Formation of water-soluble iron oxide nanoparticles derived from iron storage protein

This paper reports novel findings of an investigation of the formation of water-soluble iron oxide nanoparticles from iron-storage protein ferritin. The strategy couples thermal removal of the protein shell on a planar substrate and subsequent sonication in aqueous solution under controlled temperature. Advantages of using ferritin as a precursor include well-defined core size, core composition, water-solubility and processibility. The formation of the nanoparticles was characterized using TEM, UV-Vis and FTIR techniques. Iron oxide nanoparticles in the size range of 5-20 nm diameters were produced. In addition to thermal treatment conditions, the sonication temperature of the nanoparticles in water was found to play an important role in determining the resulting particle size. This simple and effective route has important implications to the design of composite nanoparticles for potential magnetic, catalytic, biomedical sensing and other nanotechnological applications.     

Environmentally Benign Carbonylation Reaction: Palladium-Catalyzed Hydroxycarbonylation of Aryl Halides and Benzyl Chloride Derivatives in Ionic Liquid Media

Palladium-catalyzed hydroxycarbonylations of aryl halides and benzyl chloride derivatives proceeded in ionic liquid media (l-butyl-3-methylimidazolium hexafluorophosphate (1), tetrafluoroborate (2) and Aliquat^®336 (3)). The palladium-catalyst/mixture could be recycled, after separation of the product by extraction with water. The use of ionic liquid media greatly increased the yield of benzoic acid in hydroxycarbonylation.     

Effect of impeller diameter on mean droplet diameter in circular loop reactor

Experiments in liquid-liquid dispersion were performed using a circular loop reactor designed for suspension polymerization. In order to vary widely differences in physical properties such as the viscosity, density, and interfacial tension between the two liquids concerned, polystyrene pellets were dissolved into the dispersed phase which consisted of a styrene monomer liquid. The diameter distributions and mean diameters of droplets formed were measured by stepwise changes in the impeller diameter. From these results, the effect of the impeller diameter on the breakup of droplets was determined. Correlations relating the mean droplet diameter to the operational conditions were derived.     

Characterization of platinum nanoparticle-embedded carbon film electrode and its detection of hydrogen peroxide

A method for the highly sensitive determination of acetylcholine (ACh) and choline (Ch) that employs a graphite-like carbon film electrode containing 6.5% platinum (Pt) nanoparticles was developed for use as a detector in microbore liquid chromatography (LC) with a postcolumn enzyme reactor. The film electrode was prepared by RF cosputtering carbon and Pt, which requires only a one-step formation process. This method can control the Pt content of the film at a relatively low deposition temperature (below 200 degrees C). The average size of the Pt nanoparticles was 2.5 nm. The film electrode showed excellent electrocatalytic activity, high sensitivity, and negligible baseline drift when detecting hydrogen peroxide. The electrode was modified with glucose oxidase and responded rapidly to glucose with a much more stable baseline current than at a Pt bulk electrode based sensor. Therefore, it is appropriate to employ the electrode to detect trace amounts of biomolecules, such as neurotransmitters and hormones combined with various oxidase enzymes. We used the electrode as a detector for microbore LC and observed a low detection limit of 2.5 and 2.3 fmol (10-microL injection) for ACh and Ch, respectively, which is approximately 1 order of magnitude lower than that of a Pt bulk electrode.     

A metastable phase in thermal decomposition of Ca-deficient hydroxyapatite

We investigated the microstructural changes on an atomic length scale during thermal decomposition process of Ca-deficient hydroxyapatite (Ca-def HAp) by high-resolution transmission electron microscopy (HRTEM). Ca-def HAp was prepared by hydrolysis of -tricalcium phosphate. The Ca-def HAp had a whisker-like morphology 2–5 m in length and 0.1 m in diameter that was elongated along c-axis. Thicker planer defects parallel to the (100) plane of the HAp matrix were observed as precipitation in the sample annealed at 700 and 800 °C by HRTEM observation. Thickness of the precipitation was about 10 nm and the boundaries between the precipitation and HAp matrix was coincident. The periodicity in the precipitation was parallel to the (100) plane of the HAp matrix and measured to be 1.42 nm. Since the precipitation was observed only in the sample annealed at a narrow temperature range of 700–800 °C, it was regarded as a metastable phase formed on the thermal decomposition process. Absorption peaks in IR spectra of annealed Ca-def HAp containing the metastable phase appeared at 744 and 3538 cm^–1 due to non-stoichiometric HAp with high Ca/P molar ratio. Furthermore, the results of energy dispersive X-ray spectroscopy showed that the metastable phase had higher Ca/P molar ratio than that of the matrix and stoichiometric HAp. Therefore, the metastable phase could be identified as Ca-rich metastable phase. The presence of Ca-rich metastable phase was confirmed to be associated with the thermal decomposition process.     

In vivo and in vitro evaluation of the pulsatile mode of a magnetically suspended centrifugal pump

The authors have been developing a magnetically suspended centrifugal pump (MSCP). They have devised a pulsatile mode for the MSCP, which was generated by altering rotational speed. This article describes in vitro and in vivo studies with the pulsatile mode of the MSCP. Hemolysis tests were performed in two identical circuits to compare the nonpulsatile (NP) mode and the pulsatile (P) mode. In vivo studies were performed in sheep. First, biventricular assisted circulation was instituted in the left heart with the MSCP and in the right heart with the Biopump. The native heart was induced to ventricular fibrillation. Second, a left ventricular assisted circulation was instituted as the native heart was beating. An inflow cannula was inserted into the left atrium in one sheep and into the left ventricle in the other. The normalized indices of hemolysis of the NP and P groups were 0.0025 +/- 0.0018 g/100 L, and 0.0032 +/- 0.0024 g/100 L (N = 4, not significant). During ventricular fibrillation in the P mode, the pulse pressure was 14 mmHg (the rotational speed: 1,500 to 2,600 rpm). In a beating heart, at atrial withdrawal, the pulse pressure increased from 10 to 24 mmHg (2,100 +/- 500 rpm), while at ventricular withdrawal, it decreased from 17 to 40 mmHg (2,000 +/- 500 rpm) on P mode. The MSCP in pulsatile mode did not increase hemolysis. At ventricular withdrawal, it was easier to produce a pulsation than at atrial withdrawal. The pulsatile mode of the MSCP is applicable to a left ventricular assist system.     

Occurrence of sustained increase in QT dispersion following exercise in patients with residual myocardial ischemia after healing of anterior wall myocardial infarction

Our objective was to evaluate the effect of exercise on QT dispersion over the next 3 hours, as seen on a standard 12-lead electrocardiogram in patients with healed myocardial infarction with or without residual ischemia. We measured QT and QTc dispersion before, immediately after, and 1 and 2 hours after symptom-limited, dynamic treadmill exercise tests in 28 patients with healed anterior wall myocardial infarction with (group I, n = 18) and without (group II, n = 10) residual ischemia. The same protocol was followed in 5 group I patients after successful performance of coronary angioplasty. QT and QTc dispersion did not change immediately after exercise in group II. These parameters increased in group I (QT dispersion at rest [mean +/- SD] 57 +/- 22 ms, and after exercise 87 +/- 27 ms; QTc dispersion at rest 62 +/- 25 ms, and after exercise 114 +/- 36 ms). The increases in QT and QTc dispersion were sustained for at least 2 hours. After a successful coronary angioplasty in 5 patients, these parameters no longer increased with exercise. Thus, QT dispersion increased for at least 2 hours after exercise in patients who had residual ischemia after healing of myocardial infarction. Data obtained in 5 of these patients after coronary angioplasty support the idea that residual ischemia plays a key role in the sustained increase in QT dispersion after exercise.     

Dispersing behaviour of droplets in suspension polymerization of styrene in a loop reactor

Suspension polymerization of styrene was performed using a loop reactor. The dispersing behaviour of the droplets in the course of the reaction was observed. The mean droplet diameter was determined by the energy level at the impeller region. Moreover, the final particle size distribution and mean particle size were also determined after an elapsed time of 1-2 hrs. An expression which correlated the final mean particle size with the operating conditions, such as the mixing conditions at the impeller region and the initial physical properties of the suspension system, was derived. The deposition of polymers on the reactor wall was found to be prevented due to the high fluid velocity.     

Viscous flow simulation using the discrete vortex model—the diffusion velocity method

A new numerical model is presented for viscous flow simulation using the discrete vortex model. The viscous diffusion is produced by the vortices' movement induced by the diffusion velocity introduced in this paper. It is shown that our proposed method is valid, even at Re values below the lower limit of applicability of the random vortex method and that our solutions are much smoother. In addition, our method is clearly more dependent on Re than the conventional discrete vortex method, and since our method can treat the development, separation and reattachment of the boundary layer, it dispenses with the boundary layer theory.     

Active Electrochemical Dissolution of Molybdenum and Application for Room-Temperature Synthesis of Crystallized Luminescent Calcium Molybdate Film

Crystallized luminescent calcium molybdate (CaMoO₄) film has been prepared on a molybdenum substrate in an alkaline solution containing calcium ions by active electrochemical dissolution of molybdenum at room temperature (25°C). The dissolution rate became faster with an increase of pH value. A high concentration of calcium (0.02M) and a high pH value (13) favored the reaction of film formation. The film showed only a single green emission at 536 nm with the excitation of 285 nm at liquid-nitrogen temperature (-196°C), strongly suggesting that it consisted of well-crystallized defect-free crystals.