21

Physiology & Medicine / Re: Why Do We Sometimes Miss A Word Out When Writing A Message?

« on: 03/08/2020 15:09:34 »

Your mouth and brain move quicker than your fingers. Mouth keeps pace with brain, brain assumes fingers are in step.

22

Physiology & Medicine / Re: Are All Instances Stored As A Memory, However Banal.

« on: 02/08/2020 23:07:08 »

Chances are that we synthesise plausible memories in response to some triggers, and polish the synthesis with other memories. This seems to happen under friendly interrogation of a witness: "What happened next? Can you remember what happened before...." and an entire scene gradually emerges that is at least plausible and possibly accurate, though as has often been demonstrated, quite significant chunks may be missing - the classic "gorilla experiment" is a fine example where the implausible doesn't even register in the short-term memory.

The video game is a potential clue too. What you see in a video game has no implications for real food, real sex or real fighting, so it does not make plausible connections with the deepseated things that matter. I've looked at methods of teaching people to take x-rays. If they study the science, pass the theory test, then x-ray real patients, they generally forget the theory within a year, but where we have first taught the practical side and coached a student through a real patient episode, the later theory tends to stick. Or, as the medics say, "See one, do one, teach one."

23

Physics, Astronomy & Cosmology / Re: How Do We Know Absolute Zero Is The Temperature It Is If It's Unattainable ?

« on: 02/08/2020 13:48:34 »

Absolute zero is the lowest temperature possible........
How do we know this if Absolute Zero Is unattainable ?

Make up your mind!

Anyway, the concept is derived from the Carnot efficiency equation for a perfect heat engine, η = 1 - T_cold/T_hot.
For any nonzero value of T_cold, η < 1, and we can measure the efficiency of real heat engines and show that they follow this law.

So we can hypothesise a zero value of temperature and an absolute scale such that any heat engine with a cold source at T =0  would have η = 1

The problem is one of "thermal relativity". If we have a hypothetical heat sink at T = 0 and a heat source at 0 + δT,  the efficiency with which we can extract energy from it decreases toward zero as δT → 0  so we need to expend an infinite amount of energy to cool it to T = 0.

The idea that there is no motion at T = 0 contradicts Heisenberg, as we would then be able to predict the momentum (zero) and position (right here) of a particle, with zero indeterminacy.

24

Physics, Astronomy & Cosmology / Re: If I Was Able To Stop Time, What Would The Temperature Be ?

« on: 31/07/2020 23:06:18 »

This looks like saying that in the absence of change, time is meaningless, and in the absence of time, change is meaningless. 
Need to check that I’m not misinterpreting.

The assumption of causal symmetry is one of the vanities of philosophy, which is anathema.

Time being what separates sequential events, it is the dependent quantity. Change is not dependent on what we measure, but what we measure depends on change.   

25

Physics, Astronomy & Cosmology / Re: If I Was Able To Stop Time, What Would The Temperature Be ?

« on: 30/07/2020 16:00:22 »

Time is the space between sequential events.  If you stop time, there will be no sequential events. Therefore no movement, hence no temperature.

26

COVID-19 / Re: Resurgence Of Covid-19 in Winter....WHY ? What Does 'Winter' have To Do With It

« on: 30/07/2020 11:30:14 »

Crowded pubs when the gardens closed, crowded shops as people paid their seasonal religious dues to the Retail Gods, snotty kids and sweaty parents crammed into school and church halls for nativity plays, crowded football terraces replacing spacious cricket grounds, office windows closed, distant family visits to overheated and unventilated granny houses, and a fresh intake of schoolchildren with no acquired immunity to each other's diseases.  Perfect conditions for direct transmission of live virus.

However since the country pretty well shuts down for 2 weeks over Christmas, it would behove  HM Government to do something sensible for a change, and impose a statutory, properly policed quarantine. If they gave everyone a few months' notice (like now) and clear instructions (with statutory exemptions for those who operate the Prime Minister, of course) , It Would All Be Over if not by Christmas, at least by mid January, with minimal inconvenience  to anyone and hardly any damage to the Holy Economy.

27

COVID-19 / Re: Resurgence Of Covid-19 in Winter....WHY ? What Does 'Winter' have To Do With It

« on: 29/07/2020 16:24:24 »

Cyclic stupidity - the essence of Tom & Jerry cartoons: "hey, the puddytat has gone - time to play" but we al know the puddytat is hiding round the corner with a club/gun/anvil/stick of dynamite....

A little governmental encouragement to get children back to school, then make merry and support retail/hospitality/entertainment businesses as the nights get darker, and another batch of human sacrifices will turn up in the hospital waiting room. It's economics, not biochemistry.

28

COVID-19 / Re: Do we know the dosage required to get a COVID infection?

« on: 29/07/2020 16:09:15 »

My hunch is that the prominent 5 day oscillation cycle

What 5 day oscillation?

Have a look at the daily infection graphs on this site. They all display a 5 dayish oscillation cycle.
https://www.worldometers.info/coronavirus/

It's a 7 day cycle, with peaks on Fridays. Most people will work through a low-grade infection and report sick at the end of the working week, with maybe another peak on Monday. Labs may back up their results but post them all on Friday to clear the deck for next week.

The deaths graph is odd, as that also peaks on Friday. Whilst recorded deaths peak on Mondays (because register offices are often closed at the weekend) recorded cause of death seems to peak at the end of the doctors' working week. 

As foir viral load, it's pretty obvious that the more you have, the more likely you are to infect someone else, and the morf you inhale, the more likely it is that some will penetrate your first line of defence and set up shop before the immune system gets into gear. The lack of early symptoms is interesting. It seems as if the innate immune system is very insensitive to the virus, so you can build up an overwhelming viral load before the adaptive system adapts, by which time the innate inflammatory response suddenly turns on as well, producing the excessive inflammation that can become fatal.     

29

General Science / Re: Do Ice Cubes Melt Faster In Fizzy Drinks Than Still Drinks?

« on: 28/07/2020 17:50:34 »

Could also be that some CO2 dissolves in the ice and lowers its freezing point. You might try some properly controlled experiments with, say, Sancerre and champagne, or bottled versus draught Abbott Ale, but don't waste valuable lab time with water.

30

General Science / Re: Do Ice Cubes Melt Faster In Fizzy Drinks Than Still Drinks?

« on: 28/07/2020 15:03:53 »

Apples and oranges, my friend. The fizzy drink by definition contains something (usually carbon dioxide) that is absent from the flat one, and is in a different state of motion from the convection currents in a "still" liquid.

31

Physics, Astronomy & Cosmology / Re: How Did Time Come Into Existence ?

« on: 25/07/2020 23:38:52 »

When the big bang happened last Tuesday 'Time' would have had to exist first yes for the events to occur agreed ?

No.
Time is what separates sequential events. If there are no sequential events, the concept of time is meaningless. If there were no events before the BB, time did not pre-exist the events that occurred thereafter.

32

Physics, Astronomy & Cosmology / Re: Why are we not covered in starlight?

« on: 24/07/2020 23:41:42 »

In short, the other stars are a lot further away.

33

The Environment / Re: Why is This Cloud Fuzzy

« on: 23/07/2020 14:15:20 »

Looks like a lenticular cloud. It's an interesting phenomenon caused by a standing wave formed in the lee of mountains when there is a steady wind. Rising air cools and at some point the water vapor condenses to form the cloud, but the air later descends and the water evaporates. Because the air is moving horizontally as well as vertically, the cloud is actually a dynamic structure, continually forming at the leading edge and dispersing at the trailing edge, hence the wispy appearance.

This is different from the fine weather cumulus cloud where a block of humid air has risen to the dewpoint then drifts downwind relatively en masse like a cauliflower with defined edges.  The horizontal wind speed inside a lenticular can be upwards of 30 knots and very laminar but the cloud doesn't move across the landscape, whereas a cumulus cloud is internally turbulent and drifts downwind.

34

Physiology & Medicine / Re: What is the best form of calcium supplementation for osteoporosis?

« on: 17/07/2020 21:14:14 »

For each exercise you simply push, pull, lift or whatever against a spring and a strain gauge for about 30 seconds, so the force you exert is up to you and is recorded. The exercises are designed to stress the skeleton rather than work the muscles, hence there is very little movement (around a centimeter or two) or repetition, unlike ordinary weight training. Natural self-competitiveness makes you want to at least repeat and preferably exceed your baseline at each visit, which generally happens, but the real target is to increase bone density, not muscle mass. And it seems to work.

35

Just Chat! / Re: Is there a universal moral standard?

« on: 17/07/2020 11:50:30 »

A multibillionaire buys all Lithium on earth and then send them to the sun for fun. You can imagine the next story.

Just remembered - no need to imagine!

Back in the 1980s the Bunker Hunt brothers decided to corner the world market in silver by judiciously buying any ingot that came on the market.

Jewellery is quite an elastic market. If a style or metal goes out of fashion, it gets reworked or recycled within the trade, and the customer is paying for workmanship, not metal content, so there was little effect there. The principal use of silver was in x-ray film, consuming several tons each day, and an increasingly essential rather than fashionable commodity.

As the silver price began to rise, the market responded first by investing in silver recovery (since most x-ray images are of people who have either died or recovered, film has little clinical value after a couple of years) then by improving film chemistry to reduce the silver content by up to 90%, then finally by switching to digital imaging. The Bunker Hunts lost their money.

So  by all means dump the lithium in the sun. It will stimulate they hydrogen economy and get rid of mobile phones, so people will start talking to their families again.

36

Technology / Re: Who is designing the English version of a urban Electric Vehicle???

« on: 10/07/2020 13:26:22 »

As it was pre-Brexit. Renault have been selling a neat little UEV in Europe for years, because it was better than the Indian one.   

Has anything come of the Welsh hydrogen fuel cell car recently? Definitely the best idea around, as the citizens of Kirkwall can testify.

37

Physics, Astronomy & Cosmology / Re: What is the difference in APPLICATION of characteristic and continuous spectrum?

« on: 29/06/2020 23:04:46 »

We don't use the entire continuous spectrum for radiography.  Low energy photons are absorbed in superficial tissue so contribute to skin burning but not to image formation. High energy photons penetrate further through tissue but discriminate less between low atomic number (low Z) and high Z absorbers, so you get less contrast between bone (containing calcium and phosphorus) and soft tissue (mostly carbon and water). So we limit the x-ray tube voltage to less than 150 kV and remove the low energy part by filtration through aluminium or copper, leaving a spectrum with a peak intensity around 40 - 70 keV which forms the most useful images for general radiology. A tungsten anode yields a fairly clean initial continuous spectrum (the characteristic lines at 60 keV are a small fraction of the useful energy) that can be tailored to the  thickness of the part to be x-rayed by simply altering the tube potential.

In mammography we are trying to image subtle differences in soft tissue density and pick out tiny calcifications. This is best done with a very narrow spectrum to minimise surface dose (from a low energy component) and low-contrast fog (from high energy photons).  It turns out that the molybdenum Kα characteristic line at 17.5 keV does the job very well. If we restrict the anode voltage to less than 30 kV and absorb the higher energy part of the continuum with a Mo filter, we get a beam that is close to ideal as long as we can compress the breast to minimise the overall absorption and scatter of the useful photons.

It would be really great to get rid of the low energy component altogether, but whilst a radionuclide source would give us a genuine line spectrum, the effective source diameter would be too large -  we need a point source with a high dose rate to get a sharp image.

38

Technology / Re: Are heat pumps viable in areas of high density housing?

« on: 23/06/2020 00:51:04 »

Ground source heating is fraught with problems, not only of infrastructure but also of diminishing efficiency in times of high demand as the ground freezes around the pipes. Airsource heating is a lot easier to install and maintain: I use a single fan unit of less than one meter square to heat and provide hot water for a family in a 1600 sq ft (160 sq m) building. It works with air temperatures down to about -5 degC and a reversible unit would also provide summer cooling (very important in high density cities). No problem with increasing source impedance - you just blow more air through on a cold day. Wind speed is irrelevant as the fan is rated for zero wind, and any air movement just helps a bit.

The real key however is efficient building design. Mine is massively insulated with a huge hot water tank. I have architect friends with a completely passive house in Maine, where even in mid winter a south-facing glass wall provides all the heat they need to keep their huge concrete slab floor warm. A builder friend in England has made three terraced town houses with passive, heat-exchange and air-source heating that demonstrate how to achieve high density and thermal efficiency. 

39

Physics, Astronomy & Cosmology / Re: Is EM radiation power affected by mass of the source?

« on: 16/06/2020 23:21:32 »

As it should be. A volt is a potential difference of one joule per coulomb, and an amp is one coulomb per second. Power is the rate of doing work, i.e. joules per second, whatever the source. Same thing with an engine burning fuel (joules per kilogram) at a given rate (kilograms per second). Hence hybrid vehicles!

40

Just Chat! / Re: Chinese search for diarrhea on t'internet ...

« on: 11/06/2020 17:25:31 »

Fear not, my friend. We fixed that many years ago by sacrificing virgins and dancing around the maypole. Nowadays the gods are propitiated by the occasional Morris dance.

If you don't believe me, ask Dominic Cummings, the scientific genius in charge of the UK's brilliant, rational response to COVID. Open the schools, teach religion (the only mandatory subject in the 1945 Education Act), and get the peasants back to work. Except in Scotland and Wales, where they don't do Morris, and Northern Ireland where the inter-christian death rates have been disappointingly low during lockdown.