Optical-power-dependent photodesorption kinetics of graphene studied by conductance response.

The photodesorption kinetics of graphene with various UV laser power is studied by conductance response. Analytical expressions of the power-dependent photodesorption kinetics of graphene in ambience are derived. The photodesorption time constant τd, steady current, and magnitude of modulation current, can be expressed as functions of the adsorption time constant τa, desorption cross section σ, and photon flux density. Under illumination the steady occupation ratio of adsorbed O2 on graphene is equal to τd/τa. It is suggested that the photodesorption of O2 on graphene is attributed the injection of photogenerated hot electrons and is restricted by the density of antibonding states of O2.

Surface-enhanced Raman scattering of graphene with photo-assisted-synthesized gold nanoparticles.

This paper presents a convenient and reliable method to prepare gold nanoparticles (AuNPs) on graphene. Photo-assisted synthesis (PAS) was employed to grow AuNPs in AuCl(4)(-) electrolyte on graphene. The size of AuNPs could be as large as 130 nm. This optical method had a steady growth rate of AuNPs. The distribution of AuNPs was well controlled by focusing the laser for PAS. The minimum diameter of the distribution was approximately 1 µm. Surface-enhanced Raman scattering of graphene due to AuNPs was observed. Electrical fields near AuNPs calculated by the finite-difference time-domain algorithm ensured that the Raman enhancement was attributed to the localized surface plasmons of AuNPs.

Fabrication of Ni nanostructures on p-Si by scanning probe lithography on Si3N4 films and selective electrodeposition.

Ni-Si nano Schottky junctions are fabricated by the combined process of scanning probe lithography and electrodeposition. The Si3N4 film was patterned by probe-induced oxidation and became a mask for selective electrodeposition of Ni on p-Si substrate. The Ni pattern consists of Ni nano dots, whose diameter is less then 60 nm. The composition and ferromagnetism of Ni dots are verified by energy dispersive spectrum and magnetic force microscopy. The schottky barrier of Ni-Si nano contact is 0.52 V determined by the I-V measurement of conducting atomic force microscopy (CAFM). From current mapping images, it shows that chemical impurity at the Ni-Si interfaces can result in the poor conductance of the junctions.

Fabrication of spatial modulated second order nonlinear structures and quasi-phase matched second harmonic generation in a poled azo-copolymer planar waveguide.

This work demonstrates that arbitrary types of spatially modulated second-order susceptibility (chi((2)) structures such as 1D and 2D, periodic and quasi-periodic structures can be obtained by using the combination of corona poling and direct laser writing (DLW) techniques. The fabrication technique is based on the photodepoling of azo-dye molecules caused by one-photon or two-photon absorption during the DLW process. Polarization and second harmonic generation (SHG) images of the fabricated structures were measured by electrostatic force microscope and SHG mapping techniques, respectively. Furthermore, quasi-phase-matched (QPM) enhanced SHG from a 1D periodically poled azo-copolymer planar waveguide is demonstrated using an optical parametric oscillator laser by scanning wavelength from 1500 to 1600 nm. The resonant wavelength of the QPM enhanced SHG is peaked at 1537 nm with FWHM is congruent to 2.5 nm.

Brain MR images segmentation using statistical ratio: mapping between watershed and competitive Hopfield clustering network algorithms.

Conventional watershed segmentation methods invariably produce over-segmented images due to the presence of noise or local irregularities in the source images. In this paper, a robust medical image segmentation technique is proposed, which combines watershed segmentation and the competitive Hopfield clustering network (CHCN) algorithm to minimize undesirable over-segmentation. In the proposed method, a region merging method is presented, which is based on employing the region adjacency graph (RAG) to improve the quality of watershed segmentation. The relation of inter-region similarities is then investigated using image mapping in the watershed and CHCN images to determine more appropriate region merging. The performance of the proposed technique is presented through quantitative and qualitative validation experiments on benchmark images. Significant and promising segmentation results were achieved on brain phantom simulated data.

Closed-circuit anesthesia preserves skin blood flow during surgery.

BACKGROUND: Closed-circuit anesthesia (CCA) has been suggested to provide better hemodynamic stability, but the relative contribution of CCA to the control of blood flow in microcirculation is not defined. It is hypothesized that isoflurane-based CCA provides a favorable skin blood flow mediating via lesser circulatory response to surgical stimulation. This study was purposed to compare the effects of isoflurane conveyed by CCA with that by semiclosed anesthesia (SCA) on the preservation of skin blood flow in the forearm. METHODS: Twenty seven patients scheduled for colorectal surgery were enrolled for the study and randomly assigned to one of two groups, either receiving CCA (n=14) or SCA (n=13). Anesthesia was induced with fentanyl (100 ig) and thiopental (4-5 mg/kg), and intubation was facilitated with pancuronium priming (0.015 mg/kg) and succinylcholine (1.25 mg/kg). Two percent isoflurane in high O2 flow (3 L/min) was given for 10 min to each patient initially to wash isoflurane in the functional residual capacity of both lungs and the breathing circuit. In the CCA group, after insoflurane wash-in the 02 flow was reduced less than 250 mL/min with isoflurane vaporizer setting adjusted to 3-5% to keep inspired isoflurane at 2% for maintenance of anesthesia. In patients of in the SCA group, anesthesia was maintained with isoflurane in 3 L/min O2 flow keeping the inspired isoflurane concentration at 2% throughout the surgery. A laser Doppler flowmetry (Moore instrument, Axminster, England) was used to measure skin blood flow (SBF) at the thenar eminence of left hand. Skin blood flow was determined and was taken as baseline (100%) at the 10th min after tracheal intubation. Thereafter, the magnitude of SBF was determined likewise every 30 minutes over the two-hour study. The hemodynamic and respiratory parameters were measured at every 5 minutes in both groups. RESULTS: In comparison with the SCA group, the CCA group had a greater magnitude of skin blood flow (106 +/- 13% vs. 75 +/- 17%; 104 +/- 14% vs. 68 +/- 14% P < 0.01) at the 60th and 120th min. Also, patients who received SCA had higher mean arterial pressure (MABP) (82 +/- 8 vs. 78 +/- 8; 89 +/- 6 vs. 77 +/- 10, P < 0.05) and heart rate (HR) (80 +/- 9 vs. 73 +/- 9; 82 +/- 15 vs. 71 +/- 14, P < 0.05) at the 60th and 120th min. CONCLUSIONS: Closed circuit technique for isoflurane anesthesia is feasible and advantageous. It not only facilitates favorable skin blood flow but also provides better hemodynamic stability in comparison with semiclosed technique for isoflurane anesthesia.