The effect of modern thermal neutron scattering sublibraries on criticality safety evaluations of wet storage pools

Within the framework of a recent criticality safety evaluation (CSE) performed for the licensing of a new commercial wet storage pool using MCNPX-2.5.0 along with the ENDF/B-VII.0 and JEFF-3.1 continuous energy cross-section libraries, the maximum permissible initial fuel-enrichment limit for water reflected configurations was found to be dependant upon the applied neutron cross section library. More detailed investigations showed that the difference is mainly caused by different sublibraries for thermal neutron scattering based on parameterizations of the S(α, β) scattering matrix. This paper addresses the main findings of these investigations and emphasizes which configurations are particularly sensitive to the parameterization of S(α, β) applied in the CSE analysis. The results are presented in an attempt, on the one hand, to assess more precisely the sensitivity upon thermal scattering modeling data in CSE of wet storage pools, and on the other hand, to assess whether the data employed in the most recent neutron data libraries can be considered as an improvement for this type of analyses.     

Fertilizer determination for yield and quality improvement of vegetable crops by mathematical optimization techniques

Techniques of Operations Research were introduced into the modelling work for determining optimal NPK-fertilizer requirements for vegetable crops which lead not only to a maximal yield but also to a special crop quality. In the model applied, 26 plant parameters were adopted to described yield and quality responses of Chinese cabbage to different NPK-nutrition. An integrative and comprehensive analysis about relationships between plant growth and nutrient supply can be carried out by using this model. Examples of model calculation for practical use, the validity of the model and a comparison of methods for fertilizer determination were demonstrated and discussed.     

Gonadal preservation in a simple testicular cyst

The authors report a case of a simple testicular cyst in a 16-week-old infant. Preoperative ultrasonography helped to diagnose this condition accurately. Gonadal preservation and enucleation of testicular cysts are possible with a careful surgical approach, and orchiectomy is not necessary.     

Sexual behavior among U.S. high school students, 1990-1995

CONTEXT: High rates of unintended pregnancy and sexually transmitted diseases (STDs), including HIV infection, among adolescents are major public health concerns that have created interest in trends in teenage sexual activity. METHODS: Nationally representative data from Youth Risk Behavior Surveys conducted in 1990, 1991, 1993 and 1995 are used to examine levels of sexual experience, age at first intercourse, current sexual activity and condom use at last intercourse among students in grades 9-12. RESULTS: The proportion of students who reported being sexually experienced remained at 53-54% from 1990 through 1995, while the percentage of sexually active students who used condoms at last intercourse rose from 46% to 54% between 1991 and 1995. Black students were more likely than white students to report being sexually experienced, being currently sexually active and having had four or more lifetime sexual partners; black students also reported a significantly younger age at first intercourse. Gender differences in sexual behavior were found more frequently among black students than among white or Hispanic students. CONCLUSIONS: Although levels of sexual experience for high school students in the United States have not risen during the 1990s, a very high percentage of students continue to be at risk for unintended pregnancy and STDs, including HIV infection.     

Compatibility of AISI 316 L stainless steel with the Li17Pbg,eutectic

The compatibility of AISI 316 L stainless steel with the Li₁₇Pb₈₃, eutectic has been studied in the temperature range 623–873 K for times up to 6000 h. In the corrosion layers formed there is a strong Ni depletion and Pb and Li penetration in the matrix.Tests at 623 K in Li₁₇Pb₈₃ on notched tensile specimens under a constant uniaxial tensile load, below the engineering yield stress, have evidenced that. many cracks filled with Pb and possibly Li are formed after relatively short times.     

Phosphorus availability on many organically managed farms in Europe

Maintaining sufficient soil phosphorus (P) levels for non-limiting crop growth is challenging in organic systems since off-farm inputs of P are restricted. This study assessed the status of P on organic farms in Europe using soil test results for extractable P. Data was obtained from published literature, unpublished theses, and various national and regional databases of soil test values. Most of the data (15,506 observations) came from field scale soil tests, but in some cases (1272 observations) values had been averaged across a farm. Farm scale and field scale data were analysed separately and the impact of farm type (arable, dairy, grassland, horticulture, mixed, poultry, unknown) was assessed. Soil test results were assigned to P classes from very low (P class 1) to very high (P class 5). The farm scale data came primarily from Norway, Sweden and Switzerland and did not indicate deficiencies in extractable P; 93% of farms fell into class 3 or above. The majority of the field scale data came from Germany and indicated sufficient or higher levels of P availability for arable and grassland systems on 60% of fields; the remaining fields had low or very low available P. Adaptations in organic systems may improve P uptake and utilization efficiency allowing yields to be maintained in the short-term, nevertheless there is cause for concern about the long-term P sustainability of some organic farming systems in Europe. This highlights the need to reassess allowable P inputs in organic farming systems to improve overall sustainability.     

Dynamics of solidification and development of morphology of Cu‐base alloys with a metastable miscibility gap in the range of the undercooled melt

The Cu‐Co system shows a metastable miscibility gap in the range of the undercooled melt. In this work the method of electromagnetic levitation (EML) and drop tube experiments have been used to examine the metastable state of Cu‐Co alloys. The experiments show that both methods allow deep undercooling of the melt into the range of the miscibility gap. Due to the deep undercooling the velocity of the solidification front is very high and the actual microstructure is frozen in. The process of demixing can be observed and the binodal has been determined with high precision. The microstructure of samples processed in the electromagnetic levitation shows an influence of the electromagnetic stirring due to the induction of electric currents into the melt. Drop tube experiments, which lead to a rapid solidification under reduced gravity conditions, in contrary result in a homogeneous distribution of spherical particles of the minority phase. For this reason space experiments under microgravity conditions in the TEMPUS facility are under consideration. In these experiments the stirring effect would be greatly reduced compared to the EML.     

A Contribution to the Investigation of Enzyme‐Catalysed Hydrolysis of Poly(ethylene terephthalate) Oligomers

Summary: One strategy to solve the problem of unwanted PET oligomer deposits in textile production is their enzymatic cleavage. In this work a selection of different enzymes (esterases, lipases) were tested for this purpose. The capacity to hydrolyse PET oligomers of some of the tested enzymes has been previously described in the literature. In order to imitate practical conditions both dry and precipitated PET oligomers were used. The decrease in the amount of cyclic trimer, the main component of the PET oligomers, was monitored by HPLC. After treatment with the lipase from Triticum aestivum a decrease of 80 wt.‐% was found. However, the effect of this lipase seems to have less to do with catalysing hydrolytic cleavages of ester groups than with the absorption of the oligomer on the enzyme protein.

Cyclic PET trimer (cyclo‐tris[ethyleneglycolterephthalate]).     

Phase selection and microstructure formation in undercooled Co–61.8 at.% Si melts under various containerless processing conditions

The hypoeutectic composition Co–61.8 at.% Si was undercooled and solidified using electromagnetic levitation, electromagnetic levitation under a static magnetic field, electrostatic levitation and glass-fluxing. The samples generally showed two thermal events, either separated or continuous depending on undercooling. In situ monitoring of the two thermal events with a high-speed camera revealed a sudden decrease of dendritic growth velocities of primary phases at a critical undercooling of 88 K. Scanning electron microscopy studies of the solidified samples showed that the CoSi compound and the CoSi₂ compound nucleate as the primary phase for low and high undercoolings, respectively. The microstructure of the samples depends not only on undercooling, but also on the onset temperature or delay time of the second thermal event. Melt convection has no effect on the primary phase selection in undercooled melts, but it has a significant effect on the delay time and therefore on microstructure formation of the samples for high undercoolings.