The formation and characterization of diamond crystallites by microwave plasma enhanced chemical vapor deposition – a comparison of gaseous and solid carbon sources as precursors

Commercial diamond powders are in irregular shapes and have been used as seeds for growing well crystallized fine diamond grits in this study. The surfaces of irregular diamond particles would serve as the seed for the subsequent growth of the diamond crystallites using microwave enhanced chemical vapor deposition (MPECVD). Both gaseous and solid carbon sources were used to transform the irregular shaped diamond seeds with sharp edges and corners along with the increase in size to the final equilibrium form of diamond crystallites. In case of gaseous carbon source, the effect of increasing methane content and applying negative dc bias voltage on the formation of diamond crystallites was significant. While in case of solid carbon source, well-faceted diamond crystallites can he extracted from the molten metal-carbon-hydrogen (M-C-H) system. Surface etch pits are numerous; especially noticeable after long exposure in hydrogen plasma. Both growth rates of diamond crystallite irrespective of the carbon sources tend to be parabolic at the later stage of growth. Electronic Publication     

A study of mass transfer in a packed bed reactor by electrochemical technique

Electrochemical method was used to study the mass transfer between the solid particles and the flowing liquid in a packed bed. From the limiting current of a single active particle immersed in inactive glass particles of the same size and shape, the mass transfer coefficients can be derived.Various size and shape of packing particles were used. The experimental results indicate that smaller packing particles have higher mass transfer coefficient. In the meantime, spherical packing particles have higher mass transfer coefficients than cylindrical particles of the same equivalent diameter. However they approach each other when liquid flowing velocity is increased.The wall-effect of the reactor on mass transfer was also observed.     

Microstructural characteristics of immersion tin coatings on copper circuitries in circuit boards

Immersion tin coating, which is used as a lead-free surface finish, is deposited on the surface of copper circuitries on circuit boards by a replacement reaction. The characteristics of immersion tin coatings and the formation of tin whiskers and the intermetallic compound (IMC) are described. A Cu₆Sn₅ phase forms at the beginning of the immersion-plating process and expands until all of the tin has been transformed into a copper-tin alloy. The IMC layer becomes thicker and the volume of the pure tin layer decreases during storage. The tin involved in the formation of whiskers must originate from the tin layer of the immersion tin coating. Therefore, the formation of tin whiskers stops when all of the tin has been expended. Moreover, relatively larger whiskers grow on thicker coating layers, which contain more tin.     

Superoxide counteracts low-density lipoprotein-induced human aortic smooth muscle cell proliferation

Previously, we demonstrated that the level of intracellular O(2)(-) is increased by low-density lipoprotein (LDL) in human aortic smooth muscle cells (HASMCs). The exact role of O(2)(-) in the LDL-induced proliferation of HASMCs, however, has not been determined. In this study, we found that the increase in the concentrations of intracellular O(2)(-) induced by native and oxidized LDL increased SMC-nitric oxide (NO) uptake rate. Moreover, the treatment of HASMCs with diethyldithiocarbamate (DETC), a superoxide dismutase inhibitor, significantly increased NO uptake rate owing to the increase in intracellular O(2)(-) concentrations. Although native and oxidized LDL decreased soluble guanylyl cyclase (sGC) protein content, they still caused a net increase in cyclic GMP production in HASMCs. In addition, when cyclic GMP production was normalized by sGC protein content and NO uptake rate, it was found to be positively dependent on the level of intracellular H(2)O(2). Finally, we simulated cell proliferation stimulated by native and oxidized LDL as a linear function of intracellular O(2)(-) and H(2)O(2) concentrations, demonstrating that O(2)(-) negatively modulated the native and oxidized LDL-stimulated HASMC proliferation through the increase in NO uptake rate.     

Research on applying direct plating to additive process for printed circuit board

The feasibility of applying direct-metallization as an additive process for printed circuit board was explored. Pd/Sn catalyst was used in the activation step and the content of Pd adsorption was found to be the controlling factor. The Pd content was affected by the conditions of various steps including condition, activation, acceleration, and promotion. The sequence of applying photoresist and activation with Pd/Sn catalyst plus promotion with Na₂S solution was also studied. It was found that a well-defined pattern could be obtained by applying the Pd/Sn catalyst layer before applying the photo-resist film. If the photoresist was applied before the activation step, copper deposition tended to develop beyond the desired pattern region on the surface. We also found that the lateral growth rate of copper deposition was inversely affected by the concentration of copper sulfate. This can be explained by a deposition model in which the lateral growth of copper deposition is caused by the charge transfer of the sulfur atom as a bridging ligand.     

Characterization of electroless Ni-based alloys for use in bipolar plates of direct methanol fuel cells

In this study, an electroless Ni-P deposit is employed as an anodic coating layer to protect the metallic bipolar plate of a direct methanol fuel cell (DMFC). An inductively coupled plasma-mass spectrometer, grazing incidence X-ray diffractometer, and potentiodynamic polarization measurements were used to study changes in the composition, crystalline structures and corrosion resistance of the Ni-P deposits at various bath pHs and temperatures. The crystalline structure of the Ni-P deposits was observed to change from crystal to amorphous as the P content increased, thus enhancing the corrosion resistance of the plate. The optimal conditions for obtaining the highest P content were found to be at pH 4.3 and 70 °C. Furthermore, the potentiostatic test for the Ni-P deposits prepared under the optimal condition was performed in a simulated anode working environment (0.5 M H₂SO₄ + 10 vol.% methanol), with the test showing that a negative corrosion current was observed at all times, therefore indicating that cathodic protection was employed throughout. Even after 10 h of potentiostatic treatment, no metal ions were found in a test solution. In addition, the result of a DMFC performance test demonstrated that bipolar plates using an anticorrosion coating of Ni-P deposits obtained a lower bulk resistance and an enhanced cell performance when compared to commercially available plates. Hence, the low-cost electroless Ni-P deposit demonstrates high potential for use as a corrosion protection layer in a DMFC bipolar plate with a Cu interlayer.     

Private Authentication Techniques for the Global Mobility Network

Numerous authentication approaches have been proposed recently for the global mobility network (GLOMONET), which provides mobile users with global roaming services. In these authentication schemes, the home network operators can easily obtain the authentication key and wiretap the confidentiality between the roaming user and the visited network. This investigation provides a solution of authentication techniques for GLOMONET in order to prevent this weakness from happening and presents a secure authentication protocol for roaming services. In addition, a round-efficient version of the same authentication protocol is presented. Comparing with other related approaches, the proposed authentication protocol involves fewer messages and rounds in communication. Tian-Fu Lee was born in Tainan, Taiwan, ROC, in 1969. He received his B.S. degree in Applied Mathematics from National Chung Hsing University, Taiwan, in 1992, and his M.S. degree in Computer Science and Information Engineering from National Chung Cheng University, Taiwan, in 1998. He works as a lecturer in Leader University and pursues his Ph.D. degree at Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan. His research interests include cryptography and network security. Chi-Chao Chang received the BS degree in Microbiology from Soochow University in 1990 and the MS degree in Computer Science from State University of New York at Albany in 1992. He is currently working as an instructor in Chang Jung Christian University and a graduate student in National Cheng Kung University. His research interests are information security, mobile agent systems, anonymous digital signatures and quantum cryptography. Tzonelih Hwang was born in Tainan, Taiwan, in March 1958. He received his undergraduate degree from National Cheng Kung University, Tainan, Taiwan, in 1980, and the M.S. and Ph.D. degrees in Computer Science from the University of Southwestern Louisiana, USA, in 1988. He is presently a professor in Department of Computer Science and Information Engineering, National Cheng Kung University. His research interests include cryptology, network security, and coding theory.     

High-performance and low platinum loading electrodeposited-Pt counter electrodes for dye-sensitized solar cells

This study demonstrates platinum (Pt) counter electrodes with low charge-transfer resistance (R_ct), low Pt loading and high active surface area can be obtained within 30 s by using the direct-current deposition in the presence of 3-(2-aminoethylamino)propyl-methyldimethoxysilane (Me-EDA-Si) as an additive. The addition of appropriate Me-EDA-Si can not only enhance the current efficiency but also inhibit the growth of semicircle-like grains, thus resulting in Pt electrode with high active surface area. Consequently, the dye-sensitized solar cells (DSSCs) fabricated with so-prepared Pt electrodes exhibited cell efficiency of 7.39% while 0.01 vol% Me-EDA-Si was added, which is much superior to that with sputtered-Pt electrodes under the same assembly conditions.     

Effects of Surfactant Addition on Dewatering of Alum Sludges

In Taiwan, surfactants are frequently used in the flotation process to aid in solid/liquid separation. Their effect on the dewatering of alum sludge was investigated. Various amounts of cationic and anionic surfactants were added to sludge samples, and the dewatering characteristics of the sludge and the water content of sludge cakes were evaluated. Both surfactants improved the dewatering of the sludge by lowering the specific resistance to filtration, decreasing the bound water content, and increasing the dewatering rate of the sludge. Different combinations of anionic and cationic surfactants and polyelectrolytes were also experimented on to study the effect of surfactant addition on the dewatering characteristics of polyelectrolyte-conditioned sludge. Experimental results indicated that both cationic and anionic surfactants adversely affected the dewatering of the conditioned sludge. The addition of surfactant to the oppositely charged polyelectrolyte proved to be most detrimental to sludge dewatering due to the precipitation between surfactant and polyelectrolyte. The addition of cationic surfactant to the cationic polyelectrolyte-conditioned sludge had the least effect.     

Ocular Stem Cell Research from Basic Science to Clinical Application: A Report from Zhongshan Ophthalmic Center Ocular Stem Cell Symposium

Stem cells hold promise for treating a wide variety of diseases, including degenerative disorders of the eye. The eye is an ideal organ for stem cell therapy because of its relative immunological privilege, surgical accessibility, and its being a self-contained system. The eye also has many potential target diseases amenable to stem cell-based treatment, such as corneal limbal stem cell deficiency, glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa (RP). Among them, AMD and glaucoma are the two most common diseases, affecting over 200 million people worldwide. Recent results on the clinical trial of retinal pigment epithelial (RPE) cells from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) in treating dry AMD and Stargardt’s disease in the US, Japan, England, and China have generated great excitement and hope. This marks the beginning of the ocular stem cell therapy era. The recent Zhongshan Ophthalmic Center Ocular Stem Cell Symposium discussed the potential applications of various stem cell types in stem cell-based therapies, drug discoveries and tissue engineering for treating ocular diseases.