Synthesis of Various Water-Soluble C60 Derivatives and Their Superoxide-Quenching Activity

In order to examine the utility of fullerene as a medicinal application, we evaluated the reaction between fullerene derivatives and active oxygen species in vitro. This paper describes the synthesis of various water-soluble C₆₀ derivatives (cationic and anionic) and evaluation of their superoxide (O₂^-) quenching activity. Cationic C₆₀ derivatives showed fairly high efficiency.     

Thermal analysis and mechanism of α-Zn2SiO4:Mn formation from zinc oxalate dihydrate under hydrothermal conditions

Reaction of zinc oxalate dihydrate in high-temperature water at 200–400 °C was investigated to understand the mechanism of α-Zn₂SiO₄:Mn²⁺ formation and specifically why zinc oxalate dihydrate forms α-Zn₂SiO₄ crystalline phase at a higher rate compared with other water soluble and insoluble zinc sources studied in our previous works. From experiments under hydrothermal conditions, it was determined that the dehydration of zinc oxalate dihydrate became suppressed as the temperature and pressure increased. From thermal analyses, zinc oxalate dihydrate, which dehydrates at 160 °C in air, was stable at conditions up to 300 °C in water and this resulted in the lack of formation of the intermediate phase, hemimorphite, which forms at 150–175 °C from other zinc compounds (e.g. ZnO). The stability of the zinc oxalate dihydrate under hydrothermal conditions can possibly be attributed to changes in the chemical equilibrium with temperature and pressure which leads to the compound having less reactivity with silica so that reaction paths to form hemimorphite and β-Zn₂SiO₄ become unfavorable. Zinc oxalate dihydrate as starting material provided α-Zn₂SiO₄ at a higher formation rate than other starting materials.     

Technical note: A tool for determining rotational tilt axis with or without fiducial markers

Virtually all reliable TEM tomographic reconstructions in life science depend upon cross-correlating successive images in a tilt-stack, and then using gold nanobeads as fiducial markers for determining the relative image rotation axis. Although the rotational tilt angle is one of the essential parameters affecting the quality of tomographic reconstructions, little is discussed about its determination. We provide here a simple tool based on the property of Fast Fourier Transformation for determining this rotation axis offset angle. Our method uses two publicly-available software packages (IMOD and ImageJ), and can be used on any TEM-based image stack, which is useful for images with poor bead distribution or situations where such beads are not visible. We illustrate this procedure with two different biological samples, one of which is a plunge frozen cryo-sample with fiducials and the other an epon-embedded thin section without fiducials. Prior knowledge of the rotational tilt angle facilitates further processing tomograms. With cross-correlation and the FFT-obtained rotational tilt angle, we reconstructed tomograms, of which the cross-section did not show “arc” distortion. This tool could be easily incorporated into any software for the alignment with or without fiducials.     

Improving protocol capacity by scheduling random access on WLANs

The MAC protocol is important, especially for wireless LAN because of limited bandwidth. A great deal of research has been carried out and some of proposed schemes are effective. Specifically, considerable effort has been devoted to improving the IEEE 802.11 standard which is utilized widely. Previous theoretical analysis gave the upper bound of IEEE 802.11 DCF throughput which is far below the channel capacity and corresponding algorithm was proposed, which can achieve the throughput close to the upper bound. It seems that we cannot expect to enhance the throughput much more in a usual way. In the meantime, besides throughput, there are some other issues for DCF such as fairness and QoS support. However, except for several hybrid protocols, most proposals were either based on contention mode or schedule mode and neither of the two modes has possessed the good characters of the other. In this paper, we propose a new MAC scheme used for DCF (with no control node) that dynamically adapts to traffic changes without degradation of delay in the case of low traffic load and achieves high throughput which is close to transmission capacity in saturated case. The key idea is to divide the virtual frame into two parts, i.e., schedule part and contention part, and to enable each node to reserve a slot in schedule part. Unlike conventional hybrid protocols, every node does not have to intentionally reset any parameter according to the changing traffic load except its queue length. A distinguishing feature of this scheme is the novel way of allowing WLANs to work with low delay as in the contention-based mode and achieve high throughput as in the schedule-based mode without complicated on-line estimation required in previous schemes. This makes our scheme simpler and more reliable. Through an analysis of simulation results, we show that our scheme can greatly improve the throughput with low delay.     

Hierarchical Three-Dimensional Layer-by-Layer Assembly of Carbon Nanotube Wafers for Integrated Nanoelectronic Devices

We report a general approach to overcome the enormous obstacle of the integration of CNTs into devices by bonding single-walled carbon nanotubes (SWNTs) films to arbitrary substrates and transferring them into densified and lithographically processable "CNT wafers". Our approach allows hierarchical layer-by-layer assembly of SWNTs into organized three-dimensional structures, for example, bidirectional islands, crossbar arrays with and without contacts on Si, and flexible substrates. These organized SWNT structures can be integrated with low-power resistive random-access memory.     

pDUAL, a multipurpose, multicopy vector capable of chromosomal integration in fission yeast

A novel series of plasmid vectors named pDUAL have been developed. These vectors enable one to introduce not only multicopies of genes with episomal maintenance but also a single copy with chromosomal integration into the fission yeast, Schizosaccharomyces pombe. The multicopy plasmids can be easily converted to fragments for chromosomal integration by digestion of the plasmids with a certain restriction endonuclease before transformation of the yeast cells. The resultant fragments, lacking the autonomously replicating sequence, are designed for targeting into the chromosomal leu1 locus by homologous recombination. Whether the transformants are the results of episomal maintenance of the plasmid or homologous gene targeting can be readily checked by their requirement for uracil or leucine, or by the PCR diagnostic analysis. Furthermore, we propose the use of pDUAL derivatives for PCR-based chromosomal tagging of a gene to introduce several tags into 5'-terminus of a gene, employing a set of primers. Using these all-in-one vectors, a suitable mode of expression of a cloned gene can be selected for individual analysis without any complicated subcloning processes.     

G-lambda: Coordination of a Grid scheduler and lambda path service over GMPLS

At iGrid2005, we conducted a live demonstration where our Grid scheduling system co-allocated computing and network resources with advance reservation through Web services interfaces using the Grid Resource Scheduler (GRS), the Network Resource Management System (NRM), which is capable of GMPLS network resource management, and a GMPLS-based network test-bed, for the first time. The goal of the G-lambda project is to define a standard Web services interface (GNS-WSI) between GRS and NRM that is acceptable for both application service providers and commercial network operators, and which can be used as a tool for realizing new and emerging commercial services.