41

Technology / Re: How does a fingerprint reader work?

« on: 12/01/2019 21:27:29 »

Put simply, these devices work in three main ways: imaging, electrical/capacitive fingerprinting and sonic fingerprinting. The complexity and recency of introduction occur in that order.

In imaging, which is the oldest but also the weakest (easiest to fool), a light source at an angle to the skin surface emits a beam or light which reflects off the skin surface and reflections are focused by a lens and detected by photosensitive surface. The pattern of reflections is stored as a 2D image and used to authenticate the user. It's easy to fool because anything that produces the correct pattern will activate the detector.

In capacitative detection, the device compares the electrical capacitance profile of the skin surface, which will change across the skin surface owing to the patterns of ridges and folds. As the pattern of ridges and folds will vary so the capacitance function will vary; this capacitance variation pattern can be used to authenticate the user.

The most recent introduction is an ultrasonic approach. This uses an ultrasound source to bounce sound waves off the surface and store the reflection pattern; this is the hardest to fool but works a bit like the imaging system: the sound waves bounce off the topography of the skin surface in different ways according to the ridge pattern.

I hope that explains things for you?

42

Physiology & Medicine / Re: What could cause a too high potassium count?

« on: 08/01/2019 07:55:00 »

You have referred to the most common causes of hyperkalaemia (raised potassium). For clarity, these are:

Renal failure (acute or chronic)
Antihypertensive drugs (beta blockers, ACE inhibitors)
Diabetes
Excessive potassium ingestion

These are also other, rarer causes like adrenal insufficiency (Addison's disease) where the adrenal cortex fails to produce adequate mineralocorticoid (pro-sodium-elevating) steroids; this leads to hyponatraemia and hyperkalaemia.

Have all of these been excluded?

43

Physiology & Medicine / Re: Are there any naturally occurring proteins not encoded in DNA?

« on: 03/01/2019 09:31:09 »

Two clever, and interesting answers so far! I'd not thought about collagen like that before...

44

Just Chat! / HAPPY NEW YEAR 2019!

« on: 01/01/2019 09:32:48 »

My very best wishes to everyone; welcome to 2019; let's hope it's fun, prosperous and productive for us all!

What's everyone up to today?

45

Just Chat! / Merry Christmas!

« on: 25/12/2018 09:50:15 »

Happy Christmas everyone!

Just dropping by to wish everyone a very Merry Christmas; have a lovely day (evening for the Aussies among you who were already tucking into turkey, and in one case curry, as I was going to bed!).

BW

Chris

46

Physiology & Medicine / Re: If you feel well are you healthy?

« on: 01/12/2018 11:01:54 »

Part of the reason that we feel unwell when we are ill is because the immune response is releasing chemical signals called cytokines.

These circulate in the blood and provoke the symptoms of malaise that accompany illness, including fever, fatigue and aching muscles.

This means that, in general, the more pronounced the immune response the more severe the symptoms. And sometimes this can be maladaptive.

Indeed, in some of the patients I've treated in the past, giving them steroids to damp down the immune response has been helpful in mitigating their symptoms.

An example of this is the treatment of bacterial meningitis: when antibiotics are given, the dying bacteria release inflammatory debris that can provoke a very profound inflammatory reaction which can be destructive in its own right.

By blunting that response temporarily, you can improve the clinical outcome. Scientists recently showed that aspirin given as an anti-inflammatory can also be very beneficial in the treatment of TB meningitis: https://www.thenakedscientists.com/articles/interviews/aspirin-tuberculous-meningitis

Notwithstanding the above, it's not true that a person with a weaker immune response will feel better when challenged by the same infection, because they will most likely ultimately develop a more severe, invasive disease, which will compromise them in other ways.

So, the bottom line is that feeling unwell is a side effect of an immune response. But the absence of an immune response is not a guarantee of a symptom-free illness experience...

47

Cells, Microbes & Viruses / Re: When to use italics in a write up?

« on: 29/11/2018 16:59:28 »

Species names in long, abbreviated and species / group name forms are traditionally italicised: e.g. Streptococcus sp. and Strep. pneumoniae

If you were saying "Streptococcal infection", you probably wouldn't italicise that.

48

Physiology & Medicine / Re: How can cortisol be managed to keep levels OK for health and pain relief?

« on: 28/11/2018 23:57:36 »

Hmm, but not all steroid molecules are made equal. Relative to cortisol some steroid preps are much more bioactive, meaning that they access and stimulate their targets much more powerfully. So although they suppress endogenous steroid production, what you replace it with is much more potent.

49

Physiology & Medicine / Re: How can cortisol be managed to keep levels OK for health and pain relief?

« on: 27/11/2018 18:19:34 »

Exogenous steroids (like prednisolone and dexamethasone) are best taken in the morning because this mirrors the natural steroid surge that accompanies waking. Regular use of an exogenous steroid will cause a reduction in the body's own steroid production, so topping up the morning surge is least disruptive to your circadian cycle. If you take the steroid later in the day then it provokes wakefulness and this can lead to disturbed sleep or insomnia.

50

Plant Sciences, Zoology & Evolution / Re: Why do most humans have traces of Neanderthal DNA?

« on: 27/11/2018 09:08:08 »

Both species definitely share ancestors, which is why our DNA is so similar in the first place, but Neanderthals and anatomically modern humans diverged from one another 200-300,000 years ago. Current thinking is that the last ancestor we both share is Homo erectus, which was spawned about 1.8 million years ago. Neanderthals disappeared about 30-40,000 years ago.

Because they are relatively recently extinct, Neanderthal remains are a good prospect for DNA recovery, and about 10 years ago scientists completed the Neanderthal genome project; this is the Neanderthal equivalent of the Human Genome Project that decoded all 3 billion letters of the human DNA code.

Armed with this sequence, and because we are so closely related, it's possible to align the Neanderthal DNA makeup with the modern human genome and to highlight areas that are shared and areas that are distinct.

Areas of the genome that are shared by both were inherited from an ancestor to both Neanderthals and us and will be universally present. Similarly, sequences that are specific to one species or the other - having evolved after the two species split - will be exclusively present in each species.

But there will also be regions of the genome that are variably shared in human and Neanderthal populations, indicating gene mixing. This is the example you highlight of some human populations carrying Neanderthal sequences but not others. It is also the evidence that tells palaeontologists and geneticists that the two species interbred, which is how these gene sequences came to be variably shared.

51

Physics, Astronomy & Cosmology / Re: What are gravitons and how do they explain gravity?

« on: 17/11/2018 08:31:19 »

Hi @miniguy

There are a number of theories for how gravity "works"; the most popular -  and evidence-based - is Einstein's theory of general relativity, which proposes that mass deforms the fabric of the universe - Spacetime.

People talk about a bowling ball sitting in the centre of a trampoline to make a dent that causes other bodes to roll down into the "gravity well" created by the bowling ball; this is why massive bodies, like stars, cause moving bodies like planets to deviate from a straight trajectory and instead adopt an orbital path.

Meanwhile, quantum mechanics (QM) has investigated how gravity can be fitted into what we call the "standard model", which is the collection of particles and force carriers that make up matter in the Universe around us. This QM theoretical model invokes a particle as the force carrier to convey gravitational attraction. This notional particle is the graviton. So the idea would be that objects are attracted to one another by constantly giving away and receiving a stream of gravitons between them. And like photons, these notional particles would travel at the speed of light.

The problem is that no one has ever seen a graviton, and all the theories that have so far tried to merge what we do know about gravity with QM yield nonsense results. So, for now, gravitons remain a theory among theories.

52

Geology, Palaeontology & Archaeology / Re: What is this ridged fossil found in Somerset?

« on: 05/11/2018 08:11:31 »

PS @Sandmidj - I modified your post to insert the image into the body text so it's immediately visible. To do this yourself, if you need to, you go to "attachments" below the text box (where you uploaded the image in the first place) and click on the "insert" link next to the image name. You can do this at the time of uploading, no need to modify later. I think it helps because the image is presented at full size and people have less work to do to review the picture. chris

53

Geology, Palaeontology & Archaeology / Re: What is this ridged fossil found in Somerset?

« on: 05/11/2018 08:09:27 »

Could be bits of fossilised marine algae. I found some nice fossilised wood pieces in Teignmouth, Devon, a few years back; the appearance is quite similar.

54

Geology, Palaeontology & Archaeology / Re: What is this ridged fossil found in Somerset?

« on: 03/11/2018 22:29:22 »

The first thing I thought about were fossilised ripples, but, as I pointed out, there are ridges on both sides, which made me question my original instinct. I've seen quite a lot of examples of ripple patterns, especially in the rocks in NW Australia where I spent a bit of time, but none had ripples on both sides.

55

Geology, Palaeontology & Archaeology / Re: What is this ridged fossil found in Somerset?

« on: 03/11/2018 15:59:03 »

Interesting how the ridged profile is symmetrical on both sides of the specimen.

This needs @Bass to make a diagnosis. It's above my paygrade.

56

Chemistry / Re: Why is there an asterisk next to an author's name in a journal paper?

« on: 28/10/2018 13:52:04 »

Usually this refers to the "corresponding author" (i.e. the person to write to about the paper), or can sometimes be used when applied to two first authors to indicate that both made a equal contribution to the work.

To find out what the asterisk means refer to the author details legend below the list of names. In electronic publications this is usually a clickable option next to the author list. In print copy journals they usually put the legend somewhere on page 1.

57

Chemistry / Re: How do you make a mirror?

« on: 19/10/2018 05:11:47 »

I've used a similar approach to silver-coat the inside-surface of a round-bottomed flask in order to make a scientifically-inspired Christmas baubal. The ammonia solution is very strong and you need good ventilation.

I'm not sure what the tin chloride solution does and why you need that - anyone know?

58

That CAN'T be true! / Re: Do photons, neutrinos and dark matter have a structure?

« on: 15/10/2018 10:46:25 »

Er either I'm really jetlagged or none of this makes any sense whatsoever...

59

Question of the Week / Re: QotW - 18.09.30 - Is second hand smoke more dangerous than smoking a cigarette?

« on: 07/10/2018 15:46:30 »

For many carcinogens and poisons (including cigarette smoke), risk increases with exposure.

Interesting choice of words, @evan_au , begging me to enquire what carcinogens and poisons do not follow a dosage-dependent relationship?

60

Physiology & Medicine / Re: What is the pathophysiology and histopathology of cataract?

« on: 07/10/2018 09:53:32 »

This is a very helpful article about the biochemistry and pathogenesis of cataract formation, which might help you.