Evaluation of low pressure leak flows in metallic vacuum vessels for detection systems using helium dissolved in an external water cooling jacket

Vacuum containment vessels are often utilized in industrial and research applications to isolate equipment and experiments from the surrounding environment. The development of leaks in these vessels may result in damage to internal components and facility downtime. The inclusion of a vessel integrity monitoring system (VIMS) in such a facility allows detection of leak formation, characterization of leak size, and provides a tool for the evaluation of the risk for significant damage to the facility with continued operation.The proposed vessel integrity monitoring system (VIMS) evaluated herein utilizes helium dissolved in a water jacket surrounding a vacuum vessel for the detection of leaks. The Water jacket and vacuum vessel that are considered in these analyses are part of athermal management and isolation system for a cold neutron moderator in the High FluxIsotope Reactor. However, the results of the theoretical and computational evaluations are of use to a variety of similar low pressure applications. The concentration of helium in the vacuum vessel is monitored using commercially available Residual Gas Analyzer(RGA) technology to detect leaks as they develop. Conservative system simulations indicate that using existing technology a leak as small as 5 x 10 ® m can be detected in less than 3 hours when the vacuum vessel volume is 29 liters or less, demonstrating the feasibility of the proposed system

Genetic architecture of dispersal behaviour in the post-harvest pest and model organism Tribolium castaneum

Dispersal behaviour is an important aspect of the life-history of animals. However, the genetic architecture of dispersal-related traits is often obscure or unknown, even in well studied species. Tribolium castaneum is a globally significant post-harvest pest and established model organism, yet studies of its dispersal have shown ambiguous results and the genetic basis of this behaviour remains unresolved. We combine experimental evolution and agent-based modelling to investigate the number of loci underlying dispersal in T. castaneum, and whether the trait is sex-linked. Our findings demonstrate rapid evolution of dispersal behaviour under selection. We find no evidence of sex-biases in the dispersal behaviour of the offspring of crosses, supporting an autosomal genetic basis of the trait. Moreover, simulated data approximates experimental data under simulated scenarios where the dispersal trait is controlled by one or few loci, but not many loci. Levels of dispersal in experimentally inbred lines, compared with simulations, indicate that a single locus model is not well supported. Taken together, these lines of evidence support an oligogenic architecture underlying dispersal in Tribolium castaneum. These results have implications for applied pest management and for our understanding of the evolution of dispersal in the coleoptera, the world’s most species-rich order

Alpha kinase 3 signaling at the M-band maintains sarcomere integrity and proteostasis in striated muscle

Muscle contraction is driven by the molecular machinery of the sarcomere. As phosphorylation is a critical regulator of muscle function, the identification of regulatory kinases is important for understanding sarcomere biology. Pathogenic variants in alpha kinase 3 (ALPK3) cause cardiomyopathy and musculoskeletal disease, but little is known about this atypical kinase. Here we show that ALPK3 is an essential component of the M-band of the sarcomere and define the ALPK3-dependent phosphoproteome. ALPK3 deficiency impaired contractility both in human cardiac organoids and in the hearts of mice harboring a pathogenic truncating Alpk3 variant. ALPK3-dependent phosphopeptides were enriched for sarcomeric components of the M-band and the ubiquitin-binding protein sequestosome-1 (SQSTM1) (also known as p62). Analysis of the ALPK3 interactome confirmed binding to M-band proteins including SQSTM1. In human pluripotent stem cell-derived cardiomyocytes modeling cardiomyopathic ALPK3 mutations, sarcomeric organization and M-band localization of SQSTM1 were abnormal suggesting that this mechanism may underly disease pathogenesis

Next Generation Nuclear Plant Methods Technical Program Plan

One of the great challenges of designing and licensing the Very High Temperature Reactor (VHTR) is to confirm that the intended VHTR analysis tools can be used confidently to make decisions and to assure all that the reactor systems are safe and meet the performance objectives of the Generation IV Program. The research and development (R&D) projects defined in the Next Generation Nuclear Plant (NGNP) Design Methods Development and Validation Program will ensure that the tools used to perform the required calculations and analyses can be trusted. The Methods R&D tasks are designed to ensure that the calculational envelope of the tools used to analyze the VHTR reactor systems encompasses, or is larger than, the operational and transient envelope of the VHTR itself. The Methods R&D focuses on the development of tools to assess the neutronic and thermal fluid behavior of the plant. The fuel behavior and fission product transport models are discussed in the Advanced Gas Reactor (AGR) program plan. Various stress analysis and mechanical design tools will also need to be developed and validated and will ultimately also be included in the Methods R&D Program Plan. The calculational envelope of the neutronics and thermal-fluids software tools intended to be used on the NGNP is defined by the scenarios and phenomena that these tools can calculate with confidence. The software tools can only be used confidently when the results they produce have been shown to be in reasonable agreement with first-principle results, thought-problems, and data that describe the “highly ranked” phenomena inherent in all operational conditions and important accident scenarios for the VHTR

Symptoms of anxiety and depression are related to cardiovascular responses to active, but not passive, coping tasks

Objective: Anxiety and depression have been linked to blunted blood pressure (BP) and heart rate (HR) reactions to mental stress tests; however, most studies have not included indices of underlying hemodynamics nor multiple stress tasks. This study sought to examine the relationships of anxiety and depression with hemodynamic responses to acute active and passive coping tasks. Methods: A total of 104 participants completed the Hospital Anxiety and Depression Scales and mental arithmetic, speech, and cold pressor tasks while BP, HR, total peripheral resistance, and cardiac output (CO) were assessed. Results: After adjustment for traditional risk factors and baseline cardiovascular activity, depression scores were negatively associated with systolic BP, HR, and CO responses to the mental arithmetic task, while anxiety scores were inversely related to the systolic BP response to mental arithmetic. Conclusion: High anxiety or depression scores appear to be associated with blunted cardiac reactions to mental arithmetic (an active coping task), but not to the cold pressor test or speech tasks. Future research should further examine potential mechanisms and longitudinal pathways relating depression and anxiety to cardiovascular reactivity

Mechanistic investigations of the Fe(ii) mediated synthesis of squaraines

The scission and homologation of CO is a fundamental process in the Fischer–Tropsch reaction. However, given the heterogeneous nature of the catalyst and forcing reaction conditions, it is difficult to determine the intermediates of this reaction. Here we report detailed mechanistic insight into the scission/homologation of CO by two-coordinate iron terphenyl complexes. Mechanistic investigations, conducted using in situ monitoring and reaction sampling techniques (IR, NMR, EPR and Mössbauer spectroscopy) and structural characterisation of isolable species, identify a number of proposed intermediates. Crystallographic and IR spectroscopic data reveal a series of migratory insertion reactions from 1Mes to 4Mes. Further studies past the formation of 4Mes suggest that ketene complexes are formed en route to squaraine 2Mes and iron carboxylate 3Mes, with a number of ketene containing structures being isolated, in addition to the formation of unbound, protonated ketene (8). The synthetic and mechanistic studies are supported by DFT calculations

Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa

Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its dietary overlap with native gastropods.A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) dietary overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Küster, 1841) and Melanoides tuberculata (Müller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed.The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research

Next Generation Nuclear Plant Methods Technical Program Plan

One of the great challenges of designing and licensing the Very High Temperature Reactor (VHTR) is to confirm that the intended VHTR analysis tools can be used confidently to make decisions and to assure all that the reactor systems are safe and meet the performance objectives of the Generation IV Program. The research and development (R&D) projects defined in the Next Generation Nuclear Plant (NGNP) Design Methods Development and Validation Program will ensure that the tools used to perform the required calculations and analyses can be trusted. The Methods R&D tasks are designed to ensure that the calculational envelope of the tools used to analyze the VHTR reactor systems encompasses, or is larger than, the operational and transient envelope of the VHTR itself. The Methods R&D focuses on the development of tools to assess the neutronic and thermal fluid behavior of the plant. The fuel behavior and fission product transport models are discussed in the Advanced Gas Reactor (AGR) program plan. Various stress analysis and mechanical design tools will also need to be developed and validated and will ultimately also be included in the Methods R&D Program Plan. The calculational envelope of the neutronics and thermal-fluids software tools intended to be used on the NGNP is defined by the scenarios and phenomena that these tools can calculate with confidence. The software tools can only be used confidently when the results they produce have been shown to be in reasonable agreement with first-principle results, thought-problems, and data that describe the “highly ranked” phenomena inherent in all operational conditions and important accident scenarios for the VHTR

An investigation into non-linear optical processes using high power picosecond laser pulses

The design of a high power, synchronously pumpled dye laser is described. The laser is pumped using a Q-switched and modelocked Nd:YAG laser and the performance with both rhodamine 6G and DCM dyes is described. High efficiency is achieved by using a stable resonator design for the oscillator. The time-bandwidth product is 0.63 and the pulse duration is ≃ 70 ps. The output beam is confirmed to be near-diffraction limited. The cavity length tuning characteristics are described. It is shown that the optimum cavity length corresponds to a minimum pulse duration, maximum energy and a maximum energy stability. The design of a longitudinally pumped dye amplifier is described. Pulse energies of up to 1 mJ are obtained in rhodamine 6G and 250 &mu;J in DCM. A mathematical model for a pulsed synchronously pumped dye laser is described. The effect of cavity mismatch is calculated. The results show that for longer cavities the pulses are smoother but longer in duration. For shorter cavities, the pulses shape is dominated by amplification of the leading edge of the pulses which results in pulse structure. The effect of a longer pump train is described. The resultant pulses are substantially shorter with comparable peak power. The effect of longitudinal pumping is described. The results show that the laser has comparable efficiency while the pulse profiles are smoother and more symmetrical than for transverse pumping. Stimulated Raman scattering (SRS) in H2, D2 and CH4 using picosecond pulses from a Nd:YAG laser is described. The experimental results using focussed and waveguided pump geometries are described. Good agreement with theory is found. The design of a Raman oscillator/amplifier using 100 ps pulses at 1.064 &mu;m is described. Using CH_4 at approximately 30 atm pressure, lst Stokes generation at 1.54 &mu;m is measured with an energy efficiency of 30%. SRS in four organic liquids with Raman shifts in the region of 2900 cm-1, is described. A maximum energy efficiency of 82% is achieved in acetone with 532 nm pump pulses. Raman thresholds are measured using 1.064 &mu;m pump pulses and the experimental results exhibit an intensity-length dependence. Multiple SRS in CH_4 using tunable dye laser pulses is described. An efficiency of 72% is measured for 1st Stokes generation. An efficiency of 5.7% was measured to 3rd Stokes. The tuning range was 1.09 &mu;m to 1.186 &mu;m. Non-linear processes in single mode optical fibres are described. The stimulated Raman threshold is measured and the Raman conversion is shown to limit the power throughput. Four photon mixing (FPM) in birefringent fibres is described. Using a tunable dye laser, Stokes and anti-Stokes components with shifts of 2200 cm^-1 are measured. The FPM threshold exhibits a coherence length effect. A conversion efficiency of 18% is measured. FPM is described using 100 ps pulses at 1.064 &mu;m from a Nd:YAG laser. Using a fibre having a birefringence of 3 x 10-4, a frequency shift of 2073 cm-1 is measured with an energy conversion efficiency of 1%.</p