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- Author or Editor: J. Lee x
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Abstract
A (D3C)2O (d6-acetone) target was irradiated with semi-monoenergetic neutrons generated from 9Be(p,n)9B reaction with 20 MeV protons to convert 13C and oxygen nuclides in the target into 14C. With both liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) we measured the (D3C)2O (d6-acetone) liquid targets, which were combustible and easy to afford CO2 for the AMS measurements. The 14C yield measured by the LSC method turned out to be 80 times larger than that by the AMS method. This large discrepancy may be attributed to the loss of 14C atoms during the sample pretreatment in the AMS method such as combustion and cryogenic trapping of CO2. It means that 14C newly produced by nuclear reactions can exist in various chemical forms, i.e., C3D6O, CO, CO2, hydrocarbons, etc., and a simple sample pretreatment right after production can cause serious isotopic fractionation. Therefore, using the AMS method, extreme caution in sample pretreatment should be exercised when the 14C yield produced immediately by nuclear reaction is measured.
Abstract
The new polycyclic nitramine 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) has been focused as a considerable amount of research recently on investigating its polymorphs, relative stability, and respective reaction chemistry. It is known as CL-20 popularly, CL-20 is a very high-energy and relatively high oxygen balance value crystalline compound whose method of synthesis and detailed performance data are still classified. 5-oxo-3-nitro-1,2,4-triazole (NTO, or nitrotriazolone) was an insensitive molecule comparison general explosives, and the NTO based polymer bonded explosives (PBX) was a low vulnerability explosive. Both energetic materials are all very important high explosives, which is used in a variety of military formulations widely owing to the properties of high energy and desensitization of PBX, many researchers have demonstrated the usefulness of above two energetic materials in explosive component. In this work, the thermal decomposition characteristics of explosives CL-20 and NTO were studied using thermal analytical techniques (TG, DSC), then the compatibility of above two explosives with silicone rubber, and the decomposition kinetic parameters such as activation energies of decomposition, the frequency factor of the decompose reaction are also evaluated by non-isothermal DSC techniques.
Abstract
Radiation treatment in the presence of catalysts such as anatase, P25 and bentonite showed efficient removal of TCE (trichloroethylene) and PCE (perchloroethylene) compared with gamma-irradiation alone. Gamma-ray pretreatment of P25 and bentonite enhanced the decomposition of TCE and PCE, respectively. The change in the catalysts by gamma-rays was characterized by their EPR spectra. For anatase and bentonite, the peaks in the spectra increased significantly, and the pattern of the spectra changed in the case of P25. The relationship between the peaks and pollutant decomposition should be further clarified due to the complexity of the spectra.
Abstract
This work presents a low-level background gamma spectrometry system capable of achieving rapid determination of90Sr without chemical separation, in a soil sample when the90Sr to 
-ray emitting nuclide concentration ratio exceeds 10. The system consists of a highly efficient HPGe central detector operated in coincidence or anticoincidence with a NaI(Tl) guard detector and a NaI(Tl) backscatter detector. Experimental results indicate that the bremstrahlung radiation from a pure 
-emitter can be distinguished with respect to the differences in normal and coincidence spectra. The90Sr activity can be directly detemined in the sample in less than 1 hour with a minimum detectable concentration (MDC) estimated at 0.002 Bq·g–1 for a sample containing no appreciable -ray nuclides or other high energy, -emitting nuclides. In actual measurement, a 0.06 Bq·g–1 MDC for contaminated soils is achieved.
The effects of red grape, wild grape and black raspberry wines on the quality of ground pork during a 15 days refrigerated storage period were investigated. The levels of phenolic compounds were the highest in black raspberry wine (P<0.05). In contrast, the antioxidant capacities according to ferric reducing antioxidant potential (FRAP) and trolox equivalent antioxidant capacity (TEAC) were not significantly different among the wines (P>0.05). The addition of 5% and 10% wine influenced the quality of ground pork by decreasing pH, inhibiting the progression of lipid oxidation and the formation of total volatile basic nitrogen (TVB-N), and stabilizing the red colour of the ground pork compared to control samples to which no wine was added. In ground pork, addition of red grape wine led to lower concentrations of thiobarbituric acid reactive substances (TBARS, 0.19–0.39 mg kg−1) and TVB-N values (69.1–119.9 mg kg−1) than wild grape (0.16–0.43 mg kg−1 and 72.0–194.1 mg kg−1, respectively) or black raspberry wine (0.33–0.58 mg kg−1 and 81.7–225.4 mg kg−1, respectively) up to 10 days of storage. Results from the present study suggested that the quality of ground pork was affected by wine type and storage period. These effects could be due to phenolic compounds as well as other chemical components of the wines.
Abstract
High resolution inductively coupled plasma mass spectrometry coupled with an on-line flow injection system (FI-HR-ICP-MS) was applied to determine the ultra-trace level 99Tc in soil. The flow injection system (PrepLab
) was composed of two TEVA-SpecÒresins, reduced remarkably the sample amounts and the analysis time, compared to the conventional analytical methods. In the flow injection system, Mo and Ru were sufficiently eliminated by using the flow injection system, with the decontamination factors of 1.6.104 and 9.9.105, respectively. With the present method, it was possible to determine ultra-low level of 99Tc in 3-6 g soil at 3–5 hours of analysis time per sample. The relative standard deviation for each sample was less than 4%. The detection limits for 99Tc was 85 fg.ml–1 (0.05 mBq.ml–1), which was calculated from the three times standard deviation of the count rate of the blank.
Abstract
The addition of suitable cross-linking agents with norbornene-based monomers has significant effects on the thermal properties of the resulting polymers formed by olefin metathesis. Ethylidene norbornene (ENB) and endo-dicyclopentadiene (endo-DCPD) were mixed separately with various loadings of three different cross-linking agents and then polymerized with the addition of Grubbs’ catalyst. The polymerization kinetics and resulting glass transition temperature (T g) of the systems were evaluated by differential scanning calorimetry (DSC). The addition of the first cross-linking agent, norbornadiene (CL-1), to both endo-DCPD and ENB resulted in decreasing glass transition temperatures with increasing concentrations. In contrast, the addition of the other two cross-linking agents (CL-2 and CL-3), which were both custom synthesized bifunctional norbornyl systems, to both endo-DCPD and ENB resulted in a monotonic increases in T g with cross-linker concentration. By tailoring the loading of these custom cross-linking agents, the properties of these polymer systems can be controlled for various applications, including self-healing composites.
Abstract
This article addresses the potential effectiveness of blind review in selecting and funding research proposals in a “scientifically small” country. By analyzing 474 responses of the blinded reviewers ever worked for Korea Science and Engineering Fund, it was found that blind review is fairly effective. About two thirds of the blinded reviewers were unable to recognize the applicants accurately. The applicant detection was affected by (1) physical age, (2) professional experience, and (3) geographical location of doctoral education of the applicant, (4) review experience, (5) rank of employing universities of the reviewers, and (6) similirity of research interest between an applicant and a reviewer. It was also found that blind review was more strongly advocated by those who had made a wrong guess or who had given up guessing. Implications of the findings and future research directions were discussed.
To investigate the pathogens that racing pigeons in Taiwan are exposed to, a total of 3764 pigeons from 90 lofts were analysed by collection of blood samples in the period between October 2000 and September 2001. The haemagglutination inhibition (HI) test was performed to detect antibodies against Newcastle disease virus (NDV), type 2 avian paramyxovirus (APMV-2), and egg drop syndrome '76 virus (EDS-76V). The agar-gel precipitin (AGP) test was used to detect antibodies against fowl adenovirus (FAV), goose parvovirus (GPV), and avian reovirus (REO). The virus neutralisation (VN) test was applied to detect antibodies against the serotypes FAV-1 and FAV-8. A rapid serum agglutination test was applied for the detection of antibodies against Mycoplasma spp. Antibodies to several infectious agents were found, including NDV (43.3%), EDS-76V (19.2%), FAV (0.8%), REO (0.5%), APMV-2 (0.2%), Mycoplasma columbinum (10.3%), M. columborale (7.1%), M. synoviae (1.8%) and M. gallisepticum (1.3%). Antibodies against GPV, FAV-1, and FAV-8 were not detected in any serum sample. NDV seroprevalence was significantly higher in pigeons of more than one year of age than in pigeons younger than one year. ND or EDS-76 seroprevalence of pigeons vaccinated with ND vaccine or EDS-76 vaccine was significantly higher than that of pigeons that did not receive any vaccination.
