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Three-dimensional (3D) integration using through-silicon vias (TSVs) and low-volume lead-free solder interconnects allows the formation of high signal bandwidth, fine pitch, and short-distance interconnections in stacked dies. There are several approaches for 3D chip stacking including chip to chip, chip to wafer, and wafer to wafer. Chip-to-chip integration and chip-to-wafer integration offer the ability to stack known good dies, which can lead to higher yields without integrated redundancy. In the future, with structure and process optimization, wafer-to-wafer integration may provide an ultimate solution for the highest manufacturing throughput assuming a high yield and minimal loss of good dies and wafers. In the near term, chip-to-chip and chip-to-wafer integration may offer high yield, high flexibility, and high performance with added time-to-market advantages. In this work, results are reported for 3D integration aider using a chip-to-wafer assembly process using 3D chip-stacking technology and fine-pitch interconnects with lead-free solder. Stacks of up to six dies were assembled and characterized using lead-free solder interconnections that were less than 6 [micro]m in height. The average resistance of the TSV including the lead-free solder interconnect was as low as 21 m[OMEGA].

The replacement of lead (Pb)-bearing solders used in the electronic industry with Pb-free solders will become a reality in the near future. Several promising Pb-free solders have recently been identified, including Sn--0.7Cu, Sn--3.5Ag, Sn--3.8Ag--0.7Cu, and Sn--3.5Ag--4.8Bi (in wt. % with slight variations in composition). These are all Sn-rich solders with melting temperatures between 210[degrees]C and 227[degrees]C, and are recommended for various soldering applications, including surface mount technology (SMT), plated-through-hole (PTH), ball grid array (BGA), flip-chip bumping, and others. Although a considerable amount of information on Pb-free solders has been published in the last few years, the database on these new materials is still at an infant stage compared with that for Pb-containing solders. This paper addresses several aspects of the current fundamental materials understanding associated with Pb-free solders and various issues regarding their imminent use in electronic interconnect applications, including microstructure-processing-property relations, mechanical properties, intefacial reactions, and the thermal-fatigue life and failure mechanisms of Pb-free solder joints.

Thermal behaviors of EAF dust, water-washed EAF dust, and EAF dust/heavy clay mixtures with wet mixing process were characterized by TG/ DTA analysis. The ionic concentrations of some metal ions and anions in the supernatant from water-washing process were evaluated by ICP and IC analysis. Weight loss of water-washed EAF dust above the temperature range of 1000℃ was significantly decreased because of the washing effect of chloride and sulfate compounds. The variation of volatile ZnO and PbO contents were not detected in 20wt% D dust-80wt% clay sample. The wet mixing process not only enhanced the homogeneous mixing of EAF dust and clay particles, but also reduced the volatilization of heavy metals(Zn, Pb, etc.) at the high temperature range.

Brick samples were prepared through vitrification process with two different kinds of EAF dust. Leaching concentrations of various metal ions and anions for the bricks(20wt% EAF dust-80wt% clay) were evaluated by ICP and IC analysis. The results of leaching test showed that the concentration of ions leached from bricks were proportional to the square root of time and saturated with leaching time. The saturated concentrations of alkali and alkali-earth metal ions were 0.1-250ppm; on the other hand, the heavy metal ions were 0-0.084ppm. The efflorescence mechanism of EAF dust-clay bricks was studied by quantitative analysis for the effects of various metal ions and anions. Efflorescence formed on the brick surfaces which were immersed in DI water and dried slowly in the air were characterized by SEM, EDS and XRD. The results of EDS and XRD showed that the main component of the efflorescence was water soluble Na2SO4 .

Current baculovirus expression systems typically produce soluble proteins that accumulate within the infected insect cell or are secreted into the growth medium. A system has now been developed for the incorporation of foreign proteins, along with the matrix protein, polyhedrin, into baculovirus occlusion bodies. Initial studies showed that a recombinant virus expressing a translational fusion between polyhedrin and GFP did not form occlusion bodies. However, a baculovirus coexpressing native polyhedrin and the polyhedrin-GFP fusion protein formed occlusion bodies that fluoresced under UV light, demonstrating that they included the polyhedrin-GFP fusion protein. This was confirmed by immunoblot analysis. Thus, incorporation of a foreign protein into occlusion bodies depends on an interaction between native polyhedrin and the polyhedrin fusion protein. Electron microscopy demonstrated that the occlusion bodies containing GFP also incorporated virions as expected. These ColorPol occlusion bodies were as infectious to insect larvae as occlusion bodies produced by wild-type virus. This new system expands the capabilities for foreign gene expression by baculoviruses, which has implications for biopesticide design, novel vaccine delivery systems, and fusion protein purification applications.

AbstractTwo aspects of hypernatremia are emphasized in this discussion: pathogenesis and treatment. Hypernatremia rarely develops with increased water loss alone; there must be a mechanism that interferes with water intake. In treating hypernatremia, the speed of correction is important because the volume regulation mechanisms restore the brain volume to normal when hypernatremia is chronic. Thus, too rapid correction of chronic hypernatremia results in brain edema. The calculation of fluid volume needed to correct hypernatremia can be obtained with use of various formulae described here for the fluid that contains dextrose in water or for hypotonic saline solution. Accurate prediction of the fluid volume requirement demands the knowledge of urine output and its electrolyte content, but when the information is not available, urine may be assumed to be isotonic in its electrolyte content.Copyright © 2002 S. Karger AG, Basel

Embryonic stem (ES) cells, which have pluripotency in differentiation, have been considered as an excellent source for cell replacement therapy of damaged tissues. Although neurotrophic factors induce neural differentiation in neural precursor cells, their actions in ES cells are not clear. This study was designated to examine the effect of brain-derived neurotrophic factor (BDNF) on neural differentiation in mouse ES cells. Undifferentiated mouse ES cells were maintained at suspension culture in the presence of leukemia inhibitory factor (LIF), and neural precursor cells were isolated from the subventricular zone (SVZ) of the 2–3 day old mice brain. Oct-4 was expressed in undifferentiated ES cells and neural precursor cells, of which expression was markedly decreased by induction of differentiation. RT-PCR analysis showed that neural differentiation of ES cells induced expression of various neural markers, and that BDNF increased their expression. Western blot analysis demonstrated that BDNF induced expression of synaptophysin, a neuronal marker, and inhibited expression of glial fibrillary acidic protein, a glial marker. Undifferentiated ES cells expressed TrkA, TrkB and TrkC, of which expressions were increased during differentiation. Neural differentiation increased their expression, and BDNF further increased them. The treatment of BDNF during differentiation decreased expression of Notch1. These results indicated that BDNF induces neural differentiation and inhibits glial differentiation in ES cells as well as neuronal precursor cells.

X protein of hepatitis B virus (HBV-X) is a transactivator to a wide variety of viral and cellular transcriptional regulatory elements. Since HBV-X does not act on a common cis-regulatory element of a wide variety of regulatory elements nor does it bind to DNA directly, it has been proposed that HBV-X acts indirectly through protein-protein interactions with other transcription factors or signal transducing pathway. In order to determine the functional domain of HBV-X, we have constructed and analyzed a number of deletion and site specific mutants. Our results showed that leucine zipper-like sequences were found in the C-terminal region of HBV-X and were very important for its transactivating activity. In the analysis of deletion mutants, seven conserved and strong basic amino acids (amino acids 135-141) were essential for the transactivating activity of HBV-X.

Bacillus thuringiensis NT0423 newly isolated from sericultural farms in Korea produces quite atypical bipyramidal crystals of a common major band of ca. 130 kDa, and has dual specificity against Lepidoptera and Diptera. To enforce the Diptera toxicity of B. thuringiensis NT0423, cryIVD and cytA genes were transformed into B. thuringiensis NT0423. The transformant B. thuringiensis PT0529 was obtained from introduction of pCG5 into B. thuringiensis NT0423 by electroporation. The expression of crystal proteins in B. thuringiensis PT0529 was characterized by SDS-PAGE and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were clearly observed in B. thuringiensis PT0529. Furthermore, the toxicity of B. thuringiensis PT0529 against Diptera was highly enforced by synergistic effect.Copyright 1995, 1999 Academic Press, Inc.

Effect of IIIVratio on the quality of GaN epilayers has been investigated. GaN films were grown on the c-plane of sapphire by using radio frequency (RF) nitrogen plasma-assisted molecular beam epitaxy (MBE). A home-made III–V nitride MBE system consisted of an inductively coupled RF nitrogen plasma source and solid source effusion cells were used to grow GaN films. The results of reflection high energy electron beam diffraction (RHEED) and double crystal X-ray diffraction indicate that crystal quality of GaN epilayers is strongly dependent on the Ga flux. Room temperature photoluminescence spectrum of undoped GaN epilayer is peaked at 3.39 eV and no discernible yellow luminescence resulting from ion damages are observed. Effect of Mg flux on the carrier concentration of p-GaN have also been investigated. Fairly uniform p-doping concentration as high as 5.33 × 1018/cm3throughout the GaN crystal were obtained. The sample grown with TGa= 900°C and TMg= 130°C exhibits very streaky RHEED patterns and the highest p-type doping concentration.

The present study investigated the expression of ligand and receptor for leptin, and the effect of leptin supplementation on preimplantation development of porcine in vitro-fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos. The IVF embryos were produced using frozen boar semen and SCNT embryos were obtained by nuclear transfer of fetal fibroblasts into enucleated oocytes. In Exp. 1, in vitro-matured porcine oocytes and embryos in 2-, 4-, and 8-cell as well as morula and blastocyst stages derived from IVF or SCNT were immunostained for leptin ligand and receptor with their specific antibodies. The expression of leptin ligand and receptor proteins was detected in oocytes and all stages of IVF and SCNT embryos. The IVF (Exp. 2; n = 635, 630, 633, 635, respectively) or SCNT oocytes (Exp. 3; n = 256, 258, 251, 258, respectively) were cultured in modified North Carolina State University (mNCSU)-23 medium supplemented with various concentrations (1, 10, 100, or 1000 ng/mL) of leptin. For the control group, IVF (n = 635) or SCNT embryos (n = 249) were cultured without leptin supplementation (0 ng/mL leptin). Embryo development and cell number in blatoscysts after differential staining according to a modified staining procedure (Thouas et al. 2000 Reprod. Biomed. Online 3, 25?29) were evaluated. The IVF or SCNT embryos were randomly distributed, and experiments were replicated at least 11 times. The differences in embryo development among experimental groups were analyzed using one-way ANOVA after arcsine transformation (without arcsine transformation for cell number of blastocysts) to maintain homogeneity of variance. Post hoc analyses to identify between-group differences were performed using the LSD test. In SCNT embryos, the cleavage rate was not different in leptin-treated groups (73.8, 77.5, 75.7, or 78.7%, respectively) compared to the control (76.3%). The rate of blastocyst formation (at 166 h after the day of injection of donor cells) in SCNT embryos was significantly increased (P < 0.05) in 1000 ng/mL leptin-supplemented group (20.2%) compared with the control (12.9%) and 1 ng/mL leptin-supplemented (12.5%) groups. Supplementing mNCSU-23 with 1000 ng/mL leptin also significantly increased (P < 0.05) the number of total cells (54.6) and trophectoderm (TE) cells (39.1) in SCNT blastocysts (n = >25) compared with the control [45.1 (total cells) and 31.6 (TE cells)] and 10 ng/mL leptin-supplemented group [44.4 (total cells) and 31.7 (TE cells)]. In IVF embryos, leptin supplementation did not affect pre-implantation embryo development and cell number in blastocysts. In conclusion, the present study demonstrated the expression of leptin ligand and receptor proteins in porcine in vitro matured oocytes, IVF and SCNT embryos, and the embryotropic role of leptin in the SCNT embryo development.  This study was supported by the Advanced Backbone IT Technology Development (IMT 2000-C1-1) and the Korean Ministry of Science and Technology (M10310060000-03B4606-00000).

The present study investigated the expression of ligand and receptor for leptin, and the effect of leptin supplementation on preimplantation development of porcine in vitro-fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos. The IVF embryos were produced using frozen boar semen and SCNT embryos were obtained by nuclear transfer of fetal fibroblasts into enucleated oocytes. In Exp. 1, in vitro-matured porcine oocytes and embryos in 2-, 4-, and 8-cell as well as morula and blastocyst stages derived from IVF or SCNT were immunostained for leptin ligand and receptor with their specific antibodies. The expression of leptin ligand and receptor proteins was detected in oocytes and all stages of IVF and SCNT embryos. The IVF (Exp. 2; n = 635, 630, 633, 635, respectively) or SCNT oocytes (Exp. 3; n = 256, 258, 251, 258, respectively) were cultured in modified North Carolina State University (mNCSU)-23 medium supplemented with various concentrations (1, 10, 100, or 1000 ng/mL) of leptin. For the control group, IVF (n = 635) or SCNT embryos (n = 249) were cultured without leptin supplementation (0 ng/mL leptin). Embryo development and cell number in blatoscysts after differential staining according to a modified staining procedure (Thouas et al. 2000 Reprod. Biomed. Online 3, 25?29) were evaluated. The IVF or SCNT embryos were randomly distributed, and experiments were replicated at least 11 times. The differences in embryo development among experimental groups were analyzed using one-way ANOVA after arcsine transformation (without arcsine transformation for cell number of blastocysts) to maintain homogeneity of variance. Post hoc analyses to identify between-group differences were performed using the LSD test. In SCNT embryos, the cleavage rate was not different in leptin-treated groups (73.8, 77.5, 75.7, or 78.7%, respectively) compared to the control (76.3%). The rate of blastocyst formation (at 166 h after the day of injection of donor cells) in SCNT embryos was significantly increased (P < 0.05) in 1000 ng/mL leptin-supplemented group (20.2%) compared with the control (12.9%) and 1 ng/mL leptin-supplemented (12.5%) groups. Supplementing mNCSU-23 with 1000 ng/mL leptin also significantly increased (P < 0.05) the number of total cells (54.6) and trophectoderm (TE) cells (39.1) in SCNT blastocysts (n = >25) compared with the control [45.1 (total cells) and 31.6 (TE cells)] and 10 ng/mL leptin-supplemented group [44.4 (total cells) and 31.7 (TE cells)]. In IVF embryos, leptin supplementation did not affect pre-implantation embryo development and cell number in blastocysts. In conclusion, the present study demonstrated the expression of leptin ligand and receptor proteins in porcine in vitro matured oocytes, IVF and SCNT embryos, and the embryotropic role of leptin in the SCNT embryo development.  This study was supported by the Advanced Backbone IT Technology Development (IMT 2000-C1-1) and the Korean Ministry of Science and Technology (M10310060000-03B4606-00000).