The investigation of bubble mobility in channel flow with wavy porous media walls

Gangloff Jr., John J.,Hwang Jr., Wook R.,Advani Jr., Suresh G. Elsevier 2015 International journal of multiphase flow Vol.70 No.-

<P><B>Abstract</B></P> <P>During composites processing, thermoset polymer resin is injected into network of densely packed continuous fibers with the goal of complete saturation. The formation and entrapment of gas bubbles, due to the presence of air or volatiles during processing, will create voids in the cured composite. Voids can degrade the mechanical properties and increase design risks and costs. Thus, there is a need to understand the two phase flow of resin and bubbles through channels within fibrous porous media. A two-phase flow model of a channel containing resin and gas bubbles is presented. The boundaries of the channel are porous media with sinusoidal wavy or corrugated walls, which represents the wavy nature of the porous media. This causes the change in bubble movement dynamics, due to the non-uniform pressure gradient induced by non-rectilinear walls. Parameters such as porous media permeability, channel waviness, and channel width are studied to investigate the influence of wavy porous wall effects on the two-phase flow and how these parameters may influence the likelihood of bubble entrapment. By maximizing the bubble mobility, which is the ratio of average bubble velocity to average resin velocity, one can remove the bubbles from the system before the resin cures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A 2D resin flow through a wavy or corrugated channel+porous media is modeled. </LI> <LI> Wavy channel+porous media flow is compared to wavy channel+slip velocity model. </LI> <LI> 2D resin flow shows good matching of slip velocity model versus porous media solution. </LI> <LI> Two-phase bubble flow through a cylindrical wavy channel+porous media is modeled. </LI> <LI> Results show the ideal waviness and channel width for maximized bubble mobility. </LI> </UL> </P>

Fatigue crack formation and growth from localized corrosion in Al–Zn–Mg–Cu

Kim, Sangshik,Burns, James T.,Gangloff, Richard P. Elsevier 2009 Engineering fracture mechanics Vol.76 No.5

<P><B>Abstract</B></P><P>The effect of precorrosion on the fatigue life of aluminum alloy 7075-T6511 was measured, physical characteristics of corrosion topography plus fatigue damage were established by microscopy, and a corrosion modified equivalent initial flaw size (CM-EIFS) was established using fracture mechanics modeling. Fatigue life is reduced by clustered corrosion pits on the L–S surface from laboratory-EXCO exposure. Cracks initiate from pits clustered as a semi-elliptical surface micronotch rather than the deepest pits, consistent with shape-dependent stress intensity. Marker band analysis establishes that the number of cycles to form a crack about a pit cluster can be a significant fraction of total fatigue life. The CM-EIFS, back-calculated from fracture mechanics analysis of measured fatigue life, equals measured initiating-pit cluster size provided that important inputs are provided; such favorable comparison validates this approach to corrosion-fatigue interaction. Calculated CM-EIFS provides a metric to characterize alloy corrosion damage, and can be used to forward-model the effects of stress and loading environment on fatigue life distribution, critical for efficient alloy development. Use in prognosis of the fatigue performance of a service-corroded surface is hindered by uncertain non-destructive characterization of corrosion topography.</P>

SWCNT growth on Al/Fe/Mo investigated by <i>in situ</i> mass spectroscopy

Kim, S-M,Zhang, Y,Teo, K B K,Bell, M S,Gangloff, L,Wang, X,Milne, W I,Wu, J,Jiao, J,Lee, S-B IOP Pub 2007 Nanotechnology Vol.18 No.18

<P>The effect of temperature on the growth of single-walled carbon nanotubes (SWCNTs) was investigated over the range of 725–900 °C. A cold-wall reactor consisting of a heated stage (on which the substrate for SWCNT growth (Al/Fe/Mo) was placed) and a showerhead (from which C<SUB>2</SUB>H<SUB>2</SUB> was introduced vertically into the reactor) was used for the growth. The heating was found to play two roles: (1) it generated complex hydrocarbon radicals during the growth process, as well as (2) promoting catalytic nanoparticles on the substrate during the annealing process. The optimum temperature for the highest SWCNT yield was found to be ∼860 °C. For the first time, <I>in situ</I> mass spectroscopy was used to identify the growth precursors generated from thermal pyrolysis of C<SUB>2</SUB>H<SUB>2</SUB> within this temperature range. The peak of the radicals found (C<SUB>6</SUB>H<SUB>9</SUB>, C<SUB>5</SUB>H<SUB>9</SUB> and C<SUB>6</SUB>H<SUB>13</SUB>) and the highest catalyst support particle density (Fe catalyst supported on Al<SUB><I>x</I></SUB>O<SUB><I>y</I></SUB>) was correlated to the maximum yield of single walled carbon nanotubes at the optimum growth temperature of ∼860 °C. Bottom gate SWCNT-FETs (single-walled carbon nanotube based field effect transistors) were fabricated showing a high transconductance of ∼0.12 µS and on/off ratio of ∼10<SUP>5</SUP> which are both comparable to other state-of-the-art SWCNT-FET. </P>

S6K1 controls pancreatic 관 cell size independently of intrauterine growth restriction.

Um, Sung Hee,Sticker-Jantscheff, Melanie,Chau, Gia Cac,Vintersten, Kristina,Mueller, Matthias,Gangloff, Yann-Gael,Adams, Ralf H,Spetz, Jean-Francois,Elghazi, Lynda,Pfluger, Paul T,Pende, Mario,Bernal- American Society for Clinical Investigation 2015 The Journal of clinical investigation Vol.125 No.7

<P>Type 2 diabetes mellitus (T2DM) is a worldwide heath problem that is characterized by insulin resistance and the eventual loss of 관 cell function. As recent studies have shown that loss of ribosomal protein (RP) S6 kinase 1 (S6K1) increases systemic insulin sensitivity, S6K1 inhibitors are being pursued as potential agents for improving insulin resistance. Here we found that S6K1 deficiency in mice also leads to decreased 관 cell growth, intrauterine growth restriction (IUGR), and impaired placental development. IUGR is a common complication of human pregnancy that limits the supply of oxygen and nutrients to the developing fetus, leading to diminished embryonic 관 cell growth and the onset of T2DM later in life. However, restoration of placental development and the rescue of IUGR by tetraploid embryo complementation did not restore 관 cell size or insulin levels in S6K1-/- embryos, suggesting that loss of S6K1 leads to an intrinsic 관 cell lesion. Consistent with this hypothesis, reexpression of S6K1 in 관 cells of S6K1-/- mice restored embryonic 관 cell size, insulin levels, glucose tolerance, and RPS6 phosphorylation, without rescuing IUGR. Together, these data suggest that a nutrient-mediated reduction in intrinsic 관 cell S6K1 signaling, rather than IUGR, during fetal development may underlie reduced 관 cell growth and eventual development of T2DM later in life.</P>

Biocompatibility study of lithium disilicate and zirconium oxide ceramics for esthetic dental abutments

Céline Brunot-Gohin,Jean-Luc Duval,Sandra Verbeke,Kayla Belanger,Isabelle Pezron,Gérard Kugel,Dominique Laurent-Maquin,Sophie Gangloff,Christophe Egles 대한치주과학회 2016 Journal of Periodontal & Implant Science Vol.46 No.6

Purpose: The increasing demand for esthetically pleasing results has contributed to the use of ceramics for dental implant abutments. The aim of this study was to compare the biological response of epithelial tissue cultivated on lithium disilicate (LS2) and zirconium oxide (ZrO2) ceramics. Understanding the relevant physicochemical and mechanical properties of these ceramics will help identify the optimal material for facilitating gingival wound closure. Methods: Both biomaterials were prepared with 2 different surface treatments: raw and polished. Their physicochemical characteristics were analyzed by contact angle measurements, scanning white-light interferometry, and scanning electron microscopy. An organotypic culture was then performed using a chicken epithelium model to simulate peri-implant soft tissue. We measured the contact angle, hydrophobicity, and roughness of the materials as well as the tissue behavior at their surfaces (cell migration and cell adhesion). Results: The best cell migration was observed on ZrO2 ceramic. Cell adhesion was also drastically lower on the polished ZrO2 ceramic than on both the raw and polished LS2. Evaluating various surface topographies of LS2 showed that increasing surface roughness improved cell adhesion, leading to an increase of up to 13%. Conclusions: Our results demonstrate that a biomaterial, here LS2, can be modified using simple surface changes in order to finely modulate soft tissue adhesion. Strong adhesion at the abutment associated with weak migration assists in gingival wound healing. On the same material, polishing can reduce cell adhesion without drastically modifying cell migration. A comparison of LS2 and ZrO2 ceramic showed that LS2 was more conducive to creating varying tissue reactions. Our results can help dental surgeons to choose, especially for esthetic implant abutments, the most appropriate biomaterial as well as the most appropriate surface treatment to use in accordance with specific clinical dental applications.

Biocompatibility study of lithium disilicate and zirconium oxide ceramics for esthetic dental abutments

Brunot-Gohin, Celine,Duval, Jean-Luc,Verbeke, Sandra,Belanger, Kayla,Pezron, Isabelle,Kugel, Gerard,Laurent-Maquin, Dominique,Gangloff, Sophie,Egles, Christophe Korean Academy of Periodontology 2016 Journal of Periodontal & Implant Science Vol.46 No.6

Purpose: The increasing demand for esthetically pleasing results has contributed to the use of ceramics for dental implant abutments. The aim of this study was to compare the biological response of epithelial tissue cultivated on lithium disilicate ($LS_2$) and zirconium oxide ($ZrO_2$) ceramics. Understanding the relevant physicochemical and mechanical properties of these ceramics will help identify the optimal material for facilitating gingival wound closure. Methods: Both biomaterials were prepared with 2 different surface treatments: raw and polished. Their physicochemical characteristics were analyzed by contact angle measurements, scanning white-light interferometry, and scanning electron microscopy. An organotypic culture was then performed using a chicken epithelium model to simulate peri-implant soft tissue. We measured the contact angle, hydrophobicity, and roughness of the materials as well as the tissue behavior at their surfaces (cell migration and cell adhesion). Results: The best cell migration was observed on $ZrO_2$ ceramic. Cell adhesion was also drastically lower on the polished $ZrO_2$ ceramic than on both the raw and polished $LS_2$. Evaluating various surface topographies of $LS_2$ showed that increasing surface roughness improved cell adhesion, leading to an increase of up to 13%. Conclusions: Our results demonstrate that a biomaterial, here $LS_2$, can be modified using simple surface changes in order to finely modulate soft tissue adhesion. Strong adhesion at the abutment associated with weak migration assists in gingival wound healing. On the same material, polishing can reduce cell adhesion without drastically modifying cell migration. A comparison of $LS_2$ and $ZrO_2$ ceramic showed that $LS_2$ was more conducive to creating varying tissue reactions. Our results can help dental surgeons to choose, especially for esthetic implant abutments, the most appropriate biomaterial as well as the most appropriate surface treatment to use in accordance with specific clinical dental applications.