Interfacial modulus mapping of layered dental ceramics using nanoindentation

Antonios L Theocharopoulos,rew J Bushby,Ken MY P'ng,Rory M Wilson,K Elizabeth Tanner,Michael J Cattell 대한치과보철학회 2016 The Journal of Advanced Prosthodontics Vol.8 No.6

PURPOSE The aim of this study was to test the modulus of elasticity (E) across the interfaces of yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. MATERIALS AND METHODS YTZP core material (KaVo-Everest, Germany) specimens were either coated with a liner (IPS e.max ZirLiner, Ivoclar-Vivadent) (Type-1) or left as-sintered (Type-2) and subsequently veneered with a pressable glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). A 5 µm (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across the exposed and polished interfaces of both specimen types. The multiple point load – partial unload method was used for E determination. All materials used were characterized using Scanning Electron Microscopy (SEM) and X – ray powder diffraction (XRD). E mappings of the areas tested were produced from the nanoindentation data. RESULTS A significantly (P<.05) lower E value between Type-1 and Type-2 specimens at a distance of 40 µm in the veneer material was associated with the liner. XRD and SEM characterization of the zirconia sample showed a fine grained bulk tetragonal phase. IPS e-max ZirPress and IPS e-max ZirLiner materials were characterized as amorphous. CONCLUSION The liner between the YTZP core and the heat pressed veneer may act as a weak link in this dental multilayer due to its significantly (P<.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be reliable predictors of E and useful evaluation tools for layered dental ceramic interfaces.

Interfacial modulus mapping of layered dental ceramics using nanoindentation

Theocharopoulos, Antonios L,Bushby, Andrew J,P'ng, Ken MY,Wilson, Rory M,Tanner, K Elizabeth,Cattel, Michael J The Korean Academy of Prosthodonitics 2016 The Journal of Advanced Prosthodontics Vol.8 No.6

PURPOSE. The aim of this study was to test the modulus of elasticity (E) across the interfaces of yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. MATERIALS AND METHODS. YTZP core material (KaVo-Everest, Germany) specimens were either coated with a liner (IPS e.max ZirLiner, Ivoclar-Vivadent) (Type-1) or left as-sintered (Type-2) and subsequently veneered with a pressable glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). A $5{\mu}m$ (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across the exposed and polished interfaces of both specimen types. The multiple point load - partial unload method was used for E determination. All materials used were characterized using Scanning Electron Microscopy (SEM) and X - ray powder diffraction (XRD). E mappings of the areas tested were produced from the nanoindentation data. RESULTS. A significantly (P<.05) lower E value between Type-1 and Type-2 specimens at a distance of $40{\mu}m$ in the veneer material was associated with the liner. XRD and SEM characterization of the zirconia sample showed a fine grained bulk tetragonal phase. IPS e-max ZirPress and IPS e-max ZirLiner materials were characterized as amorphous. CONCLUSION. The liner between the YTZP core and the heat pressed veneer may act as a weak link in this dental multilayer due to its significantly (P<.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be reliable predictors of E and useful evaluation tools for layered dental ceramic interfaces.

Promoter methylation of the Wnt/β‐catenin signaling antagonist <i>Dkk‐3</i> is associated with poor survival in gastric cancer

Yu, Jun,Tao, Qian,Cheng, Yuen Y.,Lee, Kwan Y.,Ng, Simon S. M.,Cheung, Kin F.,Tian, Linwei,Rha, Sun Y.,Neumann, Ulf,Rö,cken, Christoph,Ebert, Matthias P. A.,Chan, Francis K. L.,Sung, Joseph J. Y. Wiley Subscription Services, Inc., A Wiley Company 2009 Cancer Vol.115 No.1

<P><B>Abstract</B></P><P><B>BACKGROUND:</B></P><P>Abnormal activation of the Wnt/β‐catenin signaling pathway is common and critical in the pathogenesis of digestive cancers. In this study, the authors investigated the promoter methylation of the dickkopf homolog 3 gene <I>Dkk‐3</I> in these cancers and its prognostic significance in gastric cancer.</P><P><B>METHODS:</B></P><P><I>Dkk‐3</I> methylation was assessed in 173 patients with gastric cancers (including 104 patients who were followed for up to 4090 days) and in 128 patients with colorectal cancer. Cell growth was evaluated by using a colony‐formation assay. For survival analyses, the authors used Kaplan‐Meier plots, the log‐rank test, and Cox proportional regression.</P><P><B>RESULTS:</B></P><P><I>Dkk‐3</I> was silenced or down‐regulated in 12 of 17 gastric cancer cell lines (70.6%) and in 3 of 9 colon cancer cell lines (33.3%). The loss of gene expression was associated with promoter methylation, which could be restored by demethylating agents. Ectopic expression of <I>Dkk‐3</I> suppressed colony formation. Moreover, methylation of <I>Dkk‐3</I> was detected in 117 of 173 primary gastric tumors (67.6%) and in 67 of 128 colorectal tumors (52.3%). The clinical significance and the prognostic value of <I>Dkk‐3</I> methylation also were examined in 104 gastric cancers and in 84 colorectal cancers. Multivariate analysis indicated that <I>Dkk‐3</I> methylation was associated significantly and independently with poor disease survival (relative risk, 2.534; 95% confidence interval, 1.54–4.17; <I>P</I> = .002) in gastric cancer, but not in colorectal cancer. Kaplan‐Meier survival curves revealed that patients who had <I>Dkk‐3</I> methylated gastric cancers had a significantly shorter survival (median, 0.76 years) compared with patients who did not have <I>Dkk‐3</I> methylation (median, 2.68 years; <I>P</I> < .0001; log‐rank test).</P><P><B>CONCLUSIONS:</B></P><P>Epigenetic silencing of the <I>Dkk‐3</I> gene by promoter methylation was a common event in gastric cancer and was associated with a poor outcome in such patients. Cancer 2009. © 2008 American Cancer Society.</P>

Crack analysis of reinforced concrete members with and without crack queuing algorithm

P.L. Ng,F.J. Ma,A.K.H. Kwan 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.1

Due to various numerical problems, crack analysis of reinforced concrete members using the finite element method is confronting with substantial difficulties, rendering the prediction of crack patterns and crack widths a formidable task. The root cause is that the conventional analysis methods are not capable of tracking the crack sequence and accounting for the stress relief and re-distribution during cracking. To address this deficiency, the crack queuing algorithm has been proposed. Basically, at each load increment, iterations are carried out and within each iteration step, only the most critical concrete element is allowed to crack and the stress re-distribution is captured in subsequent iteration by re-formulating the cracked concrete element and re-analysing the whole concrete structure. To demonstrate the effectiveness of the crack queuing algorithm, crack analysis of concrete members tested in the literature is performed with and without the crack queuing algorithm incorporated.

A Modified Procedure (One-stage Fermentation) for Evaluating Flour Cracker-making Potential

L. Lee,P. K. W. Ng,J. F. Steffe 한국산업식품공학회 2002 산업 식품공학 Vol.6 No.2

Mode Change of a Gamma-Ray Pulsar, PSR J2021+4026

Zhao, J.,Ng, C. W.,Lin, L. C. C.,Takata, J.,Cai, Y.,Hu, C.-P.,Yen, D. C. C.,Tam, P. H. T.,Hui, C. Y.,Kong, A. K. H.,Cheng, K. S. American Astronomical Society 2017 The Astrophysical journal Vol.842 No.1

<P>A glitch of a pulsar is known as a sudden increase in the spin frequency and spin-down rate (frequency time derivative), and it can be caused by a sudden release of the stress built up in the solid crust of the star or pinned vortices in the superfluid interior. PSR J2021+4026 is the first pulsar that shows a significant change in the gamma-ray flux and pulse profile at the glitch that occurred around 2011 October 16. We report the results of timing and spectral analysis of PSR J2021+4026 using similar to 8 yr Fermi. Large Area Telescope data. We find that the pulsar stayed at a high spin-down rate (similar to 4% higher than the pre-glitch value) and a low gamma-ray state (similar to 18% lower) for about 3 yr. after the glitch. Around 2014 December, the spin-down rate and gamma-ray flux gradually returned to pre-glitch values within a timescale of a. few months. The phase-resolved spectra and pulse profiles after the relaxation are also consistent with those before the glitch. The observed long-term evolution of the spin-down rate and the gamma-ray flux indicates that the glitch triggered a mode change in the global magnetosphere. We speculate that the glitch changed. the local magnetic field structure around the polar cap and/or the inclination angle of the. dipole axis, leading to. a change in the electric current circulating in the. magnetosphere.</P>

Mammalian Systems Biotechnology Reveals Global Cellular Adaptations in a Recombinant CHO Cell Line

Yusufi, F.N.K.,Lakshmanan, M.,Ho, Y.S.,Loo, B.L.W.,Ariyaratne, P.,Yang, Y.,Ng, S.K.,Tan, T.R.M.,Yeo, H.C.,Lim, H.L.,Ng, S.W.,Hiu, A.P.,Chow, C.P.,Wan, C.,Chen, S.,Teo, G.,Song, G.,Chin, J.X.,Ruan, X. Cell Press 2017 Cell systems Vol.4 No.5

Effective development of host cells for therapeutic protein production is hampered by the poor characterization of cellular transfection. Here, we employed a multi-omics-based systems biotechnology approach to elucidate the genotypic and phenotypic differences between a wild-type and recombinant antibody-producing Chinese hamster ovary (CHO) cell line. At the genomic level, we observed extensive rearrangements in specific targeted loci linked to transgene integration sites. Transcriptional re-wiring of DNA damage repair and cellular metabolism in the antibody producer, via changes in gene copy numbers, was also detected. Subsequent integration of transcriptomic data with a genome-scale metabolic model showed a substantial increase in energy metabolism in the antibody producer. Metabolomics, lipidomics, and glycomics analyses revealed an elevation in long-chain lipid species, potentially associated with protein transport and secretion requirements, and a surprising stability of N-glycosylation profiles between both cell lines. Overall, the proposed knowledge-based systems biotechnology framework can further accelerate mammalian cell-line engineering in a targeted manner.

High-energy Emissions from the Pulsar/Be Binary System PSR J2032+4127/MT91 213

Takata, J.,Tam, P. H. T.,Ng, C. W.,Li, K. L.,Kong, A. K. H.,Hui, C. Y.,Cheng, K. S. American Astronomical Society 2017 The Astrophysical journal Vol.836 No.2

<P>PSR. J2032+4127 is a radio-loud gamma-ray-emitting pulsar; it is orbiting around a high-mass Be type star with a very long orbital period of 25-50 years, and is approaching periastron, which will occur in late 2017/early 2018. This system comprises a young pulsar and a Be type star, which is similar to the so-called gamma-ray binary PSR. B1259-63/LS2883. It is expected therefore that PSR. J2032+4127 shows an enhancement of high-energy emission caused by the interaction between the pulsar wind and Be wind/disk around periastron. Ho et al. recently reported a rapid increase in the X-ray flux from this system. In this paper, we also confirm a rapid increase in the X-ray flux along the orbit, while the GeV flux shows no significant change. We discuss the high-energy emissions from the shock caused by the pulsar wind and stellar wind interaction and examine the properties of the pulsar wind in this binary system. We argue that the rate of increase of the X-ray flux observed by Swift indicates (1) a variation of the momentum ratio of the two-wind interaction region along the orbit, or (2) an evolution of the magnetization parameter of the pulsar wind with the radial distance from the pulsar. We also discuss the pulsar wind/Be disk interaction at the periastron passage, and propose the possibility of formation of an accretion disk around the pulsar. We model high-energy emissions through the inverse-Compton scattering process of the cold-relativistic pulsar wind off soft photons from the accretion disk.</P>

Original research Papers : A Modified Procedure (One-stage Fermentation) for Evaluating Flour Cracker-making Potential

( L. Lee ),( P,K,W. Ng ),( J. F. Steffe ) 한국산업식품공학회 2002 산업 식품공학 Vol.6 No.2

Synthesis of Sub-Micron Nickel Particles Coated onto Aluminum Powders via a Modified Polyol Process

J. L. Cheng,H. H. Hng,H. Y. Ng,P. C. Soon,Y. W. Lee 대한금속ᆞ재료학회 2008 METALS AND MATERIALS International Vol.14 No.5