of epidermally deposited matrix from reorienting pronephric duct migration. These results are incorporated into an integrated model of pronephric duct guidance consistent with all present evidence, proposing roles for the previously implicated glial cell-line derived neurotrophic factor and its receptor as well as for laminin 1 and α6β1 integrin.
A crucial role for Fgfr2-IIIb signalling in epidermal development and hair follicle patterning
Authors: Petiot Anita , Conti Francesco J. A. , Grose Richard , Revest Jean-Michel , Hodivala-Dilke Kairbaan M. , Dickson Clive
Published: October 2003

To understand the role Fgf signalling in skin and hair follicle development, we analysed the phenotype of mice deficient for Fgfr2-IIIb and its main ligand Fgf10. These studies showed that the severe epidermal hypoplasia found in mice null for Fgfr2-IIIb is caused by a lack of the basal cell proliferation that normally results in a stratified epidermis. Although at term the epidermis of Fgfr2-IIIb null mice is only two to three cells thick, it expresses the classical markers of epidermal differentiation and establishes a functional barrier. Mice deficient for Fgf10 display a similar but less severe epidermal hypoplasia. By contrast, Fgfr2-IIIb–/–, but not Fgf10–/–, mice produced significantly fewer hair follicles, and their follicles were developmentally retarded. Following transplantation onto nude mice, grafts of Fgfr2-IIIb–/– skin showed impaired hair formation, with a decrease in hair density and the production of abnormal pelage hairs. Expression of Lef1, Shh and Bmp4 in the developing hair follicles of Fgfr2-IIIb–/–mice was similar to wild type. These results suggest that Fgf signalling positively regulates the number of keratinocytes needed to form a normal stratified epidermis and to initiate hair placode formation. In addition, Fgf signals are required for the growth and patterning of pelage hairs.
Control of dendritic development by theDrosophila fragile X-relatedgene involves the small GTPase Rac1
Authors: Lee Alan , Li Wenjun , Xu Kanyan , Bogert Brigitte A. , Su Kimmy , Gao Fen-Biao
Published: October 2003

Fragile X syndrome is caused by loss-of-function mutations in the fragile X mental retardation 1 gene. How these mutations affect neuronal development and function remains largely elusive. We generated specific point mutations or small deletions in the Drosophila fragile X-related (Fmr1) gene and examined the roles of Fmr1 in dendritic development of dendritic arborization (DA) neurons in Drosophila larvae. We found that Fmr1 could be detected in the cell bodies and proximal dendrites of DA neurons and that Fmr1loss-of-function mutations increased the number of higher-order dendritic branches. Conversely, overexpression of Fmr1 in DA neurons dramatically decreased dendritic branching. In dissecting the mechanisms underlying Fmr1 function in dendrite development, we found that the mRNA encoding small GTPase Rac1 was present in the Fmr1-messenger ribonucleoprotein complexes in vivo. Mosaic analysis with a repressor cell marker (MARCM) and overexpression studies revealed that Rac1 has a cell-autonomous function in promoting dendritic branching of DA neurons. Furthermore, Fmr1 and Rac1 genetically interact with each other in controlling the formation of fine dendritic branches. These findings demonstrate that Fmr1 affects dendritic development and that Rac1 is partially responsible for mediating this effect.
The β-catenin/VegT-regulated early zygotic geneXnr5is a direct target of SOX3 regulation
Authors: Zhang Chi , Basta Tamara , Jensen Eric D. , Klymkowsky M. W.
Published: October 2003

In Xenopus laevis, β-catenin-mediated dorsal axis formation can be suppressed by overexpression of the HMG-box transcription factor XSOX3. Mutational analysis indicates that this effect is due not to the binding of XSOX3 to β-catenin nor to its competition with β-catenin-regulated TCF-type transcription factors for specific DNA binding sites, but rather to SOX3 binding to sites within the promoter of the early VegT- andβ-catenin-regulated dorsal-mesoderm-inducing gene Xnr5. Although B1-type SOX proteins, such as XSOX3, are commonly thought to act as transcriptional activators, XSOX3 acts as a transcriptional repressor of Xnr5 in both the intact embryo and animal caps injected with VegT RNA. Expression of a chimeric polypeptide composed of XSOX3 and a VP16 transcriptional activation domain or morpholino-induced decrease in endogenous XSOX3 polypeptide levels lead to an increase in Xnr5expression, as does injection of an anti-XSOX3 antibody that inhibits XSOX3 DNA binding. These observations indicate that maternal XSOX3 acts in a novel manner to restrict Xnr5 expression to the vegetal hemisphere.
The RNA-binding protein Vg1 RBP is required for cell migration during early neural development
Authors: Yaniv Karina , Fainsod Abraham , Kalcheim Chaya , Yisraeli Joel K.
Published: October 2003

After mid-blastula transition, populations of cells within the Xenopus embryo become motile. Using antisense morpholino oligonucleotides, we find that Vg1 RBP, an RNA-binding protein implicated in RNA localization in oocytes, is required for the migration of cells forming the roof plate of the neural tube and, subsequently, for neural crest migration. These cells are properly determined but remain at their site of origin. Consistent with a possible role in cell movement, Vg1 RBP asymmetrically localizes to extended processes in migrating neural crest cells. Given that Vg1 RBP is a member of the conserved VICKZ family of proteins, expressed in embryonic and neoplastic cells, these data shed light on the likely role of these RNA-binding proteins in regulating cell movements during both development and metastasis.
Wnts and Hedgehogs: lipid-modified proteins and similarities in signaling mechanisms at the cell surface
Authors: Nusse Roel
Published: October 2003

This review compares the signaling mechanisms of the Wnt and the Hedgehog proteins. Although Wnts and Hedgehogs are unrelated proteins, they are both modified by lipids, possibly through the action of enzymes that are related to each other. At the surface of target cells, the reception of Wnt and Hedgehog signals is regulated by several molecules, some of which, in particular the Frizzled and Smoothened receptors, are related to each other. Several other aspects of Wnt and Hedgehog transport and signaling are discussed, as well as the possible origin of these pathways.
Control of geometrical sources of error in residual stress analysis by energy-dispersive X-ray diffraction
Authors: Alfonso J A , Greaves E D , Lavelle B , Sajo-Bohus L
Published: October 2003

A theoretical expression that describes the influence of instrumental errors in the determination of residual stress by energy-dispersive X-ray diffraction (EDXRD) is derived. The calculation predicts the shift in the diffraction peak energy with variation in the angle Ψ as a function of the misalignment parameters. A simple model that allows evaluation and monitoring of instrumental adjustment for residual stress measurements by EDXRD is shown. Good agreement between experimental and theoretical data is obtained using the model developed.
Strain patterns induced by press-fitting and by an external load in hip arthroplasty: A photoelastic coating study on bone models
Authors: Cristofolini L , Metti C , Viceconti M
Published: October 2003

The success of prostheses is highly dependent upon load transfer and bone stresses. Reflection photoelasticity is a viable technique for measuring stress patterns in vitro. However, when a cementless stem is tested, the resultant stresses under load are the sum of the implantation stresses and of those induced by load application. Separating these two components is a critical issue that so far has not been thoroughly solved using photoelasticity.

Implantation strains and strain under load were measured separately by a suitable procedure: the photoelastic coating was applied to the femur after stem press-fitting. Thus, when an external load is applied (e.g. to simulate a physiological activity), the fringe patterns indicate the effect of the external load alone. Implantation strains are measured independently, after load removal; the stem is extracted and stresses are released, causing a new fringe pattern. The method was used to investigate the stress pattern caused by press-fitting of two cementless hip stems and that caused by a load applied to the implanted femora.

Different isochromatic and isoclinic patterns were observed for the strain distribution caused by load application and by press-fitting for two stem designs. Differences in press-fit pattern and load transfer were successfully detected between the two designs.
Integrating thermoelastic and numerical stress methods for reliable analysis
Authors: Greene R. J , Patterson E. A
Published: October 2003

Two case studies are presented which employ the experimental technique of thermoelastic stress analysis in order to verify finite element models of components from an off-road bicycle. The design of the finite element simulations is detailed and selection of elements and loading conditions justified. The use of a thermoelastic detector with a focal plane array allows full-field maps of surface stress to be determined, which are subsequently used in an evaluation of the finite element simulations. Good agreement is shown between the simulations and the experimental data, and the paper concludes that this current generation of thermoelastic detectors provides a valuable method of validation for complex finite element models.
An experimental study on the mixed-mode crack tip deformation fields in polymethyl methacrylate
Authors: Luo P-F , Huang F. C
Published: October 2003

Stereo vision was used to measure the full three-dimensional deformation field around the crack tip region of a compact tension shear (CTS) specimen made of polymethyl methacrylate (PMMA) subjected to mixed-mode (I/II) loading. The stress intensity factors (SIF), K1 and KII, were then estimated using both measured in-plane and out-of-plane deformation fields. The KI and KII values determined from in-plane displacements are in very good agreement with those determined from out-of-plane displacement. The far-field J integral values computed using the line integral are compared with those evaluated using the measured KI and KII values. The extent of the region near a mixed-mode crack tip where the plane stress solutions can reasonably predict the in-plane and out-of-plane displacements was investigated. Experimental results indicate that the solution of the out-of-plane displacement derived on the basis of the plane stress condition does not provide a good approximation to the experimental data for distances from the crack tip within half the specimen thickness. However, there is good agreement between the in-plane displacement measurements and the computed results, even for r/h < 0.5.
Frictional shakedown in a complete contact
Authors: Saez R , Mugadu A , Fuenmayor J , Hills D. A
Published: October 2003

The phenomenon of frictional shakedown is investigated by considering a complete contact configuration for which a stable partial slip regime exists; a tilted square-ended rigid punch is pressed against an incompressible half-plane by an offset constant normal load and subject to an oscillatory shearing force. The analysis shows that analogies might be drawn with conventional plasticity nomenclature and that, under certain conditions, Melan's lower bound theorem of plastic shakedown may be invoked, leading to the elimination of steady state slip. The implications of these results to fretting contacts are discussed.
Experimental study of double cold expansion of holes
Authors: Stefanescu D
Published: October 2003

This paper examines experimentally the effect of double cold expansion on the residual stress field and fatigue behaviour of fastener holes in plates. Measurements of the hoop strain generated by the progressive drawing of the mandrel through the hole, of the retained expansion and of the surface residual stresses were performed on both cold and double cold expanded specimens. Fatigue testing and a fracture surface examination were also carried out for all specimens. It was found that double cold expansion reduces the through-thickness variation of the residual stress field generated and improves the behaviour of fastener holes under fatigue loading.
Measurement of residual stresses in T-plate weldments
Authors: Wimpory R. C , May P. S , O'Dowd N. P , Webster G. A , Smith D J , Kingston E
Published: October 2003

Tensile welding residual stresses can, in combination with operating stresses, lead to premature failure of components by fatigue and/or fracture. It is therefore important that welding residual stresses are accounted for in design and assessment of engineering components and structures. In this work residual stress distributions, obtained from measurements on a number of ferritic steel T-plate weldments using the neutron diffraction technique and the deep-hole drilling method, are presented. It has been found that the residual stress distributions for three different plate sizes are of similar shape when distances are normalized by plate thickness. It has also been found that the conservatisms in residual stress profiles recommended in current fracture mechanics-based safety assessment procedures can be significant—of yield strength magnitude in certain cases. Based on the data presented here a new, less-conservative transverse residual stress upper bound distribution is proposed for the T-plate weldment geometry. The extent of the plastic zone developed during the welding process has also been estimated by use of Vickers hardness and neutron diffraction measurements. It has been found that the measured plastic zone sizes are considerably smaller than those predicted by existing methods. The implications of the use of the plastic zone size as an indicator of the residual stress distributions are discussed.
A technique for the determination of post-yield material properties from the small punch test
Authors: Zidan A. A , Brookfield D. J
Published: October 2003

The aim of the present work was to determine post-yield material properties from small punch test results, i.e. from the force-displacement curve obtained in such a test. This determination was made by comparing the experimental curve with a large set of previously determined finite element (FE) curves for differing post-yield properties expressed in terms of Ramberg and Osgood parameters. A simple cost function was then used to find the closest FE curve and thus provide an estimate of the post-yield properties. This estimate was then updated using an optimization technique based on the Matlab ‘fminsearch’ function and an interface with the ABAQUS FE code, giving a reliable estimate of the post-yield material properties. The FE analysis and model were validated by comparison with other small punch tests and the FE curves were additionally used to determine von Mises stresses, equivalent plastic strains and displacements.

The method used to determine post-yield properties from small specimens has been demonstrated by determining the material properties of stainless steel. The technique is particularly relevant to those steels used in pressure vessels.
Quadrilateral finite elements for multilayer sandwich plates
Authors: Nayak A. K , Moy S. S. J , Shenoi R. A
Published: October 2003

The bending behaviour of isotropic and laminated composite and sandwich plates has been analysed using two new C° assumed strain quadrilateral finite element formulations based on a refined form of Reddy's higher-order theory. The assumed strain approach ensures that there are no parasitic spurious zero energy modes and no shear locking. The element performances are evaluated on some standard plate tests involving closed-form solutions and experimental results. All results indicate that the present elements have satisfactory convergence properties, accuracy in the results and freedom from any major defects.
Evaluation of plastic limit load of piping branch junctions subjected to out-of-plane moment loadings
Authors: Xuan F-Z , Li P-N , Tu S-T
Published: October 2003

Under out-of-plane moment loadings, the piping branch junctions (also called tees in engineering) exhibit three kinds of failure mode, namely collapse failure of the branch pipe, global collapse of the intersection due to plastic hinges forming along the intersection line and local instability of the main pipe at the flank. In this work, the common piping branch junctions utilized in petrochemical and power industries with a failure mode of global collapse were investigated, and a new approximate formula for an out-of-plane plastic limit moment was presented. The formula was built on the following process: firstly, an equation between the out-of-plane limit moment and internal force of the branch pipe along the intersection is set up on the basis of the force equilibrium condition. Regarding this internal force as an external load for the main pipe shell, the internal force and moment along the intersection of the main pipe, under the plastic limit state, are then obtained. Finally, referring to the von Mises yield criterion, the approximate plastic limit load of the piping branch junctions subjected to the out-of-plane moment is derived. The accuracy of the new formula is validated by comparison with finite element analysis and experimental results.
A review of the general theory of thermoelastic stress analysis
Authors: Pitarresi G , Patterson E. A
Published: October 2003

Thermoelastic stress analysis (TSA) is now a well-known experimental technique providing information on the surface stress field in structures. Many studies have assessed the potential of the technique for a number of applications and some useful and detailed reviews of these investigations are available, focusing mainly on the experimental aspects related to the measurement of the thermoelastic signal. In this work, instead, a complete and detailed insight into the origins of the various forms of the equations describing the thermoelastic effect is given with reference to the concepts of the thermodynamic theory of a continuum. A discussion on the theory leading to the thermoelastic effect law is intended to give a useful overview of the applications and real limitations of TSA.
The effect of high compressive loading on residual stresses and fatigue crack growth at cold expanded holes
Authors: Stefanescu D , Dutta M , Wang D Q , Edwards L , Fitzpatrick M. E
Published: October 2003

The effect of monotonic compressive loading on the residual stresses developed at cold expanded fastener holes has been investigated using the neutron and X-ray diffraction techniques. Monotonic loading models the effect of the peak of a fatigue loading sequence experienced before a crack is initiated. It was found that the compressive loading significantly affected the residual stress distribution. A low load relaxed only the stresses near to the bore of the hole, whereas a larger load affected the stress distribution over a greater area. Residual stresses measured at the mandrel entrance face were more affected by the compressive loading than the residual stresses measured at the other segments of thickness. The comparison between the X-ray and neutron diffraction results showed that the techniques complemented each other well, enabling a three-dimensional residual stress distribution to be derived. This distribution was used for modelling the effect of compressive loading on fatigue crack growth, using a linear elastic fracture mechanics approach and assuming a stabilized residual stress field.
Stress analysis of V-notches with and without cracks, with application to foreign object damage
Authors: Nowell D , Dini D , Duó P
Published: October 2003

Gas turbine engines can be subject to ingestion of small hard particles, leading to foreign object damage. This can take the form of sharp V-notches in the leading edge of blades and there is a need to predict the initiation and propagation behaviour of fatigue cracks growing from the base of the notch. The notch geometry is quite extreme and is not normally covered in standard references for notch stress concentration factors. Similarly, stress intensity factor solutions for this geometry are not widely available. This paper uses the dislocation density approach to solve the two-dimensional elastic problem of a V-notch with a radiused root. Stress concentration factors are found for the notch itself, and stress intensity factors are determined for cracks growing away from the notch for cases of applied and residual stress distributions. Comparisons are made with existing notch solutions from the literature.
Fatigue design in the presence of stress concentrations
Authors: Susmel L , Taylor D
Published: October 2003

This paper reports a comparative study of some recent methods developed for the estimation of high-cycle fatigue behaviour of components containing stress concentrations. It begins by reviewing some existing methods for the prediction of fatigue limits: the stress-life method, linear elastic fracture mechanics, the Kitagawa-Takahashi and Atzori-Lazzarin approaches and the method of Smith and Miller. Two new methods are described which have been developed during the last few years: the crack modelling method (CMM) and the critical distance method (CDM). These methods were tested by comparing their predictions with experimental data using a large database of 88 different notch geometries and materials. Notches were divided into three types: blunt, sharp and short. The CDM was found to be very successful for all types of notch, giving predictions within 20 per cent of experimental values in the great majority of cases. The CMM encountered difficulties with short notches; correction factors were developed to overcome this problem. Both methods can be used very easily in conjunction with finite element analysis, making them more useful than previous methods for the prediction of high-cycle fatigue in engineering components.
Delamination modelling of a curved composite beam subjected to an opening bending moment
Authors: Wang W , Shenoi R. A
Published: October 2003

A theoretical approach is developed for the case of delamination of a curved composite beam under an opening bending moment. This is based on linear curved beam theory coupled with fracture mechanics concepts. The general solution is applied to analyse a specific case of delamination occurring at the mid-plane. The effects of the arc angle of delamination crack and the radius of curvature of the beam on the critical load are also studied.
X-ray residual stress analysis of cylindrically curved surfaces—estimation of circumferential distributions of residual stresses
Authors: Oguri T , Murata K , Sato Y
Published: October 2003

A new measuring technique utilizing X-ray diffraction is proposed in order to estimate the circumferential distributions of residual stresses on convex/concave cylindrical surfaces. This technique requires neither tilting X-ray beams in the circumferential direction in which the X-ray incident angle tends to be limited nor adjusting the normal of the irradiation area to the reference axis of the ψ angle. The circumferential distributions of the circumferential stress and of the axial stress are estimated from the diffraction angles at ψ = 0° and the axial stresses obtained by the stress measurement on multiple inclined areas on the cylindrical surfaces under the configuration of the axial stress measurement using the iso-inclination scanning method. This estimate technique was applied to two round bars of steel, one with circumferential distributions of the residual stresses and the other with almost uniform stresses. The distribution functions of the residual stresses were expanded to a couple of Fourier series, and the coefficients of them were determined by the least-squares method. The estimated distributions of the residual stresses were in good agreement with the actual ones.
Experimental investigation of corner-supported architectural glazing under pulse pressure loading
Authors: Goodfellow A. M , Schleyer G. K
Published: October 2003

City centre bombings demonstrate the vulnerability of buildings to the effects of an explosion. Glazing panels on buildings, which shatter in the blast, are the main cause of injury due to the high-velocity fragments produced. A special test facility recently developed in the University of Liverpool Impact Research Centre has been used to investigate the dynamic behaviour of glazing components under pulse pressure loading. The type of glazing system studied in this work is supported at discrete points, unlike conventional glazing systems, which are usually supported along all edges. Novel experimental techniques have been used successfully to apply dynamic pressure pulses to full-size, 1 m by 1 m by 10mm thick glazing panels supported at four corner points under controlled laboratory conditions.
Strain-concentration factor of plane-strain notched rectangular bars under pure bending
Authors: Majima T , Ishizaka T
Published: October 2003

A new strain-concentration factor (SNCF) has been defined for plane-strain notched rectangular bars under pure bending. The nominal strain for this new SNCF is obtained from an assumed linear distribution of the longitudinal strain on the net section. This nominal strain is defined under the triaxial stress state at the net section. The new SNCF provides reasonable values for the non-linear distributions of the longitudinal strain, while the conventional SNCF provides unreasonable values. The new SNCF increases from its elastic value to a peak value with plastic deformation. On further deformation it gradually decreases and then increases up to the value at the general yielding. The relation between the new SNCF and M/MY, the ratio of the applied bending moment to the bending moment at yielding at the notch root, is independent of the stress- strain curve up to general yielding.
Laser non-conduction limited heating and prediction of surface recession velocity in relation to drilling
Authors: Yilbas B S , Shuja S Z
Published: October 2003

Lasers find application in modifying the characteristics of metallic surfaces in industry. In the present study, a laser non-conduction heating situation is investigated and the recession velocity of the surface is computed after considering: (a) constant temperature evaporation at the surface and (b) the steady evaporation condition. It is found that, in the initial phase of evaporation, the velocity of the liquid-vapour interface (recession velocity) predicted from constant temperature evaporation at the surface condition is more realistic than that corresponding to the steady evaporation situation. Moreover, as evaporation progresses, the magnitude of the surface temperature increases because of recoil pressure developed at the vapour-liquid interface. Consequently, the surface temperature rises and the recession velocity is determined from a steady heating situation in place of that predicted from constant temperature evaporation at the surface condition.
Cogeneration—the development and implementation of a cogeneration system for a chemical plant, using a reciprocating heavy fuel oil engine with a supplementary fired boiler
Authors: Coelho M , Nash F , Linsell D , Barciela J. P.
Published: October 2003

The contribution of cogeneration plants to a reduction in primary energy consumption will be important not only in lowering emissions to the atmosphere but also in cutting production costs by increasing the overall efficiency of fuel conversion to the electricity and heat used by process industries. This paper demonstrates the importance of the interactions of the utility needs of a process with the development and design of a cogeneration system to maximize fuel efficiency and achieve environmental compliance for a chemical plant. The cogeneration system in this project is based on a diesel cycle engine burning heavy fuel oil (HFO), driving an alternator and with an exhaust gas heat recovery boiler supplementary fired with either HFO or natural gas. The normal operation of the cogeneration plant is with the engine running at 95–100 per cent maximum continuous rating (MCR) with the supplementary firing of the boiler modulating to meet the process requirements for saturated steam at 10 barg. In addition to recovering waste heat from the engine exhaust gas (EEG), supplementary firing using the excess oxygen in the exhaust gas enables the process steam required by the plant to be produced without the loss of energy involved in heating combustion air. At the same time the reduced volume of oxygen available to the flame reduces peak temperature and NOx emissions, this being further enhanced by the phased combustion design of the burner. The technology demonstrated in this application is generally as used in gas turbine cogeneration cycles burning natural gas. The use of HFO in this instance necessitated the use of a reciprocating engine driven generator and the development of supplementary firing of the exhaust gases. The successful development of the technology enables this reciprocating engine based cogeneration system to be scaled up or, possibly more importantly, down utilizing HFO, natural gas or renewable derived liquid or gaseous fuels. Its implementation using spark ignition engine generators retrofitted to economic boilers may be one way general industry in the United Kingdom might meet its climate change levy (CCL) targets for energy reduction and help approach the government's carbon reduction requirements.
IPRP (Integrated-Pyrolysis Regenerated Plant): Gas turbine and externally heated rotary-kiln pyrolysis as a biomass and waste energy conversion system. Influence of thermodynamic parameters
Authors: Fantozzi F , D'Alessandro B , Bidini G
Published: October 2003

Sustainability is one of the main goals to achieve in order to guarantee a future for future generations and requires, among other issues, the recourse to renewable energy sources and the minimization of waste production. These two issues are contemporarily achieved when converting waste and residual biomass into energy.

This paper presents an innovative concept for energy conversion of the abovementioned residual fuels; it combines a rotary-kiln pyrolyser, where the residual energy sources are converted into a medium lower heating value (LHV) syngas, with a gas turbine that produces energy, and also provides waste heat to maintain the endothermic pyrolysis reaction. Byproducts of the reaction include char and tars that have an interesting energetic content and may also be used to provide supplementary heat to the process.

Through software modelling the paper analyses the influence on performance of main thermodynamic parameters, showing the possibilities of reaching an optimum for different working conditions that are characteristic of different sizes of gas turbines. This is interesting both for medium-to-big size power plants, where the IPRP efficiency is comparable to a grate-based incinerator, but at lower investment costs, and in the micro-small scale, for which there is no available technology on the market.
Evaluation of nitric oxide kinetics in high-pressure flames (up to 5 atm)
Authors: Ravikrishna R. V. , Laurendeau N. M.
Published: October 2003

Nitric oxide kinetics in laminar, counterflow diffusion flames at pressures from 1 to 5 atm are assessed by comparing predictions of NO concentration ([NO]) using comprehensive chemical kinetic mechanisms with highly quantitative laser-induced fluorescence (LIF) measurements. The most recent Gas Research Institute (GRI) mechanism, version 3.0, is used and is compared with the older version 2.11 mechanism. Results indicate that there is significant improvement in the predictive capability of the GRI 3.0 mechanism over the 2.11 mechanism with regard to predicting the magnitude of [NO] as well as the trend of [NO] variation with pressure. However, there is still substantial difference between [NO] predictions and measurements, especially at lower pressures, indicating a need for further refinement of NO kinetics.
Performance and wall static pressure measurements on centrifugal compressor diffusers
Authors: Issac J. M. , Sitaram N , Govardhan M
Published: October 2003

The results of experimental studies on performance and wall static pressure distribution in the diffuser passage of a low specific speed centrifugal compressor are given. The performance tests were carried out with vaneless, vane and low-solidity vane diffusers at speeds of 2500, 3000 and 3500r/min. Diffuser wall static pressures measured at 3000r/min for four flow coefficients on the shroud and hub walls are reported. The peak energy coefficient is maximum for the vane diffuser. The operating range of the low-solidity vane diffuser is wider than that of the vane diffuser. At high flow coefficients, the static pressure rise is substantially lower for the vane diffuser, as the incidence on the vane leading edge is very high. The low-solidity vane diffuser did not suffer a large drop in static pressure near the leading edge. The most probable reason may be the large area available in the low-solidity vane diffuser for flow adjustment and weaker flow separation zones on account of the lower number of vanes.
Resonant and stationary waves in axially travelling thin plates
Authors: Luo A C J
Published: October 2003

The subharmonic wave solutions of axially travelling, prebuckled and post-buckled plates are developed analytically, and the conditions for resonant and stationary waves are presented. From this investigation, the plate buckling caused by translation motion and compressive loading is different, and the local buckling motion for travelling plates cannot be obtained. The small motion of travelling buckled plates will jump to large motion with increasing translation speed. The phenomena can be observed in axially travelling shell structures. The prediction of resonant and stationary waves in travelling structures is useful for experimental measurement, observation and structural design. In addition, the procedure presented in this paper is applicable for investigation of non-linear structural vibrations.
Dynamic model of a deep-groove ball bearing including localized and distributed defects. Part 1: Theory
Authors: Sopanen J , Mikkola A
Published: October 2003

This study proposes a dynamic model of a deep-groove ball bearing with six degrees of freedom. The model includes descriptions of non-linear Hertzian contact deformation and elastohydrodynamic (EHD) fluid film. The geometry, material properties and diametral clearance of the bearing are given as the input to the proposed model. The bearing force and torque components are calculated from the relative displacements and velocities between bearing rings. Distributed defects, such as the waviness of the inner and outer ring, and localized defects, such as inner and outer ring defects, are taken into consideration in the proposed model. The proposed ball bearing model could be used in the general multi-body or rotor dynamics computer code as an interference element between the rotor and the housing. The numerical results obtained from the model are compared with those found in the literature in Part 2 of this paper.
Dynamic model of a deep-groove ball bearing including localized and distributed defects. Part 2: Implementation and results
Authors: Sopanen J , Mikkola A
Published: October 2003

The model of the ball bearing proposed in Part 1 is implemented and analysed using a commercial multi-body system software application (MSC. ADAMS). The effect of the diametral clearance of the bearing on the natural frequencies and vibration response of the rotor-bearing system is studied. The diametral clearance is found to have a significant effect on the level of vibration as well as on the natural frequencies. Low-order waviness, also known as out-of-roundness, is found to generate vibration at frequencies of the waviness order multiplied by the rotation speed. On the other hand, the waviness orders close to the number of balls in the bearing (z± 1 and z) are found to generate vibrations at the ball passage inner ring and ball passage outer ring frequencies. Various excitations produce sum and difference frequencies. Localized defects in the inner and outer ring are found to generate vibrations at bearing defect frequencies. The simulation results are in line with the analytical and experimental results available in the literature.
Prediction of vibroacoustic excitation due to the timing chains of reciprocating engines
Authors: Sopouch M , Hellinger W , Priebsch H H
Published: October 2003

Timing drive systems of recent passenger car engines are usually equipped with chain or synchronous belt drives. The comparatively low stiffness of chains and belts, combined with the large moments of inertia, resulting from moving parts of camshafts and valvetrains, lead to natural frequencies in the frequency range between 80 and 250 Hz for the entire timing drive [1]. Obviously, engine orders dominating the noise excitation are in the same frequency range, and resonance effects cannot be avoided. Furthermore, a guarantee is requested that occurring vibration amplitudes do not exceed acceptable limits. Hence, the predicted results of the primary dynamics of the timing drive are key data for the design analysis of a combustion engine. Besides the low frequency range excitation determined by main engine orders, higher-order structure-borne noise excitation is gaining more importance. This is particularly true for chain-driven systems where specific effects lead to considerable excitation of the engine structure in a higher frequency range (typical whine noise). The excitations are caused by the polygon effect, meshing impacts between chain links and sprockets and impacts in the engagement and disengagement between chain, sprockets and guides. This paper presents a comprehensive multi-body dynamics (MBD) model and the relevant simulation environment, which takes into account the entire timing drive as a fully coupled system. While simple MBD models (e.g. longitudinal span representation) are sufficient for the prediction of the primary dynamics of the timing drive, usually the analysis of higher-frequency dynamics and structural excitation requires a high degree of discretization of drive components to ensure a high-quality representation of the physical behaviour. This leads to a discrete model of chains and belts. Each link or tooth is taken into account separately by its mass properties, viscoelastic characteristics and by its contacts to sprockets, pulleys and guides. This paper describes the mathematical modelling of relevant engine components and the relevant interaction of different force elements. In particular, the consideration of the elastic contact between bodies represented by their real surface shapes is outlined. Finally, simulation results and their comparison with experimental data are presented for a chain-driven system, with discussion of low-frequency primary dynamics and higher-frequency structural excitation. Discrete models have also been developed for timing belts, but their verification with measurements is not completely finished. Hence, this paper only gives an overview of modelling issues.
Boundary and eigenvalue problems for generally restrained anisotropic plates
Authors: Grossi R O , Nallim L
Published: October 2003

The present paper deals with the determination of the boundary and eigenvalue problems that describe the static and dynamic behaviour of anisotropic tapered plates with edges elastically restrained against rotation and translation and nonsmooth boundaries. It is demonstrated that this type of boundary restrictions leads to unstable boundary conditions and that the presence of corner points when the boundary is elastically restrained against translation generates additional boundary conditions. This is particularly interesting in the case of triangular plates.
Exploration of a twelve-bar linkage network
Authors: Baker J E
Published: October 2003

Among the scattered publications on multiloop linkages are a very few concerned with alternative closure modes and special configurations. A certain planar network of twelve bars and eight double-hinges, introduced more than a century ago, has received less attention in this regard than is its due. Here, prior work is built upon to make a more systematic investigation of its various forms and the transformations from one to another.
A Facile Synthesis of 2,4-Disubstituted 3-Fluoroquinolines via Intramolecular Cyclization of o-Cyanomethylamino-β,β-difluorostyrenes
Authors: Wada Yukinori , Mori Takashi , Ichikawa Junji
Published: October 2003

o-Cyanomethylamino-β,β-difluorostyrenes are treated with base (LiTMP, NaH, or K2CO3) to generate the corresponding carbanions, which in turn readily undergo intramolecular replacement of the vinylic fluorine and subsequent elimination to afford 2,4-disubstituted 3-fluoroquinolines in good yield.
Temperature-Dependent Solid-state Luminescence and Reversible Phase Transition of (n-Bu4N)[Au(SC6H3-3,5-Me2)2]
Authors: Watase Seiji , Kitamura Takayuki , Kanehisa Nobuko , Nakamoto Masami , Kai Yasushi , Yanagida Shozo
Published: October 2003

The solid-state luminescence, thermal behavior, and phase transition of the gold(I) complex with 3,5-dimethylbenzenethiolate are discussed. The emission decay process of this complex switches accompanied by the reversible phase transition without destruction of the crystal lattice.
Preparation and Fluorescent Properties of Rhodamine B–hexadecylamine-intercalated Graphite Oxide Thin Film
Authors: Matsuo Yoshiaki , Fukutsuka Tomokazu , Sugie Yosohiro
Published: October 2003

Thin film samples of Rhodamine B–hexadecylamine-intercalated graphite oxides were prepared by cast method from chlorofolm solution of Rhodamine B and hexadecylamine-intercalated graphite oxide. The emission maxima red-shifted with increasing Rhodamine B content in the sample. The tilted alkylamine may prevent the formation of nonfluorescent Rhodamine B H-dimer.
A New Method for the Preparation of Aluminum and Titanium Tris(2,6-diphenylphenoxide) Reagents and Their Application in Organic Synthesis
Authors: Sato Atsushi , Hattori Asuka , Ishihara Kazuaki , Saito Susumu , Yamamoto Hisashi
Published: October 2003

A new method for the preparation of aluminum and titanium trisphenoxides was realized using tetraallyltin or α-pinene as a proton-trapping agent. Thus obtained chlorotitanium reagent was converted to the corresponding cation-type reagent, which proved to be an effective catalyst for epoxide rearrangements.
Controlling the Hydrophobic Properties of Water-soluble Stilbene Dendrimers
Authors: Hayakawa Junpei , Momotake Atsuya , Nagahata Ritsuko , Arai Tatsuo
Published: October 2003

The Intramolecular energy transfer from the dendron subunit to the stilbene core in water-soluble stilbene dendrimer 2 increased from 49% to ca. 100% by added salt.
Framework Assembly Engineering. Effects of Nitro Groups on Assemblies of Phenyldicarboxylates
Authors: Ma Ai-Qing , Shi Zhan , Xu Ru-Ren , Pang Wen-Qin , Zhu Long-Guan
Published: October 2003

A novel 2-D complex [Cu(nbdc)(phen)(H2O)] (nbdc = 2-nitro-1,4-benzenedicarboxylate dianion and phen = 1,10-phenanthroline) has been synthesized and structurally characterized by single crystal X-ray analysis. It exhibits nice fluorescent property. The modifying group plays a key role in the assembly of the framework.
Stabilization of a Self-assembled Coordination Nanotube by Covalent Link
Authors: Tominaga Masahide , Kato Masanori , Okano Takashi , Sakamoto Shigeru , Yamaguchi Kentaro , Fujita Makoto
Published: October 2003

A newly designed oligopyridine ligand in which two tris(3,5-pyridine) units are linked by an alkyl spacer is complexed with (en)Pd(NO3)2 leading to the self-assembly of a coordination nanotube with an empty cavity. The covalent link in the ligand considerably stabilizes the tube because the tube framework without the covalent link does not assemble unless a template is employed. Size-discriminated alkane inclusion by the tube is also disclosed.
Novel and Efficient Organic Liquid Electrolytes for Dye-sensitized Solar Cells Based on a Ru(II) Terpyridyl Complex Photosensitizer
Authors: Hara Kohjiro , Nishikawa Takeshi , Sayama Kazuhiro , Aika Kenichi , Arakawa Hironori
Published: October 2003

We have developed a novel and efficient organic liquid electrolyte composed of 1-ethyl-3-methylimidazolium iodide, iodine (I2), and acetonotrile solvent for a nanocrystalline TiO2 solar cell sensitized with a Ru(II) terpyridyl complex. A solar energy-to-electricity conversion efficiency of 8.0% was attained under AM 1.5 irradiation (100 mW cm−2).