Physical properties of transition to chaos in RF-driven Josephson junction analog

An analog circuit is used to investigate the behavior of the transition to chaos in the rf-driven Josephson junction under the variation of excitation amplitude and frequency with McCumber parameter >1. A series of transitions is observed, including a hysteretic jump, symmetry breaking, period doubling, and intermittency prior to chaos, and the transition boundaries are given in a state diagram in the vs. parameter space. Thus, the sequence of transitions to chaos can be inferred from this diagram. Based on these results, the harmonic balance method and Floquet theory are applied to study the instability of the transition series. It is suggested that all these transitions to chaos can be explained as parametric excitations. In addition, the transition boundaries in the state diagram can be satisfactorily computed from the conditions with a Floquet multiplier =±1.     

Calculation of water droplet impingement using the coupled method of rigid body dynamics and the moving particle semi-implicit method

When a liquid droplet impacts on a solid surface, it recoils to the center of that surface after reaching its maximum spreading diameter. The mechanism of droplet recoiling is not fully understood. To simulate this recoiling of a droplet, a particle method is a good choice because it does not require grids for simulating fluid motions, and can easily handle a large deformation of fluid. In this study, the coupled method of rigid body dynamics and the moving particle semi-implicit (MPS) method (Park and Jeun, 2011) was used to calculate three-dimensional droplet impingement. Also, the previous surface tension model for MPS (Nomura et al., 2001) was revised to get a more realistic surface tension force. A two-step calculation was performed. In the first step, a MPS calculation was performed with particles that were considered to have no mass or volume. In the second step, rigid body dynamics came into the calculation and considered the diameters of particles being slightly lesser than the initial distance between particles. In this study, the calculated results were compared with the measured data (Kim and Chun, 2000) and the recoiling lengths of droplets for the various initial impingement speeds were estimated.     

Preparation of adsorbent for palladium ions by amination of acrylonitrile grafted polypropylene nonwoven fabrics

A new chelating fabrics are synthesized by radiation induced grafting of acrylonitrile (AN) onto polypropylene nonwoven fabrics (PP fabrics) and subsequent conversion of cyano to an imine by reaction with ethylene diimine (EDA). Influence of various parameters such as initial concentration, pH and adsorption time on the adsorption amount for palladium ions was investigated. It was found that adsorbent achieved excellent adsorption performance in palladium ion removal in the pH range of 1.88–5.70. The adsorption amount of ions increased with shaking time and initial concentration of palladium ions. The grafted and aminated fabrics were characterized by FT‐IR, TGA and SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of gamma irradiation on the thermal and mechanical properties of chitosan/PVA nanofibrous mats

Chitosan/poly(vinyl alcohol) (PVA) nanofibrous mats were prepared by the electrospinning method. The morphology and structure of electrospun nanofibers were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. SEM images showed that the uniform and bead-free fibers were obtained at concentrations greater than 8 wt%. Chitosan/PVA mats were irradiated with different doses (50–200 kGy) of ⁶⁰Co gamma rays. The effect of irradiation dose on the mechanical and thermal properties of these films was also investigated. Increasing the irradiation dose led to a decrease in tensile strength. FT-IR and DSC demonstrated that there were strong intermolecular hydrogen bonds between the chitosan and PVA molecules.     

Effect of the monascus pigment threonine derivative on regulation of the cholesterol level in mice

Different amino acid derivatives were synthesized during cultivation of a Monascus species. Derivatives exhibiting an inhibitory activity against HMG-CoA reductase were screened by in vitro tests. The threonine derivative had a high inhibitory activity of 38% while four other derivatives showed a greater than 23% activity. The orange monascus pigment showed a high activity of 36%. In vivo tests using female C57BL/6 mice were performed with the threonine derivative and orange pigment. Changes in the cholesterol and lipid levels in mice due to addition of the pigments were investigated. The total cholesterol (TC) level of mouse serum was reduced by 8–9% with the threonine derivative and by 16% with orange pigment. Supplementation with the threonine derivative and orange pigment decreased the LDL cholesterol level by 18–26% and increased the HDL cholesterol level by 1–9%. The atherogenic index (AI) value was reduced by 23–27% with pigment supplementation. The anti-atherosclerosis effect of monascus pigments can be induced by control of the lipid content in the serum rather than in the liver of mice.     

Anti‐inflammatory Potential of Quercetin‐3‐O‐β‐D‐(“2”‐galloyl)‐glucopyranoside and Quercetin Isolated from Diospyros kaki calyx via Suppression of MAP Signaling Molecules in LPS‐induced RAW 264.7 Macrophages

Diospyros kaki (DK) contains an abundance of flavonoids and has been used in folk medicine in Korea for centuries. Here, we report for the first time the anti‐inflammatory activities of Quercetin (QCT) and Quercetin 3‐O‐β‐(“2”‐galloyl)‐glucopyranoside (Q32G) isolated from DK. We have determine the no cytotoxicity of Q32G and QCT against RAW 264.7 cells up to concentration of 50 μM. QCT and Q32G demonstrated potent anti‐inflammatory activities by reducing expression of nitric oxide (NO), tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, IL‐6 inducible NO synthase (iNOS), cyclooxygenase (COX)‐2, and mitogen‐activated protein kinase (MAPKs) in mouse RAW 264.7 macrophages activated with lipopolysaccharide (LPS). Both QCT or Q32G could decrease cellular protein levels of COX‐2 and iNOS as well as secreted protein levels of NO, PGE₂, and cytokines (TNF‐α, IL‐1β, and IL‐6) in culture medium of LPS‐stimulated RAW 264.7 macrophages. Immunoblot analysis showed that QCT and Q32G suppressed LPS‐induced MAP kinase pathway proteins p‐p38, ERK, and JNK. This study revealed that QCT and Q32G have anti‐inflammatory potential, however Q32G possess comparable activity as that of QCT and could be use as adjuvant to treat inflammatory diseases.     

A Study on the Impact and Solidification of Liquid Metal Droplets during Thermal Spray Deposition onto a Substrate with Concentric Grooves or Ridges

In this study, a numerical investigation has been performed on the spreading and solidification of a coating material droplet onto the rigid substrate in the thermal spray process. The computational model is validated through the comparison of the predicted numerical result and the experimental data for flat substrate. An analysis of the deposition formation on a substrate with small concentric grooves or ridges was performed. To examine the characteristic of the impact and solidification of a liquid droplet on the substrate with concentric grooves or ridges, a parametric study was conducted with various shapes and sizes of concentric grooves or ridges.     

A study of the thermal and mechanical properties of electron beam irradiated HDPE/EPDM blends in the presence of triallyl cyanurate

The enhancing effects of cross-linking by the addition of 1, 3, and 5 wt% of triallyl cyanurate (TAC) to blends containing 80 wt% of high-density polyethylene (HDPE) and 20 wt% of ethylene–propylene diene monomer (EPDM) during electron beam irradiation were investigated. More specifically, the thermal and mechanical properties were studied as a function of the electron beam irradiation dose and an amount of the cross-linking agent, such as triallyl cyanurate (TAC). The results showed that the values of the gel content, thermal stability, tensile properties, impact strength, and rheology increased with increasing irradiation dose up to 150 kGy. For higher doses, the values decreased. Addition of the cross-linking agent to the HDPE/EPDM blends showed an enhanced cross-linking effect of various properties during electron beam irradiation. The addition of 3 wt% of TAC led to the highest thermal and mechanical properties. An irradiation dose of 150 kGy with the addition of 3 wt% TAC was the optimal condition to obtain blends with the best properties.     

Tumors of the orbit. Pitfalls of the surgical approach in 37 children with orbital tumor

The authors review their experience with 37 children with orbital tumors, summarizing their surgical techniques, the indications applied, and the pitfalls of each surgical approach. Tumors located in the retro-ocular or intraorbital space were surgically excised through a transcranial approach (28 cases), while for tumors in other sites lateral orbitotomy (5 cases), medial orbitotomy (1 case) and biopsy (3 cases) were performed. A transcranial approach was used for tumors with intracranial extension and for those located in the orbital apex and deep medial orbital compartment. Lateral orbitotomy was used for tumors located in the superior, temporal or inferior compartment of the orbit and those in the lateral apex. A medial orbitotomy was used for tumors located medial to the optic nerve. Outcomes of the surgical intervention varied, depending on the pathology, location and extent of the individual tumors. To obtain optimal exposure and minimize functional deficits, the pitfalls of surgical approaches to orbital tumors are discussed.