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Physiology & Medicine / Re: What Are The Advantages To Taking Vinegar Everyday?

« on: 26/10/2024 01:09:10 »

As a small molecule, vinegar might be absorbed directly in the gut, to be further processed by the liver.

But is it possible that vinegar is an indirect nutrient?
- It is produced by a narrow set of microbes
- Among the multitude of microbes in your microbiome, are there varieties which can metabolise vinegar, producing other useful products?
- And are there pathogenic bacteria which are kept under control by vinegar?

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Question of the Week / Re: QotW - 24.11.01 - If dinosaurs hadn't gone extinct, would humanity have emerged?

« on: 26/10/2024 01:01:26 »

It is possible that evolution got locked into a dead-end, with large, fast, meat-eaters
- These preyed on heavily-armoured vegetarians at ground level
- The very large vegetarians that could eat tree leaves were probably protected by sheer bulk

There were a lot of smaller dinosaurs and mammals scurried around in the undergrowth.

If your computer locks up, reset it... 

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Question of the Week / Re: QotW - 24.10.25 - Are isotopes distributed similarly on other planets?

« on: 20/10/2024 03:51:25 »

Radioactive C14 present at the formation of the Earth would all be gone (half-life 5,700 years), but it is continually produced by cosmic rays smashing into Nitrogen in the atmosphere.
- If a planet had little Nitrogen in the atmosphere (like Mars), then there would be less C14.

Stable C13 and C12 isotopes are produced in supernova explosions, but the ratio of them would depend on the type of star exploding.
- Red giants shed a lot of their atmosphere, and the carbon present here would be primarily C12, formed by fusing helium.
- So the isotopic composition of carbon in a planet or star would be determined by the mix of events seeding the molecular clouds from which they formed.

Even on Earth, the ratio of C12 and C13 varies slightly in different places, due to plant photosynthesis (plants prefer C12 to C13).

More dramatically:

at the time of the Permian extinction 252 Mya when the [C12/C13] ratio changed abruptly by 1%

Presumably, a large source with a different C12/C13 ratio was dumped into the atmosphere.
For more detail on this event:
https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event#Dating

With elements having very different origins, the concentration would vary dramatically with the events forming their molecular gas clouds.
- The heavier elements (Silver and above) are mostly formed in neutron star collisions/disruptions.
- A difference in the proximity of these events would make a big difference in the concentration of heavy elements in a star or planet
See periodic table at: https://en.wikipedia.org/wiki/Nucleosynthesis#Timeline

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Chemistry / Re: Dexpan alternative question

« on: 13/10/2024 07:43:58 »

I wouldn't have found it, because I wouldn't have known what to search for...

But Google is really effective.

AI systems are even more "effective", in the sense that if they don't know the answer, they will just invent an answer.
- But they are less effective at providing a list of references
- And they consume a lot more electricity than Google queries!

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General Science / Re: Does All Of Mathematics Come Down To Simple Arithmetic?

« on: 13/10/2024 07:38:54 »

Turing's symbols are more basic (and more flexible) than arithmetic, and are better able to represent all of mathematics.

The familiar "Commutative" property of addition, subtraction and multiplication is a result of the integers forming a mathematical "Field".
- Real numbers (1-dimensional) also form a Field, so the commutative property applies there, too.
- Imaginary numbers (2-Dimensional) also form a Field
- However, when you get to Quaternions (3-dimensional), these do not forma Field, and the commutative property does not apply in general (apart from special cases like "multiply by 1" or "multiply by 0").
- Most Matrix operations are also not commutative.

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General Science / Re: Does All Of Mathematics Come Down To Simple Arithmetic?

« on: 12/10/2024 04:35:47 »

The mathematician Peano attempted to define arithmetic on natural numbers, based on the number 0 and using a "+1" or successor function - effectively counting up.
https://en.wikipedia.org/wiki/Peano_axioms

You could say that addition is repeated counting
- And multiplication is repeated addition
- And exponentiation is repeated multiplication

SImilarly, subtraction is counting down, and division is repeated subtraction (although, often with a remainder).

You can also do any computation with integers that you could do with floating point numbers, with suitable scaling.
- I recall in first year university, a first computing assignment was to calculate the value of e^x on a computer with 32-bit floating point and 32-bit integers.
- The standard answer using floating point is about 8 lines of code, and will generate an answer accurate to about 6 decimal digits (for  positive x; negative x suffers severe rounding errors)
- With another couple of lines of code, you can get similar accuracy for negative x
- I thought that wasn't enough of a challenge, so I did the calculation to around 130 decimal places (ie the width of the printer), using integer arithmetic. But it took a lot more than 10 lines of code - I had to write routines for multiple-precision addition, subtraction, multiplication and division, using integer arithmetic.

Similarly, you could write code for square roots, integration, differentiation using integer arithmetic.
- Symbolic maths packages use logical operations on integers (or in general, symbols, where letters are also symbols), and can use the symbolic results to drive floating point calculations of the results.
- Even some of the recent "energy efficient" AI systems have changed from using floating point to using integer arithmetic, as it requires fewer logical operations.

In a thought experiment, Turing invented a simple computer, which could (in theory) compute anything that is computable... And it didn't have a concept of floating point numbers or integers; it was purely symbolic....
https://en.wikipedia.org/wiki/Turing_machine

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Question of the Week / Re: QotW - 24.10.18 - Do spiders know how to make webs innately?

« on: 12/10/2024 04:07:34 »

The machinery to manufacture multiple kinds of silk is encoded in their genes.
Why not the behavioural mechanisms to make use of it?

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General Science / Re: Is There A Pattern In The Number Pi?

« on: 30/09/2024 06:28:47 »

Pi can be represented by a very simple pattern:
π/4 = 1 - 1/3 + 1/5 - 1/7 + etc

This series is very slow to converge, so it's not of any practical use to calculate π

But it does illustrate some important aspects:
- 1/1000001 is zero in the first 6 decimal places
- So any pattern that you might detect in the first 6 decimal places will be destroyed by adding in this factor which does not affect the first 6 decimal places.
- The series continues forever, so it will destroy any other pattern you detect in the decimal expansion

It is necessary that the digits of π (or any transcendental number) do not form a repeating pattern
- But it is not sufficient

If you want to represent π, you could use the infinite series, or adopt the standard mathematical shorthand, and just write "π".

https://www.forbes.com/sites/kevinknudson/2016/04/18/everything-you-wanted-to-know-about-pi-part-4-infinite-series/

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Physiology & Medicine / Re: Is There Any Safe Amount Of Smoking?

« on: 29/09/2024 21:53:31 »

You could always sit around a campfire and talk to your friends - the friendship will benefit your health, just as the smoke impairs it.

I think the next battleground for Established Industry & Social Norms vs Public Health will be health warnings on alcoholic drinks - apparently, alcohol intake increases the risk of around 7 cancers (including breast cancer).
- I see the current arguments about vapes as merely an extension of the long-running battle with Big Tobacco.

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Plant Sciences, Zoology & Evolution / What is the Origin of Naked Clams (Shipworms)?

« on: 29/09/2024 11:22:40 »

On a recent Naked Scientists podcast, there was an interview about eating "naked clams", otherwise known as shipworms.

Chris asked when these evolved, given that long-distance sea voyages have really only taken off since around the year 1500.
- In Townsville I saw an example of the steps taken in the 1700s to prevent shipworm damage: cover the entire hull with copper.

I have recently visited the Australian Dinosaur Trail, in central Queensland.

The area where Richmond is now located was once under an inland sea, and they have many marine fossils. Most of the local fossils on display were dated at around 100 million years ago.
- One of the fossils on display at Kronosaurus Korner is a log, which had apparently been washed away and floated out to sea, before sinking and becoming fossilised
- This log shows signs of severe infestation with shipworm
- So I guess the shipworms have been around as long as there have been floating logs to digest.

https://www.kronosauruskorner.com.au/

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Shipworm_caption.png (761.54 kB . 830x497 - viewed 95 times)

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Question of the Week / Re: QotW - 24.09.06 - What is the shutter speed of the eye?

« on: 02/09/2024 10:25:19 »

Focal Length
The human eye has a fixed focal length of around 22mm, which gives a similar field of view to a traditional film camera with a 50mm focal length.

But camera lenses come in a wide variety of focal lengths - and a camera with a zoom lens might have a range of 60:1 in focal length (and corresponding wide range in field of view). 

Saccades
The human eye does not focus on just one image, but darts around parts of the image, allowing the high-resolution macula to dwell on different parts of the image for short periods of time. Saccades are the quick movements from one part of the image to another, occurring around 3-5 times per second, and lasting about 50ms each time. The brain suppresses the blurry image during the saccades, making them effectively unconscious and invisible to the viewer.
- The image collection time on one part of the retina is limited to 200-300ms, which could be considered the maximum "exposure time"
- But the brain is able to build up a detailed image across a number of saccades, forming a composite image like the popular "panorama" photo, or "stacking" in astrophotography.

An interesting comparison here... They suggest that the human eye can't see any more detail after looking at a scene for more than 10 to 15 seconds:
https://www.cambridgeincolour.com/tutorials/cameras-vs-human-eye.htm

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Question of the Week / Re: QotW - 24.09.06 - What is the shutter speed of the eye?

« on: 01/09/2024 11:42:03 »

Some thoughts...

Aperture
The human pupil size varies from 2 mm diameter in bright light to 8 mm under dark conditions. Smartphone camera lenses are in a similar range.
However, consumer hand-held cameras have a light-collecting diameter of around 20mm, and perhaps 100mm with professional telephoto lenses. This means they can collect a lot more photons, under the same conditions.

Fastest Detectable Event
For both cameras and the human eye, extremely short events can be detected if they generate enough photons during the period when the camera aperture (or eyelid) is open. So this is not a characteristic of a camera or the eye.

Minimum Exposure Time
As Alan mentioned, the flicker fusion frequency of the human eye is around 20 frames per second for most people, so you could say that the minimum exposure time for the human eye is around 50ms.
- Some consumer cameras have a minimum exposure time of 1/1000 second, and are able to freeze very fast events which are a blur to the human eye.

Maximum Exposure Time
When making star trails, or using a tracking mount, astrophotography can use exposure times of hours.

The flicker fusion frequency suggests that the maximum exposure time of the human eye is somewhere around 5-10ms in bright conditions.
- Under low-light conditions, the human eye is able to integrate light over a longer period - but I suspect not more than a second. So you could call this the maximum exposure time.

Photon Sensitivity
In modern astronomical CCDs, about 80% of incoming photons striking the sensor will generate a detectable charge in a pixel (the rest are reflected, or strike wiring, etc).

I heard that the human eye requires two photons to strike the same cone cell within a short period to register a flash of light. This will reduce thermal noise, but also reduces sensitivity compared to a CCD camera.

Thermal Noise
Thermal noise generates lots of charges all the time in a CCD camera, so to improve the signal-to-noise ratio, visible-light astronomical telescopes are cooled to liquid nitrogen temperatures.
- Infra-red telescopes like James Webb must be cooled to <7K.
- With a non-cooled sensor, consumer-grade cameras need to collect a lot of photons to ensure that the image stands out above the thermal noise.
- To reduce thermal noise, consumer cameras typically use tricks like taking a reference exposure with the shutter closed, to measure the average thermal noise, and subtract that from the image with the shutter open. This works better with relatively bright objects which generate more than half of the charge of the thermal noise.

Colour Sensitivity
Consumer cameras are able to take colour photos under very low-light conditions, if the exposure time is long enough.

However, the human cone cells which detect colour are only effective under brightly lit conditions; in the dark, human eyesight falls back to the black-and white rod cells, with lower resolution than the cone cells of the central vision.

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Question of the Week / Re: QotW - 24.08.30 - What would the Earth be like without 'the giant impact?'

« on: 25/08/2024 10:31:19 »

In terms of geology, Theia splashed a lot of Earth's crustal material (light Silica/Aluminum minerals) into orbit, forming the Moon. Without this, Earth would have had a much thicker crust, covering the entire planet.
- With a planet-wide crust, there would be no floating continents, no continental drift, and no subducting of carbon-containing compounds
- This appears to be the situation on both Mars and Venus. CO2 builds up in the atmosphere; in the case of Venus, it led to a runaway greenhouse gas effect.

The impact may also have impacted Earth's insides, too - some of Theia's heavy core may have punched into the mantle, producing an asymmetry we see in the mantle today. It may even have affected Earth's magnetic field (speculation!).

Finally, some speculate that if Theia originated in the outer solar system, it may have brought a lot of the water that is now in Earth's oceans.

But it was a long time ago; the Earth has been resurfaced many times by continental drift, so it is hard to reconstruct the details.

https://en.wikipedia.org/wiki/Theia_(planet)

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Plant Sciences, Zoology & Evolution / Why are horses cannier than we first thought?

« on: 18/08/2024 08:44:51 »

The recent Naked SCientists story asked why are "Horses cannier than we first thought"?

It could be because they live in herds, and have to negotiate a complex pecking order (or perhaps biting and kicking order), every day.

So perhaps  it is important for a horse to recognise individuals and know how to interact appropriately with each?

https://www.thenakedscientists.com/articles/interviews/horses-cannier-we-first-thought
 

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Technology / Re: What is the impulse response of the world?s economy?

« on: 28/07/2024 05:08:45 »

Apparently, Cloudstrike took down about1% of computers running Microsoft Windows, world-wide  (presumably, the others were either turned off at the time, or running some other brand of anti-virus software).

A lot of cloud servers run some form of LINUX, so presumably even less than 1% of cloud servers went down. 

A lesson in interconnectedness - a supply chain is only as strong as its weakest link!

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Question of the Week / Re: QotW - 24.08.02 - What is the universe expanding into?

« on: 27/07/2024 06:18:16 »

Another metaphor is cooking a raisin cake: all the raisins move away from each other in 3D.
- But the cake expands into the volume of the oven, so it doesn?t really answer the question.

We don?t know if the universe is finite or infinite. If the universe is infinite, the expansion is slightly easier to explain, because 2 x infinity = infinity
- This means that an infinite universe can expand into itself
- this is based on Cantor?s mathematics of infinite numbers, which is not really intuitive in our finite experience!
- Rationale: It is possible to create a 1 to 1 correspondence between a number z and number 2 x z, where z can range from minus infinity to plus infinity

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Technology / What is the impulse response of the world?s economy?

« on: 23/07/2024 08:02:09 »

The recent Microsoft/Clodstrike outage gave a 1-day kick to the world?s economy.

It was felt immediately at airports and ATMs.

After a few days, it is showing up in empty supermarket shelves

I suspect that the flow-on effects will continue reverberating for weeks or perhaps months?

In electrical engineering terms, this is the impulse response of a system.

Will this measure the impulse response of the world economy?

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Question of the Week / Re: QotW - 24.07.19 - Can you extract DNA from fossils?

« on: 18/07/2024 10:02:39 »

There is another way you can infer the DNA code of a fossil, and that is by looking at the protein sequence (genomics=DNA genome vs proteomics=protein ).
- Protein is more stable than DNA, so is likely to be readable for longer than the DNA
- By sequencing some proteins which are stable, and common in fossils - eg hair or muscle tissue, it is possible to narrow down the DNA which generated these proteins
- This will be only a small sample of the approximately 25,000 proteins encoded by a creature's DNA
- The mapping from DNA to proteins is not unique, as there are several DNA sequences which can generate any amino acid (64 DNA triplets select for 20 amino acids + a couple of punctuation marks).
        - Plus, a protein is often spliced together from several shorter DNA sequences
- But it may be enough to tell how related two fossils are, by measuring the number of places that their proteins diverge.

This won't work in really old fossils, where the protein is severely degraded, or entirely replaced by minerals.

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General Science / Re: How does ChatGPT work?

« on: 18/07/2024 09:52:05 »

Is it simply training statistically a model so that it can put together words that make sense?

I heard a description that "A Large Language Model (eg ChatGPT) is a sophisticated auto-complete.".
https://podcasts.apple.com/gb/podcast/the-ai-fix/id1753381111

In a few years (which may be too slow anyway), each organisation may come to an arrangement so that the details of code written by GPT software for their use are kept secret and never added to the bank of data available for ChatGPT to use in the future.

My employer said that no-one should use a public LLM, as company Intellectual Property could be incorporated into the LLM, and be reproduced in the public domain. They were going to provide an in-house LLM.
- I imagine that all inputs and outputs of the LLM are already "owned" by the operator of the LLM! (Who reads the fine print, anyway?)
- The in-house LLM is now available, but I haven't tried it, as yet
- It seems that the younger generation have embraced this technology more swiftly than old guys like me...

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Question of the Week / Re: QotW - 24.07.19 - Can you extract DNA from fossils?

« on: 14/07/2024 00:10:23 »

Straight after hearing this question on The Naked Scientists podcast, the next podcast in my feed was Science Friday, with an interview with Svante Paabo, who won the 2022 Nobel Prize for extracting DNA from Neanderthal bones...
https://www.nobelprize.org/prizes/medicine/2022/advanced-information/

In cold and dry conditions, Neanderthal DNA has remained reasonably intact for tens of thousands of years.
- The shotgun-sequencing technologies for DNA deveoped during the human genome project have certainly helped stitch together the degraded Neanderthal (and more recently, Denisovan) DNA, where the long strands of DNA have been broken into very short segments.
- In contrast, the much warmer and moist conditions in Indonesia have so far prevented recovery of usable DNA from the Flores "hobbit", even though it is a much younger fossil.
- The record for DNA recovery currently stands at 1 million years, from a wooly mammoth frozen in Siberian ice
https://en.wikipedia.org/wiki/Ancient_DNA
 
For extremely old fossils, where the organic material has been completely replaced by silicate minerals, there is no DNA left to decode
- Even when the organic material is still preserved (such as mosquitos caught in amber) the DNA is badly degraded over time, dashing the Dinosaur-recreating hopes of Jurassic Park -  at least, with currently foreseeable technologies.

There is another place where you can retrieve fossil DNA, and that is from the DNA of living species.
- There is "fossil" DNA from our ancestors in all our genomes
- By sequencing the DNA of related living species, it is possible to draw a "family tree" of each gene
- This allows an extrapolation of what the DNA probably looked like, for some extinct species.
- The goal of generating a genome for the earliest ancestor of all life on Earth is a huge extrapolation, with no consensus, as yet