Ion channeling study of epitaxy of iron based Heusler alloy films on Ge(111)

We have investigated perfection of atomic rows on iron-based Heusler alloy films on Ge(111) planes by using ion channeling technique in order to find the dominant factors for the perfection. Fe₃Si/Ge(111) and Fe₂CoSi/Ge(111) have a high quality of atomic rows at the heterointerface like that of perfect crystals. Fe_3−xMn_xSi/Ge(111) (x = 0.84, 0.72 and 0.36) interfaces have imperfection of atomic rows which may be controlled by both the lattice mismatch with the Ge substrate and the Mn-Si pairs due to the site disorder in the film with the Mn content x > 0.75. Analysis of axial channeling parameters employed in this study is very useful for quantitative evaluation of perfection of atomic rows at the heterointerface.     

Enhancement in skin permeation of 5-aminolevulinic acid using l-menthol and its derivatives

Enhancing effect of l-menthol and its derivatives, l-menthyl formate, l-menthyl acetate, and l-menthyl propionate, on skin permeation of 5-aminolevulinic acid (ALA) through Yucatan micropig full-thickness skin was investigated using a Franz-type diffusion cell. ALA solutions were prepared using ethanol-water mixed solvents with l-menthol or the derivative. Skin permeation coefficients (Kp) of ALA with more than 3.0 wt% of l-menthol was significantly larger than that without l-menthol. In addition, Kp of ALA with the derivative increased as follows: l-menthol approximately l-menthyl propionate < l-menthyl formate < l-menthyl acetate. These results suggest that l-menthol and the derivative are effective to enhance ALA skin permeation.     

Charge contrast imaging of suspended nanotubes by scanning electron microscopy

A method of rapidly identifying and imaging suspended nanotubes by scanning electron microscopy is reported. Nanotubes are visible in high contrast and even at low magnification. The contrast can be explained by considering the effect that the charge on the nanotube has on the substrate. The proposed mechanism is general and should apply to any charged nanostructure in proximity to a surface or interface. This represents a new contrast mechanism in scanning electron microscopy.     

Influence of gas adsorption on optical transition energies of single-walled carbon nanotubes

The photoluminescence (PL) spectra of suspended single-walled carbon nanotubes (SWNTs) were measured in an ethanol gas atmosphere. When the gas pressure was decreased, the PL peaks were initially blue-shifted to a small extent before a rapid blue-shift took place at a transition pressure that depended on the temperature and diameter of the SWNT being measured. This pressure dependence is due to the adsorption of ethanol molecules on the SWNT surface. The optical transition energies measured below the transition pressure are intrinsic to the SWNT.     

Fates of foodborne pathogens in raw hams manufactured rapidly using a new patented method

To manufacture raw ham in an efficient manner, we recently developed a new system in which presliced pork loin was used, and the processing time was reduced to 5% of the conventional method. This study aimed to examine whether this raw ham could be as safe as ham produced by the conventional method. Pork loin spiked with enterohemorrhagic Escherichia coli serotype O157:H7, Listeria monocytogenes serotype 1/2c, Salmonella enterica serovar Enteritidis, and Staphylococcus aureus were processed using either the new or conventional method. The fate of the foodborne pathogens and behavior of hygiene indicator bacteria were examined. Whereas nitrite had disappeared during the conventional packaging process, the reduced processing time in the new system allowed for the ham to be vacuum packed with retention of the nitrite (6.9±1.2 ppm, P<0.01). This accounts for the prominent decrease in L. monocytogenes (2.3 log reduction in 35 days) and S. aureus (3.3 log reduction in 13 days) counts during storage. E. coli O157 and Salmonella Enteritidis were likely resistant to the nitrite in the ham. However, they were unable to multiply in the ham and decreased gradually as in the conventionally produced ham. The bacteriostatic nature of the raw ham was also indicated by the gradual decrease in coliforms (1.3 log reduction in 13 days) in nonspiked ham. In conclusion, the raw ham produced using presliced pork loin is practically as safe as conventionally produced raw ham. It is worth validating these results in a small-scale production setting.     

Characterization of transient expression system for retroviral vector production

The production of retroviral vectors using a transient expression system has been improved to obtain a high-titer virus preparation that is difficult to produce using packaging cell lines due to the cytotoxic or cytostatic effect of transgenes. Here, we used one such production method, the so-called Q-vector system, and examined its potential for virus production. The Q-vector system could produce a similar level of viral vectors compared with the packaging cell system but the production seemed to depend on the size and nature of transgenes. In the process of investigation of the quantitative difference in viral components between the transient expression system and the packaging cell system, we found that the Q-vector system could express higher amounts of viral RNA and proteins compared with the packaging cell system. However, this did not lead to a higher virus titer compared with that produced by the packaging cell system. This suggests that retroviral RNA transcribed from the plasmid in the transient system seemed to be used mainly for translation and only some of the RNA molecules were packaged in viral particles.     

Molecular typing to trace Listeria monocytogenes isolated from cold-smoked fish to a contamination source in a processing plant

In this study, Listeria monocytogenes contamination in a cold-smoked fish processing plant in Osaka, Japan, was examined from 2002 to 2004. A total of 430 samples were collected and divided into five categories: raw fish, materials during processing, processing equipment, environment, and finished products. A total of 59 finished products were examined throughout this study. L. monocytogenes was isolated from four of these samples during summer and autumn but was not found during winter or spring. During the warmer seasons, L. monocytogenes was more prevalent on processing equipment, especially slicing machines (8 of 54 samples in summer and autumn versus 1 of 50 samples in winter and spring). L. monocytogenes was not detected on whole skins removed from 23 frozen raw fish. L. monocytogenes strains isolated from 56 samples were characterized by serotyping, pulsed-field gel electrophoresis, and three PCR-based methods. Seventy-seven L. monocytogenes strains were recognized as contaminants of the samples: 2 distinguishable strains were identified in each of 13 samples, 3 strains were identified in 2 samples, 5 strains were identified in 1 sample, and the other 40 strains were identified in 40 samples. Combining the results from these techniques, 77 strains were classified into 13 different types. Three of these types prevailed throughout the plant, and two of the three were also isolated from final products. The DNA subtype found in the product was also found on the slicing machines. Our findings suggest that the slicing machines at this plant were the source of the product contamination. Implementing an appropriate cleaning regime for the slicing machines was effective in preventing contamination.     

Single-walled carbon nanotube growth from highly activated metal nanoparticles

We demonstrate that any metal, even gold, silver, and copper, can act as a catalyst for SWCNT synthesis in chemical vapor deposition (CVD). Metal nanoparticles 3 nm or less in diameter, introduced into CVD ambience immediately after heat treatment at 800-950 degrees C in air, produce SWCNTs. The activation method is effective for copper and various noble metals as well as for iron-family elements. This implies that any metal particle may produce SWCNTs when its size becomes 1-3 nm. In other words, carbon atoms can form SWCNTs in a self-assembling fashion on nanoparticles without the specific functions of iron-family elements.     

Mechanism underlying specificity of proteins targeting inorganic materials

Adhesion force analysis using atomic force microscopy clearly revealed for the first time the mechanism underlying the specific binding between a titanium surface and ferritin possessing the sequence of Ti-binding peptide in its N-terminal domain. Our results proved that the specific binding is due to double electrostatic bonds between charged residue and surface groups of the substrate. Furthermore, it is also demonstrated that the accretion of surfactant reduces nonspecific interactions, dramatically enhancing the selectivity and specificity of Ti-binding peptide.     

Single-walled carbon nanotube growth with non-iron-group “catalysts” by chemical vapor deposition

Various materials have been found to “catalyze” carbon nanotube growth in chemical vapor deposition (CVD) when they become nano-sized particles. These involve not only metals, such as Pd, Pt, Au, Ag, and Cu, but also semiconductors, such as Si, Ge, and SiC. Alumina and diamond nanoparticles also produce carbon nanotubes. These “catalysts”, which are better called “seeds”, can be categorized into two types: one type forms a eutectic liquid or highly-mobile alloy with carbon, and carbon atoms precipitate from the eutectic alloy; the other type remains as a solid phase and form a carbon surface layer during CVD growth. In this paper, we review recent studies of SWCNT growth with these non-iron-group materials and highlight the mechanisms involved.