bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced Abdominal Adiposity and Improved Glucose Tolerance in Growth Hormone-Treated Girls with Turner Syndrome
Authors: Wooten Nicole , Bakalov Vladimir K. , Hill Suvimol , Bondy Carolyn A.
Published: March 2008

Background: Individuals with Turner syndrome (TS) are at increased risk for impaired glucose tolerance and diabetes mellitus. It is unknown whether pharmacological GH treatment commonly used to treat short stature in TS alters this risk.

Objective: Our objective was to compare adiposity and glucose tolerance in GH-treated vs. untreated girls with TS.

Methods: In a cross sectional study, GH-treated girls with TS (n = 76; age 13.6 ± 3.7 yr) were compared to girls with TS that never received GH (n = 26; age 13.8 ± 3.5 yr). Protocol studies took place in the NIH Clinical Research Center from 2001–2006 and included oral glucose tolerance tests, body composition analysis by dual-energy x-ray absorptiometry, and abdominal fat quantification by magnetic resonance imaging. GH was not given during testing.

Results: Total body fat (35 ± 8 vs. 28 ± 8%, P < 0.0001), sc abdominal fat (183 vs. 100 ml, P = 0.001), and intraabdominal fat (50 vs. 33 ml, P < 0.0001) were significantly greater in untreated girls. Fasting glucose and insulin were similar, but the response to oral glucose was significantly impaired in the untreated group (28 vs. 7% with impaired glucose tolerance, P = 0.006). A specific excess of visceral fat and insulin resistance was apparent only in postpubertal girls that had never received GH. GH-treated girls demonstrated lower adiposity compared with untreated girls for an average of 2 yr after discontinuation of GH.

Conclusions: Abdominal adiposity is significantly lower and glucose tolerance significantly better in GH-treated vs. untreated girls with TS, suggesting that beneficial effects upon body composition and regional fat deposition outweigh transient insulin antagonism associated with GH administration.
Androgen Deprivation Therapy in Prostate Cancer and Metabolic Risk for Atherosclerosis
Authors: Shahani Sadeka , Braga-Basaria Milena , Basaria Shehzad
Published: March 2008

Context: Prostate cancer (PCa) is the most common cancer in men. Androgen-deprivation therapy (ADT) is generally employed in the treatment of locally advanced and metastatic PCa. Although its use as an adjuvant therapy has resulted in improved survival in some patients, ADT has negative consequences. Complications like osteoporosis, sexual dysfunction, gynecomastia, and adverse body composition are well known. Recently, metabolic complications like insulin resistance, diabetes, dyslipidemia, and metabolic syndrome have emerged, which may be responsible for the increased cardiovascular mortality in this population.

Evidence Acquisition: A MEDLINE search was conducted for articles published over the last 20 yr based on the key words androgen deprivation therapy AND insulin resistance, hyperglycemia, diabetes, dyslipidemia, metabolic syndrome, and cardiovascular disease. Relevant studies in non-PCa populations evaluating the association between testosterone and metabolism were also reviewed and briefly mentioned where relevant.

Evidence Synthesis: Prospective studies evaluating early (3–6 months) metabolic changes of ADT show development of hyperinsulinemia; however, glucose levels remain normal. Cross-sectional studies of men undergoing long-term (≥12 months) ADT reveal higher prevalence of diabetes and metabolic syndrome compared with controls. Furthermore, men undergoing ADT also experience higher cardiovascular mortality.

Conclusion: Long-term prospective studies of ADT are needed to determine the timing of onset of these metabolic complications and to investigate the mechanism behind them. In the meantime, we recommend baseline and serial screening for fasting glucose, lipids, and other cardiovascular risk factors in men receiving ADT. Glucose tolerance tests and cardiac evaluation may be required in selected cases.
The Rac activator Tiam1 prevents keratinocyte apoptosis by controlling ROS-mediated ERK phosphorylation
Authors: Rygiel Tomasz P. , Mertens Alexander E. , Strumane Kristin , van der Kammen Rob , Collard John G.
Published: March 2008

Tiam1 is a ubiquitously expressed activator of the small GTPase Rac. Previously, we found that Tiam1 knockout (KO) mice are resistant to DMBA-induced skin tumorigenicity, which correlated with increased apoptosis in keratinocytes of the skin epidermis. Here, we have studied the mechanisms by which Tiam1 protects against apoptosis. We found that Tiam1-KO keratinocytes show increased apoptosis in response to apoptotic stimuli, including growth factor deprivation and heat-shock treatment. Expression of catalytically active Tiam1, but not inactive Tiam1, rescues the apoptosis susceptibility of Tiam1-KO keratinocytes, indicating that this defect is caused by impaired Tiam1-mediated Rac activation. Apoptosis induced by growth factor starvation correlates with impaired ERK phosphorylation in Tiam1-KO keratinocytes. Moreover, Tiam1-KO keratinocytes contain lower levels of intracellular reactive oxygen species (ROS) when compared with wild-type cells. The ROS content of keratinocytes is dependent on both Tiam1 and the activity of NADPH oxidase (Nox), and is required for ERK-mediated survival signaling. Indeed, Tiam1 deficiency or the inhibition of intracellular ROS production blocks ERK phosphorylation and sensitizes wild-type keratinocytes to apoptotic stimuli. Our results indicate that the Rac activator Tiam1 controls the intracellular redox balance by Nox-mediated ROS production, which regulates ERK phosphorylation and the susceptibility of keratinocytes to apoptotic signaling.
Transforming signals resulting from sustained activation of the PDGFβ receptor in mortal human fibroblasts
Authors: Petti Lisa M. , Ricciardi Elizabeth C. , Page Heather J. , Porter Kristen A.
Published: March 2008

The platelet-derived growth factor β receptor (PDGFβR) plays an important role in proliferation and motility of fibroblasts. We have been investigating the effects of sustained PDGFβR activation in mortal human diploid fibroblasts (HDFs), which are typically difficult to transform. We have previously shown that the bovine papillomavirus E5 protein, through its ability to crosslink and constitutively activate the PDGFβR, induces morphological transformation, enhanced growth and loss of contact inhibition (focus formation) in HDFs. Here, we characterized two E5 mutants as being severely defective for focus formation but still competent for enhanced growth, suggesting that proliferation is insufficient for loss of contact inhibition. These E5 mutants were then used in a comparative study to distinguish the PDGFβR signaling intermediates required for the enhanced growth phenotype from those required for focus formation. Our data suggested that a PI 3-kinase (PI3K)-AKT-cyclin D3 pathway, a Grb2-Gab1-SHP2 complex and JNK played a role in the enhanced growth phenotype. However, a SHP2-p66Shc-p190BRhoGAP complex and ROCK were implicated exclusively in focus formation. We speculate that a SHP2-p66Shc-p190BRhoGAP signaling complex recruited to the activated PDGFβR promotes a distinct Rho-dependent process required for focus formation but not growth of HDFs.
A20 is a negative regulator of BCL10- and CARMA3-mediated activation of NF-κB
Authors: Stilo Romania , Varricchio Ettore , Liguoro Domenico , Leonardi Antonio , Vito Pasquale
Published: March 2008

The molecular complex containing CARMA proteins, BCL10 and TRAF6 has been identified recently as a key component in the signal transduction pathways that regulate activation of the nuclear factor κB (NF-κB) transcription factor. Here, we report that the inducible protein A20 negatively regulates these signaling cascades by means of its deubiquitylation activity. We show that A20 perturbs assembly of the complex containing CARMA3, BCL10 and IKKγ/NEMO, thereby suppressing activation of NF-κB. Together, our results further define the molecular mechanisms that control activation of NF-κB and reveal a function for A20 in the regulation of CARMA and BCL10 activity in lymphoid and non-lymphoid cells.
The multi-FERM-domain-containing protein FrmA is required for turnover of paxillin-adhesion sites during cell migration of Dictyostelium
Authors: Patel Hitesh , König Ireen , Tsujioka Masatsune , Frame Margaret C. , Anderson Kurt I. , Brunton Valerie G.
Published: March 2008

FERM domain proteins, including talins, ERMs, FAK and certain myosins, regulate connections between the plasma membrane, cytoskeleton and extracellular matrix. Here we show that FrmA, a Dictyostelium discoideum protein containing two talin-like FERM domains, plays a major role in normal cell shape, cell-substrate adhesion and actin cytoskeleton organisation. Using total internal reflection fluorescence (TIRF) microscopy we show that FrmA-null cells are more adherent to substrate than wild-type cells because of an increased number, persistence and mislocalisation of paxillin-rich cell-substrate adhesions, which is associated with decreased motility. We show for the first time that talinA colocalises with paxillin at the distal ends of filopodia to form cell-substrate adhesions and indeed arrives prior to paxillin. After a period of colocalisation, talin leaves the adhesion site followed by paxillin. Whereas talinA-rich spots turnover prior to the arrival of the main body of the cell, paxillin-rich spots turn over as the main body of the cell passes over it. In FrmA-null cells talinA initially localises to cell-substrate adhesion sites at the distal ends of filopodia but paxillin is instead localised to stabilised adhesion sites at the periphery of the main cell body. This suggests a model for cell-substrate adhesion in Dictyostelium whereby the talin-like FERM domains of FrmA regulate the temporal and spatial control of talinA and paxillin at cell-substrate adhesion sites, which in turn controls adhesion and motility.
Cell-surface and mitotic-spindle RHAMM: moonlighting or dual oncogenic functions?
Authors: Maxwell Christopher Alan , McCarthy James , Turley Eva
Published: March 2008

Tumor cells use a wide variety of post-translational mechanisms to modify the functional repertoire of their transcriptome. One emerging but still understudied mechanism involves the export of cytoplasmic proteins that then partner with cell-surface receptors and modify both the surface-display kinetics and signaling properties of these receptors. Recent investigations demonstrate moonlighting roles for the proteins epimorphin, FGF1, FGF2, PLK1 and Ku80, to name a few, during oncogenesis and inflammation. Here, we review the molecular mechanisms of unconventional cytoplasmic-protein export by focusing on the mitotic-spindle/hyaluronan-binding protein RHAMM, which is hyper-expressed in many human tumors. Intracellular RHAMM associates with BRCA1 and BARD1; this association attenuates the mitotic-spindle-promoting activity of RHAMM that might contribute to tumor progression by promoting genomic instability. Extracellular RHAMM-CD44 partnering sustains CD44 surface display and enhances CD44-mediated signaling through ERK1 and ERK2 (ERK1/2); it might also contribute to tumor progression by enhancing and/or activating the latent tumor-promoting properties of CD44. The unconventional export of proteins such as RHAMM is a novel process that modifies the roles of tumor suppressors and promoters, such as BRCA1 and CD44, and might provide new targets for therapeutic intervention.
Trans-endocytosis of CD47 and SHPS-1 and its role in regulation of the CD47–SHPS-1 system
Authors: Kusakari Shinya , Ohnishi Hiroshi , Jin Feng-Jie , Kaneko Yuka , Murata Takaaki , Murata Yoji , Okazawa Hideki , Matozaki Takashi
Published: March 2008

CD47 and SHPS-1 are transmembrane proteins that interact with each other through their extracellular regions and constitute a bidirectional cell-cell communication system (the CD47–SHPS-1 system). We have now shown that the trans-interaction of CD47 and SHPS-1 that occurred on contact of CD47-expressing CHO cells and SHPS-1-expressing CHO cells resulted in endocytosis of the ligand-receptor complex into either cell type. Such trans-endocytosis of CD47 by SHPS-1-expressing cells was found to be mediated by clathrin and dynamin. A juxtamembrane region of SHPS-1 was indispensable for efficient trans-endocytosis of CD47, which was also regulated by Rac and Cdc42, probably through reorganization of the actin cytoskeleton. Inhibition of trans-endocytosis of CD47 promoted the aggregation of CD47-expressing cells with the cells expressing SHPS-1. Moreover, CD47 expressed on the surface of cultured mouse hippocampal neurons was shown to undergo trans-endocytosis by neighboring astrocytes expressing endogenous SHPS-1. These results suggest that trans-endocytosis of CD47 is responsible for removal of the CD47–SHPS-1 complex from the cell surface and hence regulates the function of the CD47–SHPS-1 system, at least in neurons and glial cells.
Interaction between Anillin and RacGAP50C connects the actomyosin contractile ring with spindle microtubules at the cell division site
Authors: D'Avino Pier Paolo , Takeda Tetsuya , Capalbo Luisa , Zhang Wei , Lilley Kathryn S. , Laue Ernest D. , Glover David M.
Published: March 2008

Anillin, one of the first factors recruited to the cleavage site during cytokinesis, interacts with actin, myosin II and septins, and is essential for proper organization of the actomyosin contractile ring. We employed affinity-purification methodology coupled with mass spectrometry to identify Anillin-interacting molecules in Drosophila cells. We isolated several actin and myosin proteins, three of the five Drosophila septins and RacGAP50C (Tum), a component of the centralspindlin complex. Using drug and RNA interference (RNAi) treatments we established that F-actin is essential for Anillin cortical localization in prometaphase but not for its accumulation at the cleavage furrow after anaphase onset. Moreover, septins were not recruited to the cleavage site in cells in which Anillin was knocked down by RNAi, but localized to central-spindle microtubules, suggesting that septins travel along microtubules to interact with Anillin at the furrow. Finally, we demonstrate that RacGAP50C is necessary for Anillin accumulation at the furrow and that the two proteins colocalize in vivo and interact in vitro. Thus, in addition to its role in activating RhoA signalling, RacGAP50C also controls the proper assembly of the actomyosin ring by interacting with Anillin at the cleavage furrow.
Evaluating a new flexible soldering system for electronics small and medium enterprises
Authors: Monfared R P , West A A , Vera D A , Conway P P
Published: March 2008

A new flexible soldering system for small to medium European electronics manufacturers is proposed by a group of European industrialists and academics as part of an EC-funded research project. The proposed soldering facility is intended to assist electronics small to medium-sized enterprises (SMEs) in tackling the ever growing market need for lower volume and higher variety of soldering printed circuit boards. A business evaluation study was carried out as part of this project to understand and highlight the impact of change in soldering methods within the project collaborators’ businesses. The development of the proposed soldering system is discussed briefly in the current paper and the adopted evaluation approach using business process modelling and process simulation is explained.
Integrating rough set clustering and grey model to analyse dynamic customer requirements
Authors: Chen C , Wang L
Published: March 2008

Customer requirements analysis is of critical importance in design for mass customization. The present paper investigates two important issues in customer requirements analysis. The first is clustering for the customer requirements and the product features (functional requirements), and the consistency analysis approach is applied to link customer groups with clusters of product features. The second issue concerns trends analysis of dynamic customer requirements and functional requirements on the basis of consistency analysis of customer groups and product feature clusters. A novel methodology integrating popular clustering techniques (such as fuzzy clustering and rough set) and grey theory is proposed for accomplishing the two tasks. It focuses on customer group based knowledge of customer requirements from the transaction records. This is used to provide decision support for product development by analysing historical data. A case study is presented to illustrate the proposed method.
Fabrication of high melting-point porous metals by lost carbonate sintering process via decomposition route
Authors: Zhang L P , Zhao Y Y
Published: March 2008

Porous metals with high melting points can be manufactured by the lost carbonate sintering (LCS) process either via the dissolution route or via the decomposition route. In the current paper, porous copper and steel samples with porosity in the range of 50 to 85 per cent and cell size in the range of 50 to 1000 μm have been produced via the decomposition route. The effectiveness of carbonate loss and the characteristics of the decomposition route have been studied. In comparison with the dissolution route, the decomposition route can be applied to a wider range of conditions and often requires shorter times to achieve a complete carbonate removal. The porous metal samples produced by the decomposition route generally have higher tensile strength and higher flexural strength than those produced by the dissolution route.
Improvement of forming limit by rotary nosing with a relieved die
Authors: Kuboki T , Ohde Y , Murata M
Published: March 2008

Rotary nosing with ‘relieved die’ is proposed for the shrinking tip diameter of a tube. Press nosing or spinning is conventionally used for shrinking the tip diameter. In press nosing, while the forming limit is low, productivity is high. In spinning, although the forming limit is very high, the productivity is very low. The present proposed rotary nosing is an intermediate method that is expected to achieve a higher forming limit than press nosing and realize higher productivity than spinning. In this present research, the forming limit was first examined experimentally and the mechanism was studied by finite element analysis. Based on the results, rotary nosing with a relieved die was proposed. The relieved die consists of three partial cones so that the die geometry is easily cut out using an ordinary lathe. This type of die can be easily and widely applied for industrial use. The effect of the proposed method was numerically evaluated with regard to the pushing force and hoop stress. Finally, the effect of rotary nosing was verified experimentally and the range was clarified where rotary nosing has a higher forming limit than conventional press nosing.
Surface roughness prediction model for CNC machining of polypropylene
Authors: Dhokia V G , Kumar S , Vichare P , Newman S T , Allen R D
Published: March 2008

Cutting strategy research has traditionally been focused on hard materials that are intrinsically difficult to machine. An increase in the desire for personalized products has led to the requirement of the direct machining of polymers for personalized products. Little research is evident in the literature on the analysis of optimal machining parameters for machining materials such as polypropylene. One of the vital factors that affects the quality of polypropylene products and the respective machining strategy is surface roughness.

This research is aimed at extracting information on the machining of polypropylene materials. A surface roughness predictive model based on neural networks has been developed. The design of experiments approach is used to obtain an adequate predictive model for the process planning which is further utilized as an input to the predictive model. The model mainly hinges on three independent variables namely spindle speed, feed rate, and depth of cut. Extensive experimental work on different network topologies and training algorithms has been performed to predict the behaviour of the surface roughness for machined polypropylene products. The results illustrate the benefits of being able to determine surface roughness values. This allows for the determination of optimal cutting strategies and tooling for the required surface roughness. The performance predictive model has been found to be satisfactory over the dataset for polypropylene machining. Hypothesis testing has also been carried out to identify the confidence of the predictive model.
Tool wear aspects when applying high-speed tapping on grey cast iron
Authors: A A Bezerra , R T Coelho
Published: March 2008

Tool wear is a very important subject affecting the economics of machining, especially in tapping, since it is one of the last operations to be performed within most operation sequences. In the present study, some aspects of tapping such as the mechanisms and types of wear were investigated in taps working at conventional and high-speed cutting (HSC). Additionally, different types of coatings and cooling/lubrication conditions were used. The tapping operation (M8 × 1.25) was performed in through holes with two cutting speeds (30 and 60 m/min) in grey cast iron GG25. Lubrication conditions tested were dry and with minimal quantity of lubricant. Tap materials were manufactured by powder metallurgy and coated with (TiAl)N and with TiCN. A go—non-go gauge criterion was used to assess tool life. The wear and surface aspects of the tools and workpiece were evaluated by scanning electron microscopy and energy dissipation spectroscopy. Torque signals were also measured during the tests.

The main wear mechanism observed was adhesion, although some abrasion and diffusion may also have occurred, and the main type of wear was flank wear. The adhesion of workpiece material on the tool was the main and decisive factor ending tool life. Tool coatings proved to be an efficient way to minimize adhesion. Torque signals followed the same pattern as the flank wear and no significant change was observed when the cutting speed was increased.
Arbitrary Lagrangian Eulerian analysis on cutting with a honed tool
Authors: Kishawy H A , Deiab I M , Haglund A J
Published: March 2008

A thermo-elasto-viscoplastic two-dimensional finite element analysis of the effects of different edge radii on the mechanics of orthogonal metal cutting is presented. The shear stress distribution was used to quantify the stagnation point as well as the minimum chip thickness needed to form a chip when using a honed cutting edge. The determined location of the stagnation point using the shear stress distribution agrees well with location calculated using the velocity profile in the vicinity of the cutting edge. The plastic flow of the material around the honed cutting edge and below the machined surface was studied. The ploughing force generated while cutting with a carbide tool was calculated. Contour plots of stress, strain, temperature, and velocity in the cutting zone were analysed along with contact stresses and temperature profiles on the rake face.
Automated inspection using database technology within the aerospace industry
Authors: Tiwari A , Vergidis K , Lloyd R , Cushen J
Published: March 2008

Many manufacturing processes have become fully automated resulting in high production volumes. However, this is not the case for inspection. Shortening the inspection times in manufacturing industry using the available information resources can result in the reduction of production lead-time and overall costs. Rapid advances in machine tool technology have resulted in fast processing computer numerical control (CNC) machines that are capable of manufacturing parts at high speeds, turning their manual inspection process into a bottleneck. However, most CNC machines record the operations that they perform as realization logs. This paper proposes an approach that utilizes these realization logs for automating the inspection process. The automation occurs with the implementation of a software tool that imports and compares the realization logs with the manufacturing instructions for a manufactured part. The output of the tool is an inspection report that lists all the identified skipped or mishandled operations for that part. The proposed inspection approach is compared with the manual practice within an aerospace manufacturer. The results demonstrate drastic reduction in production lead-time while producing accurate and reliable inspection reports in an automated manner.
An experimental investigation of turbulent boundary layer flow over surface-mounted circular cavities
Authors: Dybenko J , Savory E
Published: March 2008

Turbulent boundary layer flow over cavities of circular planform has been measured experimentally by examining pressures at the cavity surfaces and velocity and turbulence in the cavity wake for cavity depths ( h) of 0.20, 0.47, and 0.70 D (cavity diameter). Tests were conducted at a constant Mach number of 0.08 resulting in Re X = 7.3 × 106 and ReD = 1.3 × 105. Velocity measurements acquired in the cavity wake, using hot-wire anemometry, suggest the existence of an asymmetric trailing vortex for h/D ≍ 0.5. The increased amplitude of broadband low-frequency pressure oscillations observed at h/ D ≍ 0.5 may be a result of the high level of flow asymmetry and cavity drag observed for this depth and not for other depths tested. Also, a faint peak is seen in the power spectrum for this depth at a Strouhal number related in previous work to cavity feedback resonance. Contours of fluctuation pressures at the cavity surfaces are also presented. Details of a flow-switching control mechanism for the asymmetric trailing vortex noted for h/D ≍ 0.5 are also presented herein. Good agreement was noted between the present results and those from previous investigations.
Numerical study on self-sustained oscillation characteristics of cavity flameholders in a supersonic flow
Authors: Sun M B , Liang J H , Wang Z G
Published: March 2008

Self-sustained oscillation characteristics of two-dimensional cavity-based flameholders in a cold supersonic flow were investigated in the present numerical study. The unsteady flowfields were calculated using hybrid Reynolds-averaged Navier—Stokes/large eddy simulation (RANS/LES) method. The key cavity parameters that were varied include cavity aft wall angle and cavity length to depth ratio. The hybrid model favourably captured the large scale unsteady characteristics and revealed the evolution process of cavity free shear layer. Pressure fluctuation spectra agreed well with theoretical predictions. The hybrid RANS/LES data indicate that cavity shape and size both have significant effects on the oscillation characteristics. As the cavity length to depth ratio decreases, oscillation frequency corresponding to maximum oscillation amplitude shifts to higher values. Most of the oscillation modes are greatly suppressed as the cavity aft wall angle decreases. Contrast to the steep aft wall cavity, only higher frequency modes remain in the oscillation of the cavity with small aft wall angle.
Solar sail attitude control through in-plane moving masses
Authors: Bolle A , Circi C
Published: March 2008

A three-axis solar sail attitude control system for interplanetary missions is proposed: required steering is achieved by means of a small control mass in the solar sail plane, whereas roll-axis control is achieved through the rotation of ballast with two masses at the extremities. The satellite is fixed at the sail geometrical centre: this solution avoids the difficulties arising from the employment of an out-of-plane control boom with the satellite at the end, i.e. pointing problems for optical payloads and communication antennas. A circular sailcraft of 220 kg with characteristic acceleration ac = 0.5 mm/s2 is considered, and the control system performances are presented in terms of pointing accuracy for a rendezvous mission to Mercury. The dynamical model takes into account the perturbation torque because of an offset between the centre of pressure and the geometrical sail centre, as well as the Sun gravity-gradient effect and a perturbation torque on the roll axis.
Non-linear aeroelastic investigations of store(s)-induced limit cycle oscillations
Authors: Abbas L K , Chen Q , Marzocca P , Milanese A
Published: March 2008

In the current work, the study of the aeroelastic behaviour of a wing with external store(s), such as a missile or drop fuel tank, is presented. The aeroelastic governing equations derived for a cantilever wing with coupled bending and torsion modes account for structural and aerodynamic non-linearities. Coupling terms retained in the aeroelastic governing equations are due to: (a) the non-linear beam theory, (b) the aerodynamic non-linearities of a quasi-steady model with stall, and (c) the non-linear kinematics terms of the store(s). As presented in the paper, this aircraft configuration can induce pathologies, such as store(s)-induced limit cycle oscillations (or si-LCOs), very different from the one of a clean wing configuration, and from the one obtained from the linearized form of the aeroelastic governing equations. Time domain simulation, phase portrait, and bifurcation analyses are performed for various velocities, initial conditions, and store(s)-sensitive parameters — such as store mass, number, location along the wing — to examine the dynamic aeroelastic instabilities of the system (e.g. the onset of flutter and LCO). Numerical studies indicate the presence of regions of subcritical Hopf-bifurcation, corresponding to an unstable LCO, for velocities below the linear flutter velocity.
Aerostat for electrical power generation —concept feasibility
Authors: Aglietti G S , Markvart T , Tatnall A R , Walker S J
Published: March 2008

The current paper examines the feasibility of using a high altitude tethered aerostat as a platform for producing a substantial quantity of electric energy and transmitting it to Earth using the mooring cable.

Based on realistic values for the relevant engineering parameters that describe the technical properties of the materials and subsystems, a static analysis of the aerostat in its deployed configuration has been carried out. The results of the computations, although of a preliminary nature, demonstrate that the concept is technically feasible. There are, nevertheless, issues to be addressed to improve the performance. However none of these issues is deemed to negate the technical feasibility of this concept. A test case is investigated in terms of preliminary sizing of the aerostat, including mooring cable and solar cell coverage, and it shows the capability to deliver power to the ground in excess of 95 kW. A brief assessment of the cost has also been carried out to investigate the potential gains offered by this system to produce solar electric energy.
Formation, structure, and development of near-field wing tip vortices
Authors: Karakus C , Akilli H , Sahin B
Published: March 2008

The current experimental study investigates the details of the formation, structure, and development of wing tip vortices that are generated by an aerofoil of NACA0012 profile having a rectangular planform of 151 mm chord using the particle image velocimetry technique. Experiments have been carried out at different angles of attack, which affect the vortex strength, vortex size, tangential velocity, and vorticity distribution along the downstream stations at chord lengths ranging from x/ c = 0.1 to 1.6, at a fixed free-stream velocity of 212 mm/s corresponding to the Reynolds number, Rec = 32 000 based on the chord length. The radius of the vortex core is found to vary approximately between 5 and 7.5 per cent of the chord length of the wing. The results show that the flow around the tip is dominated by the structures of multiple vortices. The maximum normalized tangential velocity increases with increasing angle of attack. The peak magnitude of the tangential velocity is ∼15 per cent of the free-stream velocity for an angle of attack of α = 4°, whereas it is ∼40 per cent of the free-stream velocity for α = 12°.
Development of the model and hierarchy controller of the quad-copter
Authors: Zhang Y , Kondak K , Lu T , Du J , Bernard M , Wang G
Published: March 2008

The work is a contribution to stable attitudes controlling and accurate position tracking of the small scale quad-copter. Based on the rigid body theory, the kinematics and dynamics of the quad-copter are derived. The flying quad-copter has four input control voltages and three attitude angles and three translation movements, which can be treated as an under-actuated system. With some states controlling the other states, the under-actuated system can be fully controlled. The hierarchical synthesis control algorithm is designed to fulfil this function. The compensated proportional derivative (PD) control algorithm and the invert dynamics algorithm are used as the kernel of the controller in this hierarchy control structure. The simulation and experiment show that the control method can control the quad-copter stably. In contrast with hierarchical uncompensated PD controller, the accuracy of the experiment results with the compensated controller has greatly been improved.
Finite element analysis of a subtrochanteric fractured femur with dynamic hip screw, dynamic condylar screw, and proximal femur nail implants — a comparative study
Authors: Sowmianarayanan S , Chandrasekaran A , Kumar R Krishna
Published: March 2008

Selection of the correct type of implant for fracture fixation has become a very interesting problem in the orthopaedic community. The present work studies the biomechanical behaviour of the femur with three different implant configurations for simple transverse subtrochanteric fracture and the intact femur using finite element analysis. The implants considered in this study are as follows: dynamic hip screw (DHS), dynamic condylar screw (DCS), and proximal femur nail (PFN). The modelling software Unigraphics and finite element simulation software ANSYS are used for the present analysis. The three implants are compared for deflection, stress, and strains. The simulation also includes modelling of the cortical defect near the fracture. An estimation of the critical depth of the cortical defect based on the von Mises stress is obtained using this study on the DHS implant. The displacement and principal stress on the proximal femur have been compared for all the implant models. The stresses on the cortical screws for DCS and DHS implants have also been compared. The result shows that the DHS and DCS implants behave in a similar way to the intact femur compared with the PFN implant.
The use of acellular matrices for the tissue engineering of cardiac valves
Authors: Knight R L , Wilcox H E , Korossis S A , Fisher J , Ingham E
Published: March 2008

Tissue-engineering approaches to cardiac valve replacement have made considerable advances over recent years and it is likely that this application will realize clinical success in the near future. Research in this area has been driven by the inadequacy of the currently available cardiac valve prostheses for younger patients who require multiple reoperations as they grow and develop. Tissue engineering has the potential to provide a valve capable of the same growth, repair, and regeneration as a natural valve and could improve outcomes for patients of all ages. Owing to the function and physical environment of the cardiac valve, the development of tissue-engineered replacements is unusual in that the biomechanical properties of the construct must dominate the biological properties in order for the valve to be functional at the time of implantation. As a result of this, conventional tissue-engineering scaffolds based on biodegradable polymers or collagen may not at present be suitable in this situation because of their initial limited strength. Research into the use of acellular xenogeneic and allogeneic matrices for tissue-engineered heart valves has consequently become extremely popular since the biomechanical properties of the valve can potentially be preserved with an optimal decellularization technique that removes the cells without damaging the matrix. A number of acellular scaffolds have already been tested clinically both unseeded and preseeded with cells and these have met with variable results. This article reviews the concepts involved and the advantages and disadvantages of the different approaches to tissue engineering a living cardiac valve.
Can compressive stress be measured experimentally within the annulus fibrosus of degenerated intervertebral discs?
Authors: Chu J Y , Skrzypiec D , Pollintine P , Adams M A
Published: March 2008

The aims were to assess the ability of a pressure transducer to measure compressive stress within the annulus fibrosus of degenerated intervertebral discs. Measurements could help to explain the mechanisms of disc failure and low back pain.

The methods used were as follows. Thirteen full-depth cores of annulus, 7 mm in diameter, were removed from the middle and outer annuli of two severely degenerated human discs and constrained within a metal cylinder. Then static compressive forces were applied by a planeended metal indenter of diameter 6.8 mm, while a strain-gauged pressure transducer, side mounted in a needle of diameter 0.9 mm and calibrated in saline, was pulled through the issue. The transducer output was converted into stress, and the average measured stress was compared with the nominal applied stress. Measurements were repeated at up to 21 load levels, with the transducer oriented vertically and horizontally.

The results showed that the measured and applied stress were linearly related (average r2=0.98) with a mean gradient (calibration factor) of 0.98 (vertical stress) and 0.92 (horizontal stress). Gradients ranged between 1.28 and 0.73. Damaged transducers grossly under-recorded ‘stress’ even though their output remained proportional to applied load.

It was concluded that pressure transducers can measure compressive stress inside a degenerated human annulus. The tissue is sufficiently deformable to allow efficient coupling of stress between the matrix and transducer membrane. Damage to the transducer can give misleading results.
Relationship between disc injury and manual lifting: A poroelastic finite element model study
Authors: Natarajan R N , Williams J R , Lavender S A , An H S , Andersson G B
Published: March 2008

Understanding how failure originates in a lumbar motion segment subjected to loading conditions that are representative of manual lifting is important because it will pave the way for a better formulation of the exposure—injury relationship. The aim of the current investigation was to use a poroelastic finite element model of a human lumbar disc to determine its biomechanical characteristics under loading conditions that corresponded to three different, commonly occurring lifting activities and to identify the most hazardous type of loading with regard to damage to the disc. The current study showed that asymmetric lifting may increase the risk of back injury and pain. Lifting that involved lateral bending (asymmetric lifting) of the trunk was found to produce stresses at a localized area in the annulus, annuluar fibres, end plates, and facet joints that were higher than their respective tissue failure strength. Thus asymmetric lifting, if performed over a large number of cycles, might help to propagate this localized failure of the disc tissue to a larger area, owing to fatigue. The analyses also showed that largest fluid exchange between the nucleus and the end plates occurred during asymmetric lifting. If the fluid exchange is restricted owing to end plate calcification or sclerosis of the subchondral bone, high intradiscal pressure might develop, leading to higher disc bulge causing back pain.
Pore-scale analysis of Newtonian flow in the explicit geometry of vertebral trabecular bones using lattice Boltzmann simulation
Authors: Zeiser T , Bashoor-Zadeh M , Darabi A , Baroud G
Published: March 2008

The geometric and transport properties of trabecular bone are of particular interest for medical engineers active in orthopaedic applications and more specifically in hard tissue implantations. This article resorts to computational methods to provide some understanding of the geometric and transport properties of vertebral trabecular bone. A fuzzy distance transform algorithm was used for geometric analysis on the pore scale, and a lattice Boltzmann method (LBM) for the simulation of flow on the same scale. The transport properties of bone including the pressure drop, elongation, and shear component of dissipated energy, and the tortuosity of the bone geometry were extracted from the results of the LBM flow simulations. Whenever suitable, dimensionless numbers were used for the analysis of the data. The average pore size and distribution of the bone were found to be 746μm and between 75 and 2940μm, respectively. The permeability of the flow in the cavities of the specific bone sample was found to be 5.05×10-8 m2 for the superior—inferior direction which was by a factor of 1.5—1.7 higher than the permeability in the other two anatomical directions (anterior—posterior). These findings are consistent with experimental results found 3 years prior independently. Tortuosity values approached 1.05 for the superior—inferior direction, and 1.13 and 1.11 for the other two perpendicular directions. The low tortuosities result mainly from the large bone porosity of 0.92. The flow on the pore scale seems to be shear dominated but 30 per cent of the energy dissipation was because of elongational effects. The converging and diverging geometry of the bone explains the significant elongation and deformation of the fluid elements. The transition from creeping flow (the Darcy regime), which is of interest to vertebral augmentation and this study, to the laminar region with significant inertia effects took place at a Reynolds number of about 1—10, as usual for porous media. Finally, the authors wish to advise the readers on the significant computational requirements to be allocated to such a virtual test bench.
Effects of electroacupuncture on a degenerated intervertebral disc using an in-vivo rat-tail model
Authors: Lai A , Chow D H K , Siu W-S , Holmes A D , Tang F-H , Leung M C
Published: March 2008

Electroacupuncture (EA) has long been used as conservative treatment for low back pain (LBP). Its effect on relief of back pain has been demonstrated in many clinical studies. However, whether it has any effect on the biological properties of an intervertebral disc, which is one of the major causes of LBP, is still unclear. The aim of this study was, therefore, to investigate the effects of EA with different simulation frequencies on an intervertebral disc with simulated degeneration using an in-vivo rat-tail model. In this study, 33 rats were used. Disc degeneration was simulated in the rat caudal 8—9 disc via continuous static compressive loading of 11 N for 2 weeks. EA with a frequency of 2 or 100 Hz was then applied to the degenerated disc for 3 weeks with 3 sessions/week and 20 min/session. The intervertebral disc height was measured before and after compression as well as after EA intervention for 3 weeks. The static compression was found to result in a reduction in the disc height of about 22 per cent. There was no evidence that this change could be reversed after resting or the EA intervention. However, EA at 100 Hz was found to induce a further decrease in disc height, which was not shown for the rats after resting or EA at 2 Hz. The results of this study showed that effects of EA on disc degeneration are frequency dependent and adverse effects could result if EA at a certain frequency was used.
Can extra-articular strains be used to measure facet contact forces in the lumbar spine? An in-vitro biomechanical study
Authors: Zhu Q A , Park Y B , Sjovold S G , Niosi C A , Wilson D C , Cripton P A , Oxland T R
Published: March 2008

Experimental measurement of the load-bearing patterns of the facet joints in the lumbar spine remains a challenge, thereby limiting the assessment of facet joint function under various surgical conditions and the validation of computational models. The extra-articular strain (EAS) technique, a non-invasive measurement of the contact load, has been used for unilateral facet joints but does not incorporate strain coupling, i.e. ipsilateral EASs due to forces on the contralateral facet joint. The objectives of the present study were to establish a bilateral model for facet contact force measurement using the EAS technique and to determine its effectiveness in measuring these facet joint contact forces during three-dimensional flexibility tests in the lumbar spine. Specific goals were to assess the accuracy and repeatability of the technique and to assess the effect of soft-tissue artefacts.

In the accuracy and repeatability tests, ten uniaxial strain gauges were bonded to the external surface of the inferior facets of L3 of ten fresh lumbar spine specimens. Two pressure-sensitive sensors (Tekscan) were inserted into the joints after the capsules were cut. Facet contact forces were measured with the EAS and Tekscan techniques for each specimen in flexion, extension, axial rotation, and lateral bending under a ±7.5 N m pure moment. Four of the ten specimens were tested five times in axial rotation and extension for repeatability. These same specimens were disarticulated and known forces were applied across the facet joint using a manual probe (direct accuracy) and a materials-testing system (disarticulated accuracy). In soft-tissue artefact tests, a separate set of six lumbar spine specimens was used to document the virtual facet joint contact forces during a flexibility test following removal of the superior facet processes.

Linear strain coupling was observed in all specimens. The average peak facet joint contact forces during flexibility testing was greatest in axial rotation (71±25 N), followed by extension (27±35 N) and lateral bending (25±28 N), and they were most repeatable in axial rotation (coefficient of variation, 5 per cent). The EAS accuracy was about 20 per cent in the direct accuracy assessment and about 30 per cent in the disarticulated accuracy test. The latter was very similar to the Tekscan accuracy in the same test. Virtual facet loads (r.m.s.) were small in axial rotation (12 N) and lateral bending (20 N), but relatively large in flexion (34 N) and extension (35 N).

The results suggested that the bilateral EAS model could be used to determine the facet joint contact forces in axial rotation but may result in considerable error in flexion, extension, and lateral bending.
A novel approach to the prediction of musculotendon paths
Authors: Marsden S P , Swailes D C
Published: March 2008

One of the most important aspects of the modelling of musculoskeletal systems is the determination of muscle moment arms which are dependent upon the paths of the muscles. These paths are often required to wrap around passive structures that can be modelled as simple geometric shapes. A novel technique for the prediction of the paths of muscles modelled as strings when wrapping around smooth analytical surfaces is presented. The theory of geodesics is used to calculate the shortest path of the string on the surface and a smoothness constraint is used to determine the correct solutions for the string path between insertions. The application of the technique to tapered cylinders and ellipsoids is presented as an extension of previous work on right-circular cylinders and spheres. The technique is assessed with reference to a particular biomechanical scenario; string lengths and moment arms are calculated and compared with alternative approximate methods. This illustrates the potential of the technique to provide more accurate muscle moment arm predictions.