1

Physics, Astronomy & Cosmology / Re: What are the physics of brakes?

« on: 03/09/2024 19:21:23 »

I would say the heat is transferred to the water in the boiler by conduction, the water is then pumped and the heat is transferred from the water to the radiators by condution , again. Not exactly what you requested but then I am quite pedantic, as you know.

2

General Science / Re: Is the Curie Effect Reversible

« on: 30/07/2024 15:27:28 »

Some confusion, I think. A permanent magnet will become permanently demagnetised above the  Curie temperature but a piece of soft iron simply changes from ferromagnetic to paramagnetic, and this change is reversible. So you could just wind a coil around a chunk of soft iron to make a precise thermostat switch. The clever bit is engineering the CT to whatever you need for soldering, but I notice that current Weller adverts are all for gas soldering irons or electronic variable-temperature units.

3

General Science / Re: Do germinating tomatoes kill off competing plants?

« on: 12/06/2024 10:26:46 »

In the real world, once the initial shoot reaches the surface of the soil, it can spread, and shade out all of the lower shoots.
- This video is a bit artificial, in that the underground shoots manage to get some light through the sides of the glass container...

The first shoot to reach the air can transpire, and suck up nutrients from the soil. The other underground shoots can't transpire, and so have a much lower supply of water and nutrients.

4

General Science / Re: Do germinating tomatoes kill off competing plants?

« on: 12/06/2024 08:51:47 »

The "competition" model neatly explains the "maze solving" property of slime moulds too. Problem is that it reduces the wondrous concept of intelligence to one of simple chemistry! Very humbling.

5

General Science / Re: Do germinating tomatoes kill off competing plants?

« on: 12/06/2024 07:30:23 »

Nice video and an interesting observation.

Yes, this is possible. Some trees - acer family - release toxins that suppress the growth of rival species, ostensibly to give their own offspring a better chance.

I suppose there are two things possibly happening here with the tomato: one is that the dominant plant does release things locally that destroy the competing plants. The other is that the dominant plant hungrily devours all available nutrients, and water, and the smaller plants cannot compete. So once they run out of supplies from their seed, they perish. Or it could be both.

6

General Science / Re: Do germinating tomatoes kill off competing plants?

« on: 10/06/2024 16:44:33 »

Entirely sensible. Many plants produce toxins to kill off their competitors  - roses being particularly adept at this. It seems as though exposure to light and air triggers the effect in this case.

7

Physics, Astronomy & Cosmology / Re: Why is air a thermal insulator?

« on: 02/02/2024 11:08:54 »

This sort of thing

Sorry i cannot believe convection

Is the reason why I posted stuff that led to this
"For reasons of repetitive antagonism, this user is currently not responding to messages from;
BoredChemist"

It's not just that he can't science, it's that he refuses to science.

8

General Science / Re: What Is Gray?

« on: 20/01/2024 00:19:08 »

Nonsense, most people drive in a way to prevent damage to their car, seat belt or no, the idea of imminent demise is not really a thought.  Seatbelts save lives.

OK imagine that one day you are asked to drive to a meeting across town. They give you  an armoured truck to make the trip.
Then, the next day, for the  same trip, they give you a rickety old schoolbus  which has a bottle of nitro-glycerine on the  next seat and dodgy suspension.

Do you drive the same way in both cases, or do you adjust your driving according to the apparent risk?

Anyway, here's some data. from
https://en.wikipedia.org/wiki/Reported_Road_Casualties_Great_Britain


Seat belt death.png (118.79 kB . 1024x650 - viewed 1103 times)

9

Chemistry / Re: How to keep molten plastic in liquid state foor long

« on: 30/10/2023 13:20:41 »

Perfluoroisobutene is a breakdown product of decomposing Teflon(ptfe) and is extremely toxic and acts similar to the war gas carbonyl chloride(phosgene). As far as I remember it is more toxic than carbonyl chloride but I may be open to correction on this. The effect of these substances is pulmonary oedema and one drowns in one's own exudate.

10

Geek Speak / Re: How to make VLOOKUP tell the difference between zero & blank

« on: 28/10/2023 18:15:34 »

Can  you make a copy of the data but using  isnumber and isblank to clarify things for the lookup?

11

General Science / Re: Broad (Fava) Beans: Difference between frozen & fresh

« on: 28/08/2023 11:13:59 »

Pesticides?

That's probably the only thing we can rule out.

The problem is that "broad beans" covers a large range of slightly different plants.
So the differences might not arise from how they were treated but simply be because they are different strains.

12

General Science / Re: Broad (Fava) Beans: Difference between frozen & fresh

« on: 27/08/2023 23:05:24 »

Don't know about beans, but most frozen vegetables are "fresher than fresh" because they are harvested at peak flavor, then cleaned, blanched and frozen within hours, whereas fresh vegetables will have been harvested by demand rather than optimally,  then stored unprocessed for several days at ambient temperature.

From the given account it looks as though there is some hydrolytic or thermal reaction that produces a red color  (is the water really black or very deep red?) either slowly at room temperature (in the fresh or late-harvested veg) or quickly when boiled. Redness is usually associated with ripening so it may be that optimum harvest for beans is at maximum water content (certainly the case for peas, preferentially harvested at dawn) so the frozen ones aren't wrinkly.

But Mendel's famous peas were definitely two related genetic strains, one inherently wrinkly - maybe the frozen bean grower's contract is principally for the smooth variety. 

13

General Science / Re: Broad (Fava) Beans: Difference between frozen & fresh

« on: 27/08/2023 20:18:35 »

Pesticides?

Or some chemical reaction that takes time, hence the water color changes?

Is it a possibility that Beans harvested during Different time periods vary alike seasonal changes?

14

Physiology & Medicine / Re: Is "neurodiverse" medicalisation of human nature?

« on: 22/07/2023 22:03:13 »

BC, we are all a bit odd, so are we all neurodiverse? In that case the term loses it's meaning

No
The difference is between "some people are 'different' " and "some people are 'wrong' ".

There are spectra of intelligence and height; everyone is on them somewhere.
Does that mean that height and intelligence are meaningless?

15

Physiology & Medicine / Re: Is "neurodiverse" medicalisation of human nature?

« on: 22/07/2023 18:52:20 »

The problem with newspeak is that it takes as axiomatic that any adjective describing a deviation from the norm is in some way unacceptable and discriminatory,

That's the exact opposite of what recognising neurodiversity is about.
"Neurodiversity is a proposed framework that argues there is intrinsic diversity in human brain function and cognition, and that certain things currently classified as neurodevelopmental disorders are differences and disabilities but are not necessarily pathological."

16

Geek Speak / Re: Why is Windows 7 still updating 3 years after updates were discontinued?

« on: 17/06/2023 23:30:21 »

Hi.

I switch the router off before I put the computer on....

    It could be an old one your computer downloaded sometime ago.    It may be a failed update - something went wrong.     Rather then just break or stop everything completely, the system is designed to roll-back to the state before it attempted to install the update and then it will re-attempt installation at a later time.   Microsoft often end up releasing patches for their patches and/or replacing a patch with one that actually works.   Therefore, your computer might try and install the (presumably old and faulty) update several more times (maybe once a week for ever more).   Sadly, it may never find a later update that actually works because Microsoft are under no obligation to make one any longer.
    If it's annoying you can probably roll back your system to an even earlier state, where it was stable and did seem to have all the latest updates (at that time), then switch off the automatic updates completely.   BEFORE you start experimenting make a System restore point now,  (see for example:  https://www.dell.com/support/kbdoc/en-uk/000132661/system-restore-in-windows-7     an old help page that told you how to create a Restore point in Win 7) so you can get back to what you have now.  With some hours of work you can probably identify exactly which update is the one causing a problem BUT it's probably not worth the time - it will be quicker to just keep rolling back a bit further and trying it until the problem is gone.   You have an outdated system anyway, it hardly matters if you roll it back another month or two.

Best Wishes.

17

Geek Speak / Re: Why is Windows 7 still updating 3 years after updates were discontinued?

« on: 17/06/2023 14:17:27 »

Hi.

1.   From what you're describing, that was finishing up an update that was downloaded from the last time you switched the computer on  (a year ago etc.)

2.    Microsoft didn't actually stop all updates.   They merely didn't guarantee to provide any more.   However, your computer is still going to look for updates unless you specifically switch that feature off.   If it's in Microsoft's interests then they can continue to provide updates.     For example,  it is in their interests to collect data they can use.  So running their anti-virus tool on your computer and collecting data is something they are likely to do.

3.     The Windows Operating System is a collection of programs rather than one just program.   For example, you can probably run the .NET framework which is still used by Windows today.    If there are updates for any bits of Windows that you can use, it's likely that your computer will still get those updates.

- - - - - - - -
    As you probably know, the main problem is just that Microsoft don't guarantee to provide updates, which means they don't guarantee to fix or patch exploits that might have found since support for the Operating System was discontinued.   As such it's not particularly safe to connect your old computer to the internet.   You may also want to switch off any wireless connections to the outside world  (e.g. Bluetooth and Wi-Fi if it has that).    However, if you do keep the computer isolated ("air-gaped") from any external networks then the computer can go on being used for ever more.   Indeed you can connect it to the internet if you wish - just be aware that it isn't safe, you could be handing information out to anyone  and/or  receiving information that has been maliciously corrupted.

Best Wishes.

18

General Science / Re: BP Monitor Cuff Inflation

« on: 26/11/2022 13:24:41 »

My monitor inflates to a pressure that can be preset by the user. If it encounters a systolic pulse too early on the ramp down it will repressurise to a higher initial pressure and then proceed as normal. My heartbeat tends to be rather irregular at times, however it does not seem to interfere with the measurements.

19

General Science / Re: BP Monitor Cuff Inflation

« on: 26/11/2022 12:33:15 »

A few of us were messing about with a monitor in a coffee break at work ages ago.
I measured my blood pressure and the guy who owned it looked surprised.
When he used it the cuff would inflate a bit, pause, then inflate some more.
My blood pressure was low enough that it could be measured on the first "step".
Presumably the monitor checked on something at that pressure and if it sensed that the blood was still flowing, it inflated some more.
If your monitor does something similar but without the pause an your BP is near the cut off between "about 160" and "about 220" then that would explain the data in your graph.

20

General Science / Re: How much water vapour in human breath

« on: 25/11/2022 12:05:29 »

The air leaves your lungs practically saturated with water (at 37 ^oC) regardless of your metabolic rate.
The excess water mainly leaves via the kidneys.
I think that actual value is about 6% by volume or 4% by weight.