Metode Antagonistik Langsung untuk Skrining Bakteri Laut Penghasil Senyawa Anti-methicillin-resistant Staphylococcus aureus (MRSA)

Metode yang berbasis antagonistik langsung antara bakteri laut dan Staphylococcus aureus resistan metisilin (Methicillin-resistant Staphylococcus aureus, MRSA) berhasil digunakan untuk skrining bakteri laut penghasil senyawa anti-MRSA. Metode ini menggunakan medium agar lapis ganda untuk mendukung pertumbuhan bakteri laut dan MRSA. Beberapa bakteri laut penghasil senyawa anti-MRSA berhasil diisolasi dengan metode ini. Suatu bakteri laut, strain O-BC30 merupakan bakteri yang paling kuat menghambat pertumbuhan MRSA. Isolat-isolat bakteri yang didapat menunjukkan aktivitas yang stabil terhadap MRSA dan aktivitas ini juga konsisten dengan aktivitas ekstrak yang diperoleh dari sel bakteri yang dikultur pada medium agar. Metode ini sangat berguna dan efisien untuk skrining bukan hanya bakteri penghasil senyawa anti-MRSA tetapi juga bakteri penghasil antibiotik

KamLAND-Zenによる136Xeのニュートリノを伴わない二重ベータ崩壊における有質量マヨロン放出過程の探索

要約のみTohoku University清水格課

KamLAND-Zenによる136Xeのニュートリノを伴わない二重ベータ崩壊における有質量マヨロン放出過程の探索

要約のみTohoku University清水格課

Discrimination of Cherenkov light in Liquid Scintillator for Neutrinoless Double Beta Decay Experiment

　A liquid scintillator containing a tetrakis（isopropyl acetoacetato）zirconium has been developed for ZICOS experiment. We will use 180 tons of liquid scintillator containing 75 kg of 96Zr in the inner balloon（45 kg in fiducial volume）surrounding 64 % photo coverage of 20 inch photomultiplier. In order to reach the sensitivity ≥1027 years, we have to reduce 95 % of 208Tl decay backgrounds at least. Using Monte Carlo simulation, we could demonstrate new method using the hit pattern of PMT which received Cherenkov light, and could reduce 93 % of 208Tl background with 78 % efficiency for 0νββ signal. For the discrimination of Cherenkov light, we measured the timing pulse shape of Zr loaded liquid scintillator using FADC digitizer, and we found an inconsistent pulse shape at the rise timing with the template of scintillation. Also the event with an inconsistent pulse shape seems to have a directionality

Precise pulse shape measurement of Cherenkov light using sub-MeV electrons from Sr-90/Y-90 beta source

The precise spectral pulse shape from Cherenkov lights was directly measured by using sub-MeV electrons from 90Sr/90Y beta source. The observed shape was clearly different from the shape of scintillation light. The pulse rise and fall （decay） time for Cherenkov light were 0.8 ns and 2.5 ns, respectively. They were actually shorter than those times of scintillation light which were also measured by 1.6 ns and 6.5 ns, respectively. This clear Thisclearclear difference of rise time will be used for the pulse shape discrimination in order to select PMTs which receive Cherenkov lights, and the topological information due to Cherenkov light will be used for the reduction of backgrounds from 208Tl beta decay which should be major backgrounds observed around Q-value （3.35MeV）of 96Zr neutrinoless double beta decay

Direct measurement of spectral shape of Cherenkov light using cosmic muons

The spectral pulse shape of Cherenkov lights was directly measured by using cosmic muons. The observed decay times for early and late timing were 5.0 and 5.2ns, respectively. They were actually shorter than the time of scintillation lights which were also measured as 9.3ns and 9.2ns, respectively. However we could not see the difference of the rise time between scintillation and Cherenkov lights. This was due to the slow response of our DAQ equipment, photomultiplier and FADC digitize

Development of pulse shape discrimination for Cherenkov lights in liquid scintillator

With a liquid scintillation used for ZICOS experiment, we measured pulse shapes in case of several radio isotopes, 60Co, 137Cs, 133Ba, and 57Co. Taking FADC timing at 60 nsec for the peak position, FADC spectra from 58.5 nsec to 80 nsec were almost same shape for each RI, however, before 58.5 nsec, we have found that those were different shape. Especially, in case of 57Co, the energy is lower than Cherenkov threshold, so that the spectra should not include Cherenkov light. Using those spectra between 57.0 nsec and 58.0 nsec（3 bins）, we calculated simply χ2 and it was clearly discriminated that χ2 ≥ 0.1 should be include Cherenkov lights. This was also confirmed by Compton electrons with fixed energy and fixed direction. Obtained detection inefficiency of Cherenkov lights was observed by 21.4 ± 9.6 %. According to Compton edge events which have almost same direction as the incident γ and backgrounds events which should have isotropic direction, the detection inefficiency were 10.4 ± 0.5 % and 49.1 ± 1.4 %, respectively. They were quite different values and the inefficiency of both fixed energy and Compton edge events were statistically same. This is a direct evidence that Cherenkov lights should keep their topology even if they are emitted by around 1 MeV electron

Plaque Assay of Oncorhynchus masou Virus (OMV)

Plaque assays for salmonid virus, Oncorhynchus masou virus (OMV), were examined and compared with infectious haematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV), combining various fish cell-lines and three overlays. OMV produced the plaques only in chinook salmon embryo (CHSE-214) cells and rainbow trout gonad (RTG-2) cells, irrespective of overlays used, but plaque formation of IHNV and IPNV differed in different cell-lines according to the overlays used. The plaquing procedure using CHSE-214 cells gave a ten-fold higher number of plaques than RTG-2 cells. Among three overlays of methylcellulose, gum tragacanth, and agarose, methylcellulose overlay facilitated OMV plaque formation, and the plaques were most clearcut and easily enumerated. On the whole, the combination of methylcellulose overlay and CHSE-214 cell-line was the most suitable for plaque assay of OMV as well as IHNV and IPNV