The effect of Am241 on UK plutonium recycle options in thorium-plutonium fuelled LWRs – Part II: BWRs

UK plutonium is expected to be managed using uranium-plutonium (U-Pu) mixed oxide (MOX) fuels in Light Water Reactors (LWRs). However, studies have shown that thorium-plutonium (Th-Pu) may be preferential. Part I of this study considered the effect of americium (Am) in UK Pu in Pressurized Water Reactors (PWRs) and found that, while the reactivity response was sensitive to isotopic and spectral variations, trends were predictable. Part II focusses on separation of Am in Boiling Water Reactors (BWRs) and compares fuel performance to the uniformly distributed and spatially separated cases outlined in Part I. Comparable incineration rates are achievable but, while a single PWR assembly bears a greater mass of Am/Pu than a single BWR assembly, the full BWR core may be capable of operating with significantly greater fissile masses. Transmutation of Am241 to Am242 appears preferable to fast fission of Am241 as increased incineration occurs in lower void, bottom-of-assembly locations

The effect of Am241 on UK plutonium recycle options in thorium-plutonium fuelled LWRs – Part I: PWRs

UK plutonium is expected to be managed using uranium-plutonium (U-Pu) mixed oxide (MOX) fuels in Light Water Reactors (LWRs). However, studies have shown that thorium-plutonium (Th-Pu) may be preferential. Research has mostly focussed on recycle of reactor grade Pu with limited minor actinide (MA) content. This study will determine if large quantities of americium (Am) in UK Pu may be restrictive to recycle schemes by determining the effect this has on reactivity feedback coefficients, fissile loading and incineration potential. Addition of Am is shown to result in predictable trends in reactivity feedback coefficients and spatial separation of Am and Pu is found to offer potential advantages over uniformly loaded fuel in terms of maximising fissile loading and incineration. Separation may also offer benefits in terms of targeting Am destruction, particularly if multiple recycle schemes are pursued, as this would maximise the fissile loading requirements while keeping reactivity feedback coefficients negative

Isotopic and spectral effects of Pu quality in Th-Pu fueled PWRs

UK plutonium (Pu) management is expected to focus on the use of uranium-plutonium (U-Pu) mixed oxide (MOX) fuel. However, research has shown that thorium-plutonium (Th-Pu) may be a viable alternative, offering favourable performance characteristics. A scoping study was carried out to determine the effect of isotopic composition and spectral hardening in standard and reduced moderation Pressurised Water Reactors (PWRs and RMPWRs). Lattice calculations were performed using WIMS to investigate safety parameters (Doppler Coefficient (DC), Moderator Temperature Coefficient (MTC), Void Coefficient (VC) – in this case Fully Voided Reactivity (FVR) – and Boron Worth (BW)), maximum theoretically achievable discharge burnup, Pu consumption and transuranic (TRU) composition of spent nuclear fuel (SNF) for the two reactor types. Standard grades of Pu were compared to a predicted UK Pu vector. MTC and FVR were found to be strongly influenced by the isotopic composition of the fuel. MTC was determined to be particularly sensitive to positive ‘peak’ contributions from fissile isotopes in the energy range 0.1–1 eV which diminish as the Pu content increases. The more extreme nature of the perturbation in FVR cases results in key differences in the contributions from fissile isotopes in the thermal energy range when compared with MTC, with no positive contributions from any isotope <500 eV. Where the requirement for MTC to remain negative was the limiting factor, a higher maximum fissile loading, discharge burnup and Pu consumption rate were possible in the PWR than the RMPWR, although the two reactors types typically produced similar levels of U233. However, for the majority of Pu grades the total minor actinide (MA) content in SNF was shown to be significantly lower in the RMPWR. Where FVR is the limiting factor, the maximum fissile loading and discharge burnup are similar in both reactor types, while increased Pu consumption rates were possible in the PWR. In this case, lower concentrations of U233 and MAs were found to be present in the PWR. These results are for a single pass of fuel through a reactor and, while the response of fissile isotopes at given energies to temperature perturbations will not vary significantly, the maximum achievable discharge burnup, Pu consumption rate and TRU build-up would be very different in a multi-recycle scenario.The first author is grateful for the financial support of the Engineering and Physical Sciences Research Council (EPSRC), Thor Energy, the Whitworth Society and the Institution of Engineering and Technology

Toxic metal enrichment and boating intensity: sediment records of antifoulant copper in shallow lakes of eastern England

Tributyltin (TBT), an aqueous biocide derived from antifouling paint pollution, is known to have impacted coastal marine ecosystems, and has been reported in the sediment of the Norfolk and Suffolk Broads, a network of rivers and shallow lakes in eastern England. In the marine environment, the 1987 TBT ban has resulted in expanded use of alternative biocides, raising the question of whether these products too have impacted the Broads ecosystem and freshwaters in general. Here we examine the lake sediment record in the Norfolk and Suffolk Broads for contamination by copper (Cu) (as an active biocide agent) and zinc (Zn) (as a component of booster biocides), to assess their occurrence and potential for causing environmental harm in freshwater ecosystems. We find that, after the introduction of leisure boating, there is a statistically significant difference in Cu enrichment between heavily and lightly boated sites, while no such difference exists prior to this time. At the heavily boated sites the onset of Cu enrichment coincides with a period of rapid increase in leisure boating. Such enrichment is maintained to the present day, with some evidence of continued increase. We conclude that Cu-based antifouling has measurably contaminated lakes exposed to boating, at concentrations high enough to cause ecological harm. Similar findings can be expected at other boated freshwater ecosystems elsewhere in the world

Genomic Expansion of Magnetotactic Bacteria Reveals an Early Common Origin of Magnetotaxis with Lineage-specific Evolution

The origin and evolution of magnetoreception, which in diverse prokaryotes and protozoa is known as magnetotaxis and enables these microorganisms to detect Earth’s magnetic field for orientation and navigation, is not well understood in evolutionary biology. The only known prokaryotes capable of sensing the geomagnetic field are magnetotactic bacteria (MTB), motile microorganisms that biomineralize intracellular, membrane-bounded magnetic single-domain crystals of either magnetite (Fe3O4) or greigite (Fe3S4) called magnetosomes. Magnetosomes are responsible for magnetotaxis in MTB. Here we report the first large-scale metagenomic survey of MTB from both northern and southern hemispheres combined with 28 genomes from uncultivated MTB. These genomes expand greatly the coverage of MTB in the Proteobacteria, Nitrospirae, and Omnitrophica phyla, and provide the first genomic evidence of MTB belonging to the Zetaproteobacteria and “Candidatus Lambdaproteobacteria” classes. The gene content and organization of magnetosome gene clusters, which are physically grouped genes that encode proteins for magnetosome biosynthesis and organization, are more conserved within phylogenetically similar groups than between different taxonomic lineages. Moreover, the phylogenies of core magnetosome proteins form monophyletic clades. Together, these results suggest a common ancient origin of iron-based (Fe3O4 and Fe3S4) magnetotaxis in the domain Bacteria that underwent lineage-specific evolution, shedding new light on the origin and evolution of biomineralization and magnetotaxis, and expanding significantly the phylogenomic representation of MTB

Chronic psychosocial and financial burden accelerates 5-year telomere shortening: findings from the Coronary Artery Risk Development in Young Adults Study.

Leukocyte telomere length, a marker of immune system function, is sensitive to exposures such as psychosocial stressors and health-maintaining behaviors. Past research has determined that stress experienced in adulthood is associated with shorter telomere length, but is limited to mostly cross-sectional reports. We test whether repeated reports of chronic psychosocial and financial burden is associated with telomere length change over a 5-year period (years 15 and 20) from 969 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a longitudinal, population-based cohort, ages 18-30 at time of recruitment in 1985. We further examine whether multisystem resiliency, comprised of social connections, health-maintaining behaviors, and psychological resources, mitigates the effects of repeated&nbsp;burden on telomere attrition over 5 years. Our results indicate that adults with high chronic burden do not show decreased telomere length over the 5-year period. However, these effects do vary by level of resiliency, as regression results revealed a significant interaction between chronic burden and multisystem resiliency. For individuals with high repeated&nbsp;chronic burden and low multisystem resiliency (1 SD below the mean), there was a significant 5-year shortening in telomere length, whereas no significant relationships between chronic burden and attrition were evident for those at moderate and higher levels of resiliency. These effects apply similarly across the three components of resiliency. Results imply that interventions should focus on establishing strong social connections, psychological resources, and health-maintaining behaviors when attempting to ameliorate stress-related decline in telomere length among at-risk individuals

Perineal descent and patients’ symptoms of anorectal dysfunction, pelvic organ prolapse, and urinary incontinence

Contains fulltext : 89793.pdf (publisher's version ) (Closed access)INTRODUCTION AND HYPOTHESIS: The aim of this dynamic magnetic resonance (MR) imaging study was to assess the relation between the position and mobility of the perineum and patients' symptoms of pelvic floor dysfunction. METHODS: Patients' symptoms were measured with the use of validated questionnaires. Univariate logistic regression analyses were used to study the relationship between the questionnaires domain scores and the perineal position on dynamic MR imaging, as well as baseline characteristics (age, body mass index, and parity). RESULTS: Sixty-nine women were included in the analysis. Only the domain score genital prolapse was associated with the perineal position on dynamic MR imaging. This association was strongest at rest. CONCLUSIONS: Pelvic organ prolapse symptoms were associated with the degree of descent of the perineum on dynamic MR imaging. Perineal descent was not related to anorectal and/or urinary incontinence symptoms.1 juni 201

Metal-macrofauna interactions determine microbial community structure and function in copper contaminated sediments

Peer reviewedPublisher PD

Identification of a novel splice variant form of the influenza a virus m2 ion channel with an antigenically distinct ectodomain

Segment 7 of influenza A virus produces up to four mRNAs. Unspliced transcripts encode M1, spliced mRNA2 encodes the M2 ion channel, while protein products from spliced mRNAs 3 and 4 have not previously been identified. The M2 protein plays important roles in virus entry and assembly, and is a target for antiviral drugs and vaccination. Surprisingly, M2 is not essential for virus replication in a laboratory setting, although its loss attenuates the virus. To better understand how IAV might replicate without M2, we studied the reversion mechanism of an M2-null virus. Serial passage of a virus lacking the mRNA2 splice donor site identified a single nucleotide pseudoreverting mutation, which restored growth in cell culture and virulence in mice by upregulating mRNA4 synthesis rather than by reinstating mRNA2 production. We show that mRNA4 encodes a novel M2-related protein (designated M42) with an antigenically distinct ectodomain that can functionally replace M2 despite showing clear differences in intracellular localisation, being largely retained in the Golgi compartment. We also show that the expression of two distinct ion channel proteins is not unique to laboratory-adapted viruses but, most notably, was also a feature of the 1983 North American outbreak of H5N2 highly pathogenic avian influenza virus. In identifying a 14th influenza A polypeptide, our data reinforce the unexpectedly high coding capacity of the viral genome and have implications for virus evolution, as well as for understanding the role of M2 in the virus life cycle

corona Is Required for Higher-Order Assembly of Transverse Filaments into Full-Length Synaptonemal Complex in Drosophila Oocytes

The synaptonemal complex (SC) is an intricate structure that forms between homologous chromosomes early during the meiotic prophase, where it mediates homolog pairing interactions and promotes the formation of genetic exchanges. In Drosophila melanogaster, C(3)G protein forms the transverse filaments (TFs) of the SC. The N termini of C(3)G homodimers localize to the Central Element (CE) of the SC, while the C-termini of C(3)G connect the TFs to the chromosomes via associations with the axial elements/lateral elements (AEs/LEs) of the SC. Here, we show that the Drosophila protein Corona (CONA) co-localizes with C(3)G in a mutually dependent fashion and is required for the polymerization of C(3)G into mature thread-like structures, in the context both of paired homologous chromosomes and of C(3)G polycomplexes that lack AEs/LEs. Although AEs assemble in cona oocytes, they exhibit defects that are characteristic of c(3)G mutant oocytes, including failure of AE alignment and synapsis. These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable ‘zippering’ of TFs to form the central region of the Drosophila SC. We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12. However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells