A compendium of Caenorhabditis elegans regulatory transcription factors: a resource for mapping transcription regulatory networks

Background Transcription regulatory networks are composed of interactions between transcription factors and their target genes. Whereas unicellular networks have been studied extensively, metazoan transcription regulatory networks remain largely unexplored. Caenorhabditis elegans provides a powerful model to study such metazoan networks because its genome is completely sequenced and many functional genomic tools are available. While C. elegans gene predictions have undergone continuous refinement, this is not true for the annotation of functional transcription factors. The comprehensive identification of transcription factors is essential for the systematic mapping of transcription regulatory networks because it enables the creation of physical transcription factor resources that can be used in assays to map interactions between transcription factors and their target genes. Results By computational searches and extensive manual curation, we have identified a compendium of 934 transcription factor genes (referred to as wTF2.0). We find that manual curation drastically reduces the number of both false positive and false negative transcription factor predictions. We discuss how transcription factor splice variants and dimer formation may affect the total number of functional transcription factors. In contrast to mouse transcription factor genes, we find that C. elegans transcription factor genes do not undergo significantly more splicing than other genes. This difference may contribute to differences in organism complexity. We identify candidate redundant worm transcription factor genes and orthologous worm and human transcription factor pairs. Finally, we discuss how wTF2.0 can be used together with physical transcription factor clone resources to facilitate the systematic mapping of C. elegans transcription regulatory networks. Conclusion wTF2.0 provides a starting point to decipher the transcription regulatory networks that control metazoan development and function

Community use of H2S (hydrogen sulphide) as a verification tool for water safety plans

Through the development of Water Safety Plans at the household level it is important that while the community understand their system of water delivery, measures are taken to protect their water source. It has been found that the cycle and introduction of Water Safety Plans will only be complete with the introduction of household’s water treatment and safe storage. In the rural setting of Sri Lanka the households are often the producer of water, it is important that the household is empowered to mitigate risks and has a method to test their water for harmful microbiological contamination. The H2S provides a tool for verification and provides an extrinsic motivation for the use of effective purification methods. Through the implementation of the Water Safety Plans and the verification by the use of H2S Kit, can households be confident their water is safe to drink

Evolution and nucleosynthesis of helium-rich asymptotic giant branch models

There is now strong evidence that some stars have been born with He mass fractions as high as $Y \approx 0.40$ (e.g., in $\omega$ Centauri). However, the advanced evolution, chemical yields, and final fates of He-rich stars are largely unexplored. We investigate the consequences of He-enhancement on the evolution and nucleosynthesis of intermediate-mass asymptotic giant branch (AGB) models of 3, 4, 5, and 6 M$_\odot$ with a metallicity of $Z = 0.0006$ ([Fe/H] $\approx -1.4$). We compare models with He-enhanced compositions ($Y=0.30, 0.35, 0.40$) to those with primordial He ($Y=0.24$). We find that the minimum initial mass for C burning and super-AGB stars with CO(Ne) or ONe cores decreases from above our highest mass of 6 M$_\odot$ to $\sim$ 4-5 M$_\odot$ with $Y=0.40$. We also model the production of trans-Fe elements via the slow neutron-capture process (s-process). He-enhancement substantially reduces the third dredge-up efficiency and the stellar yields of s-process elements (e.g., 90% less Ba for 6 M$_\odot$, $Y=0.40$). An exception occurs for 3 M$_\odot$, where the near-doubling in the number of thermal pulses with $Y=0.40$ leads to $\sim$ 50% higher yields of Ba-peak elements and Pb if the $^{13}$C neutron source is included. However, the thinner intershell and increased temperatures at the base of the convective envelope with $Y=0.40$ probably inhibit the $^{13}$C neutron source at this mass. Future chemical evolution models with our yields might explain the evolution of s-process elements among He-rich stars in $\omega$ Centauri.Comment: 21 pages, 16 figures, accepted for publication by MNRAS. Stellar yields included as online data table

A3_10 Christmas Spirit

In this article we explore the amount of energy that can be produced from Christmas spirit. We investigated an event shown in the movie ‘Elf ’ where Santa Claus’ sleigh needs the energy of Christmas spirit to raise it off the ground and back into the air. We found that to raise the sleigh required a total Christmas spirit of 4.51 × 10^14 J which is a significant amount. We find that each person shown in the film would need to produce 2.89 × 10^12 J, yet if this Christmas spirit was shared amongst everyone in the world they would only need to produce 71.0 kJ

A3_6 Tribbling Times

In the Star Trek universe, tribbles are small furry creatures whose population increases exponentially. Using the assumption made by Spock, that a tribble has 10 children every 12 hours, we find the growth constant for a tribble population to be 0.1998. From this, assuming the tribbles have an unlimited food supply, we find that the time needed for the tribble family to grow such that it fills USS Enterprise is 4.5 days

Neutron-Capture Nucleosynthesis and the Chemical Evolution of Globular Clusters

Elements heavier than iron are almost entirely produced in stars through neutron captures and radioactive decays. Of these heavy elements, roughly half are produced by the slow neutron-capture process (s-process), which takes place under extended exposure to low neutron densities. Most of the s-process production occurs in stars with initial masses between roughly 0.8 and 8 M , which evolve through the Asymptotic Giant Branch (AGB) phase. This thesis explores several topics related to AGB stars and the s-process, with a focus on comparing theoretical models to observations in the literature on planetary nebulae, post- AGB stars, and globular cluster stars. A recurring theme is the uncertainty of 13C-pocket formation, which is crucial for building accurate models of s-process nucleosynthesis. We first investigated whether neutron-capture reactions in AGB stars are the cause of the low sulphur abundances in planetary nebulae and post-AGB stars relative to the interstellar medium. Accounting for uncertainties in the size of the partial mixing zone that forms 13C pockets and the rates of neutron-capture and neutron-producing reactions, our models failed to reproduce the observed levels of sulphur destruction. From this, we concluded that AGB nucleosynthesis is not the cause of the sulphur anomaly. We also discovered a new method to constrain the extent of the partial mixing zone using neon abundances in planetary nebulae. We next aimed to discover the stellar sites of the s-process enrichment in globular clusters that have inter- and intra-cluster variation, with the examples of M4 (relative to M5) and M22, respectively. Using a new chemical evolution code developed by the candidate, we tested models with stellar yields from rotating massive stars and AGB stars. We compared our model predictions for the production of s-process elements with abundances from s-poor and s-rich populations. We found that rotating massive stars alone do not explain the pattern of abundance variations in either cluster, and that a contribution from AGB stars with 13C pockets is required. We derived a minimum enrichment timescale from our best-fitting chemical evolution models and, although the value depends on the assumptions made about the formation of 13C pockets, our estimate of 240–360 Myr for M22 is consistent with the upper limit of 300 Myr inferred by isochrone fitting. Lastly, there is accumulating evidence that some stars (e.g., in ! Centauri) have been born with helium mass fractions as high as 40%. This motivated us to explore the impact of helium-rich abundances on the evolution and nucleosynthesis of intermediate-mass (3–6 M ) AGB models. We found that the stellar yields of s-process elements are substantially lower in He-rich models, largely as a result of less intershell material being mixed into the envelope. We also found evidence that high He abundances could restrict the s-process production by 13C pockets to stars with lower initial masses

A3_3: A Pretty Positive Guy

In this paper we discuss the potential energy associated with a sphere of hydrogen once all of its electrons have been removed, which we have used as an approximation for a person. We calculated this energy to be 4.8x10^29 J. We compared this value to known processes and it was found to be extremely energetic, billions of times greater than nuclear explosions and of a similar magnitude to the Sun’s energy output. We also found that the same process when applied to an approximation of an ant has 1.5 × the energy of the Tsar bomb

A3_2: Waving to the ISS

The aim of this paper was to determine how long it takes the ISS to repeat an orbit. We created an orbital simulation of the International Space Station (ISS) using official orbital data, from which we found that the time taken for the ISS to travel along a pre-travelled orbit (same latitude and within 1o longitude) was 6 days 21 hours and 21 minutes