Thermal stress driven Sn whisker growth: in air and in vacuum

Whisker growths from matte tin electroplating have been observed during thermal cycling up to 1,000 cycles either in air or in vacuum. The density, length, and width of thermal stress whiskers depend on the plating thickness of 2 and 5 μm in the present study. Whiskers grown on the 2 μm plating are longer and thinner than those on 5 μm plating. In both cases, whiskers grow thinner and faster in vacuum than in air. These apparent variations come from the grain sizes and the thermal stress distributions in the electroplating, intrinsically different in 2 and 5 μm thick films. The grain structure of whisker root, particularly grain boundary cracks oxidized in air, determines the stress concentration to drive the whisker growth. Cracking caused by oxidation was rarely observed in vacuum hence causes thin and straight whiskers even from thick plating. Our results indicate that the stress concentration at whisker root grain is essential for controlling whisker growth morphology, and has a critical impact on various electronic applications.     

Effect of plate thickness on very low‐cycle fatigue properties of butt welded joints containing weld defects. Study of acceptable defect size in girth welds of gas pipelines (Report 2)

Summary

To develop a joining technology for thick ceramics, the fundamental characteristics of high‐power CO₂ laser welding of 87% A1₂O₃ ceramics have been investigated. The results suggest that a penetration depth of 20 mm is possible at a welding speed of 6.5 mm/sec and laser power of 10 kW. The porosity ratio is lower at lower input powers, also tending to decrease with a decreasing welding speed at the same input power. The bending strength decreases with an increasing porosity ratio. Porosities, especially large sink mark porosities at the bead centre, strongly affect the bending strength of welded joints in alumina ceramics. The root bending strength of 4 mm thick butt‐welded plate has the same value as the base material.     

Fluoroscopic bone fragment tracking for surgical navigation in femur fracture reduction by incorporating optical tracking of hip joint rotation center

A new method for fluoroscopic tracking of a proximal bone fragment in femoral fracture reduction is presented. The proposed method combines 2-D and 3-D image registration from single-view fluoroscopy with tracking of the head center position of the proximal femoral fragment to improve the accuracy of fluoroscopic registration without the need for repeated manual adjustment of the C-arm as required in stereo-view registrations. Kinematic knowledge of the hip joint, which has a positional correspondence with the femoral head center and the pelvis acetabular center, allows the position of the femoral fragment to be determined from pelvis tracking. The stability of the proposed method with respect to fluoroscopic image noise and the desired continuity of the fracture reduction operation is demonstrated, and the accuracy of tracking is shown to be superior to that achievable by single-view image registration, particularly in depth translation.     

Electrochemical Characterization of a Porous Pt Nanoparticle ＂Nanocube-Mosaic＂ Prepared by a Modified Polyol Method with HCI Addition

Porous and single crystalline platinum (Pt) nanoparticles (NPs) have been successfully synthesized by reduction of H₂PtCl₆·6H₂O and then investigated by optical spectroscopy and transmission electron microscopy. H₂PtCl₆·6H₂O was reduced using ethylene glycol in the presence of polyvinylpyrrolidone under highly acidic conditions (pH < 1) to form single crystalline Pt particles about 5 nm in size. These particles were then stacked via {100} facets, forming 50-nm length porous nanocubes with a mosaic structure. The porous Pt NPs exhibited excellent catalytic properties for methanol oxidation. In particular, the electrochemical surface area was ∼63 m²/g, five times higher than that for non-porous Pt NPs prepared using a conventional method. We suggest that the high catalytic activity of porous Pt NPs is due to a combination of the crystalline structure having exposed {100} facets and a porous morphology.      

On-line electrodialytic salt removal in electrospray ionization mass spectrometry of proteins

Salts and buffers, commonly used in isolation and stabilization of biological analytes, have a deleterious effect on electrospray ionization mass spectrometry (ESI-MS). Excessive concentrations of salts lead to ion suppression and adduct formation, which mask or complicate ion signals. In this work, we describe a salt remover (SR), configured as a three-compartment flow-through system, where the central compartment is separated from the outer compartments by a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM). One platinum electrode is placed in each of the outer compartments, where water or electrolyte is flowing. The CEM electrode is held at a negative potential relative to the AEM side; cations/anions migrate by electrophoresis to the CEM/AEM receiver liquids, respectively. Proteins have poorer electrophoretic mobility relative to the buffer components, permitting removal of the salt. The salt-free proteins proceed to the ESI source. The capillary scale SR (internal volume 2.5 μL) described here effectively desalted continuous flows of NaCl solutions (200 mequiv/L at 1 μL/min, equivalent to a flux of 200 nequiv/min with 88% efficiency) and achieved >99.8% salt removal with 154 mM NaCl (isotonic saline) at 1 μL/min. With optimized current, >80% of concurrently present 20 μM protein was transmitted. Desalting efficiency and analyte loss was evaluated with different salt concentration and flow rate combinations under different applied current. Good-quality ESI-MS spectra of cytochrome c, myoglobin, and lysozyme as test proteins in a saline solution, passed through the SR, are demonstrated.     

Time‐of‐flight mobilities for conducting dendrimers composed of p‐phenylenevinylene dendron and triphenylamine surface group

Charge‐carrier transport property of the conducting dendrimer films composed of p‐phenylenevinylene with generation numbers of two and three as a dendron and triphenylamine as a surface group, which were prepared by spin‐coating from the chloroform solutions, was investigated by a time‐of‐flight technique. For both dendrimer films, hole‐carrier transport took place preferentially compared with electron‐carrier transport, and typical dispersive hole‐carrier transport was observed. The hole‐carrier drift mobilities of the two‐generation dendrimer film were one order of magnitude larger than those of the three‐generation dendrimer film. The difference of the hole‐carrier drift mobilities between the two‐generation and three‐generation dendrimers was due to the difference of the molecular geometric structure and/or the difference of the molecular weight ratio of nitrogen atom in the triphenylamine unit to the dendrimer molecule. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Clonazepam oral droplets for the treatment of acute epileptic seizures

Oral droplet formulations of clonazepam (CZ) were developed to examine their potentials as an alternative to i.v. administration for the treatment of acute epileptic seizures. Propylene glycol containing 2.5% (wt/wt) CZ with or without 5.0% (wt/wt) oleic acid (OA) was prepared as a solution by heating at 90 degrees C and subsequently lowering the temperature to 30 degrees C. The droplet (20 microL) was administered to the oral cavity between the lower gum and bottom lip before CZ precipitation started. With a droplet of propylene glycol loaded with 2.5% (wt/wt) CZ and 5.0% (wt/wt) OA, the plasma concentration reached 20 ng/mL (minimal effective concentration) within 10 min and was maintained between 20 and 60 ng/mL, less than a toxic level, for a period of 60 min. For a droplet of propylene glycol loaded only with CZ at 2.5% (wt/wt), it took more than 15 min for the plasma concentration to reach 20 ng/mL. It is suggested that a droplet of CZ/OA/propylene glycol (2.5:5.0:92.5, wt/wt) might be useful as an alternative to i.v. injection of CZ for the treatment of acute epileptic seizures.     

Biomimetic deposition of hydroxyapatite on a synthetic polypeptide with β sheet structure in a solution mimicking body fluid

Deposition of a hydroxyapatite layer with similar structure to bone mineral is an attractive approach to the fabrication of bioactive coating layers to achieve direct bonding to living bone. To get successful coating of a hydroxyapatite layer on an organic polymer using a biomimetic solution, it is essential to find organic substrates that can effectively induce heterogeneous nucleation of hydroxyapatite after exposure to the body environment. Our previous study showed that sericin, a type of silk protein, has the ability to induce hydroxyapatite nucleation in a biomimetic solution when the sericin has a β sheet structure. To confirm the effectiveness of the β sheet structure in hydroxyapatite nucleation, we focused on investigating hydroxyapatite deposition on a synthetic polypeptide with a β sheet structure in a biomimetic solution. The β sheet forming polypeptides with and without carboxyl groups, poly(FE)₃FG, poly(FQ)₃FG, poly(LE)₃LG and poly(LQ)₃LG, were synthesized in this study. All the polypeptides had mainly β sheet structure. After soaking the polypeptide films in 1.5SBF, which has 1.5 times the inorganic ion concentrations of human blood plasma, hydroxyapatite formed on the surfaces of the polypeptides with carboxyl groups, poly(FE)₃FG and poly(LE)₃LG, within 2 days, but not on those without carboxyl groups, poly(FQ)₃FG and poly(LQ)₃LG. We confirmed that the β sheet structure was effective for hydroxyapatite nucleation even in the synthetic polypeptide. This finding is useful for the future design of organic polymers that can effectively induce nucleation of hydroxyapatite.     

Self-assembled molecular nanowires of 6,13-Bis(methylthio)pentacene: growth, electrical properties, and applications

We demonstrate a comprehensive study of self-assembled molecular nanowire, including molecular design, one-dimensional crystal growth, resistivity measurement of individual wire, and application to a field-effect transistor. Appropriate molecular design and control of interfacial interactions lead to single crystalline wire growth with an extensive pi-stacking motif. Resistivity measurements of an individual molecular wire indicate that these structural features are advantageous for electrical transport. Finally, field-effect transistors with single- and double-wire channels were fabricated to give some indication of the potential application of the molecular wires.     

Development of a Dense Electrolyte Thin Film by the Ink-Jet Printing Technique for a Porous LSM Substrate

Recently, the fabrication and development of novel solid oxide fuel cell (SOFC) structures were conducted with the aim of enhancing power generation. Newly cathode-supported honeycomb-type SOFC with a promising power/volume ratio is under development. However, the conventional processing techniques used for the fabrication of different SOFC cell components (electrolyte and electrode) are not compatible with the newly constructed honeycomb structure. The ink-jet printing technique may offer the ability to design and fabricate SOFC components on honeycomb substrates and complex 3D structures. In this study, the formation of a dense Gadolinium-doped ceria thin film on a cathode-supported LaSrMnO₃ substrate by the ink-jet printing technique was investigated.