Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

Eman Z. Al-Shehri,Afnan O. Al-Zain,Alaa H. Sabrah,Sarah S. Al-Angari,Laila Al Dehailan,George J. Eckert,Mutlu Özcan,Jeffrey A. Platt,Marco C. Bottino 대한치과보존학회 2017 Restorative Dentistry & Endodontics Vol.42 No.3

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3) particles at different pressures. Materials and Methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05). Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

Al-Shehri, Eman Z.,Al-Zain, Afnan O.,Sabrah, Alaa H.,Al-Angari, Sarah S.,Dehailan, Laila Al,Eckert, George J.,Ozcan, Mutlu,Platt, Jeffrey A.,Bottino, Marco C. The Korean Academy of Conservative Dentistry 2017 Restorative Dentistry & Endodontics Vol.42 No.3

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide ($Al_2O_3$) particles at different pressures. Materials and Methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and ${\chi}^2$ tests (${\alpha}=0.05$). Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

Anomalous temperature dependence of the superelastic behavior of Ti-Nb-Mo alloys

Al-Zain, Y.,Kim, H.Y.,Koyano, T.,Hosoda, H.,Nam, T.H.,Miyazaki, S. Elsevier Science 2011 Acta materialia Vol.59 No.4

The effect of test temperature on the superelasticity of Ti-27Nb and various Ti-Nb-Mo alloys is investigated. A deviation in the stress at which martensitic transformation starts (σ<SUB>β-α'</SUB>') from the behavior expected from the Clausius-Clapeyron relationship is confirmed in all alloys. The degree of deviation is found to be in inverse proportion to the electron-to-atom ratio. However, no deviation is observed in the stress at which the reverse transformation finishes (σ<SUB>α'</SUB>'<SUB>-β</SUB>). All alloys exhibit anomalous electrical resistivity during cooling. X-ray diffraction (XRD) and transmission electron microscopy investigations show that the volume fraction of the athermal ω (ω<SUB>ath</SUB>) phase increases with a decrease in temperature. An in situ XRD experiment obtained during a loading-unloading cycle shows that the β and ω<SUB>ath</SUB> phases transform into the α'' phase during loading. The annihilation of the ω<SUB>ath</SUB> phase within the α'' phase allows σ<SUB>α'</SUB>'<SUB>-β</SUB> to obey the Clausius-Clapeyron relationship. As a result, a large hysteresis loop is produced.

Room temperature aging behavior of Ti-Nb-Mo-based superelastic alloys

Al-Zain, Y.,Sato, Y.,Kim, H.Y.,Hosoda, H.,Nam, T.H.,Miyazaki, S. Elsevier Science 2012 ACTA MATERIALIA Vol.60 No.5

The effect of room temperature (RT) aging on the superelasticity of Ti-Nb-Mo-based superelastic alloys is investigated. The results show that annealing at relatively low temperatures such as 973K after severe cold rolling results in poor resistance to the effect of RT aging. The transformation stress increases considerably due to the formation of an isothermal ω phase at RT. Addition of Sn is partially effective in suppressing the RT aging effect in the specimens annealed at 973K. The RT aging effect is suppressed by increasing the annealing temperature, due to the annihilation of lattice defects or non-equilibrium vacancies introduced during cold rolling, which are responsible for accelerating the diffusion process, however, superelasticity is reduced by annealing at higher temperatures, due to a decrease in the critical stress for slip deformation (σ<SUB>CSS</SUB>). The specimen annealed at 1173K followed by aging at 773K exhibits stable superelasticity with a high resistance to the effect of RT aging. Annealing at 1173K causes the annihilation of lattice defects or non-equilibrium vacancies, while aging at 773K induces precipitation of the α phase, which in turn causes an increase in σ<SUB>CSS</SUB>, and further enhances the resistance to the RT aging effect by enriching the matrix with β-stabilizing elements.

Shape memory properties of TiNbMo biomedical alloys

Al-Zain, Y.,Kim, H.Y.,Hosoda, H.,Nam, T.H.,Miyazaki, S. Elsevier Science 2010 Acta materialia Vol.58 No.12

Mo is added to Ti-Nb alloys in order to enhance their superelasticity. The shape memory properties of Ti-(12-28)Nb-(0-4)Mo alloys are investigated in this paper. The Ti-27Nb, Ti-24Nb-1Mo, Ti-21Nb-2Mo and Ti-18Nb-3Mo alloys exhibit the most stable superelasticity with a narrow stress hysteresis among Ti-Nb-Mo alloys with Mo contents of 0, 1, 2 and 3at.%, respectively. The ternary alloys reveal better superelasticity due to a higher critical stress for slip deformation and a larger transformation strain. A Ti-15Nb-4Mo alloy heat-treated at 973K undergoes (211)<111>-type twinning during tensile testing. Twinning is suppressed in the alloy heat-treated at 923K due to the precipitation of the α phase, allowing the alloy to deform via a martensitic transformation process. The Ti-15Nb-4Mo alloy exhibits stable superelasticity with a critical stress for slip deformation of 582MPa and a total recovery strain of 3.5%.

Risk factors associated with the recent cholera outbreak in Yemen: a case-control study

Fekri Dureab,Albrecht Jahn,Johannes Krisam,Asma Dureab,Omer Zain,Sameh Al-Awlaqi,Olaf Mü,ller 한국역학회 2019 Epidemiology and Health Vol.41 No.-

OBJECTIVES: The cholera outbreak in Yemen has become the largest in the recent history of cholera records, having reached more than 1.4 million cases since it started in late 2016. This study aimed to identify risk factors for cholera in this outbreak. METHODS: A case-control study was conducted in Aden in 2018 to investigate risk factors for cholera in this still-ongoing outbreak. In total, 59 cholera cases and 118 community controls were studied. RESULTS: The following risk factors were associated with being a cholera case in the bivariate analysis: a history of travelling and having had visitors from outside Aden Province; eating outside the house; not washing fruit, vegetables, and khat (a local herbal stimulant) before consumption; using common-source water; and not using chlorine or soap in the household. In the multivariate analysis, not washing khat and the use of common-source water remained significant risk factors for being a cholera case. CONCLUSIONS: Behavioural factors and unsafe water appear to be the major risk factors in the recent cholera outbreak in Yemen. In order to reduce the risk of cholera, hygiene practices for washing khat and vegetables and the use and accessibility of safe drinking water should be promoted at the community level.

NTP-ERSN verification with C5G7 1D extension benchmark and GUI development

Lahdour, M.,El Bardouni, T.,El Hajjaji, O.,Chakir, E.,Mohammed, M.,Al Zain, Jamal,Ziani, H. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.4

NTP-ERSN is a package developed for solving the multigroup form of the discrete ordinates, characteristics and collision probability of the Boltzmann transport equation in one-dimensional cartesian geometry, by combining pin cells. In this work, C5G7 MOX benchmark is used to verify the accuracy and efficiency of NTP-ERSN package, by treating reactor core problems without spatial homogenization. This benchmark requires solutions in the form of normalized pin powers as well as the vectors and the eigenvalue. All NTP-ERSN simulations are carried out with appropriate spatial and angular approximations. A good agreement between NTP-ERSN results with those obtained with OpenMC calculation code for seven energy groups. In addition, our studies about angular and mesh refinements are carried out to produce better quality solution. Moreover, NTP-ERSN GUI has also been updated and adapted to python 3 programming language.

Schiff Base Ligand Coated Gold Nanoparticles for the Chemical Sensing of Fe(III) Ions

Jimoh, Abiola Azeez,Helal, Aasif,Shaikh, M. Nasiruzzaman,Abdul Aziz, Md.,Yamani, Zain H.,Al-Ahmed, Amir,Kim, Jong-Pil Hindawi Limited 2015 Journal of nanomaterials Vol.2015 No.-

<P>New Schiff base-coated gold nanoparticles (AuNPs) of type AuNP@L (where L: thiolated Schiff base ligand) have been synthesized and characterized using various spectroscopic techniques. The AuNPs and AuNP@L were imaged by transmission electron microscopy (TEM) and were confirmed to be well-dispersed, uniformly distributed, spherical nanoparticles with an average diameter of 8–10 nm. Their potential applications for chemosensing were investigated in UV-Vis and fluorescence spectroscopic studies. The AuNP@L exhibited selectivity for Fe<SUP>3+</SUP>in an ethanol/water mixture (ratio 9 : 1 v/v). The absorption and emission spectral studies revealed a 1 : 1 binding mode for Fe<SUP>3+</SUP>, with binding constants of8.5×<SUP>105</SUP>and2.9×<SUP>105</SUP> M<SUP>−1</SUP>, respectively.</P>