Tunable supercurrent through semiconductor nanowires

Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.     

Isolation and characterization of orf viruses from Korean black goats

Five cases of orf virus infection in Korean black goats were diagnosed in our laboratory between 2010 and 2011. One orf virus (ORF/2011) was isolated from an ovine testis cell line (OA3.Ts) for use as a vaccine candidate. Sequences of the major envelope protein and orf virus interferon resistance genes were determined and compared with published reference sequences. Phylogenetic analyses revealed that orf viruses from Korean black goats were most closely related to an isolate (ORF/09/Korea) from dairy goats in Korea. This result indicates that the orf viruses might have been introduced from dairy goats into the Korean black goat population.     

Protective efficacy of commercial inactivated Newcastle disease virus vaccines in chickens against a recent Korean epizootic strain

Despite the intensive vaccination policy that has been put in place to control Newcastle disease virus (NDV), the recent emergence of NDV genotype VII strains in Korea has led to significant economic losses in the poultry industry. We assessed the ability of inactivated, oil-emulsion vaccines derived from La Sota or Ulster 2C NDV strains to protect chickens from challenge with Kr-005/00, which is a recently isolated Korean epizootic genotype VII strain. Six-week-old SPF chickens were vaccinated once and challenged three weeks later via the eye drop/intranasal route. All vaccinated birds were fully protected from disease, regardless of the vaccine strains used. All vaccinated and challenged groups showed significant sero-conversion 14 days after challenge. However, some vaccinated birds, despite being protected from disease, shed the challenge virus from their oro-pharynx and cloaca, albeit at significantly lower titers than the unvaccinated challenged control birds. The virological, serological, and epidemiological significance of our observations with regard to NDV disease eradication is discussed.     

Experimental infection of chickens, ducks and quails with the highly pathogenic H5N1 avian influenza virus

Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype have spread since 2003 in poultry and wild birds in Asia, Europe and Africa. In Korea, the highly pathogenic H5N1 avian influenza outbreaks took place in 2003/2004, 2006/2007 and 2008. As the 2006/2007 isolates differ phylogenetically from the 2003/2004 isolates, we assessed the clinical responses of chickens, ducks and quails to intranasal inoculation of the 2006/2007 index case virus, A/chicken/Korea/IS/06. All the chickens and quails died on 3 days and 3-6 days post-inoculation (DPI), respectively, whilst the ducks only showed signs of mild depression. The uninoculated chickens and quails placed soon after with the inoculated flock died on 5.3 and 7.5 DPI, respectively. Both oropharyngeal and cloacal swabs were taken for all three species during various time intervals after inoculation. It was found that oropharyngeal swabs showed higher viral titers than in cloacal swabs applicable to all three avian species. The chickens and quails shed the virus until they died (up to 3 to 6 days after inoculation, respectively) whilst the ducks shed the virus on 2-4 DPI. The postmortem tissues collected from the chickens and quails on day 3 and days 4-5 and from clinically normal ducks that were euthanized on day 4 contained the virus. However, the ducks had significantly lower viral titers than the chickens or quails. Thus, the three avian species varied significantly in their clinical signs, mortality, tissue virus titers, and duration of virus shedding. Our observations suggest that duck and quail farms should be monitored particularly closely for the presence of HPAIV so that further virus transmission to other avian or mammalian hosts can be prevented.     

Control measures to African swine fever outbreak: active response in South Korea,preparation for the future,and cooperation

African swine fever (ASF) is one of the most complex infectious swine diseases and the greatest concern to the pig industry owing to its high mortality and no effective vaccines available to prevent the disease. Since the first outbreak of ASF in pig farms, ASF has been identified in 14 pig farms in four cities/counties in South Korea. The outbreak was resolved in a short period because of the immediate control measures and cooperative efforts. This paper reviews the ASF outbreak and the experience of successfully stopping ASF in pig farms in South Korea through active responses to prevent the spread of ASF. In addition, suitable changes to build a sustainable pig production system and collaborative efforts to overcome the dangerous animal disease, such as ASF, are discussed.     

Development of real-time onion disease monitoring system using image acquisition

In this study, real-time disease monitoring was conducted on onion which is the most representative crop in Republic of Korea, using an image acquisition system newly developed for the mobile measurement of phenotype. The purpose of this study was to improve the accuracy of prediction of disease and state variables by processing images acquired from monitoring. The image acquisition system was consisted of two parts, a motorized driving system and a PTZ (pan, tilt and zoom) camera to take images of the plants. The acquired images were processed as follows. Noise was removed through an image filter and RGB (red, green and blue) colors were converted to HSV (hue, saturation and value), which enabled thresholding of areas with different colors and properties for image binarization by comparing the color of onion leaf with ambient areas. Four objects with the most significant browning in the onion leaf to the naked eye were selected as the samples for data acquired. The thresholding method with image processing was found to be superior to the naked eye in identifying accurate disease areas. In addition, it was found that the incidence of disease was different in each disease area ratio. As a result, the use of image acquisition system in image processing analysis will enable more prompt detection of any changes in the onion and monitoring of disease outbreaks during the crop lifecycle.     

Productivity and energy partition of late lactation dairy cows during heat exposure

Three late-lactation Holstein cows were used to determine the effects of environmental temperature on performance and energy partitioning. Each cow was housed in a respiratory chamber for 30 consecutive days and exposed to three different conditions of environmental temperature: (i) 20°C and 20°C (20°C), (ii) 25°C and 20°C (25°C), (iii) 30°C and 25°C (30°C) during the day and night, respectively. The temperature was switched in an interval of 10 days. Humidity in the chamber was maintained at 55–65% through the entire experimental period. The daily mean as well as morning and evening rectal temperatures of Holstein cows increased linearly ( P  < 0.05) as chamber temperature increased. There was a significant linear reduction in dry matter (DM) intake ( P  < 0.05) and an increase in DM digestibility ( P  < 0.05). The response in milk yield, however, was not affected by heat stress. There were no significant differences among treatments for intake energy, heat production, net energy for lactation and net energy for gain. This results of this study disagreed with the assumption that late lactation cows gave priority to increasing body tissue at the expense of milk production under thermal stress.     

Surveillance of ASF-infected pig farms from September to October 2019 in South Korea

Fourteen African swine fever (ASF) outbreaks occurred in the pig farms in the northwestern region of South Korea, near the border with North Korea, from September 16, 2019 to October 9, 2019. Active and passive surveillance on the ASF-infected farms indicated that the infection was limited only to pigsties where the infected pigs were detected on the farm for the first time before further transmission to other pigsties and farms. This early detection could be one of the pivotal factors for the prompt eradication of ASF in domestic pig farms within 1 month in the northwestern region of South Korea.