Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications

As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au-Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au-Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Two distinct phases, Au5Sn and AuSn, were deposited at a composition of 30at.%Sn. The Au-Sn flip-chip joints were formed at 300 and 400 degrees without using any flux. In the case where the samples were reflowed at 300 degrees, only an (Au,Ni)3Sn2 IMC layer formed at the interface between the Au-Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)3Sn2 and (Au,Ni)3Sn, were found at the interfaces of the samples reflowed at 400 degrees. As the reflow time increased, the thickness of the (Au,Ni)3Sn2 and (Au,Ni)3Sn IMC layers formed at the interface increased and the eutectic lamellae in the bulk solder coarsened.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Salmonella typhimurium harboring plasmid expressing interleukin-12 induced attenuation of infection and protective immune responses

IL-12 is known to be an essential cytokine which appears to provide protective immunity against intracellular bacteria, such as Salmonella. In this study, we investigated the possibility of developing a vaccine using IL-12 against virulent Salmonella. We used the host defense system activated by cytokine IL-12. The highly virulent Salmonella strain (Salmonella typhimurium UK-1) was transformed with cytokine-expressing plasmids. These live, wild-type pathogens were used as vaccine strains without undergoing any other biological or genetic attenuating processes. The newly developed strains induced partial protection from infections (30-40%). Of note, the interleukin-12 transformed pathogen was safe upon immunization with low doses (103 CFU), induced IgG responses, and stimulated protective immune responses against Salmonella Typhimurium in mice (80-100%). These results suggest that IL-12 induced attenuation of wild-type Salmonella in the host infection stage and vaccine development using the wild-type strain harboring IL-12 secreting plasmids may be considered as an alternative process for intracellular bacterial vaccine development without the inconvenience of time-consuming attenuation processes

Development of the MICROMEGAS Detector for Measuring the Energy Spectrum of Alpha Particles by using a 241-Am Source

We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting {\alpha} particles emitted from an 241-Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of {\alpha} particles from the 241-Am source can be varied by changing the flight path of the {\alpha} particle from the 241 Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the {\alpha} particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for {\alpha} particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that {\alpha} particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGAS detector for {\alpha} particles under the present conditions is found to be ~ 97.3 %

Integrative Literature Review on the Antecedents of Informal Learning in the Workplace: A Conceptual Framework for Future Research

Despite the explosion of interest in informal learning in the workplace, few attempts have been made to synthesize the current literature. This article provides an integrative and analytical review of prior empirical studies, particularly focusing on what factors have been identified as antecedents of informal learning in organizations and how informal learning has been conceptualized and measured. It then suggests future avenues for theory building, research, and practice. The authors propose a conceptual framework for understanding informal learning activities using three dimensions: learning competence, intentionality, and developmental relatedness. Implications for human resource development research and practice are also discussed

Toxicity Studies on Secretio Bufonis: A Traditional Supplement in Asia

AbstractObjectivesThis study was performed to investigate the toxicity of Secretio Bufonis (SB) on male mice and assess its no-observed-adverse-effect-level (NOAEL).Materials and MethodsAfter feeding an aqueous solution of SB extracts to mice for either 1 or 8 weeks, their blood and urine were assayed and their liver and kidney morphology examined. The numerical data was analyzed by the Mann-Whitney U-test and analysis of variance test.ResultsMice administered SB in 50 mg/kg/day for 1 week had higher heart weights and higher aspartate transaminase activities; those administered SB in 0.01 and 0.05 mg/kg/day for 8 weeks had lower creatinine concentrations; and those administered SB in 0.5 mg/kg/day for 8 weeks had higher brain weights and higher blood urea nitrogen.ConclusionsThe extracts of SB had cardiac toxicity in the short term and hepatotoxicity in the long term. The NOAEL of the extract was under 5 mg/kg/day for 1 week and under 0.25 mg/kg/day for 8 weeks

Design of a dye-doped liquid crystal cell with a constant transmittance-difference contour map

Thus far, the trial-and-error method has been used to find the condition for a dye-doped liquid crystal cell with desired performances. In this paper, we report a systematic design process to find the condition for the desired performances without trial-and-error process

Suppression of Structural Fatigue by Doping in Spinel Electrode Probed by In Situ Bending Beam Method

The onset of a Jahn-Teller effect at the surface of LiMn2O4 particles during cycling in the 4 V range was previously reported to be one of the causes for the capacity fading. Furthermore, it has been reported that the Jahn-Teller effect in the 4 V range may be suppressed by the substitution of the Mn ions by either Li or other transition metal ions. However, no direct evidence has yet been reported. This study provides evidence for the onset of a Jahn-Teller effect in thin film 4 V LiMn2O4 and its suppression caused by substituting the Mn ions with Co31 and Ni21 ions using in situ bending beam method ~BBM!. The deflectograms are measured simultaneously with galvanostatic charge/discharge or cyclic voltammograms, and the onset of the Jahn-Teller effect is investigated by means of the differential strain peak which is observed at around 3.90-3.95 V during cyclic voltammetry, and the slope variation observed in the strain curves during galvanostatic charge/discharge. The suppression of the Jahn-Teller effect in the doped spinel leads to the magnitude of the differential strain peak resulting from the Jahn-Teller effect being reduced in comparison with the other two pairs of peaks, which correspond to the current peaks of the cyclic voltammogram.This work was supported by KOSEF through the Research Center for Energy Conversion and Storage (RCECS), Korea Science and Engineering Foundation (no. 2000-2-30100-012-3) and by the Ministry of Information and Communication of Korea (Support Project of University Information Technology Research Center supervised by KIPA). The authors thank Cheil Industries, Inc., for the supporting electrolytes