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Khumaeni, A.,Niki, H.,Fukumoto, K.i.,Deguchi, Y.,Kurihara, K.,Kagawa, K.,Lee, Y.I. Elsevier 2011 Current Applied Physics Vol.11 No.3
A sensitive analysis of powder samples has successfully been conducted using a strong gas breakdown plasma induced by assisting a metal mesh and a metal subtarget utilizing a transversely excited atmospheric (TEA) CO<SUB>2</SUB> laser; the metal mesh and the metal subtarget were placed on the front side and backside of the sample, respectively. The experiment was made at high pressure of air surrounding gas. In this study, the TEA CO<SUB>2</SUB> laser (1.5 J, 200 ns) was focused on the sample surface through the metal mesh. At the initial stage, a strong gas breakdown plasma was initiated by the assist of the metal mesh and finally enhanced by the metal subtarget after the laser beam struck on the metal subtarget's surface through a hole inside the sample. The strong gas breakdown plasma can effectively be applied to completely dissociate and excite the ablated atoms from the sample. Using this technique, an excellent calibration curve with zero intercept has been made using herb medicine powder sample containing different concentrations of Zn. For sensitive analysis, a detection of hazard element of Cr in commercial supplement was also carried out. The detection limit of Cr was estimated to be around 0.6 mg/kg. This present technique has high possibility to realize the analysis of powder samples with high precision and high sensitivity.
APPLICATION OF WHOLE BODY COUNTER TO NEUTRON DOSE ASSESSMENT IN CRITICALITY ACCIDENTS
Kurihara, O.,Tsujimura, N.,Takasaki, K.,Momose, T.,Maruo, Y. 대한방사선 방어학회 2001 방사선방어학회지 Vol.26 No.3
Neutron dose assessment in criticality accidents using Whole Body Counter(WBC) was proved to be an effective method as rapid neutron dose estimation at the JCO criticality acciedent in Tokai-mura. The 1.36MeV gamma-ray of 24Na in a body can be detected easily by a germanium detector. The minimum Detectable Activity(MDA) of 24Na is approximately 50Bq for 10miniute measurement by the germanium-type whole body counter at JNC Tokai Works. Neutron energy spectra at the typical shielding conditions in criticality accidents were calculated and the conversion factor, whole body activity-to-organ mass weighted neutron absorbed dose, corresponding to each condition were determined. The conversion factor for uncollied fission spectrum is 7.7[(Bq24Na/g23Na)/mGy].
Khumaeni, A.,Kurihara, K.,Lie, Z.S.,Kagawa, K.,Lee, Y.I. Elsevier 2014 Current Applied Physics Vol.14 No.3
Taking advantages of the special characteristics of a transversely excited atmospheric (TEA) CO<SUB>2</SUB> laser, the analysis of sodium aerosol has been successfully conducted by using laser-induced gas plasma spectroscopy (LIGPS) method. In this study, the sodium aerosol was deposited on a nickel metal plate; the metal plate functions as a subtarget to initiate a gas plasma. When a pulsed TEA CO<SUB>2</SUB> laser was focused on the metal surface, a large-volume and high-temperature gas plasma was induced. The fine particles of sodium then entered into the gas plasma region to be dissociated and excited. By using this technique, a semi quantitative analysis of sodium aerosol was made. The detection limit of sodium was approximately 200 ppb.
Comparison of In vivo and In vitro Techniques for Methane Production from Ruminant Diets
Bhatta, Raghavendra,Tajima, K.,Takusari, N.,Higuchi, K.,Enishi, O.,Kurihara, M. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.7
This study was conducted to compare the methane ($CH_4$) production estimated by in vivo (sulfur hexafluoride tracer technique ($SF_6$)) with that of two in vitro rumen simulation (RUSITEC) and gas production (IVGPT)) techniques. Four adult dry Holstein cows, aged $7.4{\pm}3.0$ years and weighing $697{\pm}70$ kg, were used for measuring methane production from five diets by the $SF_6$ technique. The experimental diets were alfalfa hay ($D_1$), corn silage + soybean meal (SBM) (910: 90, $D_2$), Italian rye grass hay +SBM (920: 80, $D_3$), rice straw +SBM (910: 90, $D_4$) and Sudan grass hay +SBM (920: 80, $D_5$). Each diet was individually fed to all 4 cows and 5 feeding studies of 17 d each were conducted to measure the methane production. In the RUSITEC, methane production was measured from triplicate vessels for each diet .In vitro gas production was measured for each of the diets in triplicate syringes. The gas produced after 24 and 48 h was recorded and gas samples were collected in vacuum vials and the methane production was calculated after correction for standard temperature and pressure (STP). Compared to the $SF_6$ technique, estimates of methane production using the RUSITEC were lower for all diets. Methane production estimated from 24 h in vitro gas production was higher (p<0.001) on $D_1$ as compared to that measured by $SF_6$, whereas on $D_2$ to $D_5$ it was lower. Compared to $SF_6$, methane production estimated from 48 h in vitro gas production was higher on all diets. However, methane estimated from the mean of the two measurement intervals (24+48 h/2) in IVGPT was very close to that of $SF_6$ (correlation 0.98), except on $D_1$. The results of our study confirmed that IVGPT is reflective of in vivo conditions, so that it could be used to generate a database on methane production potential of various ruminant diets and to examine strategies to modify methane emissions by ruminants.
Bhatta, R.,Tajima, K.,Kurihara, M. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.3
An experiment was conducted to study the effect of temperature and pH on in vitro nutrient degradability, volatile fatty acid profile and methane production. The fermenter used was the semi-continuous system, known as the rumen simulation technique (RUSITEC). Sixteen cylinders were used at one time with a volume of 800 ml, the dilution rate was set at 3.5%/hour, the infused buffer being McDougall's artificial saliva. Basal diet (9.6 g DM) used in RUSITEC consisted of (DM) 6.40 g Timothy hay, 1.86 g crushed corn and 1.34 g soybean meal. The food for the fermentation vessel was provided in nylon bags, which were gently agitated in the liquid phase. The experiment lasted for 17 d with all the samples taken during the last 5 d. Treatments were allocated at random to four vessels each and were (1) two temperature levels of $39^{\circ}C$ and $41^{\circ}C$ (2) two pH levels of 6.0 and 7.0. The total diet contained ($g\;kg^{-1}$ DM) 957 OM, 115 CP and $167MJ\;kg^{-1}$ (DM) GE. Although increase in temperature from $39^{\circ}C$ to $41^{\circ}C$ reduced degradation of major nutrients in vitro, it was non-significant. Interaction effect of temperature with pH also reflected a similar trend. However, pH showed a significant (p<0.05) negative effect on the degradability of all the nutrients in vitro. Altering the in vitro pH from 7 to 6 caused marked reduction in DMD from 60.2 to 41.8, CPD from 76.3 to 55.3 and GED from 55.3 to 35.1, respectively. Low pH (6) depressed total VFA production (61.9 vs. 34.9 mM) as well as acetate to propionate ratio in vitro (from 2.0 to 1.5) when compared to pH 7. Compared to pH 7, total gas production decreased from 1,841 ml to 1,148 ml at pH 6, $CO_2$ and $CH_4$ production also reduced from 639 to 260 ml and 138 to 45 ml, respectively. This study supported the premise that pH is one of the principal factors affecting the microbial production of volatile fatty acids and gas. Regulating the ruminal pH to increase bacterial activity may be one of the methods to optimize VFA production, reduce methane and, possibly, improve animal performance.