Oxide-confined monolithic, multiple-wavelength vertical-cavitysurface-emitting laser arrays with a 40-nm wavelength span

Monolithic, multiple-wavelength, vertical-cavity surface-emitting laser arrays grown by controlling the metal-organic chemical vapor deposition epitaxial growth rate on a patterned substrate, and using selective oxidation for current confinement, have been demonstrated with a periodic, graded wavelength span of 40 nm, Near room-temperature, electrically pumped continuous-wave lasing is achieved over the entire 40-nm range, with uniform threshold currents of 4.5 mA±1.0 mA, and with output powers ranging from 0.4-1.3 mW     

Monolithic, multiple-wavelength vertical-cavity surface-emitting laser arrays by surface-controlled MOCVD growth rate enhancement and reduction

Monolithic, multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays have been obtained by the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate, achieving a periodic, graded wavelength span greater than 30 nm. Room-temperature (RT), electrically pumped continuous-wave (CW) lasing is demonstrated, with uniform threshold currents of 5.5/spl plusmn/0.5 mA with typical output powers of 0.5 mW. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure and demonstrate the controlled variation of the VCSEL lasing wavelength over a widened spectral range by exploiting both effects.     

Effect of surface charge on the cellular uptake and cytotoxicity of fluorescent labeled cellulose nanocrystals

Probing of cellular uptake and cytotoxicity was conducted for two fluorescent cellulose nanocrystals (CNCs): CNC-fluorescein isothiocyanate (FITC) and newly synthesized CNC-rhodamine B isothiocyanate (RBITC). The positively charged CNC-RBITC was uptaken by human embryonic kidney 293 (HEK 293) and Spodoptera frugiperda (Sf9) cells without affecting the cell membrane integrity. The cell viability assay and cell-based impedance spectroscopy revealed no noticeably cytotoxic effect of the CNC-RBITC conjugate. However, no significant internalization of negatively charged CNC-FITC was observed at physiological pH. Indeed, the effector cells were surrounded by CNC-FITC, leading to eventual cell rupture. As the surface charge of CNC played an important role in cellular uptake and cytotoxicity, facile surface functionalization together with observed noncytotoxicity rendered modified CNC as a promising candidate for bioimaging and drug delivery systems.     

Porous graphitized carbon monolith as an electrode material for probing direct bioelectrochemistry and selective detection of hydrogen peroxide

For the first time, graphitized carbon particles with a high surface area have been prepared and evaluated as a new material for probing direct electrochemistry of hemoglobin (Hb). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging revealed that the carbon monolithic skeleton was constructed by a series of mesopores with irregular shapes and an average pore diameter of ~5.6 nm. With a surface area of 239.6 m(2)/g, carbon particles exhibited three major Raman peaks as commonly observed for carbon nanotubes and other carbon materials, i.e., the sp(3) and sp(2) carbon phases coexisted in the sample. A glassy carbon electrode modified with carbon monoliths and didodecyldimethylammonium bromide exhibited direct electron transfer between Hb molecules and the underlying electrode with a transfer rate constant of 6.87 s(-1). The enzyme electrode displayed a pair of quasi-reversible reduction-oxidation peaks at -0.128 and -0.180 V, reflecting the well-known feature of the heme [Fe(3+)/Fe(2+)] redox couple: a surface-controlled electrochemical process with one electron transfer. This reagentless biosensing approach was capable of detecting H(2)O(2), a simple molecule but plays an important role in analytical and biological chemistry, as low as 0.1 μM with linearity of 0.1-60 μM and a response time of <0.8 s, comparing favorably with other carbon based electrodes (5 s).     

Adhesion Properties of Milled CuO-CeO2/γ-Al2O3 on Metallic Substrate for Automotive Catalytic Converter

Adhesion properties of CuO-CeO₂/γ-Al₂O₃ layers on FeCrAl metallic substrate was investigated, where the hybrid preparation method between suspension and sol-gel is further combined with the mechanical milling process of the slurry. Poor coating adhesion was observed when the slurry is vigorously stirred, where the milled powders are agglomerated, and the stirring process hardly reduces the particle size. The combined method was found to significantly improve the adhesion property between the milled CuO-CeO₂ catalytic layer and the γ-Al₂O₃ washcoat, compared with the vigorous stirring of the slurry. The so-called “over-milling” phenomenon was also exhibited, where the elongated large particles are observed after sintering of the longer-milled powders, leading to the lowered adhesion quality.     

Knowledge-based tool for planning of enterprise resources in ASEAN SMEs

Manufacturing has been identified as a key pillar of growth in many Southeast Asian (ASEAN) economies. However, in the last decade many countries have become keen competitors for foreign direct investments. Many countries are trying to improve their total business capabilities by encouraging computerisation of small and medium sized enterprises (SME). Manufacturing SMEs (M-SMEs) are tasked to adopt technologically advanced programmes. With an improving public education system and more literate work force, more SMEs are better positioned to tap into the knowledge-based economy. There is tremendous amount of knowledge intensive activities within the multi-flows of the M-SMEs.Although the concept of ERP systems and artificial intelligence (AI) techniques have been around for more than two decades, this has largely remained the domain of the larger companies. ASEAN M-SMEs have been slow to implement it. In this paper, the various strategic and operational requirements of regional M-SMEs are presented and a knowledge-based resources planning model making use of AI techniques is proposed. This improved AI model makes use of the large amount of accumulated knowledge typically found in the M-SMEs, especially those in the electronics and precision engineering sectors. This includes a case study of how an electronics precision engineering company adopted the proposed AI model.     

Light-assisted synthesis of Pt-Zn porphyrin nanocomposites and their use for electrochemical detection of organohalides

Pt-Zn porphyrin nanocomposites have been synthesized using zinc porphyrin and dihydrogen hexachloroplatinate in the presence of light and ascorbic acid. TEM and AFM imaging revealed that Pt nanoparticles with an average diameter of approximately 3.5 nm were embedded within the Zn porphyrin matrix. The glassy carbon electrode was modified with Nafion-stabilized Pt-Zn porphyrin nanocomposites and used for dehalogenation of carbon tetrachloride, chloroform, pentachlorophenol, chlorobenzene, and hexachlorobenzene as five test models. The Pt-Zn porphyrin nanocomposite-modified electrode exhibited catalytic activity for the reduction of organohalides at -1.0 V versus Ag/AgCl. Raman signatures confirmed the dehalogenation of chlorobenzene by the nanocomposite-modified electrode. The above two aliphatic and three aromatic organohalides had detection limits of 0.5 microM with linearity up to 8 microM. The modified electrode was good for at least 80 repeated measurements of 4 microM chlorobenzene with a storage stability of 1 month at room temperature. The deactivation of the electrode activity was associated with the loss of platinum nanoparticles from the nanocomposite structure.     

Kinetically-calibrated solid-phase microextraction using label-free standards and its application for pharmaceutical analysis

Pre-equilibrium solid-phase microextraction (PE-SPME) has attracted considerable research attention due to shorter sampling times and better temporal resolution than afforded by equilibrium SPME (E-SPME). However, the calibration of PE-SPME is often time-consuming and requires deuterated calibrants, which if available, are often expensive. To address these challenges, we propose a simple but versatile kinetic calibration method, in which nonisotopic (label-free) compounds of interest can supplant the use of deuterated analogues, and the need to determine partitioning coefficients inherent to earlier procedures has been eliminated. Using this approach, both free and total concentrations of analytes can be simultaneously measured within complex sample systems with high accuracy and precision. This calibration method was validated against established E-SPME and solid-phase extraction techniques through the measurement of selected pharmaceuticals in progressively complex matrixes including inorganic buffers, fish blood, and municipal wastewater effluents. This calibration approach may significantly improve time and cost-effectiveness, while improving the application of the SPME approach within highly dynamic systems.     

Smart dynamic evacuation planning and online management using vehicular communication system

During disasters, swiftly and efficiently evacuating populations in hazardous situations is crucial to minimize losses. This study proposes a novel framework to address dynamic population evacuation (DPE) problems, which includes planning and online evacuation management phases facilitated by vehicular communication. In the planning phase, a shelter allocation problem (SAP) is solved dynamically for destination choice and a dynamic traffic assignment (DTA) for path choice toward the chosen destinations to obtain an initial evacuation plan. The initial plan is then enhanced by employing a vehicular ad hoc network (VANET) within the vehicular edge computing (VEC) architecture. This enhancement enables communication among evacuees, allowing them to revise their vehicle's route choice and planned destination. These revisions take into account the changing risk and traffic conditions. The proposed online DPE framework is applied to the real evacuation scenario of Mill Valley City, CA. The proposed model is evaluated with different VANET architectures, including vehicular cloud computing (VCC) and VEC. The results show that the VEC framework outperforms other configurations and improves the evacuation process compared to the scenario with an initial plan by more than 30% in network clearance time. Additionally, a performance analysis is carried out for evacuation scenarios with different penetration rates of connected vehicles in VANET.