In this session we took a historical look at the development cryptography over the past millennia, considering both ciphers (where individual characters are encrypted) and codes (where whole words or ideas are encrypted to a single symbol). We discussed the Caesar Cipher, where letters are transposed by a number of places along the alphabet. Then Substitution ciphers, where each letter of the alphabet is mapped randomly onto another. Because of the static nature of the mapping, this kind of cipher can be broken relatively easily by comparing the frequencies with which characters appear in the ciphertext with the frequency of characters in plaintext. Continue reading Ciphers, codes and how to break them – Bernard Foot
Colin gave an entertaining short talk on how electric cars work. He described the various energy sources (including electric) available in principle for automotive propulsion and compared them in terms of cost, efficiency, endurance, etc. He gave a comparison between lead-acid & Li-ion battery types. It was pointed out that the basic commercial costs of petrol/diesel and electric propulsion were approximately the same, but that electric propulsion would clearly win out in that respect unless taxation rules were changed. However, there were significant logistical implications for electric cars (availability of charging points, exchanging batteries, use of solar charging, etc.) Perhaps in the short term hybrid vehicles may prove to be a pragmatic interim solution, although currently costly and still lacking in endurance if mainly reliant on electricity.
Garth concentrated mainly on self protection of military aircraft against radar-directed terminal threat weapon systems, though pointed out that there was read-across to other platform environments and jammer resource deployments.
His talk covered briefly aircraft tactics, but emphasised the role of “soft-kill” electronic countermeasures (ECM) in terms of the use of passive decoys, and onboard and offboard active electronic techniques and technologies.
He described noise, deception and angle jamming techniques which could be used against sophisticated radars employing pulse doppler multiple target tracking & monopulse angle tracking techniques (e.g. using phased array antennas). A number of advanced repeater jammer techniques & technologies were described, including those regarded as most difficult to implement (counter-monopulse). Examples of implementation in specific aircraft types were given.
Electronic Protection Measures (EPM) used by radars to try to defeat jamming were also briefly addressed.
His talk was illustrated with a number of video clips:
Prof Peter Abrahams gave 3 particularly fascinating lectures on the Interactions of Medicine, Science and Art at this TVN Study Day.
- “Leonardo da Vinci, scientist, engineer and artist, and his relationship to modern Nobel Prize winning concepts such as CT and MRI scanning”. The talk was essentially a repeat of that given at Exeter University, and available on YouTube:
Prof Abrahams also pointed out that an app was available for the iPad “Leonardo da Vinci: Anatomy” (cost £9-99p) as a wonderful depiction of his anatomical drawings held in the Royal Collection at Windsor Castle.
As a result of a subsequent question about Leonardo’s understanding of the operation of the heart valves and aortic flow, he directed the questioner to a YouTube video which demonstrated that his understanding was 500 years ahead of his time (https://www.youtube.com/watch?v=faVlZRGyBDs).
2. “The Michelangelo Discovery- the Rothschild Bronzes and the Fitzwilliam Museum”
Prof Abrahams described how he had been asked, as an anatomical expert, to investigate the provenance of these bronzes. He also drew attention to a number of publications, including a DVD “Michelangelo – Love and Death”, still available from Amazon.
3. “The Hand of God” – covering art history, culture, anatomy, and comparative anthropology with some actual pathological case studies.
We were treated to 3 excellent speakers at this event: Continue reading U3A Explores Science at the Ri
Lack of control and unpredictability can cause stress. Stress can be defined as an environmental or physiological challenge that brings about a stress response. A stress responses is a suite of changes in the body that is brought about by the perception of a threat or challenge. Stressors elicit a stress response; these include excessive noise and heat, restraint, infection, predators, change of environment, overcrowding and isolation. When a stressor is perceived by the brain, nerve signals are sent to parts of the body such as the heart, lungs and gut and to glands such as the adrenal gland that secretes the hormones adrenalin and cortisol. There are two kinds of stress – acute or short term stress and chronic or long tern stress. Continue reading Is stress always bad for you? The Biology of Stress – Angela Wall
The notes on Richard’s talk will be published when available.
6 members of Risborough U3A attended this most interesting study day.
Robert Headland (Scott Polar Research Institute, Cambridge) spoke about the history of the exploration of the Antarctic by Sir Ernest Henry Shackleton.
Lt Cdr John Ash (ret., also of the Scott Polar Research Institute) gave 2 talks: “The Arctic, Submarines and Security: Science and Risk of a Warming Environment”, and “Exploring Frontiers in a Changed Climate”.
Lastly, the explorer and author Alex Hibbert spoke about “The Long Haul” – the unsupported crossing of the Greenland ice cap by self-haulage of equipment and supplies.
Colin described the development of artificial light from 1800, with the invention of arc light by Humphrey Davy using batteries, to today’s state-of-the-art LED (Light Emitting Diode) technology. Continue reading How it works – electric light: Colin Robinson
The Group had a most interesting 2 hour tour of The National Museum of Computing, Bletchley Park, led by Mr Robert Dowell. This covered the evolution of computing and software technology from the Colossus of WWII decrypting German Enigma and Lorentz codes, through all the decades since, culminating in devices such as the present-day IBM PC, the Apple Mac, iPad, smartphones, etc. Continue reading Guided Tour of The National Museum of Computing, Bletchley Park