Carbon/carbon composites consisting of single-walled carbon nanotube (SWCNT) buckypaper (BP) and mesophase pitch resin have been produced through impregnation of BP with pitch using toluene as a solvent. Drying, stabilization and carbonization processes were performed sequentially, and repeated to increase the pitch content. Voids in the carbon/carbon composite samples decreased with increasing impregnation process cycles. Electrical conductivity and density of the composites increased with carbonization by two to three times that of pristine BP. These results indicate that discontinuity and intertube contact barriers of SWCNTs in the BP are partially overcome by the carbonization process of pitch. The temperature dependence of the Raman shift shows that mechanical strain is increased since carbonized pitch matrix surrounds the nanotubes. 相似文献
With the fast increase of multimedia contents, efficient forensics investigation methods for multimedia files have been required. In multimedia files, the similarity means that the identical media (audio and video) data are existing among multimedia files. This paper proposes an efficient multimedia file forensics system based on file similarity search of video contents. The proposed system needs two key techniques. First is a media-aware information detection technique. The first critical step for the similarity search is to find the meaningful keyframes or key sequences in the shots through a multimedia file, in order to recognize altered files from the same source file. Second is a video fingerprint-based technique (VFB) for file similarity search. The byte for byte comparison is an inefficient similarity searching method for large files such as multimedia. The VFB technique is an efficient method to extract video features from the large multimedia files. It also provides an independent media-aware identification method for detecting alterations to the source video file (e.g., frame rates, resolutions, and formats, etc.). In this paper, we focus on two key challenges: to generate robust video fingerprints by finding meaningful boundaries of a multimedia file, and to measure video similarity by using fingerprint-based matching. Our evaluation shows that the proposed system is possible to apply to realistic multimedia file forensics tools.
In the brain, polyunsaturated fatty acids (PUFA), especially arachidonic acid and docosahexaenoic acid (DHA), are required
for regulating membrane fluidity, neuronal survival and signal transduction. Since the brain cannot synthesize n-6 and n-3
PUFA de novo, they must be supplied from the blood. However, the methods of PUFA entry into the brain are not agreed upon.
This study tested the necessity of CD36, a candidate transporter of unesterified fatty acids, for maintaining brain PUFA concentrations
by comparing brain PUFA concentrations in CD36−/− mice to their wild-type littermates. Because CD36−/− mice have been reported to have impaired learning ability, the PUFA concentrations in different brain regions (cortex, hippocampus,
cerebellum and the remainder of brain) were investigated. At 9 weeks of age, the brain was separated into the four regions
and fatty acid concentrations in total and phospholipid classes of these brain regions were analyzed using thin layer and
gas chromatography. There were no statistical differences in arachidonic acid or DHA concentrations in the different brain
regions between wild-type and CD36−/− mice, in total or phospholipid fractions. Concentrations of monounsaturated fatty acids were decreased in several phospholipid
fractions in CD36−/− mice. These findings suggest that CD36 is not necessary for maintaining brain PUFA concentrations and that other mechanisms
must exist. 相似文献
