Extensive ssDNA end formation at DNA double-strand breaks in non-homologous end-joining deficient cells during the S phase

BACKGROUND: Efficient and correct repair of DNA damage, especially DNA double-strand breaks, is critical for cellular survival. Defects in the DNA repair may lead to cell death or genomic instability and development of cancer. Non-homologous end-joining (NHEJ) is the major repair pathway for DNA double-strand breaks in mammalian cells. The ability of other repair pathways, such as homologous recombination, to compensate for loss of NHEJ and the ways in which contributions of different pathways are regulated are far from fully understood. RESULTS: In this report we demonstrate that long single-stranded DNA (ssDNA) ends are formed at radiation-induced DNA double-strand breaks in NHEJ deficient cells. At repair times ≥ 1 h, processing of unrejoined DNA double-strand breaks generated extensive ssDNA at the DNA ends in cells lacking the NHEJ protein complexes DNA-dependent protein kinase (DNA-PK) or DNA Ligase IV/XRCC4. The ssDNA formation was cell cycle dependent, since no ssDNA ends were observed in G(1)-synchronized NHEJ deficient cells. Furthermore, in wild type cells irradiated in the presence of DNA-PKcs (catalytic subunit of DNA-PK) inhibitors, or in DNA-PKcs deficient cells complemented with DNA-PKcs mutated in six autophosphorylation sites (ABCDE), no ssDNA was formed. The ssDNA generation also greatly influences DNA double-strand break quantification by pulsed-field gel electrophoresis, resulting in overestimation of the DNA double-strand break repair capability in NHEJ deficient cells when standard protocols for preparing naked DNA (i. e., lysis at 50°C) are used. CONCLUSION: We provide evidence that DNA Ligase IV/XRCC4 recruitment by DNA-PK to DNA double-strand breaks prevents the formation of long ssDNA ends at double-strand breaks during the S phase, indicating that NHEJ components may downregulate an alternative repair process where ssDNA ends are required

Sensor Fused Indoor Positioning Using Dual Band WiFi Signal Measurements

In this paper, signal strengths from known WiFi access points are used together with a particle filter to perform indoor navigation. It is shown that more information is obtained by using signals of both 2.4 and 5.0 GHz, compared to using only one frequency. Thus, using both frequencies provides a more accurate positioning. The second contribution is an algorithm where WiFi measurements are combined with pedestrian dead reckoning (PDR), which is based on step counting using an accelerometer and hypotheses of the heading using a gyroscope. This was found to provide further accuracy compared to more conventional methods

Fuel Loading of a Fluidized Bed Combustor Burning Bituminous Coal, Peat or Wood Chips

Characterisation of gas- and particle phases in the combustion chamber of a commercial size circulating fluidized bed (CFB) boiler has been carried out during tests with three different fuels: bituminous coal, peat and wood chips, for typical operating conditions of a CFB boiler. The evaluation of the test results aims at presenting data on the fuel loading in parallel with the vertical profiles of oxygen concentration to be used for validation of models and for modelling of the fuel loading. The measurements show that the char loading during peat combustion is 13% of the amount found during coal combustion. Wood combustion results in even less char, only 3.5% of the concentration during coal combustion. For all fuels, more than 80% of the mass of char is retained in the lower part of the combustion chamber, below 2 meter from the bottom plate. The oxygen concentration profiles show large variations over the cross section for all three fuels, explained as an effect of insufficient penetration of secondary air in combination with partial plugging of some of the secondary air nozzles. In the peat and wood cases some of the variation over the cross section is caused by the high volatile content of the fuel in combination with a fuel supply from only one of the furnace walls

Animal handling and stress-related behaviour at mobile slaughter of cattle

By avoiding animal transportation, mobile slaughter may have the potential to reduce animal stress. In a cross-sectional study with elements of cohort design, we investigated relationships between animal handling and stress-related animal behaviours in connection with slaughter at two Swedish slaughter plants: a newly started small-scale on-farm mobile abattoir and a relatively large-scale stationary slaughterhouse. To the stationary plant, the animals were transported on average 99 km from farms, and one third of these animals spent one night in lairage before slaughter. Data were collected during processing of 298 animals at both plants during one year. Stockperson actions and animal behaviours were observed in the driveways (2.4-7.3m long) to the stun box. Data on season, hour of day, air temperature, animal breed, animal category, animal age, carcass weight and stockperson category (plant or farm) were also collected. We used Spearman rank correlation, principal-component analysis and confirmatory factor analysis to develop a final generalised structural equation model, which contained six variables that represented observed animal backing; turning; slipping; eliminating; vocalising; and violent behaviour, regressed on a latent variable representing animal stress level. Stress level and animal behaviours were also regressed on five variables representing observed stockperson actions (touching, patting or hitting with hand; touching, patting or hitting with a tool; pushing; tail-twisting; and prodding with an electric goad) and on background variables including plant identity. The animal behaviours were modelled as counts per driveway length, clustered on farm identity. Marginal effects of stockperson actions and predictive margins of plants were calculated. The animals displayed backing and violent behaviour (kicking, goring or violent fighting) at significantly lower frequencies at the mobile plant than at the stationary one. In general, stockperson actions were significantly positively associated with animal behaviours, i.e. increased actions were associated with more frequent behaviours. Stockperson moving with tool, pushing and using electric goad were indirectly significantly associated with all animal behaviours via animal stress level. This study shows the importance of adequate cattle handling to limit pre-slaughter stress