1

Physics, Astronomy & Cosmology / Re: What Causes This Optical Effect?

« on: 22/11/2024 12:18:35 »

It's not about interior vs exterior, it's lighter side vs darker side.

When you look from the brightest lit side to the darker side, the light reflected off the window/net curtains/ half-silvered mirror is greater than the light transmitted through it from the darker side, so you only see the reflected light because your eye doesn't have sufficient dynamic range to see both.

Move to the darker side, and the light transmitted from the bright side is greater than the light reflected from the dark side, so you see through.

The way to see the "wrong" way through a "one way mirror" is to put your face right up against it, and shade around your eyes with your hands (the same way oscilloscope hoods work).

2

Geology, Palaeontology & Archaeology / Re: How Old is Soil ?

« on: 20/05/2024 15:56:14 »

I doubt it will have an age as such, it must surely be a recipe that's had ingredients added to it and modified over millennia. Freshly fallen biomass, rotted biomass, constituent parts of biomass, large grains of sand, smaller grains of sand, dust, each evolved from the previous stage.

3

Chemistry / Re: Making Your Own Gas Mask.

« on: 29/02/2024 11:09:13 »

It intrigues me that something as seemingly mundane as 'activated charcoal' appears to be a universal barrier against all poisons. I would have expected a fresh race to find a new high-tech protection against each new poison.

Aviators have a saying:

"These things will not save your life: the sky above you, the runway behind you, the fuel you left in the truck, and anything that happened yesterday."

"It's better to be down here wishing you were up there, than up there wishing you were down here." (Good for fellwalking, too)
"There are old pilots, and there are bold pilots, but there are very few old bold pilots."

4

Technology / Re: How is electrolysis of water done safely?

« on: 29/02/2024 01:11:19 »

I recall a TV prog (might have been Open Uni, can't remember) about an industrial accident at a dockyard. They were working on a ship in dry dock using pneumatic power tools and couldn't connect them because the hose connectors were the wrong type. After changing the connectors they got on with the job, and noticed that their fags were burning unusually fast, but thought nothing of it. It wasn't until after the explosion that they found out that the reason the hoses wouldn't fit the unions was that they were connecting them to the oxygen supply instead of the compressed air.

5

Physiology & Medicine / Re: Can General Anaesthetics Cause Diabetes?

« on: 11/02/2024 18:31:08 »

May I ask what symptoms do you attribute to having had a general anaesthetic?

A feeling of extreme pressure in head was the immediate symptom on waking, along with violent dizziness.

Then in the days immediately after, the following developed:
Brain fog, like a cross between conscious sedation and drunkenness
Extreme dizzy attacks, and waking with dizziness & vomiting in the night
Double vision & blurred vision
Difficulty judging speed & distance
The sight of unexpected movement puts me off balance or makes me want to throw up
Inter-pupillary distance (relating to varifocals) changes at random
Bright lights like shooting stars running across my vision
2.5 fold increase in the number of (previously occurring) ocular migraines
Dyspraxia: difficulty writing, slicing food, getting food in my mouth without it falling off fork, cutting myself shaving etc.
Poor reaction to any movement initiated by my own movement
Vomit reflex in diaphragm when swallowing
Random stabbing pains in head & neck

Symptoms are paroxysmal, and tend to be aggravated by anything increasing my blood pressure. (Arguing, straining to do jobs, straining on loo, kneeling etc)

If this question is too personal or intrusive, ignore it.

I'm happy to publish just about anything and everything relating to my healthcare, because people who are too coy to do so are just providing the NHS with protection.

Definitely worth a complaint.

I never thought of that.

Before you come back with another one I've already done years ago, such as filing a complaint with the Health Ombudsman, you might like to read Hansard, and see what the MPs who created the PHSO had to say about their handiwork:

"The Bill was always drafted to be a swiz, and now it is spelt into the Bill."

"Anyone who contemplates an office of this kind is faced with the dilemma of making it either a Frankenstein or a nonentity?a Frankenstein if it has effective powers and a nonentity if it has not. The Government, quite rightly, has opted for its being a nonentity, and in that sense it is a fraud....I congratulate the Government on its being a nonentity. A Frankenstein would, I think, have undermined the power of Ministers and would have undermined the authority of individual Members of Parliament. That, I am quite sure, is not to be.....My ultimate conclusion about this Bill is that it is a noble facade without anything behind it."

PHSOtheFacts is a pressure group campaigning against the PHSO corruption (they have given evidence in parliament, and to the HSIB, they're not just kids blogging from their bedrooms). In 2018 their lawyers filed 32 cases of Misconduct In Public Office with Scotland Yard, but the investigation had to be abandoned, not because there was no evidence, but because the Health Service Commissioners Act prevents the police, or anyone else, from accessing PHSO files.

Here are the series of reports on the PHSO commissioned by Katherine Murphy, CEO of the Patients' Association. They were taken down from the website as soon as they'd got rid of her.

https://www.dropbox.com/s/1xg5t63lk1bjv5o/PA%202014%20Report%20on%20the%20PHSO.pdf?dl=0
https://www.dropbox.com/s/duiyv4cyxfq1hui/PA%202015%20Report%20on%20the%20PHSO.pdf?dl=0
https://www.dropbox.com/s/r99b96cvcy3r8as/PA%202016%20Report%20on%20the%20PHSO.pdf?dl=0

TLDR? Here's a summary. I can tick off the top 12 of those from my own personal experience.
("Communication takes too long" looks innocuous enough on the face of it, but it's a deliberate ploy to run you out of time on the Statute of Limitations. They ambush you with the final report a few days before the 3 year limit expires.)

The NHS complaints system is a sham, and above the law, just as the MPs who created it intended.

Paragraph 9.37 of the PHSO Service Model Main Guidance is interesting:

"Where we have found that an injustice arose in consequence of maladministration or service failure but that it was fully remedied before the complaint was received by the Ombudsman then a complaint will not be upheld. (Policy requirement)"

So as you can see, all the NHS have to do to get a complaint dismissed is to claim the problem has already been fixed:

"Yes, your Honour, it was me who robbed the Nat West last month, but I've stopped robbing banks now."
"Oh, that's OK then, off you go."

And just in case the NHS are in any doubt what they need to do, this is an email from a PHSO Caseworker coaching the hospital what to say.

My original complaint in 2015 was made because cardiology deliberately lied, and denied any knowledge of my having been diagnosed with atrial fibrillation. After the PHSO went through the pretence of an investigation, and produced a report which ignored all the evidence without explanation, whilst accepting the NHS account at face value with no evidence at all, I wrote a long reply systematically dismantling it, piece by piece. They then conceded it was "flawed" and agreed to re-investigate.

After many months, they then withdrew their previous letter, saying that the second investigation had been stopped in order to "manage" the "legal risks".

I now appear to have become the unluckiest patient in the NHS, as every encounter I've had with the NHS since then seems to have resulted in my being harmed. It's like being one of the Post Office workers but worse: there's nowhere to escape from the NHS.

6

Physiology & Medicine / Re: Can General Anaesthetics Cause Diabetes?

« on: 05/02/2024 17:24:27 »

@vfhpmr

I know you Specifically asked for NHS...

https://patient.info/doctor/precautions-for-patients-with-diabetes-undergoing-surgery

But this is all i could find.
(sorry)

Thanks, but that's for diabetics who are having an anaesthetic. I didn't have diabetes then, and I think that the test will show I don't have it now.

7

Physiology & Medicine / Re: Can General Anaesthetics Cause Diabetes?

« on: 05/02/2024 16:07:27 »

I thought so too, but I haven't yet said as much to the GP who referred me for a fasting blood sugar test on the premise that it might explain the symptoms I've been experiencing since waking from a general anaesthetic 3.5 years ago. I thought I'd wait until I've checked whether I can find any evidence for it first.

I think asking another doctor or researching the question yourself would make a lot more sense than asking strangers on the internet.

I already have researched it for myself and found nothing, hence my posting this thread. Do you have any evidence that the NHS answer any of my questions when I ask them?

8

Physiology & Medicine / Re: Can General Anaesthetics Cause Diabetes?

« on: 05/02/2024 15:08:33 »

Well, that was weird...

I thought so too, but I haven't yet said as much to the GP who referred me for a fasting blood sugar test on the premise that it might explain the symptoms I've been experiencing since waking from a general anaesthetic 3.5 years ago. I thought I'd wait until I've checked whether I can find any evidence for it first.

9

Physiology & Medicine / Re: Can General Anaesthetics Cause Diabetes?

« on: 05/02/2024 13:01:13 »

I'm baffled by this strange question.

No more than I am.

What makes you think there is a connection?

I don't.

10

Technology / Re: How much abuse can a domestic microwave oven tolerate?

« on: 22/12/2023 12:31:19 »

I don't recall seeing a "minimum load" specification for a domestic microwave.

The handbook for every microwave I've ever owned says this:


Scan_20231222_0001.jpg (986.56 kB . 1650x2277 - viewed 665 times)

If you run it with no load there's nowhere for the power to go except back into the magnetron, where it doubles or triples its dissipation.

11

Question of the Week / Re: QotW - 23.12.01 - What are the physiological benefits of a runny nose?

« on: 28/11/2023 18:12:11 »

If I keep licking my lips in cold dry weather and leave it to evaporate, my lips become cracked and sore. If the lining of the nose is the same, I can see some benefit in preventing it from drying out.

12

Plant Sciences, Zoology & Evolution / Re: Why Are Baby Animals Cute?

« on: 16/11/2023 16:32:34 »

A series on the radio about it here:
https://www.bbc.co.uk/programmes/m001sd19/episodes/player

13

Physiology & Medicine / Re: How Does The Placebo Effect Work ?

« on: 15/11/2023 12:27:24 »

It takes actual belief, something some of us cannot just conjure at will.

Placebos work even when the patient knows they're a placebo.
https://www.bmj.com/content/363/bmj.k3889

14

Technology / Re: Why is my sattellite receiver behaving oddly?

« on: 30/10/2023 11:27:07 »

I don't have satellite, but my Humax Freeview box has a repertoire of software bugs that bite at random, for no obvious reason.

15

Geek Speak / Re: Complaint about Windows 11

« on: 13/10/2023 12:15:28 »

the "end" button on my keyboard doesn't seem to do anything

The End key on my computer puts the cursor to the end on the line. I use it quite a lot, and if I pressed it one day and found it had just closed the app I was in the middle of using I'd be a bit miffed.

16

General Science / Re: Is AI a useful guide to risk assessment?

« on: 24/07/2023 19:09:27 »

"could you defend your signature at an inquest?"

If I ask whether it's worth spending ?50k assessing the risk of a ?500 radio killing one in a million users, the answer from the boss will be no, and the answer from the barrister with the benefit of hindsight, yes.

17

Physics, Astronomy & Cosmology / Re: Why do kettles make a whoooarr sound?

« on: 06/07/2023 12:11:35 »

The bubbles 'pop' as they re-condense, so it stops when the water reaches boiling point, and the frequency gets lower as the kettle warms because the bubbles travel further before they reach water cold enough to condense them.

Kettles with flat bottom elements are much noisier than the old ones with wound elements immersed in the water because the flat bottoms act like the skin of a drum.

18

General Science / Re: Horizontal Lightning Conductors

« on: 22/06/2023 18:03:51 »

"Skin effect" means that high-frequency components (like lightning impulses) only travel through a thin skin on the outside of the conductor.
- That is why lightning down-conductors are made of a braid of many fine wires (with a large surface area) instead of one big conductor.

All the lightning conductors I ever recall seeing are flat copper strips. Braiding it won't make any significant difference to the skin effect because the strands aren't insulated from each other, which is why radio engineers use Litz wire to reduce skin effect. (At MF/HF, above that the usual ploy is to use silver plated copper.)

Digressing a bit, a novice mistake for radio engineers is to use tinned copper wire, in which most of the current flows through the lossy plating instead of the copper, or bare copper wire, which has the same effect by the time it's oxidised. A common technique for reducing the cost of UHF feeder is to use copper plated steel for the inner conductor, because the current isn't flowing in the steel.

"Lightning impulse" -  I'll guess it's not genuine AC with Voltage swings from +V to -V many times.   I'll assume it's a single DC spike,    from  0 (volts or amps)  to +Vmax   (or +Amax ) and back to 0  over a short time interval.    I've never really looked at a Lightning strike and seen it as a plot of  Voltage (or Current)  vs.   time,   maybe it has mutiple sinusoidal components with different frequencies.

The bit highlighted is correct.

If you have a repetitive pulse waveform with a period T1, a pulse width T2, and a rise time T3, then it will have a spectrum with components spaced apart by a frequency equal to 1/T1. At frequencies which are an integer multiple of 1/T2 there will be a null in the envelope of the spectrum where the amplitude reduces to zero, and the highest frequency component will be at 1/T3.

From this is follows that if you have a single pulse, T1 is infinite, and the spectrum will be continuous, without discretely separate frequencies, and with nulls every 1/T2, up to a maximum of 1/T3. (If you had a single infinitely narrow impulse with zero rise time it would have a spectrum which is a horizontal line flat to infinity.)  In the case of the pulse in BC's reference, the rise time is ~1.2uS, so the highest frequency component you'd expect to see in the spectrum would be about 800kHz, but since the spectrum is continuous, the majority of the energy will be at much lower frequencies. (More than half the energy will be below 400kHz)

Skin depth in copper is:
Freq.        Skin depth (μm)
50 Hz   9220
60 Hz   8420
10 kHz   652
100 kHz   206
1 MHz   65.2

19

General Science / Re: Skiving

« on: 29/05/2023 21:03:16 »

The proportion of the Tool was huge, in comparison to the job/product.

It had a yellowish oily fluid in place of a milky white cutting fluid.

Anyways, i think the Thickness of the plates being cut is not allowing it to Curl.
(guessing)

See here:


Skiving.png (8.13 kB . 1717x656 - viewed 867 times)

In order for the shaving to separate, it must bend at A in order to make room for the tool, but before A it had to bend at B, and before B, C, etc. Hence the shaving curls, because once it has bent at the tip, there's nothing applying a force to straighten it again.

If you look at the video however, you'll see that the finished fin is less that half the length of material shaved off, so it must be being compressed, and I think it might be the deformation beyond it's elastic limit as it's compressed that's straightening it, but I'm not conviced I can see where the force to do that would come from either. The shaving is sliding over a smooth lubricated surface, after all.

And if it that's it, why doesn't all swarf come off the tool straight?

ps - Why is it a $64,000 question?

It's just a turn of phrase. It derives from an old 1960s TV contest in the USA where people answered questions with a prize that doubled each time. The final question was the $64,000 question.

20

Question of the Week / Re: QotW - 23.05.05 - How fast does evolution happen?

« on: 06/05/2023 22:27:17 »

& the ones who followed Chastity or observed Abstinence.

Even Children & Adult asexuals.

(Vampires...no chance!)

They might survive as individuals, but if they're not reproducing they won't survive as a lineage.