Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.     

Dibenzothiophene desulfurizing enzymes from moderately thermophilic bacterium Bacillus subtilis WU-S2B: purification, characterization and overexpression

The moderately thermophilic bacterium Bacillus subtilis WU-S2B desulfurized dibenzothiophene (DBT) at 50 degrees C through the selective cleavage of carbon-sulfur bonds. In this study, three enzymes involved in the microbial DBT desulfurization were purified and characterized. The first two enzymes, DBT monooxygenase (BdsC) and DBT sulfone monooxygenase (BdsA), were purified from the wild-type strain, and the last one, 2'-hydroxybiphenyl 2-sulfinic acid desulfinase (BdsB), was purified from the recombinant Escherichia coli overexpressing the gene, bdsB, with chaperonin genes, groEL/ES. The genes of BdsC and BdsA were also overexpressed. The molecular weights of BdsC and BdsA were determined to be 200 and 174 kDa, respectively, by gel filtration chromatography, suggesting that both enzymes had four identical subunits. BdsB had a monomeric structure of 40 kDa. The three enzymes were characterized and compared with the corresponding enzymes (DszC, DszA, and DszB) of mesophilic desulfurization bacteria. The specific activities of BdsC, BdsA, and BdsB were 84.2, 855, and 280 units/mg, respectively, and the latter two activities were higher than those of DszA and DszB. The heat stability and optimum temperature of BdsC, BdsA, and BdsB were higher than those of DszC, DszA, and DszB. Other enzymatic properties were investigated in detail.     

Dispersion in active transport by kinesin-powered molecular shuttles

Active transport driven by molecular motors is a key technology for the continued miniaturization of lab-on-a-chip devices, because it is expected to enable nanofluidic devices with channel diameters of less than 1 microm and total channel lengths on the order of 1 mm. An important metric for a transport mechanism employed in an analytic device is dispersion, because it critically affects the sensitivity and resolution. Here, we investigate the mechanisms responsible for the dispersion of a swarm of "molecular shuttles", consisting of functionalized microtubules propelled by surface-adhered kinesin motor proteins. Using a simple model and measurements of the path persistence length, motional diffusion coefficient, and the distribution of average velocities, we found that, at the time scale relevant in the envisioned nanobiodevices, variations in the time-averaged velocities between shuttles will make a stronger contribution to the dispersion of the swarm than both the fluctuations around the time-averaged velocity of an individual shuttle and the fluctuations in path length due to wiggling within the channel. Overall, the dispersion of such molecular shuttles is comparable to the dispersion of a sample plug transported by electroosmotic flow.     

Temperature dependence of Rresistivities of SnO2-based gas sensors exposed to Co,H2, and C3H8 gases

The temperature dependence of resistivities of gas sensors made of SnO₂, Pd-doped SnO₂, and ThO₂-doped SnO₂ with Pd has been investigated in air containing reducing gases such as CO, H₂, and C₃H₈. The curves for ThO₂-doped sensors were significantly influenced by the reducing gases as compared to the sensors without ThO₂. From these results, it is found that in Pd-doped SnO₂ sensors the dopant plays an important role in oxidizing the surface of SnO₂ above 170°C, and that the addition of ThO₂ to Pd-doped SnO₂ enhances the effects of Pd by removing the adsorbed hydroxyl on SnO₂. It is also apparent that the interactions between reducing gases in air and SnO₂-based sensors depend upon the oxidizing rates of the surface of SnO₂, as well as the amounts of the adsorbed hydroxyl on SnO₂.     

The oxidation behavior of an iron-nickel alloy containing yttrium or rare earth elements between 900°C and 1200°C

A study of oxidation of an iron-nickel alloy with and without yttrium or rare earth additions is made to provide information over a range of temperature. The additions improve the oxidation resistance in air. The microfractograph features of oxide scale are discussed. It is suggested that pores existing in the interface between oxide scale and substrate may be an important factor for the good adherence which is obtained. In addition the pegging mechanism of rare earth element oxides may improve the adherence of oxide scale to substrate. An incubation period of oxidation in the alloys containing yttrium or rare earth elements is described and discussed in terms of net weight gain and weight loss due to gas evaporation.     

Phase I and pharmacologic study of irinotecan in combination with cisplatin for advanced lung cancer

Macroscopic T-type Ca2+ currents, which are often observed in fetal and neonatal cardiac muscle cells, were not found in normal (0 of 17) adult feline ventricular myocytes. However, they were present in most (15 of 21) myocytes isolated from adult feline left ventricles with long-standing pressure-overload-induced hypertrophy. This is the first study to provide evidence in a large mammal, such as the cat, that T-type Ca2+ channels may be reexpressed in adults in association with hypertrophy resulting from slow progressive pressure overload. Importantly, this expression was stable for the duration of the hypertrophy process and was not associated with abrupt pressure overload. T-type Ca2+ currents were separated from L-type Ca2+ currents by exploiting the differences in their voltage dependence of steady-state inactivation. Depolarizations from -80 mV revealed a rapidly activating inward current that peaked in magnitude at -30 mV (-1.8 +/- 0.9 [mean +/- SD] pA/pF) and fully inactivated within 100 milliseconds in 15 of 21 hypertrophied myocytes studied. Further depolarizations activated progressively less T-type Ca2+ current, so that at +10 mV the L-type Ca2+ current predominated. In the hypertrophied myocytes that demonstrated both T-type and L-type Ca2+ currents, two distinct peaks occurred in their current-voltage relations. T-type Ca2+ currents were not evident in any of the 17 normal adult feline left ventricular myocytes studied. The purpose of T-type Ca2+ currents in hypertrophy is unclear. However, their presence may make hypertrophied myocardium more prone to spontaneous action potentials and increase the likelihood for arrhythmias in partially depolarized hypertrophied myocardium.     

Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness

This paper presents a two-degree-of-freedom (two-DOF) linear encoder which can measure the position along the moving axis (X-axis) and the straightness along the axis vertical to the moving axis (Z-axis) of a precision linear stage simultaneously. The two-DOF linear encoder is composed of a reflective-type scale grating and an optical sensor head. A reference grating, which is identical to the scale grating except the scale length, is employed in the optical sensor head. Positive and negative first-order diffracted beams from the two gratings are superposed with each other in the optical sensor head to generate interference signals. The optical configuration is arranged in such a way that the direction of displacement in each axis can also be detected. A prototype two-DOF linear encoder is designed and constructed. The size of the optical sensor head is about 50 mm (X) × 50 mm (Y) × 30 mm (Z) and the pitch of the grating is 1.6 μm. It has been confirmed that the prototype two-DOF linear encoder has sub-nanometer resolutions in both the X- and Z-axes.