350 research outputs found

    Impact investigation of reactor fuel operating parameters on reactivity for use in burnup credit applications

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    When representing the behavior of commercial spent nuclear fuel (SNF), credit is sought for the reduced reactivity associated with the net depletion of fissile isotopes and the creation of neutron-absorbing isotopes, a process that begins when a commercial nuclear reactor is first operated at power. Burnup credit accounts for the reduced reactivity potential of a fuel assembly and varies with the fuel burnup, cooling time, and the initial enrichment of fissile material in the fuel. With regard to long-term SNF disposal and transportation, tremendous benefits, such as increased capacity, flexibility of design and system operations, and reduced overall costs, provide an incentive to seek burnup credit for criticality safety evaluations. The Nuclear Regulatory Commission issued Interim Staff Guidance 8, Revision 2 in 2002, endorsing burnup credit of actinide composition changes only; credit due to actinides encompasses approximately 30% of exiting pressurized water reactor SNF inventory and could potentially be increased to 90% if fission product credit were accepted. However, one significant issue for utilizing full burnup credit, compensating for actinide and fission product composition changes, is establishing a set of depletion parameters that produce an adequately conservative representation of the fuel\u27s isotopic inventory. Depletion parameters can have a significant effect on the isotopic inventory of the fuel, and thus the residual reactivity. This research seeks to quantify the reactivity impact on a system from dominant depletion parameters (i.e., fuel temperature, moderator density, burnable poison rod, burnable poison rod history, and soluble Boron concentration). Bounding depletion parameters were developed by statistical evaluation of a database containing reactor operating histories. The database was generated from summary reports of commercial reactor criticality data. Through depletion calculations, utilizing the SCALE 6 code package, several light water reactor assembly designs and in-core locations are analyzed in establishing a combination of depletion parameters that conservatively represent the fuel\u27s isotopic inventory as an initiative to take credit for fuel burnup in criticality safety evaluations for transportation and storage of SNF

    Predicting Kidney Transplant Survival using Multiple Feature Representations for HLAs

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    Kidney transplantation can significantly enhance living standards for people suffering from end-stage renal disease. A significant factor that affects graft survival time (the time until the transplant fails and the patient requires another transplant) for kidney transplantation is the compatibility of the Human Leukocyte Antigens (HLAs) between the donor and recipient. In this paper, we propose new biologically-relevant feature representations for incorporating HLA information into machine learning-based survival analysis algorithms. We evaluate our proposed HLA feature representations on a database of over 100,000 transplants and find that they improve prediction accuracy by about 1%, modest at the patient level but potentially significant at a societal level. Accurate prediction of survival times can improve transplant survival outcomes, enabling better allocation of donors to recipients and reducing the number of re-transplants due to graft failure with poorly matched donors

    Flexible Temperature Sensors on Fibers

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    The aim of this paper is to present research dedicated to the elaboration of novel, miniaturized flexible temperature sensors for textronic applications. Examined sensors were manufactured on a single yarn, which ensures their high flexibility and good compatibility with textiles. Stable and linear characteristics were obtained by special technological process and applied temperature profiles. As a thermo-sensitive materials the innovative polymer compositions filled with multiwalled carbon nanotubes were used. Elaborated material was adapted to printing and dip-coating techniques to produce NTC composites. Nanotube sensors were free from tensometric effect typical for other carbon-polymer sensor, and demonstrated TCR of 0.13%/K. Obtained temperature sensors, compatible with textile structure, can be applied in rapidly developing smart textiles and be used for health and protections purposes

    Presenting as a Mastoid Abscess

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    Introduction. Congenital cholesteatoma is a pearly white mass that rarely originates from the mastoid process. Case Report. A 21-year-old male patient presented to our department with severe right mastoid pain and postauricular fluctuant swelling for 23 days. There was no preceding history of ear complaints and examination showed a normal right ear drum. Emergency exploration of the mastoid process was done on the same day and revealed localized cholesteatoma limited only to the mastoid cavity. Conclusion. Despite a rarity, the mastoid process should be always put in mind as a site of origin for congenital cholesteatoma

    Formation of functional, non-amyloidogenic fibres by recombinant Bacillus subtilis TasA

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    Bacterial biofilms are communities of microbial cells encased within a self-produced polymeric matrix. In the Bacillus subtilis biofilm matrix the extracellular fibres of TasA are essential. Here a recombinant expression system allows interrogation of TasA, revealing that monomeric and fibre forms of TasA have identical secondary structure, suggesting that fibrous TasA is a linear assembly of globular units. Recombinant TasA fibres form spontaneously, and share the biological activity of TasA fibres extracted from B. subtilis, whereas a TasA variant restricted to a monomeric form is inactive and subjected to extracellular proteolysis. The biophysical properties of both native and recombinant TasA fibres indicate that they are not functional amyloid-like fibres. A gel formed by TasA fibres can recover after physical shear force, suggesting that the biofilm matrix is not static and that these properties may enable B. subtilis to remodel its local environment in response to external cues. Using recombinant fibres formed by TasA orthologues we uncover species variability in the ability of heterologous fibres to cross-complement the B. subtilis tasA deletion. These findings are indicative of specificity in the biophysical requirements of the TasA fibres across different species and/or reflect the precise molecular interactions needed for biofilm matrix assembly

    Translation and validation of the Malay version of the Stroke Knowledge Test

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    Background: To date, there is a lack of published studies on assessment tools to evaluate the effectiveness of stroke education programs. Methods: This study developed and validated the Malay language version of the Stroke Knowledge Test research instrument. This study involved translation, validity, and reliability phases. The instrument underwent backward and forward translation of the English version into the Malay language. Nine experts reviewed the content for consistency, clarity, difficulty, and suitability for inclusion. Perceived usefulness and utilization were obtained from experts’ opinions. Later, face validity assessment was conducted with 10 stroke patients to determine appropriateness of sentences and grammar used. A pilot study was conducted with 41 stroke patients to determine the item analysis and reliability of the translated instrument using the Kuder Richardson 20 or Cronbach’s alpha. Results: The final Malay version Stroke Knowledge Test included 20 items with good content coverage, acceptable item properties, and positive expert review ratings. Psychometric investigations suggest that Malay version Stroke Knowledge Test had moderate reliability with Kuder Richardson 20 or Cronbach’s alpha of 0.58. Improvement is required for Stroke Knowledge Test items with unacceptable difficulty indices. Overall, the average rating of perceived usefulness and perceived utility of the instruments were both 72.7%, suggesting that reviewers were likely to use the instruments in their facilities. Conclusions: Malay version Stroke Knowledge Test was a valid and reliable tool to assess educational needs and to evaluate stroke knowledge among participants of group-based stroke education programs in Malaysi
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