Adhesion improvement of copper/epoxy joints

Copper oxides have been formed to improve the adhesive strength of copper/epoxy joints. Initial adhesive strength and durability of copper/epoxy joints were compared depending upon the type of oxides, black or red oxide. Although the initial adhesive strength of black oxide treated joints was worse than that of red oxide treated joints, the durability in acidic environment was better. In order to improve the durability of red oxide treated joints, 5-amino-indazole was applied to inhibit the corrosion of oxide layer in acidic medium. With the treatment of 5-amino-indazole, initial adhesive strength was increased by 50%, and durability was improved. The loci of failure for oxide treated joints were investigated with scanning electron microscope and X-ray photoelectron spectroscopy.     

Single-cycle resonant converters: a new group of quasi-resonantconverters suitable for high-performance DC/DC and AC/AC conversionapplications

A novel resonant switch and a family of zero-current and zero-voltage mixed-mode switching quasi-resonant converters (QRCs) called single-cycle resonant converters (SCRCs) are proposed to improve the performance of the conventional QRCs. The SCRCs, which include two active switches operated with zero-current switching (ZCS) and zero-voltage switching (ZVS), respectively, show very simple operation and ease of control and analysis, and they overcome the limited load range characteristics of the conventional ZCS QRCs. The SCRCs can be applied even for a high-frequency AC chopper by replacing unidirectional switches with bidirectional ones. Steady-state operation and characteristics of the buck-type SCRCs are analyzed and compared with those of the buck-type full-wave QRC (FW-QRC). Experimental results at a a 200 kHz, 1 kW level are shown to verify the operational principle and characteristics     

Depletion of hepatic 3'-phosphoadenosine 5'-phosphosulfate (PAPS) and sulfate in rats by xenobiotics that are sulfated

Sulfation is considered a high-affinity but low-capacity conjugation mechanism that is limited by the availability of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), the cosubstrate for sulfation. Salicylamide, phenol and 1-naphthol are all known substrates for the sulfation reaction. This study was conducted to determine whether the xenobiotics that are sulfated when administered to rats will lower hepatic PAPS and its precursor, sulfate. Urinary sulfate excretion was reduced 85% to 95% by these compounds. Hepatic PAPS was reduced 73%, 39%, and 87% by salicylamide, phenol and naphthol, respectively, 2 hr after administration of 2 mmol/kg. These compounds also decreased serum sulfate concentrations by 45% to 86% and lowered hepatic sulfate concentrations. In summary, these studies demonstrate that salicylamide, phenol and 1-naphthol lower hepatic PAPS and sulfate concentrations, as well as serum sulfate concentrations. These findings imply that increased sulfation, as a result of the sulfation of xenobiotics, results in depletion of hepatic PAPS concentrations, possibly because the utilization of PAPS by the sulfotransferases exceeds its generation via sulfate activation. Thus the capacity-limited sulfation of high dosages of xenobiotics appears to be due to the reduced availability of hepatic PAPS, which in turn is limited by the availability of sulfate.     

Enantioselective solvolyses of amino acid p-nitrophenyl esters by optically active imidazole-containing copolymeric surfactants

Summary The imidazole-containing copolymeric surfactant, poly(N-methacryloyl-L-histidine methyl ester(la)-co-N,N-dimethyl-N-hexadecyl-N-(11-methacryloyloxyundecanyl)ammonium bromide(I)) was prepared and subjected to catalyze the hydrolyses of N-carbobenzoxy-d- and L-phenylalanine p-nitrophenyl esters (D-NBP and L-NBP). The copolymers exhibited enantioselective catalysis, viz., k_cat(L)/k_cat(D)=10.3 for poly(la-co-I) containing 3.7 mole % of la. The solvolytic systems employed were confirmed to form large ordered aggregate structure by electron microscopic observation.     

Urban Planning and Urban Sprawl in Korea

This research focuses on the issues of urban sprawl in Korea. The urban sprawl phenomenon began around the Seoul Metropolitan Area (SMA) at the beginning of the 1990 s. The research reviews the situation in other cities around the country, and analyzes the causes of urban sprawl, such as population concentrations around the SMA, the failure of planning systems, land conversion and land prices. In particular, this article attempts to explain the increase in land price by using empirical data on the areas under investigation. The article also attempts to present planning alternatives to prevent further urban sprawl.     

Transcriptional analysis of Marek''s disease virus (MDV) genes in MDV-transformed lymphoblastoid cell lines without MDV-activated cells

Prevention of the occurrence of diabetes-specific vascular complications is the final aim of clinical islet transplantation. Pancreatic islets isolated from adult pigs may be a suitable tissue source to transplant a large number of type 1 diabetic patients. Acute cellular rejection may be finally overcome by clinically applicable protocols for tolerance induction. However, primary nonfunction of the graft, as regularly observed in the porcine islet-to-rat xenotransplantation model, may be an additional problem. In this paper, species-specific inflammatory and immunological mechanisms are discussed which prevent early porcine islet graft function in rats but not in mice.     

Tin and Lead Loaded Plastic Scintillators for Low Energy Gamma-Ray Detection with Particular Application to High Rate Detection

It has been observed that loading plastic scintillators with tin or lead markedly increase their low energy photon detection efficiencies while retaining the characteristic short phosphor decay time of conventional plastic scintillators, These combined effects may have great impact in high rate photon detection: for instance, x-ray transmission 3-D image reconstruction applications in the biomedical field and M?ssbauer experiments in nuclear structure studies, Experimental data are here reported on a) photon detection efficiencies using a 5% tin loaded, a 7% tin loaded and a 57% lead loaded plastic scintillator with reference to a NaI(Tl) crystal in the energy range of 20-511 keV; b) high count rate detection up to 20 MHz with 153Gd (42 + 100 keV groups); and c) M?ssbauer experiments with thin discs of tin loaded plastic scintillators.