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The average electromagnetic dipole response of levels in the quasicontinuum of 197,198Au has been measured using (³He,³He') and (d,p) reactions. The extracted y-ray strength functions have been normalized according to three model assumptions for the nuclear spin distribution. An enhancement in the energy region Eγ = 3.0-6.5 MeV is observed for both isotopes. The EI component of such excess of strength is studied in detail for 198Au and is interpreted as the pygmy dipole resonance with an energy centroid of 5.9(1) MeV and exhausts about 1% of the total integrated strength. The pygmy dipole resonance is shown to have a significant impact on the calculated 197Au(n,γ)198Au cross section. [ABSTRACT FROM AUTHOR]

The nuclear level densities of 194-196Pt and 197,198Au below the neutron separation energy have been measured using transfer and scattering reactions. All the level density distributions follow the constant-temperature description. Each group of isotopes is characterized by the same temperature above the energy threshold corresponding to the breaking of the first Cooper pair. A constant entropy excess ΔS = 1.9kB and 1.1kB is observed in 195Pt and 198Au with respect to 196Pt and 197Au, respectively, giving information on the available single-particle level space for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is revealed by sequential peaks in the microcanonical caloric curve. [ABSTRACT FROM AUTHOR]

Photoneutron cross sections were measured for 94Mo, 95Mo, 96Mo, 97Mo, 98Mo, and 100Mo near the neutron threshold with quasi-monochromatic laser-Compton scattering γ rays. The photoneutron data were analyzed with the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric-deformed Gogny HFB plus QRPA model of El γ-ray strength. Combining the γ-ray strength function constrained by the present photoneutron data with either the nuclear resonance fluorescence data or the updated Oslo data to supplement the data below the neutron threshold, a thorough analysis of the reverse (n,γ) cross sections is made whenever measurements are available. The Oslo data and the corresponding uncertainties are updated based on the latest results of the S-wave neutron spacing and the average radiative width determined in particular for 96Mo. Finally, radiative neutron capture cross sections for two radioactive nuclei, 93Mo and 99Mo, are deduced with the γ-ray strength function method. [ABSTRACT FROM AUTHOR]

We have measured the 149Sm(n, α)146Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the ²H(d, n)³He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back 149Sm2O3 samples attached to the common cathode. Absolute neutron flux was measured using a small 238U fission chamber and monitored by a BF3 long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the 149Sm(n, α)146Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries. [ABSTRACT FROM AUTHOR]

The nuclear level densities and γ-ray strength functions of 138,139,140La were measured using the 139La(³He, α), 139La(³He,' ³He), and 139La(d, p) reactions. The particle-γ coincidences were recorded with the silicon particle telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these experimental results, the low-energy enhancement in the A ~ 140 region is discussed. The 137,138,139La(n, γ) cross sections were calculated at s- and p-process temperatures using the experimentally measured nuclear level densities and γ-ray strength functions. Good agreement is found between 139La (n, γ) calculated cross sections and previous measurements. [ABSTRACT FROM AUTHOR]

We obtained the total radiation widths of s-wave resonances through an R-matrix analysis of (147)Sm(n,γ) cross sections. Distributions of these widths differ markedly for resonances below and above E(n)=300 eV, which is in stark contrast to long-established theory. We show that this change, as well as a similar change in the neutron-width distribution reported previously, is reflected in abrupt increases in both the average (147)Sm(n,γ) cross section and fluctuations about the average near 300 eV. Such effects could have important consequences for applications such as nuclear astrophysics and nuclear criticality safety., (© 2012 American Physical Society)

We have measured the (149)Sm(n,α)(146)Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the (2)H(d,n)(3)He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back (149)Sm(2)O(3) samples attached to the common cathode. Absolute neutron flux was measured using a small (238)U fission chamber and monitored by a BF(3) long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the (149)Sm(n,α)(146)Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries., (© 2011 American Physical Society)

We obtained an unprecedentedly large number of s-wave neutron widths through R-matrix analysis of neutron cross-section measurements on enriched Pt samples. Careful analysis of these data rejects the validity of the Porter-Thomas distribution with a statistical significance of at least 99.997%.

Measurements of cross sections of the (95)Mo(n, alpha)(92)Zr reaction at E(n)=4.0, 5.0 and 6.0MeV were carried out at the 4.5MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area (95)Mo samples were adopted. Fast neutrons were produced through the D(d, n)(3)He reaction by using a deuterium gas target. A small (238)U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement.

To support the Nuclear Criticality Safety Program, the Oak Ridge Electron Linear Accelerator (ORELA) has been used to measure the total and capture neutron cross sections of several nuclides in the energy range from 100 eV to -600 keV. Concerns about the use of existing cross section data in nuclear criticality calculations have been a prime motivator for the new cross-section measurements. Our new capture cross sections of aluminium, silicon, chlorine, fluorine and potassium in the energy range from 100 eV to 600 keV are substantially different from the cross sections in evaluated nuclear data files of ENDF/B-VI and JENDL-3.2.

The objective of the study was to establish a pink threshold and simulate the pink defect in cooked chicken breast meat with treatment combinations that would induce significant changes in the color of raw and cooked meat. The subjective pink threshold used in judging pink discoloration was established at a* = 3.8. Samples of three color groups (normal, lighter than normal, and darker than normal) of boneless, skinless chicken breast muscles were selected based on instrumental color values. The in situ changes were induced using sodium chloride, sodium tripolyphosphate, sodium erythorbate, and sodium nitrite at two levels: present and not present. Fillets in all treatments were subjected to individual injections, followed by tumbling, cooking, and chilling. Samples were analyzed for color [lightness (L*), red/green axis (a*), yellow/blue axis (b*)] and reflectance spectra. Simulation of the pink defect was achieved in eight of the 16 treatment combinations when sodium nitrite was present and in an additional two treatment combinations when it was absent. Pinking in cooked samples was affected (P < 0.05) by L* of raw meat color. Results confirmed that it was possible to simulate the undesired pinking in cooked chicken white meat when in situ conditions were induced by sodium chloride, sodium tripolyphosphate, and sodium nitrite. The continuation of the simulation study can aid in developing alternative processing methods to eliminate potential pink defects.

Histamine concentrations were determined in semi-moist and moist cat foods which listed fish or fish solubles as one of the ingredients using the AOAC fluorometic method and a TLC procedure. Percent recovery was 73% for the AOAC and 96% for the TLC procedure, although the coefficient of variation was lower for AOAC procedure. Moist cat foods contained an average of 11 ppm histamine while semi-moist cat foods had 23 ppm histamine. High histamine content of semi-moist cat food was probably due to condensed fish solubles even though it was not one of the major ingredients. The maximum amount of histamine observed was 88.8 ppm in a semi-moist cat food sample while the minimum was 3.8 ppm in a moist cat food sample. Results from both procedure compared well.

Experiments were done to determine the influence of temperature (21, 30 and 37°C) and a w (0.76 to 0.98) on aflatoxin production by Aspergillus flavus on cowpea ( Vigna unguiculata ) seeds, meal and meal supplemented with onion. Larger quantities of aflatoxin were produced at 21 and 30°C than at 37°C. The highest amount of aflatoxin (2777 μg/20 g, dry weight basis) was observed in meal containing onion at a w 0.98 after 20 d of incubation at 21°C. A level of 870 |μg/20 g was detected in seeds at a w 0.95 after 14 d of incubation at 30°C. Meal at a w 0.96 supported production of 551 μg of aflatoxin per 20 g after 20 d at 30° C. Temperature had little influence on the optimal a w for aflatoxin production in cowpea meal. However, an increase in temperature resulted in a decreased optimal a w for aflatoxin production on whole cowpeas. When known quantities of aflatoxin were added to cowpea meal which was subsequently steamed for 5 min, only 29% was extractable using a variety of procedures, indicating that the toxin may be bound in some manner to cowpea constituents as a result of heat treatment.

Two factors, salt concentration and incubation temperature, were examined for their effect on the formation of histamine, phenethylamine, tryptamine and tyramine during miso (soybean paste) fermentation. Misos containing 5 and 10% NaCl were prepared and incubated at 25 and 35°C. The effect of each factor was determined from the chemical and microbiological changes in the misos during fermentation. Salt level was a significant factor in the formation of amines. Higher amine levels were found in low-salt (5% NaCl) formulations than in high-salt (10% NaCl) misos. Incubation temperature within the range of 25 to 35°C during fermentation had little effect on amine formation in misos.

Sound inshell runner-type peanuts, manually damaged inshell peanuts, shells, sound kernels, deskinned kernels and skins were stored in separate flasks under an atmospheric relative humidity of 100% at 28°C. After 5 d, water was adsorbed at levels of 1.2, 1.7, 3.9, 0.9, 1.0 and 9.5 g/100 g dry material, respectively. Surface disinfected components were inoculated with conidiospores of Aspergillus parasiticus NRRL 2999 and incubated under the same conditions. The time required for visible growth of the fungus was 8, 6, 4, 12, 10 and 3 d, respectively. The time for appearance of the conidiospores was 14, 10, 6, 16, 13 and 6 d. After a 3-wk incubation period, aflatoxin levels in peanut components were 111.4, 159.1, 4.4, 58.7, 99.0 and 1.5 μg/g, respectively.