bluuebunny/crossref_metadata_2025 huggingface dataset:
Posttraumatic growth, posttraumatic stress disorder and resilience of motor vehicle accident survivors
Authors: Nishi Daisuke , Matsuoka Yutaka , Kim Yoshiharu
Published: June 2010

Background

Although some previous studies have suggested that posttraumatic growth (PTG) is comprised of several factors with different properties, few have examined both the association between PTG and posttraumatic stress disorder (PTSD) and between PTG and resilience, focusing on each of the factors of PTG. This study aimed to examine the hypothesis that some factors of PTG, such as personal strength, relate to resilience, whereas other factors, such as appreciation of life, relate to PTSD symptoms among Japanese motor vehicle accident (MVA) survivors.

Methods

This cross-sectional study was performed with 118 MVA survivors at 18 months post MVA. Data analyzed included self-reporting questionnaire scores on the Posttraumatic Growth Inventory (PTGI), the Impact of Event Scale- Revised (IES-R), and the Sense of Coherence (SOC) scale, which is one of the most widely used scales for measuring resilience. Correlations between scores on the PTGI and IES-R, the PTGI and SOC scale, and the IES-R and SOC scale were established by calculating Spearman's correlation coefficients.

Results

PTGI was positively correlated with both SOC and PTSD symptoms, in spite of an inverse relationship between SOC and PTSD symptoms. Relating to others, new possibilities, and personal strength on the PTGI were correlated positively with SOC, and spiritual change and appreciation of life on the PTGI were positively correlated with PTSD symptoms.

Conclusions

Some factors of PTG were positively correlated with resilience, which can be regarded as an outcome of coping success, whereas other factors of PTG were positively correlated with PTSD symptoms, which can be regarded as signifying coping effort in the face of enduring distress. These findings contribute to our understanding of the psychological change experienced by MVA survivors, and to raising clinicians' awareness of the possibility that PTG represents both coping effort coexisting with distress and outcome of coping success.
Vascular health, diabetes, APOE and dementia: the Aging, Demographics, and Memory Study
Authors: Llewellyn David J , Lang Iain A , Matthews Fiona E , Plassman Brenda L , Rogers Mary AM , Morgenstern Lewis B , Fisher Gwenith G , Kabeto Mohammed U , Langa Kenneth M
Published: June 2010

Introduction

Evidence from clinical samples and geographically limited population studies suggests that vascular health, diabetes and apolipoprotein ε4 (APOE) are associated with dementia.

Methods

A population-based sample of 856 individuals aged 71 years or older from all contiguous regions of the United States received an extensive in-home clinical and neuropsychological assessment in 2001-2003. The relation of hypertension, diabetes, heart disease, stroke, medication usage, and APOE ε4 to dementia was modelled using adjusted multivariable logistic regression.

Results

Treated stroke (odds ratio [OR] 3.8, 95% confidence interval [CI] 2.0, 7.2), untreated stroke (OR 3.5, 95% CI 1.7, 7.3), and APOE ε4 (OR 2.8, 95% CI 1.7, 4.5) all increased the odds of dementia. Treated hypertension was associated with lower odds of dementia (OR 0.5, 95% CI 0.3, 1.0). Diabetes and heart disease were not significantly associated with dementia. A significant interaction was observed between APOE ε4 and stroke (P = 0.001).

Conclusions

Data from the first dementia study that is representative of the United States population suggest that stroke, the APOE ε4 allele and their interaction are strongly associated with dementia.
Histidine-rich glycoprotein functions cooperatively with cell surface heparan sulfate on phagocytes to promote necrotic cell uptake
Authors: Poon Ivan K H , Parish Christopher R , Hulett Mark D
Published: June 2010

HRG enhances the phagocytosis of necrotic cells via a heparan sulfate-dependent pathway that is inhibitable by heparin.

Dying cells, such as apoptotic and necrotic cells, are cleared rapidly from the site of cell death to prevent the exposure of intracellular antigenic and immunostimulatory molecules that may cause tissue injury or facilitate the development of autoimmune diseases. For the immune system to recognize and remove dying cells efficiently, professional phagocytes use a variety of mechanisms that distinguish healthy cells from dying cells. HRG, a relatively abundant heparin/HS-binding protein in human plasma, has been shown recently to tether IgG specifically to necrotic cells and aid the phagocytic uptake of necrotic cells via a FcγRI-dependent pathway. In this study, we provide direct evidence that HRG can function cooperatively with cell surface HS on the monocytic cell line THP-1 to promote necrotic cell removal. In addition, we found that the presence of heparin can markedly inhibit HRG-enhanced necrotic cell clearance by THP-1 cells, possibly by blocking the ability of HRG to interact with necrotic cells as well as THP-1 cells. Thus, these data suggest that HRG can aid the phagocytosis of necrotic cells via a HS-dependent pathway, and this process can be regulated by the presence of certain HRG ligands, such as heparin.
Palmitate Affects Insulin Receptor Phosphorylation and Intracellular Insulin Signal in a Pancreatic α-Cell Line
Authors: Piro Salvatore , Maniscalchi Eugenia T. , Monello Adelina , Pandini Giuseppe , Mascali Loriana G. , Rabuazzo Agata M. , Purrello Francesco
Published: June 2010

This study investigated in a pancreatic α-cell line the effects of chronic exposure to palmitate on the insulin and IGF-I receptor (IGF-IR) and intracellular insulin pathways. α-TC1–6 cells were cultured in the presence or absence of palmitate (0.5 mmol/liter) up to 48 h. Glucagon secretion, insulin and IGF-IR autophosphorylation, and insulin receptor substrate (IRS)-1, IRS-2, phosphatidylinositol kinase (PI3K) (p85 α), and serine-threonine protein kinase (Akt) phosphorylated (active) forms were measured. Erk 44/42 and p38 phosphorylation (P) (MAPK pathway markers) were also measured. Because MAPK can regulate Pax6, a transcription factor that controls glucagon expression, paired box gene 6 (Pax6) and glucagon gene and protein expression were also measured. Basal glucagon secretion was increased and the inhibitory effect of acute insulin exposure reduced in α-TC1 cells cultured with palmitate. Insulin-stimulated insulin receptor phosphorylation was greatly reduced by exposure to palmitate. Similar results were observed with IRS-1-P, PI3K (p85 α), and Akt-P. In contrast, with IGF-IR and IRS-2-P, the basal levels (i.e. in the absence of insulin stimulation) were higher in cells cultured with palmitate. Similar data were obtained with Erk 44/42-P and p-38-P. Pax6 and glucagon gene and protein expression were higher in cells cultured with palmitate. In these cells cultured, specifics MAPKs inhibitors were able to reduce both Pax6 and glucagon gene and protein expression. These results indicate that α-cells exposed to palmitate show insulin resistance of the IRS-1/PI3K/Akt pathway that likely controls glucagon secretion. In contrast, the IRS-2/MAPKs pathway is stimulated, through an activation of the IGF-IR, leading to increased Pax6 and glucagon expression. Our data support the hypothesis that the chronic elevation of fatty acids contribute to α-cell dysregulation frequently observed in type 2 diabetes.
Epigenetic Changes in the Hypothalamic Proopiomelanocortin and Glucocorticoid Receptor Genes in the Ovine Fetus after Periconceptional Undernutrition
Authors: Stevens Adam , Begum Ghazala , Cook Alice , Connor Kristin , Rumball Christopher , Oliver Mark , Challis John , Bloomfield Frank , White Anne
Published: June 2010

Maternal food restriction is associated with the development of obesity in offspring. This study examined how maternal undernutrition in sheep affects the fetal hypothalamic glucocorticoid receptor (GR) and the appetite-regulating neuropeptides, proopiomelanocortin (POMC) and neuropeptide Y, which it regulates. In fetuses from ewes undernourished from −60 to +30 d around conception, there was increased histone H3K9 acetylation (1.63-fold) and marked hypomethylation (62% decrease) of the POMC gene promoter but no change in POMC expression. In the same group, acetylation of histone H3K9 associated with the hypothalamic GR gene was increased 1.60-fold and the GR promoter region was hypomethylated (53% decrease). In addition, there was a 4.7-fold increase in hypothalamic GR expression but no change in methylation of GR gene expression in the anterior pituitary or hippocampus. Interestingly, hypomethylation of both POMC and GR promoter markers in fetal hypothalami was also identified after maternal undernutrition from −60 to 0 d and −2 to +30 d. In comparison, the Oct4 gene, was hypermethylated in both control and underfed groups. Periconceptional undernutrition is therefore associated with marked epigenetic changes in hypothalamic genes. Increase in GR expression in the undernourished group may contribute to fetal programming of a predisposition to obesity, via altered GR regulation of POMC and neuropeptide Y. These epigenetic changes in GR and POMC in the hypothalamus may also predispose the offspring to altered regulation of food intake, energy expenditure, and glucose homeostasis later in life.
Neurokinin B Stimulates GnRH Release in the Male Monkey (Macaca mulatta) and Is Colocalized with Kisspeptin in the Arcuate Nucleus
Authors: Ramaswamy Suresh , Seminara Stephanie B. , Ali Barkat , Ciofi Philippe , Amin Nisar A. , Plant Tony M.
Published: June 2010

Human genetics indicate that kisspeptin and neurokinin B (NKB) signaling are necessary for generating pulsatile LH release and therefore for initiation of puberty and maintaining gonadal function. In the present study, male monkeys were employed to examine 1) whether activation of the NKB receptor (NK3R) is associated with GnRH release, and 2) hypothalamic localization of these peptides using immunofluorescence histochemistry. Agonadal juveniles, in which pituitary responsiveness to GnRH was heightened by GnRH priming, were employed to indirectly examine GnRH-releasing actions of NK3R and kisspeptin receptor agonists by tracking LH after their iv injection. Castrated adults were used for immunohistochemistry. Single iv injections of NKB or senktide (an NK3R agonist) elicited robust LH discharges that were abolished by GnRH receptor antagonism (acyline) confirming the ligands’ hypothalamic action. Intermittent infusion of senktide (1-min pulse every hour for 4 h), in contrast to that of kisspeptin, failed to sustain pulsatile GnRH release. Repetitive senktide injections did not compromise the GnRH-releasing action of kisspeptin. NKB and kisspeptin were colocalized in perikarya of the arcuate nucleus and in axonal projections to the median eminence, confirming earlier findings in sheep. These results are consistent with the human genetics, and indicate that although brief activation of NK3R stimulates GnRH release, repetitive stimulation of this pathway, in contrast to that of kisspeptin receptor, fails to sustain pulsatile GnRH release. In addition, the data provide a platform for future elucidation of the interactions between NKB and kisspeptin that are required for generating pulsatile GnRH release in primates.
Knockdown of GABAA Receptor Signaling in GnRH Neurons Has Minimal Effects upon Fertility
Authors: Lee Kiho , Porteous Robert , Campbell Rebecca E. , Lüscher Bernhard , Herbison Allan E.
Published: June 2010

The amino acid γ-aminobutyric acid (GABA) is thought to play a key role in shaping the activity of the GnRH neurons throughout embryonic and postnatal life. However, the physiological roles of direct GABA inputs to GnRH neurons remain unknown. Using a Cre-LoxP strategy, we generated a targeted mouse line, in which all (98 ± 1%) GnRH neurons had the γ2-subunit of the GABAA receptor deleted. Electrophysiological recordings of GABAA-mediated postsynaptic currents from green fluorescent protein-tagged GnRH neurons with the γ2-subunit knocked out (GnRH γ2 KO) showed that the amplitude and frequency of GABAA postsynaptic currents were reduced by 70% (P < 0.01) and 77% (P < 0.05), respectively, and that the response to exogenous GABA was reduced by 90% (P < 0.01). Evaluation of male and female GnRH γ2 KO mice revealed completely normal fecundity, estrous cycles, and puberty onset. Further investigation with gonadectomy and different steroid replacement regimens showed normal basal levels of LH in both sexes, and a normal estradiol-evoked positive feedback mechanism in females. However, the increment in LH after gonadectomy in GnRH γ2 KO female mice was double that of controls (P < 0.05) and also more potently suppressed by 17-β-estradiol (P < 0.05). A similar but nonsignificant trend was observed in GnRH γ2 KO male mice. Together, these findings show that 70–90% reductions in the normal levels of GABAA receptor activity at the GnRH neuron appear to impact upon the estrogen negative feedback mechanism but are, nevertheless, compatible with normal fertility in mice.
Minireview: Inflammation and Obesity Pathogenesis: The Hypothalamus Heats Up
Authors: Thaler Joshua P. , Schwartz Michael W.
Published: June 2010

Obesity induced by high-fat (HF) feeding is associated with low-grade inflammation in peripheral tissues that predisposes to insulin resistance. Recent evidence suggests the occurrence of a similar process in the hypothalamus, which favors weight gain through impairment of leptin and insulin signaling. In addition to its implications for obesity pathogenesis, this hypothesis suggests that centrally targeted antiinflammatory therapies may prove effective in prevention and treatment of this disorder. This article highlights molecular and cellular mechanisms by which hypothalamic inflammation predisposes to diet-induced obesity.
WNT5A Regulates Chondrocyte Differentiation through Differential Use of the CaN/NFAT and IKK/NF-κB Pathways
Authors: Bradley Elizabeth W. , Drissi M. Hicham
Published: June 2010

Although genetic evidence demonstrated a requirement for Wnt5a during cartilage development, little is known about the mechanisms underlying Wnt5a-regulated chondrocyte growth and differentiation. We therefore investigated the signaling pathways by which Wnt5a influences chondrogenesis and differentiation to hypertrophy. Wnt5a treatment of chondroprogenitor cells increased chondrocyte hypertrophy and was associated with an increase in nuclear factor of activated T cells (NFAT) and a decrease in nuclear factor-κB (NF-κB) activation. In contrast, Wnt5a inhibited chondrocyte hypertrophy. This inhibition of hypertrophy occurred with the reciprocal signaling activation, in that a decrease in NFAT and an increase in NF-κB activation was observed. Furthermore, the increase in chondroprogenitor cell differentiation with Wnt5a treatment was blocked by calmodulin kinase or NFAT loss of function. In addition, the repression of chondrocyte hypertrophy observed was abrogated by NF-κB loss of function. Activation of the NFAT pathway downstream of Wnt5a also negatively regulated NF-κB activity, providing evidence of antagonism between these two pathways. Mechanistically, Wnt5a acts to increase chondrocyte differentiation at an early stage through calmodulin kinase /NFAT-dependent induction of Sox9. Conversely, Wnt5a represses chondrocyte hypertrophy via NF-κB-dependent inhibition of Runx2 expression. These data indicate that Wnt5a regulates chondrogenesis and chondrocyte hypertrophy in a stage-dependent manner through differential utilization of NFAT- and NF-κB-dependent signal transduction.
Neuronal Nogo-A regulates neurite fasciculation, branching and extension in the developing nervous system
Authors: Petrinovic Marija M. , Duncan Carri S. , Bourikas Dimitris , Weinman Oliver , Montani Laura , Schroeter Aileen , Maerki David , Sommer Lukas , Stoeckli Esther T. , Schwab Martin E.
Published: June 2010

Wiring of the nervous system is a multi-step process involving complex interactions of the growing fibre with its tissue environment and with neighbouring fibres. Nogo-A is a membrane protein enriched in the adult central nervous system (CNS) myelin, where it restricts the capacity of axons to grow and regenerate after injury. During development, Nogo-A is also expressed by neurons but its function in this cell type is poorly known. Here, we show that neutralization of neuronal Nogo-A or Nogo-A gene ablation (KO) leads to longer neurites, increased fasciculation, and decreased branching of cultured dorsal root ganglion neurons. The same effects are seen with antibodies against the Nogo receptor complex components NgR and Lingo1, or by blocking the downstream effector Rho kinase (ROCK). In the chicken embryo, in ovo injection of anti-Nogo-A antibodies leads to aberrant innervation of the hindlimb. Genetic ablation of Nogo-A causes increased fasciculation and reduced branching of peripheral nerves in Nogo-A KO mouse embryos. Thus, Nogo-A is a developmental neurite growth regulatory factor with a role as a negative regulator of axon-axon adhesion and growth, and as a facilitator of neurite branching.
Opposite roles ofDMRT1and its W-linked paralogue,DM-W, in sexual dimorphism ofXenopus laevis: implications of a ZZ/ZW-type sex-determining system
Authors: Yoshimoto Shin , Ikeda Nozomi , Izutsu Yumi , Shiba Tadayoshi , Takamatsu Nobuhiko , Ito Michihiko
Published: June 2010

A Y-linked gene, DMY/dmrt1bY, in teleost fish medka and a Z-linked gene, DMRT1, in chicken are both required for male sex determination. We recently isolated a W-linked gene, DM-W, as a paralogue of DMRT1 in Xenopus laevis, which has a ZZ/ZW-type sex-determining system. The DNA-binding domain of DM-W shows high sequence identity with that of DMRT1, but DM-W has no significant sequence similarity with the transactivation domain of DMRT1. Here, we first show colocalization of DM-W and DMRT1 in the somatic cells surrounding primordial germ cells in ZW gonad during sex determination. We next examined characteristics of DM-W and DMRT1 as a transcription factor in vitro. DM-W and DMRT1 shared a DNA-binding sequence. Importantly, DM-W dose-dependently antagonized the transcriptional activity of DMRT1 on a DMRT1-driven luciferase reporter system in 293 cells. We also examined roles of DM-W or DMRT1 in gonadal formation. Some transgenic ZW tadpoles bearing a DM-W knockdown vector had gonads with a testicular structure, and two developed into frogs with testicular gonads. Ectopic DMRT1 induced primary testicular development in some ZW individuals. These observations indicated that DM-W and DMRT1 could have opposite functions in the sex determination. Our findings support a novel model for a ZZ/ZW-type system in which DM-W directs female sex as a sex-determining gene, by antagonizing DMRT1. Additionally, they suggest that DM-W diverged from DMRT1 as a dominant-negative type gene, i.e. as a `neofunctionalization' gene for the ZZ/ZW-type system. Finally, we discuss a conserved role of DMRT1 in testis formation during vertebrate evolution.
hand2and Dlx genes specify dorsal, intermediate and ventral domains within zebrafish pharyngeal arches
Authors: Talbot Jared Coffin , Johnson Stephen L. , Kimmel Charles B.
Published: June 2010

The ventrally expressed secreted polypeptide endothelin1 (Edn1) patterns the skeleton derived from the first two pharyngeal arches into dorsal, intermediate and ventral domains. Edn1 activates expression of many genes, including hand2 and Dlx genes. We wanted to know how hand2/Dlx genes might generate distinct domain identities. Here, we show that differential expression of hand2 and Dlx genes delineates domain boundaries before and during cartilage morphogenesis. Knockdown of the broadly expressed genes dlx1a and dlx2a results in both dorsal and intermediate defects, whereas knockdown of three intermediate-domain restricted genes dlx3b, dlx4b and dlx5a results in intermediate-domain-specific defects. The ventrally expressed gene hand2 patterns ventral identity, in part by repressing dlx3b/4b/5a. The jaw joint is an intermediate-domain structure that expresses nkx3.2 and a more general joint marker, trps1. The jaw joint expression of trps1 and nkx3.2 requires dlx3b/4b/5a function, and expands in hand2 mutants. Both hand2 and dlx3b/4b/5a repress dorsal patterning markers. Collectively, our work indicates that the expression and function of hand2 and Dlx genes specify major patterning domains along the dorsoventral axis of zebrafish pharyngeal arches.
TSC1/2 tumour suppressor complex maintainsDrosophilagermline stem cells by preventing differentiation
Authors: Sun Pei , Quan Zhenghui , Zhang Bodi , Wu Tuoqi , Xi Rongwen
Published: June 2010

Tuberous sclerosis complex human disease gene products TSC1 and TSC2 form a functional complex that negatively regulates target of rapamycin (TOR), an evolutionarily conserved kinase that plays a central role in cell growth and metabolism. Here, we describe a novel role of TSC1/2 in controlling stem cell maintenance. We show that in the Drosophila ovary, disruption of either the Tsc1 or Tsc2 gene in germline stem cells (GSCs) leads to precocious GSC differentiation and loss. The GSC loss can be rescued by treatment with TORC1 inhibitor rapamycin, or by eliminating S6K, a TORC1 downstream effecter, suggesting that precocious differentiation of Tsc1/2 mutant GSC is due to hyperactivation of TORC1. One well-studied mechanism for GSC maintenance is that BMP signals from the niche directly repress the expression of a differentiation-promoting gene bag of marbles (bam) in GSCs. In Tsc1/2 mutant GSCs, BMP signalling activity is downregulated, but bam expression is still repressed. Moreover, Tsc1 bam double mutant GSCs could differentiate into early cystocytes, suggesting that TSC1/2 controls GSC differentiation via both BMP-Bam-dependent and -independent pathways. Taken together, these results suggest that TSC prevents precocious GSC differentiation by inhibiting TORC1 activity and subsequently differentiation-promoting programs. As TSC1/2-TORC1 signalling is highly conserved from Drosophila to mammals, it could have a similar role in controlling stem cell behaviour in mammals, including humans.
Development of robust fixture locating layout for machining workpieces
Authors: Fan L , Senthil Kumar A
Published: June 2010

A fixture is a device that secures and holds a workpiece to maintain its orientation and position during a manufacturing process, so that the desired workpiece quality can be achieved. Although many researchers have worked on locating accuracy analysis and tolerance analysis towards the automated generation of locating schemes for fixtures, most of them have focused on part localization, while feature errors due to geometrical inaccuracies and dimensional deviations during the mass production are usually neglected. In the current paper, a study on fixture locating layout is carried out with the robust design approach by combining the Taguchi method and the Monte-Carlo statistical method in order to increase the quality of final machining workpieces, so that the layout can be robust and insensitive to the errors. The Taguchi method is employed to study the locating effect of the locator's position at different levels and the Monte-Carlo method is applied to simulate the variation of coordinates of the locating contact points. A case study comprising drilling a hole on a prismatic workpiece is also carried out. The paper shows that the errors on the locators and workpiece have significant effects on the features to be machined and thus these variations should not be ignored.
Combining business process and failure modelling to increase yield in electronics manufacturing
Authors: Velandia D M Segura , Conway P P , Monfared R P , West A A
Published: June 2010

The prediction and capturing of defects in low-volume assembly of electronics is a technical challenge that is a prerequisite for design for manufacturing (DfM) and business process improvement (BPI) to increase first-time yields and reduce production costs. Failures at the component-level (component defects) and system-level (such as defects in design and manufacturing) have not been incorporated in combined prediction models. BPI efforts should have predictive capability while supporting flexible production and changes in business models. This research was aimed at the integration of enterprise modelling (EM) and failure models (FM) to support business decision making by predicting system-level defects. An enhanced business modelling approach which provides a set of accessible failure models at a given business process level is presented in this article. This model-driven approach allows the evaluation of product and process performance and hence feedback to design and manufacturing activities hence improving first-time yield and product quality. A case in low-volume, high-complexity electronics assembly industry shows how the approach leverages standard modelling techniques and facilitates the understanding of the causes of poor manufacturing performance using a set of surface mount technology (SMT) process failure models. A prototype application tool was developed and tested in a collaborator site to evaluate the integration of business process models with the execution entities, such as software tools, business database, and simulation engines. The proposed concept was tested for the defect data collection and prediction in the described case study.
Investigations on precision finishing of helical gears by electrochemical honing process
Authors: Misra J P , Jain N K , Jain P K
Published: June 2010

This paper presents the findings of an investigation into the effects of finishing time, electrolyte-related parameters (i.e. electrolyte temperature, composition, and concentration), voltage, and rotating speed of the workpiece on the improvement of surface quality of helical gear teeth finished by the electrochemical honing (ECH) process. Percentage improvement in average surface roughness PIRa and maximum surface roughness PIRtm, three-dimensional plots of the finished surface texture, and microhardness have been used as the measures of ECH process performance. The effects of finishing time, electrolyte temperature, and electrolyte composition have been studied through pilot experiments by varying one variable at a time, while the effects of voltage, rotating speed of the workpiece gear, and electrolyte concentration have been studied during the main experiments designed using the Box–Behnken response surface methodology approach. Scanning electron microscopy and optical profilometry before and after ECH have been used to highlight the improvement in surface quality of helical gears. A special type of cathode gear has been developed by sandwiching a conducting copper gear between two insulating gears of Bakelite, having the capability of varying the rate of electrolytic dissolution steplessly along the full profile of the workpiece gear made of EN8. Based on the results of pilot experiments, 7.5 min as finishing time, a mixture of NaCl and NaNO3 in a ratio of 3:1, and 32 °C as electrolyte temperature were found to be optimum for precision finishing of helical gears. Using the results of main experiments, regression models have been developed for the measures of process performance (i.e. PIRa and PIRtm). Analysis of variance done at the 95 per cent confidence level, to test the significance of the developed models and process variables, found that the developed models are highly significant and that voltage and electrolyte concentration have significant effects on the responses. However, no significant interaction effect has been observed. Predictions from the regression models have been validated by comparing them with the results of the confirmation experiments, which proved that the developed models are correct and acceptable.
Build time estimator for determining optimal part orientation
Authors: Nezhad A Sanati , Vatani M , Barazandeh F , Rahimi A
Published: June 2010

The build time of a part is one of the most important objective functions used for optimization problems such as determining the optimum part orientation of the part in rapid prototyping (RP) systems. The accurate build time calculation algorithms are used generally for job scheduling and pricing; however, applying the precise algorithms is usually time-consuming and much solution time is taken to compute the build time, so this is not an effective method for optimization problems. Conventional estimating methods are also applicable for constant layer slicing and do not have sufficient accuracy to be used in optimization problems. This paper presents a new build time estimator algorithm to estimate the build time of the part for use in optimization problems. The main feature of this estimating method is that it can be used for problems in which the adaptive slicing method is required. This algorithm effectively reduces the solution time to calculate the build time and so is an effective tool for solving part orientation optimization problems. The accuracy and the solution time of the proposed method are compared with the results of VISCAM RP software in several directions for a case study.
Cutter tool fault detection using a new spectral analysis method
Authors: Kalvoda T , Hwang Y-R , Vrabec M
Published: June 2010

An investigation of milling end cutter tool fault monitoring based on dynamic force in the frequency domain and time-frequency domain is presented in this paper. A new data analysis technique, the Hilbert–Huang transform (HHT), is used to analyse this process in the frequency domain and time-frequency domain. This technique is also compared with the traditional Welch's method power spectra based on the Fourier transform (FT) in the frequency domain approach. The non-linearity and non-stationarity of the cutting process are taken into account. This method is designed to track the main peak in the frequency domain and time-frequency domain (HHT). The main tool break indicator is the appearance of new frequency as a result of the cutter tool fault. The HHT analysis technique covers the physical nature of the cutting process. The cutting process is not treated like a theoretical process, which is obvious by the oscillation of the frequency around the fundamental frequency of the cutter tool. The break of the cutter tool is obvious in the presented results.
Influences of inner pressure and tube thickness on process responses of hydroforming copper tubes without axial force
Authors: Fatemi A , Biglari F , Morovvati M R
Published: June 2010

Tube hydroforming is a metal forming technique which has attracted the attention of several industries because of its ability to produce complex parts with high strength and low weight in low expense and time. In this process, a piece of tube attains the shape of the die under the pressure of inner fluid and exerted axial force. This process is able to produce a unified part in a single-step process. In order to achieve these advantages and an appropriate process, it is necessary to select convenient process and part parameters. Therefore, the present research focused on the effects of two important tube hydroforming process parameters, inner pressure and tube thickness, on process responses during the hydroforming of copper tubes without axial force. In the analytical investigation, the relationships for calculating pressures in three steps of tube hydroforming, i.e. yield pressure, ultimate plastic pressure, and calibration pressure, were developed. By using the derived pressures from these relationships, finite element investigations using a dynamic explicit code and experimental tests using tube hydroforming experimental facilities were performed. These investigations were accomplished on seamless copper tubes of four different thicknesses (0.5, 0.63, 0.9, and 1,mm) under different pressures. The results of these investigations showed that by increasing inner pressure, the thickness strain, bulging height, and von Mises equivalent plastic stress increase along with the length of the part. Also, higher tube thickness results in both higher required forming pressures in all forming steps and more capacity of enduring thickness strain and equivalent plastic stress. The results of these three different investigations showed good agreement with each other.
Large eddy simulation of natural cavitating flows in Venturi-type sections
Authors: Nouri N M , Mirsaeedi S M H , Moghimi M
Published: June 2010

Large eddy simulation (LES) is used here to model the cavitating flow at a Venturi-type section. Cavitating flows can occur in a wide range of applications. The flow is represented here by means of LES, which compared to Reynolds-averaged Navier—Stokes (RANS) has the advantage that in it the large, energy-containing structures are resolved directly, whereas most of these structures are modelled in RANS. This gives LES an improved fidelity over RANS, although, due to the time averaging, the required computational time is considerably lower for RANS than for LES. The conclusion of this work shows that the qualitative comparisons with earlier preliminary data and the simulated general cavitation behaviour correlate reasonably well with experimental observations and that the simulations have the ability to predict cavitation cycle in more detail.
Introducing the supplementary Bennett loop
Authors: Baker J E
Published: June 2010

The article sets out to correct a fallacy of 30 years ago in the depiction of the Bennett linkage by joint axes on its affiliated hyperboloid of one sheet. The procedure adopted gives rise to fresh perusals of various matters, whose outcome allows them to be of renewed purport. Of particular interest is the direct application of two of Ball's findings to the issue under scrutiny.
Mechanical Analysis of Devices in the Control Cabin of Oil and Gas Drilling Unit
Authors: Almasi A
Published: June 2010

The dynamic behaviour of electronic circuit boards and electronic devices of the console of oil and gas drilling units is investigated using an analytical model. This new analytical method confirms the modification of electronic device dynamic behaviour in the console of the drilling unit due, to dynamic interaction. It is in agreement with experimental results that show electronic circuit board failure in the oil driller console when dynamic loading is considerably less than dynamic loading values during the board vibration test.
Acoustic Emission and Gas-Phase Measurements in Two-Phase Flow
Authors: Addali A , Al-lababidi S , Yeung H , Mba D , Khan F
Published: June 2010

The two-phase liquid/gas slug flow regime phenomenon can be encountered over a range of gas and liquid flowrates. Monitoring of slugs and measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. This article presents experimental results correlating acoustic emission measurements with gas void fraction in a two-phase water/air flow regime. It is concluded that the gas void fraction can be determined by the measurement of acoustic emission, which hitherto has not been investigated.
Efficient Track Maintenance: Methodology for Combined Analysis of Condition Data
Authors: Berggren E G
Published: June 2010

Measured condition data may contain lots of information that is not efficiently used. By using techniques from the field of pattern recognition, this article outlines a methodology for eliciting new information. The methodology is demonstrated on a large set of condition data originating from track geometry quality, dynamic stiffness, and ground penetrating radar. The case study gives evidence for the importance of dynamic stiffness measurements as to determine soil- and embankment-related track problems, whereas problems originating from the upper part or the track structure do not benefit significantly.
Simulation of a dual-axis solar tracker for improving the performance of a photovoltaic panel
Authors: Alexandru C , Pozna C
Published: June 2010

This article presents the virtual prototype of the tracking system used for improving the energetic efficiency of a photovoltaic panel. From the point of view of the efficiency and safety, a polar dual-axis system has been designed. Both motions (daily and seasonal) are driven by rotary actuators, which are coupled with worm gears for blocking the system in the stationary positions. The tracking system is approached in mechatronic concept, by integrating the mechanical structure of the solar tracker and the electronic control system at the virtual prototype level. The tracking strategy aims at reducing the angular field of the daily motion and the number of actuating operations, without significantly affecting the incoming solar energy. At the same time, an algorithm for determining the optimal actuating time for the step-by-step tracking is developed. For performing the energy balance, the incident solar radiation is obtained using a method based on the direct radiation and the angle of incidence, while the energy consumption for accomplishing the tracking is determined by simulating the dynamic behaviour of the solar tracker. Finally, the validation of the simulation results is performed by comparing the virtual prototype analysis with the data achieved by experimental measurements.
Analyses of impeller—vaneless-diffuser—scroll interactions in a radial compressor
Authors: Khalfallah S , Ghenaiet A
Published: June 2010

Centrifugal compressors have reached advanced stages of their development, and it is only through a detailed understanding of their complex airflows that improvements in the overall performance will be achieved. This article presents a numerical investigation of unsteady flows through the different components of a radial compressor, emphasizing on the impeller—vaneless-diffuser—scroll interactions. A transient rotor—stator simulation model was used for the calculations carried out by means of the code CFX-TASCflow, at design point and near stall and choke operating conditions. Spectral analyses of the pressure fluctuation-related different component interactions have resulted in the amplitudes and speeds of rotation of the main energetic modes and have revealed that the flow presents a space—time periodic behaviour that may be described by the double Fourier decomposition. The spatial mode analysis was therefore introduced to describe the interaction mechanisms, whereas the time mode analysis during the working time of the machine has permitted to determine different frequencies, and hence the most prevailing modes and their originating sources. These spectral analyses have permitted a good understanding of the flow interaction mechanisms and revealed the computations limits, depending on whether one-passage or a full-rotor simulation is considered. Principally, these limitations are related to an underestimation of pressure fluctuation amplitudes and a failure in detecting all harmonics lower than the number of passages per component. Finally, this study may help in envisaging the local treatments to reduce noise levels and increase the compressor stability.
Thermoeconomic optimization of the pinch point and gas-side velocity in heat recovery steam generators
Authors: Behbahani-nia A , Sayadi S , Soleymani M
Published: June 2010

In the present article, thermodynamic and thermoeconomic analysis are applied to find the optimum values of design parameters for water-tube heat recovery steam generators (HRSGs) in combined cycle power plants. Design variables optimized in this article are pinch point and gas-side velocity. Optimization is carried out based on two different objective functions. The first one is thermodynamic, which is the summation of exergy loss due to an outflow of hot gas escaping from the HRSG through stack, and exergy destruction due to internal irreversibility inside the HRSG. The second one is a thermoeconomic objective function, which is the summation of exergy loss and destruction in terms of expenses including the cost of fuel and electricity, and the capital cost of HRSG in terms of the future value of money according to the interest rate. The capital cost of HRSG includes procurement and erection of piping and insulation, electrical panels and wiring, control and instrumentation equipment, insurance, tax, engineering, and supervision. The effects of pinch point and gas-side velocity on the components of objective functions are investigated in details. The pinch point and gas-side velocity that make these objective functions minimum are called optimum values.
Performance characteristics of multi-evaporator transcritical CO2 refrigeration cycles with hybrid compression/ejection
Authors: Sarkar J
Published: June 2010

The theoretical analyses and optimization studies of two novel multi-evaporator transcritical CO2 refrigeration systems using constant pressure mixing ejector are presented in this article. Comparisons of novel hybrid compression—ejection CO2 cycles, based on coefficient of performance (COP) improvement over conventional cycle and other optimum parameters, are also done for various operating conditions. Study shows that the cycle performance is dependent on allocation of evaporator cooling capacities for both cycles. The optimum discharge pressure for both cycle layouts compared to corresponding basic cycle reduces by the use of ejection—compression. For both cycle layouts, the effect of gas cooler exit temperature on COP improvement is negligible, whereas the COP improvement at optimum condition increases with the increase in temperature difference between evaporators. Results reveal that the CYC1 is superior due to lower discharge pressure and significantly higher COP improvement (maximum of 38.1 per cent for CYC1 whereas 21.4 per cent for CYC2 at optimum condition for the studied ranges).
Approach to assess the occurrence probability of a long-term evolution scenario of a long-lived nuclear waste repository
Authors: Chraibi H , Pierlot S
Published: June 2010

The building of a deep geological repository for the management of long-lived radioactive waste requires the implementation of a structure that allows the storage cells and the galleries to be closed after the waste packages have been put into place. These structures are known as ‘seals’ and they play an important role in demonstrating that the repository will not have any effect on people or the environment over the long term. Therefore, assessing how these seals can fail is needed to determine the feasibility of a long-lived, highly radioactive waste repository. Traditionally, safety assessments in the area of nuclear waste are deterministic and therefore overestimate the consequences of failure as they are based on the least favourable hypotheses. The current paper puts forward a complementary approach to determine the probability of occurrence of a ‘sealing fault’ scenario and shows how it has been applied on the basis of expert opinion and Bayesian networks. This work is based on research carried out by ANDRA (the French National Radioactive Waste Management Agency), which is presented in its report Dossier 2005. This report uses a conservative deterministic approach and demonstrates that the sealing fault scenario would not lead to harmful consequences. The present paper adds to the findings of this report by evaluating the probability of occurrence of this scenario based on an expert assessment. Due to the time scales and the related uncertainties, the evaluation of the probability of occurrence of the sealing fault is delicate. Thus, the limits to this exercise and possible improvements are also presented herein.
New decision support system based on operational risk assessment to improve aircraft operability
Authors: Arnaiz A , Ferreiro S , Buderath M
Published: June 2010

This paper details a new decision support that adds a proactive function to the actual line aircraft maintenance turn-around-time (TAT) process, where next-flight decisions are assisted by the health assessment function of the integrated vehicle health management (IVHM) of an aircraft. The ‘operational risk assessment’ concept appears an extended function supported on the IVHM information for calculating and evaluating the operational risk for aircraft and fleet operations. It creates or reshapes maintenance plans based on predictions of the future maintenance relevant events (e.g. component-degradation-driven repair or replacement events) and its impact on the operational planning of the aircraft/fleet. ‘Operational risk assessment’ makes it possible to turn the scheduled line maintenance into a proactively defined maintenance. The paper also illustrates the first step involved in this approach: ‘condition view’ function, which is responsible for the provision of the remaining useful life (RUL) prediction of a health managed component. This function provides the basis for the operational risk estimation on the aircraft in order to identify maintenance actions that can be deferred.
Light-Controlled Selective Metal Deposition on a Photochromic Diarylethene Film—Toward New Applications in Electronics and Photonics—
Authors: Sesumi Yusuke , Yokojima Satoshi , Nakamura Shinichiro , Uchida Kingo , Tsujioka Tsuyoshi
Published: June 2010

Selective metal deposition controlled by light irradiation was achieved for Zn, Mg, and Mn on a photochromic diarylethene (DAE) film; metal vapor atoms were deposited only on the colored film but not on the uncolored film. The deposition properties of the metals were strongly dependent on the deposition rates. Fine metal patterns were produced by laser scanning and a conventional vacuum-evaporation method without a shadow mask. Multiple-metal pattern preparation of Zn, Mg, and Mn via a maskless evaporation in a single vacuum process was also demonstrated.
Evaluation of temperature rise and bonding strength in cements used for permanent head attachments in rats and mice
Authors: Agterberg Martijn J H , Spoelstra Edwin N , Van Der Wijst Suzanne , Brakkee Jan H , Wiegant Victor M , Hamelink Ralph , Brouns Kim , Westerink Ben H , Remie René
Published: June 2010

In animal models, devices such as indwelling catheters and intracranial cannulae are often fixed on the skull to allow sampling or injection in the freely moving animal. The most commonly used method to fixate these devices is by embedding them in a ‘helmet’ of cement which is fixed to the skull with screws. Methylmethacrylate cement is commonly used for this purpose. The disadvantages of this cement are the high polymerization temperature, poor bonding to the bone and long hardening time. We have evaluated the use of glass ionomer cement, carboxylat cement and cyanoacrylic glue as alternative for methylmethacrylate cement. Temperature increase during polymerization of methylmethacrylate cement and glass ionomer cement was measured in the cement on the skull and in the brain of 14 rats in an acute model. In a chronic model, 52 rats and 91 mice were equipped with a ‘helmet’ of one of the cements. The glass ionomer ‘helmets’ were applied without or with pretreatment of the skull. The attachment of the cement to the skull was checked every day. After four weeks the bonding strengths of the cements were measured. The glass ionomer cement had less temperature increase during polymerization and good bonding capabilities when compared with methylmethacrylate cement. Mechanical pretreatment of the skull resulted in a significant increase in bonding strength of glass ionomer cement in mice and rats as compared with chemical pretreatment. Furthermore, glass ionomer cement had a shorter hardening time than methylmethacrylate cement, and when the glass ionomer cement was used in prepacked capsules, it was possible to apply the cement sterilely and easily. Cyanoacrylic glue had good bonding capabilities to the skull of mice and is also a good substitute for methylmethacrylate cement.