17,278 research outputs found
Growth of AlN films using hydrazidoalane single-source precursors
No full textAluminum nitride (AIN) films were grown on Si(100) and S(111) substrates by a low-pressure chemical vapor deposition method in the temperature range 400-800 degrees C using two hydrazidoalane dimers, [Me2Al-mu-N(H)NMe2](2) (1) and [Et2Al-mu-N(H)NMe2](2) (2) as single-source precursors. Polycrystalline AlN films were obtained on Si(111) at 800 degrees C from precursor 1. Amorphous AlN films were observed under certain growing conditions, such as on Si(100) substrates from precursor 2, or at lower temperatures. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. (C) 1999 Elsevier Science S.A. All rights reserved.We are grateful to Korea Science and Engineering Foundation for financial support of this research. Additional support to Y. Kim was provided by the Ministry of Science and Technology
Persistent photoconductivity in Hf–In–Zn–O thin film transistors
No full textPassivated Hf-In-Zn-O (HIZO) thin film transistors suffer from a negative threshold voltage shift under visible light stress due to persistent photoconductivity (PPC). Ionization of oxygen vacancy sites is identified as the origin of the PPC following observations of its temperature-and wavelength-dependence. This is further corroborated by the photoluminescence spectrum of the HIZO. We also show that the gate voltage can control the decay of PPC in the dark, giving rise to a memory action. (C) 2010 American Institute of Physics. [doi:10.1063/1.3496029]
Instability in threshold voltage and subthreshold behavior in Hf–In–Zn–O thin film transistors induced by bias-and light-stress
No full textElectrical bias and light stressing followed by natural recovery of amorphous hafnium-indium-zinc-oxide (HIZO) thin film transistors with a silicon oxide/nitride dielectric stack reveals defect density changes, charge trapping and persistent photoconductivity (PPC). In the absence of light, the polarity of bias stress controls the magnitude and direction of the threshold voltage shift (Delta V(T)), while under light stress, V(T) consistently shifts negatively. In all cases, there was no significant change in field-effect mobility. Light stress gives rise to a PPC with wavelength-dependent recovery on time scale of days. We observe that the PPC becomes more pronounced at shorter wavelengths. (C) 2010 American Institute of Physics. [doi:10.1063/1.3480547]
Influence of Cr and Mo on the passivation of stainless steel 430 (18Cr) and 444 (18Cr-2Mo): In situ XANES study
No full textWe have studied the influence of metal elements on the passivation of stainless steel (SS) 430 (18Cr) and 444 (18Cr(2)Mo) by real time X-ray absorption near edge spectroscopy. We developed an electro-chemical cell that is suitable for in situ electro-chemistry experiments. The behavior of Fe, Cr and Mo elements of SS 430 and 444 was studied in passive region reaction in a borate buffer solution (pH 7.0). We found that the Cr203/Fe,03 ratio gradually decreased with passivation time due to the oxidation of Cr2O3 to CrO42-, indicating weakening of passivity. In the meanwhile, the amount of Mo at passive films increased with passivation time. The improvement of passivity in the SS 444 is mainly attributed to the substitution of Cr oxide by Mo oxide in the passive film. (C) 2002 Elsevier Science B.V. All rights reserved.119sciescopu
Magnetic force-based multiplexed immunoassay using superparamagnetic nanoparticles in microfluidic channel
No full textThis paper describes a novel microfluidic immunoassay utilizing binding of superparamagnetic nanoparticles to beads and deflection of these beads in a magnetic field as the signal for measuring the presence of analyte. The superparamagnetic 50 nm nanoparticles and fluorescent 1 mu m polystyrene beads are immobilized with specific antibodies. When target analytes react with the polystyrene beads and superparamagnetic nanoparticles simultaneously, the superparamagnetic nanoparticles can be attached onto the microbeads by the antigen - antibody complex. In the poly( dimethylsiloxane) ( PDMS) microfluidic channel, only the microbeads conjugated with superparamagnetic nanoparticles by analytes consequently move to the high gradient magnetic fields under the specific applied magnetic field. In this study, the magnetic force-based microfluidic immunoassay is successfully applied to detect the rabbit IgG and mouse IgG as model analytes. The lowest concentration of rabbit IgG and mouse IgG measured over the background is 244 pg mL(-1) and 15.6 ng mL(-1), respectively. The velocities of microbeads conjugated with superparamagnetic nanoparticles are demonstrated by magnetic field gradients in microfluidic channels and compared with the calculated magnetic field gradients. Moreover, dual analyte detection in a single reaction is also performed by the fluorescent encoded microbeads in the microfluidic device. Detection range and lower detection limit can be controlled by the microbeads concentration and the higher magnetic field gradient
Large-amplitude flapping of an inverted-flag in a uniform steady flow – A vortex-induced vibration
No full textThe dynamics of a cantilevered elastic sheet, with a uniform steady flow impinging on its clamped-end, have been studied widely and provide insight into the stability of flags and biological phenomena. Recent measurements by Kim et al. J. Fluid Mech. 736, R1 (2013) show that reversing the sheet’s orientation, with the flow impinging on its free-edge, dramatically alters its dynamics. In contrast to the conventional flag, which exhibits (small-amplitude) flutter above a critical flow speed, the inverted-flag displays large-amplitude flapping over a finite band of flow speeds. In this talk, we use a combination of mathematical theory, scaling analysis and measurement to establish that this large-amplitude flapping motion is a vortex-induced vibration. Onset of flapping is shown mathematically to be due to divergence instability, verifying previous speculation based on a two-point measurement. Reducing the sheet’s aspect ratio (height/length) increases the critical flow speed for divergence and ultimately eliminates flapping. The flapping motion is associated with a separated flow – detailed measurements and scaling analysis show that it exhibits the required features of a vortex-induced vibration. Flapping is found to be periodic predominantly, with a transition to chaos as flow speed increases. Cessation of flapping occurs at higher speeds – increasing damping reduces the flow speed range where flapping is observed, as required. These findings have implications to leaf motion and other biological processes, such as the dynamics of individual hairs, because they also can present an inverted-flag configuration
Inertial microfluidics-based cell sorting
No full textInertial microfluidics has attracted significant attention in recent years due to its superior benefits of high throughput, precise control, simplicity, and low cost. Many inertial microfluidic applications have been demonstrated for physiological sample processing, clinical diagnostics, and environmental monitoring and cleanup. In this review, we discuss the fundamental mechanisms and principles of inertial migration and Dean flow, which are the basis of inertial microfluidics, and provide basic scaling laws for designing the inertial microfluidic devices. This will allow end-users with diverse backgrounds to more easily take advantage of the inertial microfluidic technologies in a wide range of applications. A variety of recent applications are also classified according to the structure of the microchannel: straight channels and curved channels. Finally, several future perspectives of employing fluid inertia in microfluidic-based cell sorting are discussed. Inertial microfluidics is still expected to be promising in the near future with more novel designs using various shapes of cross section, sheath flows with different viscosities, or technologies that target micron and submicron bioparticles.
Accuracy of continuous and noninvasive hemoglobin monitoring in the presence of CO2 insufflation: An observational pilot study
No full textBackground: Laparoscopic surgery has several benefits, but it requires prolonged carbon dioxide (CO2) insufflation. Several factors affect the accuracy of continuous and noninvasive hemoglobin (SpHb) monitoring, but the effects of CO2 insufflation are undetermined. This study investigated the effect of CO2 insufflation on SpHb monitoring in laparoscopic surgery. Material/Methods: Twenty patients undergoing laparoscopic gastrectomy were enrolled. Anesthesia was maintained using sevoflurane and remifentanil within an end-tidal CO2 of 30-45 mmHg. The CO2 insufflation was maintained at 12 mmHg using CO2. SpHb was monitored with a Radical-7 Pulse CO-Oximeter, and laboratory hemoglobin (tHb) was analyzed using a satellite blood analyzer. Results: Forty paired measurements were analyzed. The mean perfusion index, SpHb, and tHb were 3.10±1.77%, 10.92±1.48 g/dL, and 11.51±0.88 g/dL, respectively. SpHb underestimated tHb with a bias (precision) of -0.59 (1.28 g/dL), and the 95% limit of agreement was wide (-3.11 to 1.92 g/dL). SpHb was moderately correlated with tHb (r=0.50, 95% CI: 0.23 to 0.70). The concordance rate was 67%. DSpHb was not correlated with DtHb (r=0.29, 95% CI: -0.18 to -0.65). A similar bias, wider limits of agreement, a higher |SpHb-tHb|, but more significant correlation between SpHb and tHb were observed for the “PaCO2 <40 mmHg” range compared with the “40 mmHg £PaCO2” range. Conclusions: SpHb may have an acceptable accuracy but has a weak trending ability in the presence of CO2 insufflation, and it can be affected by PaCO2. Further research on the effects of CO2 insufflation on SpHb is needed
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