High-precision plant height measurement by drone with RTK-GNSS and single camera for real-time processing.

Conventional crop height measurements performed using aerial drone images require 3D reconstruction results of several aerial images obtained through structure from motion. Therefore, they require extensive computation time and their measurement accuracy is not high; if the 3D reconstruction result fails, several aerial photos must be captured again. To overcome these challenges, this study proposes a high-precision measurement method that uses a drone equipped with a monocular camera and real-time kinematic global navigation satellite system (RTK-GNSS) for real-time processing. This method performs high-precision stereo matching based on long-baseline lengths (approximately 1 m) during the flight by linking the RTK-GNSS and aerial image capture points. As the baseline length of a typical stereo camera is fixed, once the camera is calibrated on the ground, it does not need to be calibrated again during the flight. However, the proposed system requires quick calibration in flight because the baseline length is not fixed. A new calibration method that is based on zero-mean normalized cross-correlation and two stages least square method, is proposed to further improve the accuracy and stereo matching speed. The proposed method was compared with two conventional methods in natural world environments. It was observed that error rates reduced by 62.2% and 69.4%, for flight altitudes between 10 and 20 m respectively. Moreover, a depth resolution of 1.6 mm and reduction of 44.4% and 63.0% in the error rates were achieved at an altitude of 4.1 m, and the execution time was 88 ms for images with a size of 5472 × 3468 pixels, which is sufficiently fast for real-time measurement.

Antimicrobial susceptibilities of Listeria monocytogenes isolated in Japan.

The antimicrobial susceptibility of 201 Listeria monocytogenes isolates from foods, environments, animals and human patients in Japan was determined. All isolates were susceptible to ampicillin, the first choice of drug for listeriosis treatment, chloramphenicol, dihydrostreptomycin, erythromycin, enrofloxacin, gentamicin, kanamycin, lincomycin, nosiheptide, salinomycin, vancomycin, and virginiamycin. A human strain was resistant to oxytetracycline. The Minimum Inhibitory Concentration (MIC) for 50% of the strains and the MIC for 90% of the strains were comparable in all the isolates. This is the first investigation to compare antibiotic resistances between isolates from foods and isolates from human patients in Japan. The result showed that most of the isolates were susceptible to antibiotics used in this study.

Detection of Listeria monocytogenes from food samples by PCR after IMS-plating.

For rapid, accurate and sensitive detection of Listeria monocytogenes in food samples, colonies developed on the selective agar (Oxford agar) after immunomagnetic separation (IMS) were subjected to polymerase chain reaction (PCR) assay with the prf A1-2 primer pair. The proposed assay system was shown experimentally to be capable of specifically detecting the bacteria from food samples contaminated at more than 10(2) cfu/g. However, the enrichment culture after a short period of 16 h with the appropriate selective broth was needed before IMS-plating, because the bacterial contents in most actual food were as low as less than 10(2) cfu/g. However, even if the enrichment cultivation was employed before IMS, L. monocytogenes was detected within 3 days.

[Evaluation of selective plating media for the detection of heat- or freeze-injured Staphylococcus aureus].

The efficacy of Baird-Parker (BP) agar, mannitol-salt-egg yolk (MSEY) agar and mannitol salt (MS) agar in detecting Staphylococcus aureus FRI-100 heated at 52 degrees C for 20 min in 100 mmol/L potassium phosphate buffer was determined. Brain heart infusion agar with 1% pyruvate (BHIP agar) supported the highest recovery of injured cells and was used as the control medium. Of the three selective media, significantly higher recovery of heat-injured cells was observed on BP agar than MSEY agar, and the poorest recovery was observed on MS agar (p < 0.05). Low recovery of unheated cells was obtained for MS compared with other media (p < 0.05). A reduction in populations occurred gradually in reagent-grade water stored for 14 days at -20 degrees C. There was no significant difference between BHIP agar and MS agar in the number of freeze-injured cells recovered from 1 to 14 days.

Subtyping of Shiga toxin 2 variants in human-derived Shiga toxin-producing Escherichia coli strains isolated in Japan.

Shiga toxin 2 (Stx2) variants have been found to exhibit not only antigenic divergence, but also differences in toxicity for tissue culture cells and animals. To clarify whether all or just a subset of Stx2 variants are important for the virulence of Shiga toxin-producing Escherichia coli, we designed PCR primers to detect and type all reported variants. We classified them into four groups according to the nucleotide sequences of the Stx2 family; for example, group 1 (G1) contains VT2vha and group 2 (G2) contains VT2d-Ount. The 120 strains of Shiga toxin-producing E. coli used in this study were isolated from humans in Japan between 1986 and 1999. Among the four variant groups, the G1 gene only was detected in 23 of the 120 clinical strains (19.2%) and all belonged to the O157 serotype. G1 is considered the most important Stx2 variant group in terms of human pathogenicity. A multiplex PCR that can detect the stx1, stx2, and G1 genes was developed as a means of rapid and easy typing to better understand the roles of the different types of Stx.

[Influence of the conditions of storage and cooking on growth, invasion and survival of Salmonella enteritidis in eggs].

Basal studies for the confirmation of sanitary rules in the kitchen were performed, focusing on preventing an outbreak of food poisoning due to eggs contaminated with Salmonella Enteritidis (SE), using hen and quail eggs. SE did not grow at 5 degrees C but grew markedly at 25 degrees C in eggs. The invasion and growth of SE were marked under very humid conditions regardless of whether the eggshell was damaged. The invasion of SE into egg also occurred when eggs were taken in and out of the refrigerator. Moreover, SE was spread immediately to all non-contaminated eggs when SE-contaminated eggs were cracked into a bowl with non-contaminated eggs. In homemade mayonnaise containing 15% vinegar, sterilization took several hours to occur. On a stainless-steel bowl, SE survived for 2 weeks or more. These findings suggest that it is necessary to pay attention to secondary contamination.

High speed homology search with FPGAs.

We will introduce a way how we can achieve high speed homology search by only adding one off-the-shelf PCI board with one Field Programmable Gate Array (FPGA) to a Pentium based computer system in use. FPGA is a reconfigurable device, and any kind of circuits, such as pattern matching program, can be realized in a moment. The performance is almost proportional to the size of FPGA which is used in the system, and FPGAs are becoming larger and larger following Moore's law. We can easily obtain latest/larger FPGAs in the form off-the-shelf PCI boards with FPGAs, at low costs. The result which we obtained is as follows. The performance is most comparable with small to middle class dedicated hardware systems when we use a board with one of the latest FPGAs and the performance can be furthermore accelerated by using more number of FPGA boards. The time for comparing a query sequence of 2,048 elements with a database sequence of 64 million elements by the Smith-Waterman algorithm is about 34 sec, which is about 330 times faster than a desktop computer with a 1 GHz Pentium III. We can also accelerate the performance of a laptop computer using a PC card with one smaller FPGA. The time for comparing a query sequence (1,024) with the database sequence (64 million) is about 185 sec, which is about 30 times faster than the desktop computer.