ABSTRACT. The effects of three representative disinfectants, chlorine (sodium hypochlorite), iodine (potassium tetraglicine triiodide), and quaternary ammonium compound (didecyldimethylammonium chloride), on several exotic disease viruses were examined. The viruses used were four enveloped viruses (vesicular stomatitis virus, African swine fever virus, equine viral arteritis virus, and porcine reproductive and respiratory syndrome virus) and two non-enveloped viruses (swine vesicular disease virus (SVDV) and African horse sickness virus (AHSV)). Chlorine was effective against all viruses except SVDV at concentrations of 0.03% to 0.0075%, and a dose response was observed. Iodine was very effective against all viruses at concentrations of 0.015% to 0.0075%, but a dose response was not observed. Quaternary ammonium compound was very effective in low concentration of 0.003% against four enveloped viruses and AHSV, but it was only effective against SVDV with 0.05% NaOH. Electron microscopic observation revealed the probable mechanism of each disinfectant. Chlorine caused complete degeneration of the viral particles and also destroyed the nucleic acid of the viruses. Iodine destroyed mainly the inner components including nucleic acid of the viruses. Quaternary ammonium compound induced detachment of the envelope of the enveloped viruses and formation of micelle in non-enveloped viruses. According to these results, chlorine and iodine disinfectants were quite effective against most of the viruses used at adequately high concentration. The effective concentration of quaternary ammonium compound was the lowest among the disinfectants examined.-KEY WORDS: disinfection, electron microscopy, exotic disease virus.J. Vet. Med. Sci. 62(1): 85-92, 2000 disease for horse racing in Japan [15]. PRRSV is not an exotic disease virus in Japan now [17], but it is a new disease virus; therefore, a disinfection against this virus has not been tested well. MATERIALS AND METHODS Viruses and cell culture:The J1 strain of SVDV [23], the New Jersey strain of VSV [4], the Lisbon strain of ASFV [20], the type 4 vaccine strain of AHSV [16], the modified Bucyrus strain of EVAV [15], and the EDRD strain of PRRSV [17] were used in this study. SVDV and VSV were propagated in IBRS-2 cells [11]. ASFV and AHSV were propagated in Vero cells [16]. EVAV and PRRSV were prepared in Marc-145 cells [17]. The viral samples of SVDV, VSV, AHSV were prepared in cells cultured with the serum free medium, but those of ASFV, EVAV, and PRRSV were prepared in cells cultured with the medium containing 2% bovine serum.Virus titration: The virus titers before and after treatment with disinfectants were titrated in each of culture cells. The titration of SVDV and VSV was carried out by plaque formation method as previously described [11] and the titers were expressed as plaque-forming unit (PFU) per 0

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The magnetic anisotropy and rotational hysteresis loss in Ni-Fe/Mn-Ir bilayers were investigated for films prepared by an ultraclean sputtering deposition process. An in-plane field of 30 Oe during deposition served to define the antiferromagnetic ͑AF͒ alignment axis for the Mn-Ir layer. The Ni-Fe layer thickness was maintained at 50 Å and the Mn-Ir layer thickness ranged from 20 to 200 Å. Room temperature magnetization and torque measurements were made as a function of the Mn-Ir layer thickness d AF and the applied field. The magnetization data were obtained for fields applied in the same direction as during deposition. The magnetization data indicate a critical d AF value of 37 Å, taken as d AF cr . For d AF Ͼd AF cr , the data show hysteresis loops which are displaced along the field axis. The torque response and rotational hysteresis characteristics are sensitive to both d AF and the measuring field. ͑1͒ When d AF is much less than d AF cr , the torque curves have a sin characteristic at fields below 30-40 Oe or so which suddenly changes to a sin 2 characteristic at higher fields. With the onset of the sin 2 torque response, rotational hysteresis loss also appears but then vanishes for fields above 100 Oe or so. ͑2͒ As d AF approaches d AF cr from below, the torque response is the same as above. Here, however, the rotational hysteresis appears for fields well below the field at which the torque response assumes a sin 2 character and persists to the maximum available measuring field of 15 kOe or so. ͑3͒ When d AF exceeds d AF cr , the torque has a predominant sin character at all fields and a small sin 2 component and rotational hysteresis which only around a field of 400 Oe or so. These results, while somewhat complicated, are in accord with responses evaluated from the simple exchange anisotropy model of W. H. Meiklejohn and C. P. Bean ͓Phys. Rev. 102, 1413 ͑1956͒; 105, 904 ͑1957͔͒. Among other things, one may conclude that a rotational hysteresis which persists to high field is not intrinsic to exchange anisotropy.

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