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Your special report on the future of healthcare raises some good points, but it doesn't address the fundamental problem of the UK's National ÎçÒ¹¸£Àû1000¼¯ºÏ Service ( 21 March, p 22 ). Nye Bevan introduced the NHS in 1948 for everything "from the cradle to the grave", free of charge at the point of need. It …

In ripping through Vanuatu, Tuvalu and the Solomon Islands (21 March, p 6) , cyclone Pam has become the benchmark for massive weather events that occur far away from the energy consumption responsible for our warming weather patterns. These Pacific islands are the victims of the industrial world's energy excesses. How much will it cost …

Your interview with Denise Kandel gave the impression that mouse experiments show there is such a thing as a "gateway effect", in which nicotine use leads to the use of other drugs (7 March, p 28) . But we have solid and clear human data. Over the past 60 years, the prevalence of smoking among …

I was very interested to read your recent article on migraine, and especially about the many different categories that exist (7 March, p 38) . I was treated unsuccessfully for migraine for 14 years, before finally being diagnosed instead with the lesser-known condition called cyclical vomiting syndrome. Like migraine, CVS is episodic. It is characterised …

As a "migraineur" I appreciated your recent update on migraines. A report in New Scientist led me to search for a vagal nerve stimulation device (17 August 2013, p 12) . It has profoundly helped my condition. However, reading and concentrating on articles with such busy graphics is hard on the migraine brain. Cobble Hill, …

• Once again, we advise readers to discuss any migraine treatments with their registered physician.

I was shocked that the creators of iCub appear not to understand the implications of their effort to build a robot with a self (21 March, p 36) . They are striving to create "consciousness". Researcher Tony Prescott writes: "Sometimes it even leaves me with the surprising feeling that 'someone is home'." I can well …

I was intrigued by the Red Lady of El Mirón (21 March, p 8) , and I would venture to explain why there is so much pollen in the cave where she was buried. We can be sure that, as the article stated, this woman was highly venerated, and also that the people who buried …

I was disappointed that Bob Holmes failed to mention Ernst Mayr in his otherwise excellent article on how evolution might replay ( 14 March, p 32 ). Mayr is the undoubted pioneer in this area, and in his essay "The probability of extraterrestrial intelligent life" (in Extraterrestrials: science and alien intelligence ), he identified a …

Once again I have to read nonsense about the "butterfly effect," this time in your article on chance (14 March, p 30) . A small event may indeed have large consequences if all the effects and effects of effects are linked in a very direct and linear way. Hurricanes or tornadoes, however, are massive events …

Comments from E. O. Wilson (24 January, p 28) and subsequent letters on atheism, agnosticism and god all assume these terms have a well-defined meaning agreed by all. But they do not. To me agnosticism is the insistence that it's wrong to pretend to know what you don't know, but to Chris Ford it's "the …

Steven Miles says "True scientists would not accept such a major axiom without proof" (21 February,p 54) . True scientists would also not accept the axiom that there is no god without proof. True scientists might decide that "the weight of evidence suggests" a particular conclusion, but seldom does science state a certainty. True scientists …

Chris Ford says that agnosticism is a more scientific position than atheism or theism (28 February, p 54) . However, if someone told me there were fairies at the bottom of their garden, I wouldn't say that I was agnostic about it, simply that I didn't believe it. Since I think the chances of there …

I found Philip Ball's account of the search for Viking "sunstones" (21 March, p 40) fascinating. You can easily try out something similar yourself. First find some polarised glasses, such as those 3D specs from the cinema. Now make yourself a small square with one to six layers of Sellotape randomly stuck together. If you …

Thank you for "A world without chickens" (21 March, p 42) . We now know that birds are dinosaurs. The 22 billion domestic chickens alive must surely make them the most successful dinosaur species ever. But not even chicken dinosaurs are immune from extinction. Barham, Kent, UK

Your article on the genetic legacy of the UK states "there are inexplicably stark differences between inhabitants in the north and south of the Welsh county of Pembrokeshire" (21 March, p 54) . This can be explained by south Pembrokeshire being a stronghold of the Normans in Britain. As I recall local history, the Norman …

David Hambling describes a weapon that disturbs vision by heating the eyeball with infrared radiation (7 March, p 44) . This will, fortunately, be cheap and easy to nullify. I foresee that infrared blocking sunglasses will become the "cool" eyewear for the military and anyone planning to riot. Sawbridgeworth, Hertfordshire, UK

• We said that the largest value that can be represented by a 32-bit integer is 2,147,483,647 (13 December 2014, p 21) . Our programs would run safely if we got our data types right: we meant that a signed 32-bit integer can store values from –2,147,483,648 to 2,147,483,647.