Methods for the determination of total carbon (TC), total nitrogen (TN), and total phosphorus (TP) in cattail (Typha domingensis) using cold and thermal neutron prompt gamma activation analysis (CNPGAA and TNPGAA) have been developed in the CNPGAA and
TNPGAA facilities at the National Institute of Standards and Technology (NIST), and evaluated through the analysis of Standard
Reference Materials (SRMs) in previous studies. There are major issues that impact the sensitivities of C, N and P using CNPGAA
and TNPGAA including the effects of hydrogen content in samples, sample thickness and Compton scattering. However, interference
from chlorine (Cl) in cattails has a major impact on the detection of P. This paper compares the effects of hydrogen content,
sample thickness and Compton scattering on the sensitivities of C, N, and P between CNPGAA and TNPGAA and provides a resolution
to the Cl interference on P in cattail.
Previous studies including the development of methods for the determination of carbon, nitrogen, and phosphorus in cattail
using cold neutron prompt gamma activation (CNPGAA) and thermal neutron prompt gamma activation analysis (TNPGAA); evaluation
of the precision and accuracy of these methods through the analysis of Standard Reference Materials (SRMs); and comparison
of the sensitivity of CNPGAA to TNPGAA have been done in the CNPGAA and TNPGAA facilities at the National Institute of Standards
and Technology (NIST). This paper integrates the findings from all of these prior studies and presents recommendations for
the application of CNPGAA and TNPGAA in environmental studies of plants based on synergistic considerations of the effects
of neutron energy, matrix factors such as chlorine content, Compton scattering, hydrogen content, sample thickness, and spectral
interferences from Cl on the determination of C, N, and P. This paper also provides a new approach that simulates a sensitivity
curve for an element of interest (S), which is a function of hydrogen content (X) and sample thickness (Y) as follows: S = aX + bY + c (where a, b, and c are constants). This approach has provided more accurate results from the analysis of SRMs than traditional methods and an
opportunity to use models to optimize experimental conditions.
Inhalation of tobacco smoke is ranked second to food as a source of210Pb and210Po exposure to man. Assay of210Pb and210Po in commercially available tobacco collected from many countries have been carried out to assess the potential risk from210Po present in tobacco.The range of210Po contained in the tobacco grands varied from 10.08 to 15.0 mBq/tob or 13.0 to 20.1 mBq/g and the mean was 11.6 mBq/tob or 15.4 mBq/g. During the International Standard Smoking process about 50% of210Po present in tobaccos was transferred into the smoke and the other 50% remained in the ash and butt. About 10% of the total210Po of tobacco was inhaled by smoke through mainstream smoke. One pack-a-day smoker inhaled 24 mBq of210Po per day through smoking and the annual inhalation was 8.8 Bq. The risk of mortality from lung cancer caused by210Po in tobaccos was 18 per million persons for the above model.
This report presents results from the application of the Monte Carlo N-Particle (MCNP) computer code to the252Cf neutron activation analysis (NAA) Device in the Technical Physics Institute of the Heilongjiang Science Academy of the
People's Republic of China. The thermal and epithermal neutron flux at the sample positions and the neutron and photon fluxes
on the surfaces of the device were calculated. A comparison between the calculated and experimental thermal and epithermal
neutron fluxes at sample positions yield relative errors of less than 10% for the thermal neutron flux.
Authors:J. Zhao, L. Zhong, L. Zou, C. Zhang, L. Peng, W. Xiao, and G. Zhao
The purpose of this study was to investigate the effects of endophytic fungi from tartary buckwheat on the host sprout growth and functional metabolite production. Without obvious changes in the appearance of the sprouts, the exogenous fungal mycelia elicitors notably stimulated the sprout growth and rutin accumulation, and the stimulation effect was mainly depended on the mycelia elicitor species along with its treatment dose. Three endophytic fungi Fat6 (Bionectria pityrodes), Fat9 (Fusarium oxysporum) and Fat15 (Alternaria sp.) were screened to be the most effective candidates for promoting F. tataricum sprout growth and rutin production. With application of polysaccharide (PS, 150 mg/l) of endophyte Fat6, PS (200 mg/l) of endophyte Fat9, and PS (150 mg/l) of endophyte Fat15, the rutin yield was effectively increased to 47.89 mg/(100 sprouts), 45.85 mg/(100 sprouts) and 46.83 mg/(100 sprouts), respectively. That was about 1.5- to 1.6-fold compared to the control culture of 29.37 mg/(100 sprouts). Furthermore, the present study revealed that the biosynthesis of the functional flavonoid resulted from the stimulation of the phenylpropanoid pathway by mycelia polysaccharide treatments. Application of specific fungal elicitors could be an efficient strategy for improving the nutritional and functional quality of tartary buckwheat sprouts.
Authors:Songsheng Jiang, Zhiyuan Chang, Min Zhao, Yonggang Zhao, X. L. Zhao, and W. E. Kieser
Under an IAEA project for upgrading of reference materials, a new determination of the 129I concentration in the IAEA-375 reference material was performed. A chemical procedure was set up for the preparation of the AgI samples. Measurement of 129I was carried out using the IsoTrace Tandetron AMS facility at University of Toronto. To ensure the accuracy of the calibration, the tuning of the AMS system was iterated using not only the QC (quality control) samples but also all unknown samples. To minimize any possible current-dependent effects between 129I and 127I ions in the injection magnet, low Cs+ sputtering beam intensity (10 μA) was used. The reproducibility in determining the 129I/127I ratio in the IAEA-375 AgI samples was less than 1%. The activity concentration (CA) of 129I in the IAEA-375 reference material was determined to be 1.59±0.08 mBq . kg-1 at 95% confidence level. The present value is about 7% lower than the IAEA recommended value (1.7 mBq . kg-1) listed in 2000 or 20% lower than the recommended value (2 mBq . kg-1) listed in the IAEA AQCS Reference Material Catalogue (2002-2003). Since the IAEA recommended values for IAEA-375 materials was issued about 10 years ago and error range of the recommended values were large, the results we obtained might be useful in upgrading the recommended value.
The flux of cold neutrons that is obtainable from various high energy netron sources is studied for a particular model of
a cold neutron source when the cold moderation region of the apparatus is at 20, 70, and 298K. The maximum flux obtained with
a californium-252 source was 2.7·10−3 cold neutron per (cm2·second (source neutron)). This flux was obtained when the cold moderation region of the apparatus was at 20K and when the
thermal moderator is either polyethylene or trimethylbenzene and the cold moderator is polyethylene. This flux should allow
sensitive prompt and delayed neutron activation analysis measurements.
Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II)
(denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)3+) on (E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output Pm and the time (tm) corresponding to the Pm were obtained. The half-inhibitory concentrations (IC50) of Co(II) and Co(sep)3+ to E. coli DH5α were 15 and 42.1 mg mL−1, respectively.
The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)3+. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic
mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)3+. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)3+ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique.
Authors:L. Yang, F. Xu, L. Sun, Z. Zhao, and C. Song
Microcalorimetry was applied to study the effect of cephalosporins (cefazolin sodium and cefonicid sodium) on the E. coli growth. The microbial activity was recorded as power-time curves through an ampoule method with a TAM Air Isothermal Microcalorimeter
at 37°C. The parameters such as the growth rate constant (k), inhibitory ratio (I), the maximum power output (Pm) and the time corresponding to the maximum power output (tm) were calculated. The change tendencies of k, with the increasing of concentration (C) of the two cephalosporins, are similar which show that cefazolin sodium and cefonicid sodium have the same inhibitory mechanism.
The experimental results reveal that cefonicid sodium has a stronger antibacterial activity towards E. coli than that of cefazolin sodium and this was coincide with the clinical manifestations.