Editor's pick: Medics need psychomotor practice
Tom Chivers rebuts claims by surgeon Roger Kneebone that students lack manual dexterity because they spend too much time with flat screens (10 November, p 25). When I was at the Indiana University School of Medicine in the 1970s and 80s, we built patient simulators to enhance the examination skills of medical students, interns and residents. We called them “psychomotor skills”.
The life-size simulators were constructed of silicone rubber, urethane foam and latex to give them a lifelike feel. Students used them to practice breast examination (Betsi), pelvic examination (Gynny) and knee injury examination (Liggy). One of the most difficult skills to teach was prostate examination (Mr Bunns). We programmed these simulators with multiple pathologies and had the students examine them.
There is a need for such hands-on, real-time practice that avoids danger or discomfort to patients. A physician's manual dexterity can make the difference between failed and successful treatment.
Rain on the electric plane's parade (1)
An ion-powered plane may have lift-off (24 November, p 7). But landing a full-sized, battery-powered plane is an engineering challenge. Airliners are much lighter on landing than take-off, because the fuel tanks are empty.
Overweight landings are possible in an emergency, but often lead to structural damage. A discharged battery weighs much the same as a fully charged one, and routine landings at full weight would need stronger, and therefore heavier, undercarriages.
Also, the aerodynamic drag of the electrode arrays used may be low at 5 metres per second, but it would increase with speed. And aircraft build up static charges in flight: the little wires you may have noticed on the trailing edges of wings are there to bleed this away. How would this affect the propulsion system?
Finally, would flight in extreme electric fields – thunderstorms for example – affect the ability to produce ionic thrust?
Rain on the electric plane's parade (2)
As an engineer who has spent years on electric propulsion systems for both cars and low-speed aircraft, I found the article on ionic-propulsion flight intriguing.
A primary concern for electric aircraft is propulsion efficiency: thrust multiplied by speed per watt of power. A well-optimised system driving a propeller with an AC motor fed through an inverter can achieve 85 per cent. Any new technology will have to be close to this to be competitive. I do expect that the ion drive's efficiency will improve at higher speeds.
The ion drive also seems likely to generate ozone and nitric oxide, so may not be the most eco-friendly choice.
Rain on the electric plane's parade (3)
What will happen to a bird that flies into the ion drive? The plane will be quiet, and the gaps between its wings could give the impression it is possible to fly between them.
Rain on the electric plane's parade (4)
The MIT model may well be the first such aeroplane to fly freely. But a , developed by veteran aircraft designer Alexander de Seversky, took off vertically and flew in 1964, albeit tethered to its power supply. It could be steered by varying the voltages applied in different places. Such direct lift is an order of magnitude less efficient than aeroplane wings, so Seversky had to leave the heavy power supply on the ground, but the principle was proven.
To pour more literal cold water on the demonstration: would rain not short-circuit the ion plasma, causing loss of power, unless the electrodes were contained within a protective duct?
First class post 鈥� 15 December 2018
What if the other side thinks WE’RE the dark matter?
Kelly Reay of particles crossing to our world opening a portal to a dark-matter realm (1 December, p 36)
The real power problem is how to use less of it
It was very interesting to read Mark Lynas on the Union of Concerned 杏吧原创s' change of policy over nuclear fission power (24 November, p 24). I am, though, concerned that he did not find space to mention the relative contributions to global power use from the many different sources. He thereby implied equivalence between them that does not exist.
It is difficult to find precise numbers and sources disagree. It seems that humanity consumes some 200 million gigawatt-hours of power a year and about 90 per cent comes from fossil fuels, with fission and renewables making up the rest.
Surely, then, the most immediate and pressing problem is not to juggle around within the 10 per cent, but to radically reduce the 90 per cent. The only way to achieve that – barring the possible intervention of fusion power – will be very dramatic changes in our lifestyles.
Governments and people who feel that charging for plastic carrier bags is the scale of change needed from them are living in a fool's paradise, and need to realise that the longer they delay tackling the real issues, the more effort will be needed, and the greater the distress caused.
Reusable nappies as a toilet-training incentive
Alice Klein looks at the impacts of disposable and reusable nappies (24 November, p 22). Bringing up two babies in the 1990s, living in a flat and working part-time, cloth nappies were a perfectly easy, though unconventional, option. I even air-dried them, but I had to be organised.
I wonder whether the research comparing them to disposables took into account the fact that babies using cloth nappies tend to be toilet-trained day and night at a much earlier age – there is little more uncomfortable than a wet cloth nappy. A difference of six months to a year would lead to a child using 1100 to 2200 extra disposable diapers or nappies – a lot of extra landfill.
Treating Parkinson's with a faecal transplant
You report that an imbalance in the gut's ability to repopulate itself with new neurons and clear out the dead ones could lead to Parkinson's disease (10 November, p 7) and that the disease may start in the appendix and travel to the brain (10 November, p 18).
I wonder whether anyone has considered doing a faecal transplant from a young person to someone with the first signs of Parkinson's? This relatively simple procedure is being performed at an ever greater rate. It surely can't exacerbate the disease.
The editor writes:
• We have previously reported on faecal transplants easing the symptoms of Parkinson's disease (22 January 2011, p 8).
Is that tingle a misplaced grooming response?
Michael Marshall discusses what is now being called autonomous sensory meridian response (3 November, p 35). I have experienced this since I was a child. I have a distinct memory of where it started and therefore how it might actually happen.
My first experience of a warm, feel-good tingling, as described by other correspondents, was during visits to the “nit nurse” while at school in the 1970s. She would comb and run her fingers through the children's hair to find head lice.
I noticed the same feeling when the window cleaners were doing the windows of my classroom. I had no idea until recently that anyone else experienced similar effects. I have assumed that the nit nurse was triggering endorphins as part of a primate “grooming response” that Marshall mentions.
He seems to respond to an object being handled, as does Sarah Brocklehurst (Letters, 24 November). Is this a reaction to a stimulus eliciting an out-of-place “grooming” response? If so, I suggest “misplaced grooming response” as a more accessible term for the effect.
Reality's last stand meets one more loophole (1)
Anil Ananthaswamy reports work using cosmological sources of randomness in testing Bell's inequality (17 November, p 28) and thus quantum entanglement.
There is a further problem, which philosopher Huw Price pointed out in his Time's Arrow and Archimedes' Point (reviewed 29 June 1996, p 42).
He argued that if the laws of physics act in a time-symmetric manner (leaving aside any violation of charge, parity and time-reversal symmetry), then such experiments have a loophole, created by time symmetry. A correlation can be established by the photons coming in from the distant universe being treated as though they're going backwards in time.
This idea blows away a lot of quantum weirdness. But it seems hard for us, with our built-in arrow of time, to appreciate that quantum interactions may not have a bias between past and future.
Reality's last stand meets one more loophole (2)
As I read Ananthaswamy's article on why “normal” physics can't explain reality, I began to understand the concepts of observer reality and non-locality. But as I read on further, I didn't. A bit further on I did. By the end of the article, I didn't understand any of it or how the described experiments were supposed to help. I was entangled with myself.
The sun causes tides as well as the moon
Guy Cox says that without a large moon there wouldn't be tides on a planet to allow marine life to progress onto land (Letters, 3 November). But even on Earth, the tidal force of the sun is also quite strong – about 45 per cent of the strength of the moon's. So even without our moon, we would have tides. If Earth were at the position of Mercury, the tides would be much greater.
For the record 鈥� 15 December 2018
• Gravity waves are a feature of fluid dynamics; gravitational waves are in the fabric of space-time (Letters, 24 November and 1 December).