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Domen Seruga,Jernej Klemenc,Simon Oman,Marko Nagode Techno-Press 2023 Coupled systems mechanics Vol.12 No.5
A coupled algorithm is proposed which first considers the creation of porous structure of the material and then the simulations of response of mechanical components with porous structure to a variable load history. The simulations are carried out by the Prandtl operator approach in the finite element method (FEM) which enables structural simulations of mechanical components subjected to variable thermomechanical loads. Temperature-dependent material properties and multilinear kinematic hardening of the material can be taken into account by this approach. Several simulations are then performed for a tensile-compressive specimen made of a generic porous structure and mechanical properties of Aluminium alloy AlSi9Cu3. Variable mechanical load history has been applied to the specimens under constant temperature conditions. Comparison of the simulation results shows a considerable elastoplastic stress-strain response in the vicinity of pores whilst the surface of the gauge-length of the specimen remains in the elastic region of the material. Moreover, the distribution of the pore sizes seems more influential to the stress-strain field during the loading than their radial position in the gauge-length.
Ju Hyeon Kim,Domenic J. Previte,Kyung Jae Yoon,Kyung Mun Kim,Edwin Murenzi,Kyong Sup Yoon,J. Marshall Clark,Si Hyeock Lee 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.04
Human body and head lice are obligatory human ectoparasites. Although both body and head lice belong to a single species, Pediculus humanus, only body lice are known to be a vector of several bacterial diseases. The higher vector competence of body lice is assumed to be due to their weaker immune response than that of head lice. To test this hypothesis, immune reactions were compared between body and head lice following infections by two model bacteria, Staphylococcus aureus and Escherichia coli, and a human pathogen, Bartonella quintana. Following dermal or oral challenge, the number of these bacteria increased both in hemocoel and alimentary tract of body lice but not in head lice and the viability of the B. quintana was significantly higher in body louse feces, the major route of infection to human. In addition, body lice showed the lower basal/induced transcription level of major immune genes, cytotoxic reactive oxygen species and phagocytosis activity compared with head lice. These findings suggest that a reduced immune response may be responsible, in part, for the increased proliferation and excretion of viable bacteria which are associated with the high level of human infectivity seen in body versus head lice.
Proliferation and Excretion of Bartonella quintana in Body and Head Lice Following Oral Challenge
Ju Hyeon Kim,Domenic J. Previte,Kyong Sup Yoon,John M. Clark,Si Hyeock Lee 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04
The body and head lice (Pediculus humanus humanus and Pediculus humanus capitis, respectively) are hematophagous ectoparasites of humans and only the body louse between two is known to transmit three bacterial diseases through its feces. The proliferation profiles of Bartonella quintana, the causative agent of trench fever, inside the louse body and its excretion patterns were investigated in the two louse subspecies following oral challenge with B. quintana-infected blood meal. The initial density of B. quintana was sustained inside head lice without any noticeable proliferation for the entire period after infection. In contrast, B. quintana proliferated rapidly inside body lice and the maximum density reached at 10 days post-infection. The numbers of bacteria detected in feces from infected lice were almost the same and steadily decreased over time in both body and head lice. Nevertheless, the viability of the bacteria, as determined by fluorescence, was significantly higher in body louse feces, especially at 1 day post-infection and this tendency lasted for 11 days. These findings suggest that excretion of feces containing more viable B. quintana that is proliferated inside body lice following ingestion of infected blood meal is responsible for the higher vector competence of body lice.
Salmonella enteritis: A Rare Cause of Adult Intussusception
Toan Pham,Domenic La Paglia,Meron Pitcher 대한대장항문학회 2017 Annals of Coloproctolgy Vol.33 No.5
Intussusception is a relatively rare condition in the adult population and is commonly secondary to a malignant process. Eight to twenty percent of cases of adult intussusception are thought to be idiopathic. In children, infection has been proven to precipitate intussusception in the absence of any other cause. We present a rare case of intussusception in a healthy adult patient secondary to salmonella infection and discuss infection as a potential explanation for a proportion of the cases of adult intussusception that are thought to be idiopathic. We recommend testing for infective causes of intussusception in adults when more common causes, such as malignancy, have been excluded.
Influence of geometry and safety factor on fatigue damage predictions of a cantilever beam
Matija Pečnik,Marko Nagode,Domen Šeruga 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.1
The influence of two parameters on fatigue damage predictions of a variably loaded cantilever beam has been examined. The first parameter is the geometry of the cantilever beam and the weld connecting it to a rear panel. Variables of the geometry examined here include the cantilever length, the weld width on the critical cross-section and the angle of the critical cross-section. The second parameter is the safety factor, as set out by the Eurocode 3 standard. An analytical approach has been used to calculate the stresses at the critical cross-section and standard rainflow counting has been used for the extraction of the load cycles from the load history. The results here suggest that a change in the width and angle of the critical cross-section has a non-linear impact on the fatigue damage. The results also show that the angle of the critical cross-section has the biggest influence on the fatigue damage and can cause the weld to withstand fatigue better. The second parameter, the safety factor, is shown to have a significant effect on the fatigue damage calculation, whereby a slight increase in the endurance safety factor can cause the calculated fatigue damage to increase considerably.
A hybrid numerical flux for supersonic flows with application to rocket nozzles
Ferrero, Andrea,D'Ambrosio, Domenic Techno-Press 2020 Advances in aircraft and spacecraft science Vol.7 No.5
The numerical simulation of shock waves in supersonic flows is challenging because of several instabilities which can affect the solution. Among them, the carbuncle phenomenon can introduce nonphysical perturbations in captured shock waves. In the present work, a hybrid numerical flux is proposed for the evaluation of the convective fluxes that avoids carbuncle and keeps high-accuracy on shocks and boundary layers. In particular, the proposed flux is a combination between an upwind approximate Riemann problem solver and the Local Lax-Friedrichs scheme. A simple strategy to mix the two fluxes is proposed and tested in the framework of a discontinuous Galerkin discretisation. The approach is investigated on the subsonic flow in a channel, on the supersonic flow around a cylinder, on the supersonic flow on a flat plate and on the flow in a overexpanded rocket nozzle.
Bae, Gyu-Un,Domené,, Sabina,Roessler, Erich,Schachter, Karen,Kang, Jong-Sun,Muenke, Maximilian,Krauss, Robert ,S. Elsevier 2011 American journal of human genetics Vol.89 No.2
<P>Holoprosencephaly (HPE), a common human congenital anomaly defined by a failure to delineate the midline of the forebrain and/or midface, is associated with diminished Sonic hedgehog (SHH)-pathway activity in development of these structures. SHH signaling is regulated by a network of ligand-binding factors, including the primary receptor PTCH1 and the putative coreceptors, CDON (also called CDO), BOC, and GAS1. Although binding of SHH to these receptors promotes pathway activity, it is not known whether interactions between these receptors are important. We report here identification of missense <I>CDON</I> mutations in human HPE. These mutations diminish CDON's ability to support SHH-dependent gene expression in cell-based signaling assays. The mutations occur outside the SHH-binding domain of CDON, and the encoded variant CDON proteins do not display defects in binding to SHH. In contrast, wild-type CDON associates with PTCH1 and GAS1, but the variants do so inefficiently, in a manner that parallels their activity in cell-based assays. Our findings argue that CDON must associate with both ligand and other hedgehog-receptor components, particularly PTCH1, for signaling to occur and that disruption of the latter interactions is a mechanism of HPE.</P>