Recent Talks

A selection of recent talks held at the society, in no particular order, as recorded by our secretary

Smart Cities – the Smart Sustainable Districts Programme  on 17-3-2017

Dr Mazur explained that the Smart Sustainable Districts Programme (SSD) looked into service networks, the flow of resources, land use, etc; local teams are set up to deal with any pressing topic.  Cities have most to gain from smart initiatives, and have the money to introduce them.  The aim is that they should be acceptable to the populace, sustainable and environmentally clean.

Air pollution and transport is the topic of concern that Dr Mazur went on to discuss.  Several European cities stop traffic when air pollution is bad – London, not just in the centre but Greenwich too, merely recommends staying indoors.  Oxford Street is notorious for its levels of pollution, but the Cromwell Road is worse.

Several design approaches can be taken: with traditional vehicles, lightweight materials reduce fuel usage - improvements to petrol/diesel engines can reduce pollution.  Electric propulsion is better still, whether all electric, hybrid or using hydrogen fuel cells.  Electric vehicles come with regenerative braking, recharging their batteries when slowing for traffic lights or going downhill.  The environmental impact of driving electric vehicles is 5% of traditional vehicles.  In France electricity supply is Nuclear – and carbon free.  Germany is 50% carbon free; and the UK 10%, but rising.

Driverless cars coping with the whims of drivers of conventional cars is a serious problem, with much work going into bringing it within acceptable bounds.  However, we have self-parking cars, cars which waken dozing drivers, or apply the brakes if too close to the car in front, etc.  The technology has evolved from safety practices used in aircraft, ship, and space satellites; and is now cheap enough for use in cars – the Google car is based on the Mars Rover (a UK design).

The range of available kit is impressive: cameras see contrast differently – often better, if not in snow; radar, lidar (3D optical), and ultrasound.  This is miniaturised, with multiple units disposed around the vehicle, giving views other than that of a single driver.

Vehicle-to-Vehicle and Vehicle-to-Infrastructure (V2V, V2I) communication (when equipped) is in the offing.  The “I” could give automatic speed limit control, road work information etc.  The second Vehicle could indicate its presence while still out of sight round a corner.  But all this is open to hacking, or equipment failure.  Ethics come into it - who do you sue after an accident if there is no driver?

Inefficiency – the average car is not used for 96% of the time, 2.6% being driven, the remainder parked or in traffic jams.  Car pools improve usage.  Motorbikes use less fuel; bicycles none.  Speed bumps are a poor method of traffic calming, and another cause of inefficiency and pollution – they are (sometimes) designed not to be too uncomfortable at 20 mph, and to indicate that speed limit; but drivers do not realise this and often approach them at 30 mph, brake (producing brake dust) and accelerate away (CO2, NO2).

Shared delivery vans and taxis (Uber) reduce vehicle mileage and congestion.  Busses can be rerouted to suit the conditions.  TfL have ambitious plans for decarbonisation of all such vehicles, and the installation of many more electricity recharging points.

Other methods of traffic calming which are more congenial and environmentally friendly, particularly in side streets, include tree and shrub & planting, distinctive road surfacing, and less infrastructure (eg, kerbs, street signs).  Other smart improvements should reduce the duration of road works - knowing where to dig before starting – and collaboration between services.  The number of crashes should be reduced.  Travel time should become more dependable.

Dr Mazur closed by saying that new models for the (shared) ownership of cars will come, and new business models, for instance for delivery.

Designing & Manipulating Molecules for Tissue Engineering & Regenerative Medicine, 21-4-17

Professor Alvaro Mata first showed a picture of a salamander – an animal which can regrow a limb if need be.  A range of simpler animals can do this - humans can cope with cuts and bruises.

Nature has surprising examples of material properties: the leaf of a lotus growing in the murkiest water is self-cleaning – it is super hydrophobic.  A gecko can move across the underside of a leaf – it has myriad hairs on its feet which form hydrogen bonds (Van de Waals forces) with the leaf - the combined bonding being sufficient to take its weight.

A range of materials can be used for engineering tissue, both liquid and solid.  Closing up wounds with sutures has been practiced for thousands of years.  Metal inserts - gold and silver for instance, even glass – have been used.  In the mid-20th century procedures had advanced to be able to develop biocompatible materials such as metal alloys, cellulose, polymethyl methacrylate, hydroxy-apetite, high strength polythene, nylon, and silicone – used for artificial hips etc.  

Since then procedures have advanced from a ‘boxing glove’ level to being able to make macroscopic functional units.  Molecular level materials can be produced, which can be bioactive, even smart - there are degradable polymer and hydrogel materials.  Proteins are of nanometre dimensions, cells are micrometre, and tissues millimetre.

Peptide Amphiphiles (PA)
are molecules made up of a hydrophilic end, a central section of sheet forming amino acids and a hydrophobic end; all fully biodegradable.  In an aqueous solution the molecules self-assemble into nanofibers – the hydrophilic ends on the outside, the hydrophobic ends at the centre, with the central section forming hydrogen bonds to hold the assembly together.  With a 4nm long PA, an 8nm diameter fibre is formed.  The double arrow in the diagram shows that assembly is highly favoured over disassembly.

The outer end of the fibre presents a high concentration of the hydrophilic agent to the surroundings – very advantageous when the agent is a protein that is difficult to make/extract (and not necessarily one of the 20 proteins in the body, though one has to be careful not to cause rejection).  The agent can be considered as a therapeutic bio-implant.

The outer end of the molecule may itself be a biologically active agent, or be combined with one.  It can be designed to have positive, zero or negative charge, and to be sensitive to temperature, ph, or light – affecting the conditions under which self-assembly takes place – and whether a concentration of PA fibres assemble into a matrix. 
A matrix can hold molecules, or even cells, ready for use by the body in an extra-cellular environment.  For instance, bone marrow cells to support the formation of cartilage, bone etc.  A small cranial hole in a rat has been bridged by this means.

Elastin is made of disordered protein, and allows tissue membranes in the body to resume their shape after stretching or contracting.  At a PA interface with a solution of elastin like proteins (ELP) a membrane is spontaneously formed – depending the geometry of the equipment the membrane can form a tube or a balloon.  Such tubes can be grown to useful lengths, and to have branches.  Such elastin tubes, though not very strong are robust, and bring the possibility of engineering vessels and capillaries.  Not to replace bodily tissues but to enable laboratory testing of drugs with a patient’s fluids to ensure compatibility.  This is particularly applicable to avoid disturbing the blood/brain barrier – or the membrane around an embryo.

Professor Mata closed by saying that this field of work is still young.  Models for simulation and prediction are being improved, the uses of PAs are being developed and the range of uses extended.  Artificial cells are being investigated.

Machines for Unravelling DNA, Molecule by Molecule  by  Dr Daniel Burnham  on 17-2-2017

Dr Burnham began by describing the Francis Crick Institute, which is in Camden close to Kings Cross station.  Sir Paul Nurse saw the need for a multidisciplinary institute for biomedical discovery, organised its building and its occupancy by a number of separate biomedical centres working in this field.  The building is basically open plan with a vast atrium with four underground floors and five above ground; laboratories surround the atrium on each floor.  Dr Burnham commented that, contrary to his initial reaction, the ambience is quiet.  Each of the constituent bodies has its strengths, so advice is always at hand.  The ethos is to find new methods for treating human disease, and to speed up their introduction to general medical practice.  Outreach with the general public, particularly in Camden, is a condition of working there.

Cell Division - Bodies are made of cells, each with a nucleus containing a tiny (but of 6bn base pairs, 2m long) DNA molecule.  Dr Burnham is studying what happens to DNA during cell division.  To do this the two DNA strands are separated, and each acquires a second matching strand.  The cell then divides its constituents to either side and the centre pinches off to give two cells.  This takes about a day, the copying having been done at a rate of 70,000 base pairs a second.  All this is done with great precision – mutations do occur, but very seldom.
The first stage of cell division is to ‘un-zip’ the DNA.  This is done by a protein hexamer (a grouping of 6) which travels along the DNA.  Behind it a ‘bubble’ develops before the two new DNAs are formed and separate out.
Seeing this is not easy.  One needs to be able to see dimensions half the wavelength of observable light, impossible according to the Raleigh criterion.  However, it can be achieved by the use of flashing dies – if two adjacent elements, containing the die, flash randomly one may be on when the other is off and vice versa.  By recording the flashes over a long enough period a picture can be built up.  (The dies are made to flash by a high energy laser pulse.)  Another technique for seeing what is happening is to use a magnetic tweezer.  A magnetic bead is attached to a molecule and attracted by magnet - movement in the molecule is enhanced by the magnetic force and can be detected at the magnet.  Dr Burnham showed us pairs of 4mm magnetic cubes, which adhered to one another very strongly.
Much was already known from crystallography by x-ray imaging – but only of DNA frozen in a crystalline form.  This suggested that un-zipping the DNA was done by a mechanism that ‘walks’ steadily along the DNA.  Dr Burnham has obtained results that show it is not steady but stops and starts.  DNA division takes place in a cellular soup, and the delivery of the required building proteins may not be timely.

In order to design his experiments and make sense of the results Dr Burnham made good use of the multidisciplinary nature of the Institute.  He had to consult people who had written similar software (derived from ‘first passage time’ financial programmes to find when a threshold is reached), and then write his own – he flashed up a daunting page of lines of code.  Even then he found that he had to add retrograde movement (when the DNA temporarily re-zips) to the stochastic ‘walk’ he had already discovered, before the theory matched the results.  There are seven variable parameters in the theory, which still has unresolved difficulties…
One question after the talk was to ask how cell division was done in very early forms of life – to which the reply was, as far back as we can see, the same as now, even to having a hexamer to do the unzipping.  However there is a belief that initial life was based on RNA rather than DNA.

Dr Burnham closed by telling us about his Week in Westminster.  Nowadays Parliament invites professionals to shadow members of select committees for a week, to see how parliament works and to impart some of their knowledge.  He was paired with Nicola Blackwood, who greatly impressed him with her grasp of science and her ability to quickly understand a business presentation - and to ask probing questions.  He was completely disabused of the notion that Parliament is unscientific, and came away with a greater respect for it.

Advances in Battery Technology  by  Dr Monica Marinescu  on  20th January 2017

Dr Marinescu said that one of the main factors behind the battery development, that she is engaged in, is a desire to make electric vehicles that outclass those burning fossil fuels – and to reduce the extraction and use of fossil fuels generally.

Batteries do not produce electricity but store it, and can provide effective back up to Solar, Wind and Water generators.  They have a range of applications, supported by a range of battery types.  For vehicular use they need to be safe, versatile, and able to withstand shock.  They can be designed for a high discharge rate – and subsequent recharge rate - with large cross section internal connections.  Recharge can be from regenerative braking or a battery charger.  Hybrid cars, with back up from an internal combustion engine, can have a low (dis)charge rate battery.  Super capacitors can also have a back-up role, as they can rapidly release charge, and be recharged by regenerative braking or more slowly from the battery.

Fuel Cells, together with the means of storing their fuel (usually Hydrogen), are costly and not yet practicable.  They have average power and energy densities, so do not give rapid bursts of power.

Lithium is a light element and can be readily oxidised from Li (charged) to Li+ (the discharge state), making it a good battery anode material.  However it is very active chemically and has to be chemically combined to be stable.  Batteries need electrically conducting electrodes and an electrically conducting electrolyte; with an insulating separator.  The lithium is intercalated in the anode matrix, and as the battery is discharged Lithium ions are transferred to the cathode where it is again intercalated.  Early Li-Ion batteries used LiCoO2 for the main cathode material, but LiMn2O4, Lithium Magnesium Oxide, (with an admixture of LiCoO2) was found to be better.  A typical Li-Ion battery, as used in cars such as the Nissan Leaf, is made up of individual cells (in pouches the size of an A5 piece of paper), but housed in a robust casing.  Each has a 35 watt-hours (Wh) capacity.  A thousand of these will give 30 kWh.  A solid electrolyte interface (SEI) between the electrodes and the electrolyte is developed with use, which allows the lithium ions to pass, but otherwise protects the electrodes.  It is necessary to balance the cells to prevent any one of them from taking more than its fair share of charging current and running hot - overvoltage protection is provided, and with connections and heatsinks, the cost of the battery is twice the cost of the cells.

The “ions” can be provided by a number of materials including Sulphur and Oxygen.  A Li-S battery has a lithium anode and carbon-sulphur cathode.  Again the lithium ions transfer to the cathode during discharge.  The Li-S battery can be punctured (with a nail !) in safety – it does not explode like a Li-Ion battery.  Li-S batteries have low weight and can provide over twice the storage capacity of Li-Ion (a sulphur atom can contribute 16 electrons).  They are still under development.

Li-O could provide yet more storage capacity, but are much more difficult to design, and very much for the future.  Battery electrodes are often referred to as plates.  A simple voltaic pile such as Volta devised has metal plates of copper and zinc separated by an electrolyte formed of brine soaked cardboard (during discharge the zinc dissolved in the electrolyte and H2 was given off at the positive, Cu, plate).  A Leclanche cell has a carbon rod as the positive ‘plate’– which itself takes no part in the battery chemistry but provides a conducting path for what is effectively an oxygen electrode (from air or MnO2).

Modern electrodes generally have a porous granular composite structure; they contain reactive agents and conduct electric current to the terminals.  However simple the basic electro-chemistry, designing rechargeable batteries has problems: over what temperature range will it work?  Material lost from an electrode during discharge and regained on charge causes the electrode volume to change – can this be accommodated within the cell structure, or will it cause the cell to burst?  Will the active material distribute itself uniformly in the electrodes during charge and discharge; will it overheat if the charge is too rapid?

Will one large cell work safely or is it better to have a number of small cells; will a number of small cells share the charge or will one try to take the lot?  Battery losses increase as current rises – not just ohmic losses in the connections, but due to limits to the rate of ionic diffusion.  This particularly affects how fast a battery can be recharged – current limited charging to 80% capacity can be quite rapid, but the final 20% (if you need it) is then trickle charged to avoid damage.

Subtle changes to the physical electrode design or adding chemical modifiers can only be tested by making a cell and trying it.  The choice of electrolyte can be critical - how stable is it; what chemical reactions might take place to affect it?  Most parameters are not measurable in a closed cell, and the system will work differently if opened.  One can only measure the external performance of the cell with its losses.

The Grand Finale of Cassini on Saturn  by  Dr Greg Hunt  on  18th November 2016

Saturn orbits the Sun at ten times Earth’s radius, taking 30 Earth years to do so.  Its day length is about 10½ hours.  Despite its appearance in photographs, the surface is not solid – Saturn is a gas giant with a radius R (to the where the pressure level is 1 bar) of 60,000 km.

The Cassini-Huygens mission was launched in 1997, and followed a path via Venus, Earth, Venus to gain gravitational boosts before heading to Jupiter in 1999 and reaching Saturn in 2004.  The mission was to last until 2008, but was extended to 2010, and again to 2017 (it is now running low on thruster fuel).  This means that Saturn will have been observed for half of one of its orbits.

The Cassini spacecraft is the size of two double decker busses.  It weighs 2 tons, and at launch carried 4 tons of fuel, and a nuclear reactor to generate the 700W needed by the electrical equipment.  Dr Hunt commented that it has a 1 Megapixel camera, and 0.5 GB data storage [but, with large semiconductor feature sizes, more able to withstand cosmic rays than modern equipment - ed].

Dr Hunt’s work is to use its Magnetometer and interpret the results as it passes by Saturn and its environs.  Two magnetometers were mounted on an 11m beam to minimise the magnetic effects of the electronics in the main body of the spacecraft: one at the end of the beam, no longer operational; and that designed at Imperial College half way along the beam.  Magnetometer calibration is done by rotating the spacecraft so that its magnetic effects alternately add and subtract from measurements.  (Dr Hunt said rotation was desirable for his work, but not for the photography being done by others!)

Cassini has now done 248 orbits of Saturn, on a tour out into the Solar Wind beyond its magnetosphere, looking at the rings, and around the moons on its equatorial plane, and through the Cassini Gap between the Rings and the Planet.  The tour was designed to orbit the larger moons to gain energy for orbital adjustments and minimise the use of thruster fuel.  Two moons have well repaid their visits: Titan, which the Huygens module was built to photograph; and Enceladus.

  • Titan is Saturn’s largest moon, slightly larger than Mercury and furthest out orbiting at 20R.  It has organic material on its surface, including methane lakes.
  • Enceladus is a tenth the size of Titan, about 500 km in diameter, orbiting at 2R in Saturn’s E-ring.  It is an icy moon – covered in water ice, giving it a high albedo.  It is active: during an early flyby a magnetic field deflection was seen; there are cracks at its north pole, but it is smooth further south.  The cracks are hotter than the surroundings and emit Plumes of water – there seems to be a liquid ocean under the surface.  Enceladus is in a locked orbit with Dione, another moon, giving rise to tidal heating.  It exhibits cryo-vulcanism, covering the southern surface with new material.
Saturn has a magnetic field giving it a magnetosphere which reaches out to Enceladus so that it too has a magnetic sheath.  The lines of force of both planet and moon are in alignment.  Saturn day length is indeterminate.  The 10½ hour figure was found by the Voyager spacecraft; since then the Ulysses probe measured 10.7 hours, and Cassini has measured 10.6 hours in the northern hemisphere and 10.8 in the south – radio and magnetic measurements agree.  As a gas giant different wind speeds are possible.  It has a Great White Spot at the North Pole – with a hexagonal outline and a vortex at its centre.  It was first seen in 1989; it waxes and wanes, and this is its fifth appearance since then.  Its colour can change from blue to yellow due to chemical reactions – the yellow being due to ammonia.  The upper atmosphere is heated, and has frequent storms – which grow until they encircle the planet at which point they collapse.  Saturn is mostly made up of hydrogen and helium – hydrogen at the core being gravitationally compressed to its metallic state, in which currents can flow and generate a magnetic field.  Saturn too has auroras, and a plasma tail away from the Sun.  Saturn’s core will be at a high temperature, and even its surface is about 400OK – hotter than if it were only heated by the Sun.

Much is still to be found out about Saturn: its day length(s); the periodicity of its weather; the close alignment of its dipole and spin axes; its internal structure, etc.  In its last few months Cassini’s orbital period will be speeded up, using a flyby round Titan, from 8 days to 6½ days  and it will orbit 22 times at 30km/sec through the Cassini Gap to get even more information about the Saturn.  Its final orbit is to end on 15th September 2017 at 12pm (GMT) when it will plunge beneath Saturn’s surface.

If it was left to its own devices Cassini would not escape from Saturn’s system of moons and rings – it could fly into and contaminate Titan or Enceladus where there is the possibility of life.

JUICE – JUpiter ICy moon Explorer is a mission already being planned to look particularly at Callisto, Europa, and Ganymede; though Jupiter has magnetic quirks to be investigated, and its structure and formation are to be studied.  Ganymede has its own magnetic field, and could have an ocean.  The spacecraft will have a set of improved instruments - Imperial College are working on its fluxgate magnetometer.  Launch is planned for 2022 followed by a 7½ year journey, then an operational life from 2029 to 2033.  Seventeen countries were involved in the Cassini mission, and no doubt will be for JUICE.

Picture Shows Tiny Moon Daphnis Surfing the Rings of Saturn

Of the 62 confirmed moons that orbit Saturn, none has more pluck than Daphnis.
A tiny dot compared to the gargantuan size of Saturn, Daphnis’ orbit means that despite its small size it makes a big impact on what’s around it.  You see Daphnis ‘surfs’ on Saturn’s rings, carving through the outer layers while leaving a fantastically beautiful wake behind it.  Like a rock skimming over water you can actually see the ripples that Daphni’s tiny gravitation pull has on the gas giant.  At just 5 miles across Daphnis is well and truly minuscule when compared to Saturn’s staggering size.
Captured by NASA’s Cassini spacecraft, the ‘wavemaker’ was first spotted in 2009 as it sped through the 26-mile wide Keeler Gap found in Saturn’s outer rings.

Saturn’s rings alone are astonishing.  Stretching as far as the moon is from Earth, and yet in some places less than a kilometre thick Saturn’s rings contain dust, ice and large rocks.  Saturn itself is also a collection of impressive numbers.  It is around nine times larger than Earth and is around 900 million miles from the Sun.