From an exposure of 25.5 kiloton-years of the Super-Kamiokande detector, 900 muon-like and 983 electron-like single-ring atmospheric neutrino interactions were detected with momentum
p
e
>100 MeV/
c,
...p
μ
>200 MeV/
c, and with visible energy less than 1.33 GeV. Using a detailed Monte Carlo simulation, the ratio (
μ/
e)
DATA/(
μ/
e)
MC was measured to be 0.61±0.03(stat.)±0.05(sys.), consistent with previous results from the Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from theoretical models of atmospheric neutrino production.
A strict anaerobic bacterium, Desulfitobacterium sp. strain Y51, is capable of very efficiently dechlorinating tetrachloroethene (PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (cis-DCE) at ...concentrations as high as 960 μM and as low as 0.06 μM. Dechlorination was highly susceptible to air oxidation and to potential alternative electron acceptors, such as nitrite, nitrate or sulfite. The PCE reductive dehalogenase (encoded by the pceA gene and abbreviated as PceA dehalogenase) of strain Y51 was purified and characterized. The purified enzyme catalyzed the reductive dechlorination of PCE to cis-DCE at a specific activity of 113.6 nmol min-¹ mg protein-¹ . The apparent K m values for PCE and TCE were 105.7 and 535.3 μM, respectively. In addition to PCE and TCE, the enzyme exhibited dechlorination activity for various chlorinated ethanes such as hexachloroethane, pentachloroethane, 1,1,1,2-tetrachloroethane and 1,1,2,2-tetrachloroethane. An 8.4-kb DNA fragment cloned from the Y51 genome revealed eight open reading frames, including the pceAB genes. Immunoblot analysis revealed that PceA dehalogenase is localized in the periplasm of Y51 cells. Production of PceA dehalogenase was induced upon addition of TCE. Significant growth inhibition of strain Y51 was observed in the presence of cis-DCE, More interestingly, the pce gene cluster was deleted with high frequency when the cells were grown with cis-DCE.
A total of 137 upward stopping muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 516 detector live days. The measured muon flux is
0.39±0.04
(stat.)±0.02
(syst.)×10
−13
cm
−2s
...−1sr
−1
compared to an expected flux of
0.73±0.16
(theo.)×10
−13
cm
−2s
−1sr
−1
. Using our previously-published measurement of the upward through-going muon flux, we calculate the stopping/through-going flux ratio
R
, which has less theoretical uncertainty. The measured value of
R=0.22±0.02
(stat.)±0.01
(syst.)
is significantly smaller than the value 0.37
+0.05
−0.04(theo.) expected using the best theoretical information (the probability that the measured
R
is a statistical fluctuation below the expected value is 0.39%). A simultaneous fitting to zenith angle distributions of upward stopping and through-going muons gives a result which is consistent with the hypothesis of neutrino oscillations with the parameters sin
22
θ>0.7 and 1.5×10
−3<
Δm
2<1.5×10
−2 eV
2 at 90% confidence level, providing a confirmation of the observation of neutrino oscillations by Super-Kamiokande using the contained atmospheric neutrino events.
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