Stress analysis of overlapped crankshafts

The crankshaft is a complex component, and as such, the influence of its geometric parameters on stresses seen under service loads is not well understood. The objectives of this work are to investigate the effects of a wide range of geometric parameters on stresses in overlapped crankshafts, to find correlation between results and to formulate simple methods of predicting peak stress levels: It is intended to achieve this by use of the Finite Element (FE) and Boundary Element (BE) methods. Individual crankthrows are loaded under the important load cases of bending and torsion. Stress concentration factors are determined by normalising peak stresses with respect to the nominal stress occurring in the most appropriate section in the neck between the fillets. Analyses are carried out in 2D and 3D, making use of symmetry as far as possible. Many of the governing dimensions of the crankthrow are included in the analyses; crankpin and journal diameters, crankpin and journal overlap, and web thickness. Variations in SCF are plotted over a wide range for each of these parameters. Additionally, features such as fillet size and shape, bore-holes, dimples, cut-back webs and oil holes are investigated. It is found that the effects on stress of individual parameter changes can be superimposed to accurately predict the effect of combining various parameter changes in one model. The crankpin and journal fillet radii and the length of the minimum section between the fillets are shown to be the critical parameters in determining the peak stress levels in the crankshaft. SCFs obtained from the range of analyses performed show good agreement with the classical theory of SCFs in notched bars. Bore-holes and dimples are found to offer significant benefits in terms of peak stress reduction, in addition to their common usage of reducing the out of balance crankpin mass. The FE and BE methods give accurate results for stress analysis of crankshafts and offer several advantages over traditional experimental techniques; they are ideally suited to parametric analyses, can be carried out relatively quickly, results are repeatable because boundary conditions can be exactly defined, and the cost of analysis is significantly reduced

Dysbiosis in inflammatory bowel disease: a role for bacteriophages?

International audienceIntestinal bacteria have been implicated in theinitiation and amplification of inflammatory bowel disease (IBD). The dysbiosis theory, reviewed by Tamboli et al (Gut 2004;53:1), is that an imbalance between putative ‘‘harmful'' versus ‘‘protective'' bacterial species may promote chronic intestinal inflammation

Topical rosiglitazone is an effective anti-scarring agent in the cornea

Corneal scarring remains a major cause of blindness world-wide, with limited treatment options, all of which have side-effects. Here, we tested the hypothesis that topical application of Rosiglitazone, a Thiazolidinedione and ligand of peroxisome proliferator activated receptor gamma (PPARγ), can effectively block scar formation in a cat model of corneal damage. Adult cats underwent bilateral epithelial debridement followed by excimer laser ablation of the central corneal stroma to a depth of ~160 µm as a means of experimentally inducing a reproducible wound. Eyes were then left untreated, or received 50 µl of either 10 µM Rosiglitazone in DMSO/Celluvisc, DMSO/Celluvisc vehicle or Celluvisc vehicle twice daily for 2 weeks. Cellular aspects of corneal wound healing were evaluated with in vivo confocal imaging and post-mortem immunohistochemistry for alpha smooth muscle actin (αSMA). Impacts of the wound and treatments on optical quality were assessed using wavefront sensing and optical coherence tomography at 2, 4, 8 and 12 weeks post-operatively. In parallel, cat corneal fibroblasts were cultured to assess the effects of Rosiglitazone on TGFβ-induced αSMA expression. Topical application of Rosiglitazone to cat eyes after injury decreased αSMA expression and haze, as well as the induction of lower-order and residual, higher-order wavefront aberrations compared to vehicle-treated eyes. Rosiglitazone also inhibited TGFβ-induced αSMA expression in cultured corneal fibroblasts. In conclusion, Rosiglitazone effectively controlled corneal fibrosis in vivo and in vitro, while restoring corneal thickness and optics. Its topical application may represent an effective, new avenue for the prevention of corneal scarring with distinct advantages for pathologically thin corneas

Stress analysis of overlapped crankshafts

The crankshaft is a complex component, and as such, the influence of its geometric parameters on stresses seen under service loads is not well understood. The objectives of this work are to investigate the effects of a wide range of geometric parameters on stresses in overlapped crankshafts, to find correlation between results and to formulate simple methods of predicting peak stress levels: It is intended to achieve this by use of the Finite Element (FE) and Boundary Element (BE) methods. Individual crankthrows are loaded under the important load cases of bending and torsion. Stress concentration factors are determined by normalising peak stresses with respect to the nominal stress occurring in the most appropriate section in the neck between the fillets. Analyses are carried out in 2D and 3D, making use of symmetry as far as possible. Many of the governing dimensions of the crankthrow are included in the analyses; crankpin and journal diameters, crankpin and journal overlap, and web thickness. Variations in SCF are plotted over a wide range for each of these parameters. Additionally, features such as fillet size and shape, bore-holes, dimples, cut-back webs and oil holes are investigated. It is found that the effects on stress of individual parameter changes can be superimposed to accurately predict the effect of combining various parameter changes in one model. The crankpin and journal fillet radii and the length of the minimum section between the fillets are shown to be the critical parameters in determining the peak stress levels in the crankshaft. SCFs obtained from the range of analyses performed show good agreement with the classical theory of SCFs in notched bars. Bore-holes and dimples are found to offer significant benefits in terms of peak stress reduction, in addition to their common usage of reducing the out of balance crankpin mass. The FE and BE methods give accurate results for stress analysis of crankshafts and offer several advantages over traditional experimental techniques; they are ideally suited to parametric analyses, can be carried out relatively quickly, results are repeatable because boundary conditions can be exactly defined, and the cost of analysis is significantly reduced

Numerical modelling of MPA-CVD reactors with the discontinuous Galerkin finite element method

In this article we develop a fully self consistent mathematical model describing the formation of a hydrogen plasma in a microwave power assisted chemical vapour deposition (MPA-CVD) reactor employed for the manufacture of synthetic diamond. The underlying multi-physics model includes constituent equations for the background gas mass average velocity, gas temperature, electromagnetic field energy and plasma density. The proposed mathematical model is numerically approximated based on exploiting the discontinuous Galerkin finite element method. We demonstrate the practical performance of this computational approach on a variety of CVD reactor geometries for a range of operating conditions

Shrinking the lymphatic filariasis map of Ethiopia: reassessing the population at risk through nationwide mapping

BACKGROUND Mapping of lymphatic filariasis (LF) is essential for the delineation of endemic implementation units and determining the population at risk that will be targeted for mass drug administration (MDA). Prior to the current study, only 116 of the 832 woredas (districts) in Ethiopia had been mapped for LF. The aim of this study was to perform a nationwide mapping exercise to determine the number of people that should be targeted for MDA in 2016 when national coverage was anticipated. METHODOLOGY/PRINCIPAL FINDING A two-stage cluster purposive sampling was used to conduct a community-based cross-sectional survey for an integrated mapping of LF and podoconiosis, in seven regional states and two city administrations. Two communities in each woreda were purposely selected using the World Health Organization (WHO) mapping strategy for LF based on sampling 100 individuals per community and two purposely selected communities per woreda. Overall, 130 166 people were examined in 1315 communities in 658 woredas. In total, 140 people were found to be positive for circulating LF antigen by immunochromatographic card test (ICT) in 89 communities. Based on WHO guidelines, 75 of the 658 woredas surveyed in the nine regions were found to be endemic for LF with a 2016 projected population of 9 267 410 residing in areas of active disease transmission. Combining these results with other data it is estimated that 11 580 010 people in 112 woredas will be exposed to infection in 2016. CONCLUSIONS We have conducted nationwide mapping of LF in Ethiopia and demonstrated that the number of people living in LF endemic areas is 60% lower than current estimates. We also showed that integrated mapping of multiple NTDs is feasible and cost effective and if properly planned, can be quickly achieved at national scale

Correlation between some environmental variables and abundance of Almophrya mediovacuolata (Ciliophora: Anoplophryidae) endocommensal ciliate of an anecic earthworms (Oligochaeta: Annelida) in Bambui (North-West Cameroon)

This study was devoted to accessing the influence of some soil physico-chemical parameters on the abundance of Almophrya mediovacuolata Ngassam, 1983, astome ciliate of the digestive tract of earthworms (EW) of the species Alma nilotica collected along “Fa’a ntsa” stream in Bambui. The survey primarily involved soil samples collection from the same spots of EW collection and preparation for physico-chemical analysis; evaluation in situ of the volumic density (VD) of worms (number /dm3 soil), their dissection, isolation and counting of ciliates with respect to different portion of EW’s gut (fore, mid and hindgut). Furthermore, correlation analysis between soil physico-chemical parameters and biological responses (EW volumic density and ciliate abundance) were performed. The results reveal that EW abundance was positively and significantly correlated with the following physico-chemical parameters: Cation Exchange Capacity CEC (p <0.01) and Mg2+ (p <0.05). A positive and significant correlation was found between Almophrya mediovacuolata and the pH of KCl in the foregut and midgut (p <0.01) while a negative and significant correlation was found between the abundance of Almophrya mediovacuolata and Ca2+ in the foregut (p <0.05). Almophrya mediovacuolata were found mostly in the foregut. This result shows that each portion of the digestive tract of Alma nilotica can be considered as a set of natural microhabitat in which a number of physico-chemical factors generate ecological niches suitable for the survival of different species of microorganisms among which ciliated protozoa. The fore and midgut was noticed to be the preferential zones of Almophrya mediovacuolata.Keywords: Biotic parameters, ciliated protozoa, microhabitat, soil physico-chemical parameters

Antarctic Ice Sheet Elevation Impacts on Water Isotope Records During the Last Interglacial

Changes of the topography of the Antarctic ice sheet (AIS) can complicate the interpretation of ice core water stable isotope measurements in terms of temperature. Here, we use a set of idealised AIS elevation change scenarios to investigate this for the warm Last Interglacial (LIG). We show that LIG δ 18 O against elevation relationships are not uniform across Antarctica, and that the LIG response to elevation is lower than the preindustrial response. The effect of LIG elevation‐induced sea ice changes on δ 18 O is small, allowing us to isolate the effect of elevation change alone. Our results help to define the effect of AIS changes on the LIG δ 18 O signals, and should be invaluable to those seeking to use AIS ice core measurements for these purposes. Especially, our simulations strengthen the conclusion that ice core measurements from the Talos Dome core exclude the loss of the Wilkes Basin at around 128 ky

PPAR γ

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer’s disease, and obesity in animal models. Finally, novel specialized proresolving mediators—eicosanoids with critical roles in resolution—may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor

Role of Peroxisome Proliferator-Activated Receptor Gamma and Its Ligands in the Treatment of Hematological Malignancies

Peroxisome proliferator-activated receptor gamma (PPARγ) is a multifunctional transcription factor with important regulatory roles in inflammation, cellular growth, differentiation, and apoptosis. PPARγ is expressed in a variety of immune cells as well as in numerous leukemias and lymphomas. Here, we review recent studies that provide new insights into the mechanisms by which PPARγ ligands influence hematological malignant cell growth, differentiation, and survival. Understanding the diverse properties of PPARγ ligands is crucial for the development of new therapeutic approaches for hematological malignancies