Influence of surface roughness of Bragg reflectors on resonance characteristics of solidly-mounted resonators

The solidly mounted resonator (SMR) is fabricated using planar processes from a piezoelectric layer sandwiched between two electrodes upon Bragg reflectors, which then are attached to a substrate. To transform the effective acoustic impedance of the substrate to a near zero value, the Bragg reflectors are composed of alternating high and low acoustic impedance layers of quarter-wavelength thickness. This paper presents the influence of Bragg reflector surface roughness on the resonance characteristics of an SMR. Originally, an A1N/A1 multilayer is used as the Bragg reflector. The poor surface roughness of this Bragg reflector results in a poor SMR frequency response. To improve the surface roughness of Bragg reflectors, a molybdenum (Mo)/titanium (Ti) multilayer with a similar coefficient of thermal expansion is adopted. By controlling deposition parameters, the surface roughness of the Bragg reflector is improved, and better resonance characteristics of SMR are obtained.     

Nanoindentation characteristics of clamped freestanding Cu membranes

This research employed instrumented nanoindentation to address the issue of bending to stretching-induced deformation of clamped freestanding Cu membranes. The experimental results show that indentation-induced plastic deformation only comes into effect at the centre and the indented edge of the Cu membrane when the indenter is applied, while the other locations remain undamaged. A step-by-step evolution was presumed for the time histories of the bending to stretching-induced deformation and for the timing of the significant change in slope of the load-deflection curve. Deformation was deliberately introduced at the transition from the single-point bending indentation to the surface stretching indentation at the impact location touched with the indenter. Good elastic recovery was found at locations away from the indenter. A similar finding can be arrived at by means of finite element analysis.     

In vivo monitoring of multiple trace metals in the brain extracellular fluid of anesthetized rats by microdialysis-membrane desalter-ICPMS

We have developed an on-line analytical system involving microdialysis (MD) sampling, a carbohydrate membrane desalter (CMD), and an inductively coupled plasma mass spectrometer (ICPMS) system for the simultaneous determination of multiple trace metals in the extracellular fluid (ECF) in the brains of anesthetized rats. The microdialysate that perfused from the animal at a flow rate of 0.5 microL/min was on-line transferred to the CMD to remove the high-sodium matrix, followed by ICPMS measurement. The role of the CMD in this on-line system was investigated in detail. With prior addition of EDTA to the microdialysate to form anionic complexes of the metal analytes and the use of NH4Cl as a regenerant to exchange Na(+) with NH4(+) ions, both quantitative recovery of the trace metal analytes and quantitative removal of the sodium matrix could be achieved. Two experimental modes of the monitoring system were constructed. For those metals (e.g., Cu, Zn, and Mn) that existed at (sub)nanogram-per-milliliter concentrations in the microdialysate, the temporal resolution was 10 min when using a 10 microL loop for sample collection, followed by CMD and ICPMS; for those elements (e.g., Ca and Mg) that existed at microgram-per-milliliter levels (or greater), near-real-time analysis was possible because the microdialysate could be led, bypassing the sample loop, directly to the CMD for desalting without any time delay. Further improvement of the temporal resolution for the low-concentration elements was not possible without decreasing the detection limits of mass detection. Among the eight trace metals tested using this on-line system, the method detection limits for Cu, Zn, Mn, Co, Ni, and Pb reached subnanogram-per-milliliter levels; for electrolyte species such as Ca and Mg, the detection limits were in the range of 50-100 ng/mL. Analytical accuracy, expressed as spike recovery, was 100% +/- 15% for all of the elements tested. We demonstrate the applicability of the proposed system through the successful measurement of the basal values of Ca, Mg, Cu, Zn, and Mn in the ECF of a living rat brain and through in vivo monitoring of the concentration profiles of Mn and Pt in the ECF after the injection of drugs (MnCl2 and cisplatin) into the rats. This microdialysis system is the first to offer real-time, in vivo monitoring of trace elements such as Ca and Mg.     

Analysis of a two-dimensional photonic bandgap structure fabricated by an interferometric lithographic system

An interferometric lithographic technique and double exposure method are applied to theoretically and experimentally investigate several kinds of 2D periodic structures. The shape, lattice symmetries, and lattice constants of the 2D structures, for different substrate rotational angles, are obtained from the simulated predictions. The shape of the 2D structures can be varied by controlling the rotational angle of the substrate and the development process, and they are validated experimentally. The variation of the lattice symmetry of the 2D structure with the substrate rotational angle is discussed in detail in relation to the axial angle and lattice constant. It is found that square, circular, rectangular, and elliptical scatterers which are arranged in parallelogram, triangular, and square lattices (with different lattice constants) can be obtained. The photonic bandgaps for each condition are also investigated. When the substrate rotational angles are the same, the normalized frequency (omega a/2 pi c) of photonic bandgap structures with an equal filling factor are very similar regardless of the interference angle. The results are helpful in designing the forbidden frequency when the lattice constant and the scatterer shape can be controlled by the interferometric lithographic technique.     

Remediation of groundwater contaminated with DNAPLs by biodegradable oil emulsion

Emulsion-based remediation with biodegradable vegetable oils was investigated as an alternative technology for the treatment of subsurface DNAPLs (dense non-aqueous phase liquids) such as TCE (trichloroethylene) and PCE (perchloroethylene). Corn and olive oil emulsions obtained by homogenization at 8000rpm for 15min were used. The emulsion droplets prepared with corn and olive oil gave a similar size distribution (1-10microm) and almost all of initially injected oil, >90%, remained in a dispersed state. In batch experiments, 2% (v/v) oil emulsion could adsorb up to 11,000ppm of TCE or 18,000ppm of PCE without creating a free phase. Results of one-dimensional column flushing studies indicated that contaminants with high aqueous solubility could be efficiently removed by flushing with vegetable oil emulsions. Removal efficiencies exceeded 98% for TCE and PCE with both corn and olive oil emulsions. The results of this study show that flushing with biodegradable oil emulsion can be used for the remediation of groundwater contaminated by DNAPLs.     

UV light induced photodegradation of malachite green on TiO2 nanoparticles

The photodegradation of malachite green (MG), a cationic triphenylmethane dye, is examined both under different pH values and amounts of TiO(2). After 15W UV-365nm irradiation for 4h, ca. 99.9% of MG was degraded with addition of 0.5gL(-1) TiO(2) to solutions containing 50mgL(-1) of the MG dye. The HPLC-PDA-ESI-MS technique was used to obtain a better understanding on the mechanistic details of this TiO(2)-assisted photodegradation of the MG dye with UV irradiation. Five intermediates of the process were separated, identified, and characterized for the first time. The results indicated that the N-de-methylation degradation of MG dye took place in a stepwise manner to yield mono-, di-, tri-, and tetra-N-de-methylated MG species generated during the processes. Under acidic conditions, the results indicated that the photodegradation mechanism is favorable to cleavage of the whole conjugated chromophore structure of the MG dye. Under basic conditions, the results showed that the photodegradation mechanism is favorable to a formation of a series of N-de-methylated intermediates of the MG dye.     

A method for preparing ferric activated carbon composites adsorbents to remove arsenic from drinking water

Iron oxide/activated carbon (FeO/AC) composite adsorbent material, which was used to modify the coal-based activated carbon (AC) 12 x 40, was prepared by the special ferric oxide microcrystal in this study. This composite can be used as the adsorbent to remove arsenic from drinking water, and Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Then, the arsenic desorption can subsequently be separated from the medium by using a 1% aqueous NaOH solution. The apparent characters and physical chemistry performances of FeO/AC composite were investigated by X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Batch and column adsorption experiments were carried out to investigate and compare the arsenic removal capability of the prepared FeO/AC composite material and virgin activated carbon. It can be concluded that: (1) the main phase present in this composite are magnetite (Fe(3)O(4)), maghemite (gamma-Fe(2)O(3)), hematite (alpha-Fe(2)O(3)) and goethite (alpha-FeO(OH)); (2) the presence of iron oxides did not significantly affect the surface area or the pore structure of the activated carbon; (3) the comparisons between the adsorption isotherms of arsenic from aqueous solution onto the composite and virgin activated carbon showed that the FeO/AC composite behave an excellent capacity of adsorption arsenic than the virgin activated carbon; (4) column adsorption experiments with FeO/AC composite adsorbent showed that the arsenic could be removed to below 0.01 mg/L within 1250 mL empty bed volume when influent concentration was 0.5mg/L.     

Inhibition of polybrominated dibenzo-p-dioxin and dibenzofuran formation from the pyrolysis of printed circuit boards

Waste printed circuit boards containing brominated flame retardants were pyrolyzed in a high-temperature melting system to observe the formation behaviors of polybrominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs). In this study, the results showed that the formation of PBDD/ Fs during pyrolysis can be destroyed under controlled primary combustion conditions. There were two significant factors that influenced the extent of PBDD/F formation. The first factor was temperature. The results showed that, both the total PBDD/F content in the bottom ash and the total PBDD/F emission factor from the flue gas decrease by approximately 50% with an increase of the pyrolysis temperature from 850 to 1200 degrees C. The second factor was the addition of CaO. The possible mechanism involves the reaction between CaO and HBr to form the solid-phase product CaBr2. Thus, the addition of CaO is effective in adsorbing HBr and results in the inhibition of PBDD/F synthesis by more than 90% and further prevents the acid gases (HCl and HBr) that corrode the equipment. In conclusion, due to the persistence and toxicity of PBDD/Fs, a combined regulation for controlling both PCDD/Fs and PBDD/Fs is of great importance for environmental protection issues.     

An innovative microelectrode fabricated using photolithography for measuring dissolved oxygen distributions in aerobic granules

In this work an innovative microelectrode was successfully fabricated using photolithography for determination of dissolved oxygen distributions in aerobic granules, which were sampled from a nitrifying sequencing batch reactor. A negative photoresist, SU-8, was used as a substrate for the microelectrode and a 70 microm wide needle was photopatterned on it. The microelectrode could be renewed several times. Cyclic voltammetry analysis and dissolved oxygen measurement demonstrated that the microelectrode was stable and reliable. Dissolved oxygen distribution in a nitrifying granule was successfully monitored with the microelectrode. The profiles indicated that the main active part of the nitrifying granule was the upper 150 microm layer. Using the procedures developed in this work, microelectrodes of the desired shape could be constructed with precise size control at micrometers-scale.     

Schisandrin enhances dendrite outgrowth and synaptogenesis in primary cultured hippocampal neurons

BACKGROUND: Schisandra chinensis, commonly used in Asia for tea material and traditional Chinese medicine, is presumed to enhance mental and intellectual functions. In this study, the effects and signalling mechanisms of a purified compound schisandrin, one of the lignan of Schisandra chinensis, on primary cultured hippocampal neurons were investigated. RESULTS: Schisandrin treatment enhanced total dendritic length and branching complexity, both of which were significantly suppressed in the presence of specific blockers for calmodulin‐dependent kinase II (CaMKII), protein kinase C epsilon (PKCε), and mitogen activated protein kinase kinase (MEK). Moreover, schisandrin induced calcium influx, and phosphorylation of CaMKII, PKCε, and MEK. Inhibition of CAMKII and PKCε attenuated the schisandrin‐induced phosphorylation of PKCε and MEK, and the phosphorylation of MEK, respectively. Moreover, schisandrin also stimulated the phosphorylation of cyclic AMP responsive‐element binding protein (CREB) at Ser‐133, an effect that was blocked by KN93. In addition to its neuritogenic effects, schisandrin increased the numbers of postsynaptic density‐95‐positive and FM1‐43‐positive puncta in dendrites and synaptic boutons, respectively. CONCLUSION: In hippocampal neurons, schisandrin exhibits neurotrophic properties that are mediated by the CaMKII‐PKCε‐MEK pathway. Copyright © 2010 Society of Chemical Industry