Kinetics of Au-containing ternary intermetallic redeposition at solder/UBM interface

In this study, the effects of the under bump metallurgy (UBM) structure and Cu content in solders on the redeposition rate of Au-containing ternary intermetallics at the solder/UBM interface were investigated. A UBM structure with a Ni diffusion barrier, Au/Ni/Cu, appeared to promote the redeposition of ternary Au-containing intermetallics at the solder/UBM interface of the ternary during the solid-state aging treatment and the Au-embrittlement of the solder interconnections. Copper added to the eutectic Sn-Pb and Sn-Ag solders was observed to be very effective in retarding the redeposition by forming the ternary intermetallics in solder matrices and preventing the Au-embrittlement. These phenomena were discussed with the microstructures observed. Jointly appointed by CAAM at POSTECH     

High-performance graphene-based transparent flexible heaters

We demonstrate high-performance, flexible, transparent heaters based on large-scale graphene films synthesized by chemical vapor deposition on Cu foils. After multiple transfers and chemical doping processes, the graphene films show sheet resistance as low as ～43 Ohm/sq with ～89% optical transmittance, which are ideal as low-voltage transparent heaters. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional transparent heaters based on indium tin oxide. In addition, we confirmed that mechanical strain as high as ～4% did not substantially affect heater performance. Therefore, graphene-based, flexible, transparent heaters are expected to find uses in a broad range of applications, including automobile defogging/deicing systems and heatable smart windows.     

Graphene-based bimorph microactuators

A novel graphene-on-organic film fabrication method that is compatible with a batch microfabrication process was developed and used for electromechanically driven microactuators. A very thin layer of graphene sheets was monolithically integrated and the unique material characteristics of graphene including negative thermal expansion and high electrical conductivity were exploited to produce a bimorph actuation. A large displacement with rapid response was observed while maintaining the low power consumption. This enabled the successful demonstration of transparent graphene-based organic microactuators.     

Characterization of the quinolone resistance mechanism in foodborne Salmonella isolates with high nalidixic acid resistance

Sixteen Salmonella strains resistant to nalidixic acid isolated from kimbab, the most popular ready-to-eat (RTE) food in Korea, and chicken meat were selected for this study. The resistant strains were shown to have high minimal inhibitory concentrations (MICs) against nalidixic acid (512 ~ 4096 μg/mL). Among them, 4 Salmonella enterica serovar Haardt isolates showed multi-drug resistance (MDR) patterns with reduced susceptibility to fluoroquinolone (0.5 μg/mL of ciprofloxacin MICs). The mechanisms of quinolone resistance in the nalidixic acid resistant strains were characterized by PCR and sequence analysis. The presence of plasmid-mediated quinolone resistance (PMQR) genes and amino acid changes in the quinolone resistance determining region (QRDR) were investigated by PCR-based detection and sequencing, and the efflux pump inhibition test was also done using phe-arg-β-naphthylamide (PAβN). Although PMQR genes were not detected in any of the tested strains, the QRDR mutations were found in this study: single mutation in gyrA (Asp87Tyr, Asp87Gly, and Asp87Asn), double mutations in gyrA (Ser83Thr) and parC (Thr57Ser), and single mutation in parC (Thr57Ser). MICs of nalidixic acid were reduced by 2- to 32-folds by the efflux pump inhibitor, PAβN. Pulsed-field gel electrophoresis (PFGE) was carried out to confirm the epidemiological relationship between the nalidixic acid resistant strains. The PFGE patterns were classified into 6 groups at cutoff level of 70 ~ 100% correlation on the dendrogram. Some strains of serotype Haardt and Enteritidis showed several values of genomic identity in accordance with strains, sources, and isolation year. We suggest that point mutation on QRDR and efflux pump systems involved in antimicrobials had independent effects on drug-resistance regardless of bacterial genomic variation.     

Development of refined cuttlefish (<Emphasis Type="Italic">Todarodes pacificus</Emphasis>) oil and its use as functional ingredients

Cuttlefish (Todarodes pacificus) viscera were tried to extract bioactive oil containing high amount of ω-3 fatty acids. Cuttlefish oil (CFO) was extracted from the viscera, refined, and evaluated. The tried effective extracting condition was 9 h hot steam extraction. Raw CFO contained high ω-3 fatty acids (FA); 21.4% docosahexaenoic acid (DHA), 11.3% eicosapentaenoic acid (EPA). The raw CFO was refined by acetone fractionation at the optimum conditions (−30°C, 8 h). One advantage of the fractionated CFO was high amounts of DHA (28.6%) and EPA (14.7%). Also, another advantage of the refined CFO was its stability during 92-day storage period at 50°C. This was seen by measuring the acid values (AV<1.0) and peroxide values (POV<2.1) throughout the storage period. In conclusion, the refined CFO containing ω-3 FA (>43%) has potential as a good functional ingredient.     

An optimized placement of building drawings with moving least squares and K-means clustering

Multimedia Tools and Applications - In this paper, we propose a method that can efficiently process the arrangement of building drawings using K-means clustering and vector field constructed by...     

Die sinter bonding in air using copper formate preform for formation of full-density bondline

Pressure-assisted sinter bonding was performed in air at 250?350 °C using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures. H₂ and CO generated concurrently by the pyrolysis of copper formate at 210 °C during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes, enabling interface bonding. Moreover, Cu produced in situ by the reduction of Cu(II) accelerated the sinter bonding. Consequently, the bonding achieved at 300?350 °C under 5 MPa exhibited sufficient shear strength of 20.0?31.5 MPa after 180?300 min of sinter bonding. In addition, an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250 °C, and a near-full-density bondline was achieved after 300 s. The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.     

Assembly of Foldable 3D Microstructures Using Graphene Hinges

Origami/kirigami-inspired 3D assembly approaches have recently attracted attention for a variety of applications, such as advanced optoelectronic devices and biomedical sensors. The results reported here describe an approach to construct classes of multiple foldable 3D microstructures that involve deformations that typical conductive materials, such as conventional metal films, cannot tolerate. Atomically thin graphene sheets serve as folding hinges during a process of 2D to 3D conversion via a deterministic buckling process. The exceptional mechanical properties of graphene enable the controlled, geometric transformation of a 2D precursor bonded at selective sites on a prestretched elastomer into folded 3D microstructures, in a reversible manner without adverse effects on the electrical properties. Experimental and computational investigations of the folding mechanisms for such types of 3D objects reveal the underlying physics and the dependence of the process on the thickness of the graphene/supporting films that define the hinges.     

Label-free electrochemical impedance spectroscopy using a micro interdigitated electrode inside a PCR chip for real-time monitoring

Conventional real-time PCR using fluorescence detection requires expensive optical detection systems with fluorescence labeling. To simplify this PCR system, we proposed an electrochemical impedance spectroscopy (EIS) using an interdigitated electrode integrated inside the PCR chip. The electrode makes a direct contact with the PCR sample and does not require any labeling or immobilization pretreatment. The input AC voltage for EIS showed the lowest noise at 100 mV. Electrical impedances in a frequency domain were measured during 30 cycles in the PCR of Escherichia coli genomic DNA region (of length 180 bp, 10 ng/μl). From the analysis of EIS data, the magnitude of imaginary value steadily increased with an increase in the PCR cycles and showed the greatest change rate at 186 Hz. For comparing the quantitative performance with previous researches, the figure of merit (FM) was defined as the ratio of normalized sensitivity (NS) to the normalized root mean square error (NRMSE). The performance of the proposed EIS method is similar to that reported in other studies, and the damage of the sample monitored through electrophoresis by EIS measurement was confirmed to be negligible.

     

Discovery of Novel Biased Opioid Receptor Ligands through Structure-Based Pharmacophore Virtual Screening and Experiment

G_i-protein-biased agonists with minimal β-arrestin recruitment represent opportunities to overcome the serious adverse effects of human mu opioid receptor (μ-OR) agonists and developing alternative and safe treatments for pain. In order to discover novel non-morphinan opioid receptor agonists, we applied hierarchical virtual screening of our in-house database against a pharmacophore based on modeling the active conformations of opioid receptors. We discovered an initial hit compound, a novel μ-OR agonist with a pyrazoloisoquinoline scaffold. We applied computational R-group screening to this compound and synthesized 14 derivatives predicted to be the best. Of these, a new G_i-protein-biased compound, 1-{5-(3-chlorophenyl)-7,8-dimethoxy-3-[4-(methylsulfonyl)benzyl]-3H-pyrazolo[3,4-c]isoquinolin-1-yl}-N,N-dimethylmethanamine, showed an EC₅₀ value of 179 nm against the μ-OR. This resulted in significant pain relief for mice in the phase II period of formalin response tests. This study provides a new strategy to identify diverse sets of promising compounds that might prove useful for the development of drugs that target other G-protein-coupled receptors.