Search Results - (Author, Cooperation:D. Dong)

2018-06-02

The American Society for Pharmacology and Experimental Therapeutics (ASPET)

0090-9556

1521-009X

Chemistry and Pharmacology

Medicine

2018-04-17

The American Society for Microbiology (ASM)

0270-7306

1098-5549

Biology

Medicine

2018-08-11

The American Society for Pharmacology and Experimental Therapeutics

0022-3565

1521-0103

Medicine

2018-09-06

Royal Society

2054-5703

Natural Sciences in General

mechanical engineering

2016-04-21

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Bacterial Proteins/*chemistry/*metabolism ; CRISPR-Associated Proteins/*chemistry/*metabolism ; CRISPR-Cas Systems ; Clustered Regularly Interspaced Short Palindromic Repeats/*genetics ; Crystallography, X-Ray ; Firmicutes/*enzymology ; Genetic Engineering ; Models, Molecular ; Nucleic Acid Conformation ; Protein Binding ; Protein Structure, Tertiary ; RNA Stability ; RNA, Bacterial/*chemistry/genetics/*metabolism ; RNA, Guide/chemistry/genetics/metabolism ; Substrate Specificity

2018-08-02

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

2018-02-20

American Heart Association (AHA)

1524-4539

Medicine

Biomarkers, Cardiovascular Disease, Risk Factors, Women

2018-08-11

Nature Publishing Group (NPG)

2041-1723

Biology

Chemistry and Pharmacology

Natural Sciences in General

Physics

2018-06-20

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-03-09

Wiley-Blackwell

0002-7820

1551-2916

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

1089-7550

AIP Digital Archive

Physics

The energy distribution of hot electrons in high-field stressed amorphous silicon dioxide (SiO2) films have been measured using a vacuum emission technique. Electrons having average energies (approximately-greater-than)2 eV and an energy relaxation length of λ≈32 A(ring) are observed at all fields studied ((approximately-greater-than) 2 MV/cm). However, contrary to previous theoretical expectations, the majority of carriers in the distribution remains stable at all fields. The results are in agreement with other recent experiments (electroluminescence and carrier separation) which only measure the average energy of hot electrons in SiO2 and with recent Monte Carlo transport calculations which include scattering by both optical and acoustic phonon modes. Results for varying SiO2 thickness, metal gate thickness, oxide composition, and metal gate composition will be discussed.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Electron heating in silicon dioxide (SiO2) at electric fields (approximately-less-than)5 MV/cm is demonstrated using three different experimental techniques: carrier separation, electroluminescence, and vacuum emission. Gradual heating of the electronic carrier distribution is demonstrated for fields from 5 to 12 MV/cm with the average excess energy of the distribution reaching (approximately-greater-than)4 eV with respect to the bottom of the SiO2 conduction band edge. Off-stoichiometric SiO2 (OS-SiO2) layers are shown to behave similarly to very thin SiO2((approximately-less-than)70 A(ring) in thickness) with a transition occurring from "cool'' to "hot'' electrons as the conduction mechanism changes from direct tunneling between silicon (Si) islands in the SiO2 matrix of the OS-SiO2 material to Fowler-Nordheim emission into the conduction band of the SiO2 regions. The relationship of electron heating to electron trapping, positive charge generation, interface state creation, and dielectric breakdown is treated. The importance of various scattering mechanisms for stabilizing the electronic field-induced heating in the SiO2 and preventing current runaway and impact ionization is discussed. Scattering may be due to disorder, trapped charges, and acoustical phonons, as well as longitudinal optical phonons.

Electronic Resource

1365-246X

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Associated with non-steady magnetohydrodynamic (MHD) flow in the liquid metallic core of the Earth, with typical relative speeds of a fraction of a millimetre per second, are fluctuations in dynamic pressure of about 103 N m−2. Acting on the non-spherical core-mantle boundary (CMB), these pressure fluctuations give rise to a fluctuating net topographic torque Lt(t) (i=1, 2, 3)—where t denotes time—on the overlying solid mantle. Geophysicists now accept the proposal by one of us (RH) that Li-(t) makes a significant and possibly dominant contribution to the total torque Li*(t) on the mantle produced directly or indirectly by core motions. Other contributions are the ‘gravitational’ torque associated with fluctuating density gradients in the core, the ‘electromagnetic’ torque associated with Lorentz forces in the weakly electrically conducting lower mantle, and the ‘viscous’ torque associated with shearing motions in the boundary layer just below the CMB. the axial component L3*(t) of Li* (t) contributes to the observed fluctuations in the length of the day [LOD, an inverse measure of the angular speed of rotation of the solid Earth (mantle, crust and cryosphere)], and the equatorial components (Li* (t)) L* (t) contribute to the observed polar motion, as determined from measurements of changes in the Earth's rotation axis relative to its figure axis.In earlier phases of a continuing programme of research based on a method for determining Li(t) from geophysical data (proposed independently about ten years ago by Hide and Le Mouël), it was shown that longitude-dependent irregular CMB topography no higher than about 0.5 km could give rise to values of L3(t) sufficient to account for the observed magnitude of LOD fluctuations on decadal time-scales. Here, we report an investigation of the equatorial components (L1(t), L2(t)) = L(t) of Li(t) taking into account just one topographic feature of the CMB—albeit possibly the most pronounced—namely the axisymmetric equatorial bulge, with an equatorial radius exceeding the polar radius by 9.5 ± 0.1 km (the mean radius of the core being 3485 2 km, 0.547 times that of the whole Earth). A measure of the local horizontal gradient of the fluctuating pressure field near the CMB can be obtained from the local Eulerian flow velocity in the ‘free stream’ below the CMB by supposing that nearly everywhere in the outer reaches of the core—the ‘polosphere’ (Hide 1995)—geostrophic balance obtains between the pressure gradient and Coriolis forces. the polospheric velocity fields used were those determined by Jackson (1989) from geomagnetic secular variations (GSV) data on the basis of the geostrophic approximation combined with the assumption that, on the time-scales of the GSV, the core behaves like a perfect electrical conductor and the mantle as a perfect insulator.In general agreement with independent calculations by Hulot, Le Huy & Le Mouël (1996) and Greff-Lefftz & Legros (1995), we found that in magnitude L (t) for epochs from 1840 to 1990 typically exceeds L3(t) by a factor of about 10, roughly equal to the ratio of the height of the equatorial bulge to that strongly implied for irregular topography by determinations of L3(t) (see Hide et al. 1993). But L (t) still apparently falls short in magnitude by a factor of up to about 5 in its ability t o account for the amplitude of the observed time-series of polar motion on decadal time-scales (DPM), and it is poorly correlated with that time-series. So we conclude that unless uncertainties in the determination of the DPM time-series from observations-which we also discuss-have been seriously underestimated, the action of normal pressure forces associated with core motions on the equatorial bulge of the core-mantle boundary makes a significant but not dominant contribution to the excitation of decadal polar motion. Other geophysical processes such as the movement of groundwater and changes in sea-level must also be involved.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199®), after being repaired by Repair Material® and Triad®, using three different joint surface designs (butt, round and 45 ° bevel), were immersed onto 99·5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0–72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way anova and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2·72±0·51 Kgf) of the round joint specimens were significantly higher (P〈0·05) than those (butt: 1·66±0·38 Kgf, 45 ° bevel: 1·93±0·41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2·54±0·39 Kgf) of the specimens repaired with Triad® were significantly higher (P〈0·05) than those (1·59±0·40 Kgf) of specimens repaired with Repair Material®. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The present study used the acoustic emission (AE) technique to evaluate interactions among soldering temperature, flux treatment, and the resultant ultimate tensile strength (UTS). Scanning electron microscopy (SEM) was used to examine fracture surfaces of the solder joints. Specimens were cast from removable partial denture alloy and then placed in a jig with a gap distance of 1·0 mm. A high-frequency soldering machine with an optical pyrometer was used for soldering at 1150°C and 1200°C, respectively. The flux concentrations were 67% and 75%. The soldered specimens were subjected to tensile test at a crosshead speed of 0·05 mm/min. During testing, acoustic emissions in the frequency range of 100–1200 kHz were collected, filtered, recorded, and processed by a sensing device. The results were analysed by anova and Tukey LSD test. UTS at different temperatures showed no significant difference according to either mechanical or acoustic results. But in the 1200°C group, the UTSs and AE counts showed significant differences (P〈0·05) at both flux concentrations. SEM showed that the 1200C group had better dendritic crystal structure than did the 1150°C group. In the 1200°C group specimens with 67% flux had fewer flux inclusion bodies and dendritic crystals than did specimens with 75% flux. The 75% flux subgroup produced high-amplitude (60–70 dB) acoustic signals within the elastic deformation zone, while the 67% flux subgroup produced similar signals within the plastic deformation zone, either beyond the 0·2% yield point or before fracture.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The aims of this study were to observe the release of fluoride ions (F−) from GC-Fuji Lining-LC® glass–ionomer cement, to assess the diffusion process, and to measure fluoride diffusivity (D) in the set cement. Specimens of various dimensions and shapes, ranging from discs to cylindrical rods, were fabricated for both open and embedded modes of testing. In the open mode studies, specimens with different surface to volume ratios were selected and immersed in 37 °C distilled water. In the embedded mode studies, only one diametral surface of the rod-shaped specimens of different lengths and diameters was exposed. F− concentration was measured using a fluoride electrode. The storage solution was analysed at predetermined intervals hourly, daily, and weekly (up to 10 weeks). Immediately after each sampling, the old storage solution was discarded and replaced with new distilled water. F− release from the set cements was detectable (0·4–3·8 ppm, varied with sample geometry), even after a 10-week sampling interval. F− release was greater in ground set cements (0.37 ppm/mg powder) than in control samples of unmixed powder (0.01 ppm/mg powder) immersed for 1 h. Two mechanisms for F− release were proposed. One was short-term and involved rapid dissolution from the cement surface. The other was more gradual and resulted in the sustained diffusion of ions through the bulk cement, which can be modelled by applying a mathematical technique known as separation of variables to Fick's Second Law of Diffusion. The mean D of F− in embedded set cements of glass–ionomer was (1·4±0·5)×10−11 cm2/s, with higher apparent D observed in open mode samples [(7·6±1·4)×10−11 cm2/s].

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The effect of silanization and filler fraction on the mechnical properties of aged dental composites was investigated. Experimental composites (75/25 Bis-GMA/TEGDMA resin reinforced with 0, 12·6, 30·0, and 56·5 vol% 8 μm silanized/unsilanized BaSiO6) were fabricated into 4·7 mm diameter×2·2 mm thick discs and 3·5 mm diameter×7·3 mm thick discs for diametral tensile and compressive tests, respectively. The effect of immersion in 75% ethanol at 37 °C for 0–30 days on the diametral tensile strength (DTS) and compressive strength (CS) of the samples was evaluated and analysed by anova and Tukey LSD test. The fracture interface between filler and resin matrix was then examined by scanning electron microscope. Results and subsequent statistical evidence from DTS (18·6±7·6 MPa, silanized versus 11·7±2·6 MPa, unsilanized) and CS (85·1±29·7 MPa, silanized versus 56·0±11·3 MPa, unsilanized) strongly implies that silanization may greatly enhance the mechanical properties of the resin composites. Furthermore, it also shows that both DTS and CS increased proportionally as the filler fraction of the composites increased. However, in the unsilanized groups, DTS decreased (up to 40%) as the filler fraction increased, and CS showed no relevance to the filler fraction at all. As for the influence of aging, it was found that both DTS and CS showed a significant decrease after immersion in 75% ethanol, and silanization heavily correlated with the filler fraction of aged-resin composites. Microscopic examination of the fractured samples showed that failure primarily occurred within the resin matrix per se for silanized composites and adjacent to the filler particles for unsilanized composites. All the evidence points to the conclusion that mechanical properties of aged-resin composites can be greatly influenced by silanization and the filler fraction.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The heating up of dental composites by laser will produce acoustic emissions (AEs) that may be related to fracture mechanisms in the composites. It has been proved that the mechanical properties of dental composites are affected by storage in food simulating liquids, i.e. 75% ethanol, which has a solubility parameter approximating to that of bisphenol glycidyl dimethacrylate (BisGMA) resin. A new method was innovated to evaluate the laser-induced AEs in dental composites aged by 75% ethanol solution. Model systems (50/50 BisGMA/TEGDMA resin filled with 0% and 75 wt.% 5–10 μm silanized BaSiO6) as well as three commercial composites (Marathon One, Z100 and Herculite XRV) were used in this study. Nine samples acting as the control group were tested to establish the correlation of AEs to laser power. The effect of ageing by immersion in 75% ethanol on AEs and diametral tensile strength (DTS) was then evaluated. A quasi-continuous wave CO2 laser was used to heat up the composites. AEs of frequency 100–200 kHz were collected, filtered, recorded and processed using a 4610 Smart Acoustic Monitor. Burst patterns, which formally were assumed to be correlated to fracture mechanisms, were also identified from the data obtained at laser power ≥5 W for commercial composites and ≥4 W for model systems. Higher laser powers cause the AE to increase for all composites except unfilled model resin. AEs as a function of power for all aged systems were flat (〈100 events) below 4 W. Emissions then rose sharply to〉 1000 events at 7·1 W. Statistically significant differences were found between the AEs obtained at 5 W (commercial composites) and those at 4·3 W (model systems) for material systems and storage times. Marathon One was less affected by the laser and an abrupt change in AE was found between days 0 and 7 of storage for all commercial composites. The AE value from the unfilled model resin was found to be significantly different from that of the model composites. However, they showed an increase in AEs with length of storage time, which was inversely associated with the decreased tendency of their immersed DTS values. Laser-induced AEs may be a valuable adjunct to conventional mechanical testing.

Electronic Resource

0020-1693

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource