Nanodiamond (ND) has emerged as a promising carbon nanomaterial for therapeutic applications. In previous studies, ND has been reported to have outstanding biocompatibility and high uptake rate in various cell types. ND containing nitrogen-vacancy centers exhibit fluorescence property is called fluorescent nanodiamond (FND), and has been applied for bio-labeling agent. However, the influence and application of FND on the nervous system remain elusive. In order to study the compatibility of FND on the nervous system, neurons treated with FNDs in vitro and in vivo were examined. FND did not induce cytotoxicity in primary neurons from either central (CNS) or peripheral nervous system (PNS); neither did intracranial injection of FND affect animal behavior. The neuronal uptake of FNDs was confirmed using flow cytometry and confocal microscopy. However, FND caused a concentration-dependent decrease in neurite length in both CNS and PNS neurons. Time-lapse live cell imaging showed that the reduction of neurite length was due to the spatial hindrance of FND on advancing axonal growth cone. These findings demonstrate that FNDs exhibit low neuronal toxicity but interfere with neuronal morphogenesis, and should be taken into consideration when applications involve actively growing neurites (e.g. nerve regeneration).
BackgroundPolymerase chain reaction (PCR) ribotyping is one of the globally accepted techniques for defining epidemic clones of Clostridium difficile and tracing virulence-related strains. However, the ambiguous data generated by this technique makes it difficult to compare data attained from different laboratories; therefore, a portable technique that could supersede or supplement PCR ribotyping should be developed. The current study attempted to use a new multilocus variable-number tandem-repeat analysis (MLVA) panel to detect PCR-ribotype groups. In addition, various MLVA panels using different numbers of variable-number tandem-repeat (VNTR) loci were evaluated for their power to discriminate C. difficile clinical isolates.ResultsAt first, 40 VNTR loci from the C. difficile genome were used to screen for the most suitable MLVA panel. MLVA and PCR ribotyping were implemented to identify 142 C. difficile isolates. Groupings of serial MLVA panels with different allelic diversity were compared with 47 PCR-ribotype groups. A MLVA panel using ten VNTR loci with limited allelic diversity (0.54-0.83), designated MLVA10, generated groups highly congruent (98%) with the PCR-ribotype groups. For comparison of discriminatory power, a MLVA panel using only four highly variable VNTR loci (allelic diversity: 0.94-0.96), designated MLVA4, was found to be the simplest MLVA panel that retained high discriminatory power. The MLVA10 and MLVA4 were combined and used to detect genetically closely related C. difficile strains.ConclusionsFor the epidemiological investigations of C. difficile, we recommend that MLVA10 be used in coordination with the PCR-ribotype groups to detect epidemic clones, and that the MLVA4 could be used to detect outbreak strains. MLVA10 and MLVA4 could be combined in four multiplex PCR reactions to save time and obtain distinguishable data.
The fate of the carcinogen 3,3′‐dichlorobenzidine (DCB) in soil was evaluated with regard to persistence and binding. A Brookston clay loam soil was amended with 4 or 40 ppm 14C‐DCB and incubated under aerobic conditions for 32 weeks or under anaerobic conditions for 1 year. Mineralization occurred very slowly in aerobic soil and did not occur in anaerobic soil. Total 14C radioactivity in soil remained essentially constant during the incubations, demonstrating that volatile losses of DCB or DCB decomposition products did not occur in our incubation system. DCB was shown to bind strongly to soil. After 32 weeks of incubation, approximately 90% of the applied radioactivity remained in soil after extraction with ethyl acetate and methanol. The loss of solvent‐extractable DCB occurred mostly in the first several weeks of incubation and was accompanied by an increase in alkali‐extractable DCB. These data strongly suggest the formation of covalent linkages between DCB and soil humic components as the primary fate of DCB in the Brookston soil. The significance of humus‐bound DCB residues as potential sources of future contamination is essentially unknown.
Orthogonal frequency-division multiplexing (OFD-M) is a popular transmission technology in cognitive radio (CR) networks, because the correlation of cyclic prefix (CP) in OFDM signals can be utilized to improve the reliability of spectrum sensing of secondary users (SUs). However, the optimal spectrum sensing over multipath fading channels remains an important and challenging issue. Therefore, this work proposes an optimal Neyman-Pearson (NP) detector for spectrum sensing using the CP. To detect the OFDM signal of primary users (PUs), the log-likelihood ratio (LR) test is formulated by using the correlation characteristics of the redundancy of CP. Analytical results indicate that the LR of received samples is equivalent to their log-likelihood function (LF) plus the LR of an energy detector (ED), subsequently allowing us to gain insights on the optimal NP detector. Since many unknown parameters need to be resolved, a practical generalized log-likelihood ratio test (GLRT) is presented. Moreover, to achieve a good performance over multipath fading channels, a channel-independent GLRT (CI-GLRT) is employed to derive an estimation of correlation coefficient independent of multipath channel profiles. Simulations confirm the advantages of the proposed detectors compared with state-of-the-art detectors.
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