The last Blurbs of the year juxtaposed super-massive and micro-level science. Professor Rob Fender, Tutorial Fellow in Astrophysics, launched proceedings by inviting the audience to reconsider the reputation of Black Holes. Popular culture portrays these as fearsome sink holes in space and time into which all matter is destined to fall. While ultimately true, until the last days eventually arrive, Black Holes perform vital cosmological functions helping to keep the universe alive and well. Professor Fender began by giving the mixed audience of students and Faculty (drawn from different academic disciplines) some basic astrophysics. Trips into Black Holes are one-way tickets once the event horizon is crossed because at this point the escape velocity from the gravitational field equals the speed of light. Despite accreting complex forms of matter, Professor Fender explained that Black Holes are fundamentally identical and can be described simply in terms of their mass, spin (whether and how rapidly rotation around an axis takes place), and electrical charge. Of these properties, the speaker concentrated on mass, contrasting stellar mass (city-sized) Black Holes (typically 10-100 km across) with their super-massive counterparts. The latter occupy a space roughly the size of our solar system and have a mass of between 1 million and 1 billion times that of the Sun. Professor Fender pointed out that far from being dark, Black Holes rank among the brightest bodies in the universe, reaching at times luminosities 1014 times that of the Sun. Matter drawn into the accretion disc along a curved pathway interacts with other matter with different orbital speeds, releasing extraordinary amounts of heat through friction, and being detectable at vast distances with facilities as diverse as orbiting X-ray satellites and ground-based radio telescope arrays.
The next phase of Professor Fender’s talk was illustrated with some striking visual illustrations. These included the RXTE all-sky X-ray view of the galactic plane, which revealed Black Hole hot spots and also alternate phases of activity and inactivity. Professor Fender’s current research investigates these variations in activity. He explained that powerful jets carrying kinetic energy emanated from Black Holes, heating cosmic gas. A ‘year in the life of a Black Hole’ was chronicled. For the majority of the time, a stellar mass Black Hole emits jets but this is punctuated by a shorter luminosity phase in which X-rays are released. Professor Fender’s team work on the link between accretion of matter and jet formation. These alternate phases make the universe a brighter and warmer place than it would otherwise be. Of particular importance is the heating of gases, delaying condensation into stars, thereby prolonging the process of star formation and limiting galaxy size. In the absence of Black Holes, it is possible that star formation in our galaxy would have ceased billions of years ago. The fact we exist in a corner of the universe that has reached only the half-way point of its life-span is thus directly attributable to the operations of these galactic monsters.
After a short break, doctoral student Chico Camargo, took the Blurbs stage. Chico is among a number of current graduates funded by a Brasenose-Clarendon scholarship and is attached to Oxford’s Systems Biology Doctoral Training Centre. The talk again began with an orientation session in which the audience was reminded that human beings are composed of around 23,000 genes that can be in an ‘off’ or ‘on’ state. When switched on, DNA generates RNA and instructs it how to make protein. Every day of our lives, a multiciplicy of different genes switch on or off and interact with other genes by activating (+), repressing (-), or having no effect (0) on them. Chico’s experimental research analyses fission yeast, which has approximately 5,000 genes. Although simpler than a human being, since each gene has the same +/-/0 effects, there are nevertheless a staggering 35000x5000 possible combinations. Since natural selection lacks sufficient time to work through all possible permutations to select improvements, it follows that evolutionary mechanisms must be structured in some way. The SYSBIO DTC group is working on understanding how national variation is structured.
Chico explained the concept of the cell-cycle – an ordered sequence of events that enables one cell to generate two genetically identical duplicates. In the case of fissile yeast, the majority of mutations lead back to a common cell-cycle, or backbone. In consequence, its genetic structure is highly robust. To explain why this is the case, Chico used the analogy of computer file compression. Low complexity information is relatively easy to compress whereas high complexity information is far more challenging. Simple cycles or pathways (phenotypes) are more abundant than more complex ones and so are more likely to be found by random searching. The prevalence of simple phenotypes, therefore, gives structure to natural variation.
Questions from the audience led to further discussion. Those present wanted to know what mechanism produced simple phenotypes. It was also suggested that samples of present-day fissile yeast were selective: strains of yeast characterised by robustness were more likely to survive, giving rise to the observed results.
Blurbs was introduced and closed by the HCR President, Jonathan Griffiths, who is completing an MSt in Greek and/or Latin Language and Literature and has a specialist interest, suitable for Professor Fender’s talk, in ancient philosophical theories of apocalypse and cosmic destruction. Commenting on Brasenose’s series of graduate-Faculty talks, Jonnie said: ‘Blurbs at Brasenose seeks to bring together the established professoriate of today with the budding graduate researchers of tomorrow, offering both students and Fellows an opportunity to present their findings to a non-specialist audience from the full breadth of the academic curriculum. It is one of my favourite events in the termly calendar, and one of the major reasons that I applied to Brasenose last year: not many other Oxford colleges share this distinguished tradition. During the talks, the HCR hosts both speakers and audience with a glass of wine and refreshments, followed by dinner in Hall and post-prandial Second Desserts. On this occasion, I was curious to see how Rob and Chico’s talks would complement each other in their handling of the very big and the very small, and was treated to an intellectual feast very far from my own humble platter.’