1

The Environment / LED streetlamps - effect on wildlife?

« on: 15/02/2014 11:30:23 »

I believe it is well-known that streetlamps do affect the behaviour of wildlife, including birds.

I hear local council (in particular, Cllr Mathew Shuter) has been seriously considering replacing all the streetlamps in Cambridgeshire with LED lighting (the present installed base is dominated by low-pressure sodium, with some high-pressure sodium on a handful of more main roads). Presumably white LEDs (which also have a pronounced blue peak in their spectrum).

Although the LEDs will give vastly superior colour-performance, sodium is reasonably efficient and simple and reliable; I'm skeptical that wholesale replacement with LED is actually a smart move. It seems like the current plan is to hold off for a few years yet.

Given the relatively recent discovery of the effect of blue wavelengths in setting human biological clocks / circadian rhythms, I wondered if there's potentially big effects "unforeseen consequences" on wildlife of replacing the orangey sodium lamps with white (and strong blue) light...?

Does anyone know if there is any research? Should the council be more formally advised that this is a potential issue?

2

Geek Speak / What's going on with the Windows calculator?

« on: 28/05/2013 23:46:17 »

I just noticed some weirdness with the Windows calculator.
If I enter the following numbers, then press [1/x]   (that's the reciprocal button) I get:
5666.0   -> 1.7649135192375573596893752206142e-4
5666.1   -> 0.0001764882370590000176488237059
5666.2   -> 1.7648512230418975680350146482652e-4
5666.3   -> 1.7648200765931913241445034678715e-4
5666.4   -> 1.7647889312438232387406466186644e-4
5666.5   -> 0.000176475778699373510985617224036
5666.6   -> 1.7647266438428687396322309674231e-4
5666.7   -> 1.7646955017911659343180334233328e-4
5666.8   -> 1.7646643608385685042704877532293e-4
5666.9   -> 0.0001764633220985018263953837194939
5667.0   -> 1.7646020822304570319392976883713e-4

That's odd. Why do certain numbers not appear in scientific (e-4) notation?

Is there a bigger pattern to this?
Is this purely a display-bug, or is this the tip of a bigger iceberg?

Do you see the same? On what Windows versions?

I'm on Windows XP (sp3, on an old Pentium4 processor)

It doesn't seem to matter whether the calculator is in the "scientific" or "normal" mode.
Working with the same numbers, but x10 bigger (i.e. 56660 ... 56670) and again taking the reciprocal gives similar, yet subtly different results again! 

3

Cells, Microbes & Viruses / Can someone help me untangle the basics of chomosomes, DNA, and all that?

« on: 11/02/2013 23:11:27 »

I'm a physicist and electronics engineer. Please can you help me clarify the basics of all this molecular-biology/chromosomes/DNA stuff.   []

I know there's some good Wikipedia pages, but I haven't yet found one which gives a good overview - if you know of one, feel free to reply with a link to it.

(I'm principally interested in human side of things, although key differences in bacteria/viruses might be useful.)

Here goes:
As far as I can figure out, the chromosomes are at the top of the hierarchy. Apparently humans have 46 chromosomes, in 23 pairs.
There's some info here: http://en.wikipedia.org/wiki/Chromosome

Human cells have 23 pairs of chromosomes (22 pairs of autosomes and one pair of sex chromosomes), giving a total of 46 per cell.

This gives me several questions:

• Do all 46 chromosomes exist in (more or less) every cell?
• What's special about the (autosome) pairings? Are they physically paired in some way? Are the two chromosomes in each pair similar in some way?
• How does the X/Y sex chromosome fit in?
• Is there anything distinctive about the chromosomes - if someone gave you one of them, how would you know whether it was chromosome 5, 6, or 7? (I realise some of the lengths are more distinctive)

Each chromosome comprises one huge long chain of DNA - right?
Wikipedia has a very nice page on DNA: http://en.wikipedia.org/wiki/DNA
I'm reasonably confident I understand base-pairs G,A,T,C ; and that you have to pair A with T, and G with C. And that you can encode information by the sequence of base-pairs.

I kind-of get that you can make some sort of RNA copy that you then use to build proteins (reading the base-pairs in groups of three) - but I'm less clear about whether it matters which half (since they're complementary) of the DNA you use and what the implications are.

Now tell me, what is a 'gene'?

It seems to be a finite-length sequence of base-pairs within a DNA string...
So that begs the question What defines the start and end of a gene, within a DNA string?
http://en.wikipedia.org/wiki/Gene     doesn't seem too clear on it. Or is the answer just "it's complicated"?

In fact, what determines which end of the DNA string is the 'start' and 'end' (or head and foot in cinema-film parlance)? I understand that each half of the DNA has a 3'-end and a 5'-end and that that defines a directionality within half of it - but since the combined halves have one 3' and one 5' at each end, how do you define the overall 'start' and 'finish'?


Sorry if I'm asking some naive questions!

And finally, in principle (it might take another decade for the technology to be ready!) would it be possible for someone to extract the DNA from a flake of my skin or a drop of my blood and insert/swap it into another man's sperm, and make a baby for which I'd be the genetic father? Asked another way, is there anything 'special' about the DNA in a sperm, or is it exactly the same as in any other cell of my body?


I'm hoping you can give me a leg-up into this field. You might even have done a podcast on the topic. Links appreciated!  Thanks.

4

The Environment / Are carbon emissions too high to curb climate change?

« on: 04/12/2012 22:47:11 »

Re: http://www.bbc.co.uk/news/science-environment-20556703 and similar

While it's probably true that not enough is being done to really curb CO2 emissions...

... the various green energy schemes (wind/solar farms etc) all require up-front cost and energy "investment" and have a significant energy-payback time. Is there any element of policy-makers being naive in expecting to see drops in CO2 output just yet?

Discuss...

(I do recognise that the green energy stuff at present-scale is still merely a drop in the ocean when considered worldwide)

5

Physiology & Medicine / Why does diced beef go green/grey, well within its use-by date?

« on: 25/09/2012 00:15:20 »

On a few occasions, with meat from more than one supermarket I have observed prepacked refridgerated diced beef turning greeny/grey a day or so after purchase, yet well within its use-by date (eg 5 days within). After less than 24 hours with only minor discolouration I've used the meat with no ill-effects, but a while ago when the meat was badly discoloured a couple of days after purchase we took it back to the store for a replacement.
I've no reason to suspect the domestic fridge was insufficiently cold.


What's going on here? Is the discoloured meat harmful to eat?

6

Physiology & Medicine / Alcohol and "morning-after" stubble

« on: 19/05/2012 21:05:28 »

Another alcohol question 

There is a perception that (shaven) men have a more prominent stubble the morning after a night of heavy drinking (alcohol). It's widely portrayed in cartoons and things too.

Is the effect real?

What causes it?
Does the hair really grow faster due to alcohol, or is it that the sleep pattern is affected which in turn affects the growth, or perhaps it's just that a heavy night usually leads to a lie-in and thus more time for the hair to grow?

7

Physiology & Medicine / Metabolism of alcohol vs other things

« on: 19/05/2012 21:00:40 »

I've recently heard/read that our bodies metabolise alcohol at a constant rate (perhaps 10ml/hour) irrespective of the concentration in the blood, while other trace compounds are removed with an exponential decay (i.e. at a rate proportional to the blood-concentration).

Is this true?

If so, what is the difference in mechanism responsible for it?

Thanks.

8

General Science / Is "Shopping rage" exacerbated by (excessive) neuromarketing?

« on: 04/04/2012 23:56:43 »

I've just been re-listening to the Naked Scientists episode from 10/10/2010 and the special extended excerpt on neuromarketing.

A year or two ago the papers got all worked up over "shopping rage" - basically people being antisocial and rude to other customers and to shop assistants.

While it could just be bad manners and general increasing 'pace' of life, I do wonder whether the excessive use of neuromarketing techniques will exacerbate the problem. Do you know of any research on this possible connection?

I tend to do my regular shopping at an upmarket supermarket with wide aisles and a pale green dominant colour-scheme. On the occasions when I do find myself in an Asda or Tesco's I do feel 'mentally assaulted' as soon as I walk in the door - I find the massive discount offers on multibuy bread or bagels or whatever (often when I've barely picked up a basket) quite offensive. To me, this screams "we don't care what you came for - BUY THIS" - which I find arrogant and disrepectful. Similarly, butting random (out of place) things on the ailse-ends with big discounts just feels like a deliberate attempt to hijack my train of thought. In contrast, I find the pale-green themed store a relative oasis of calm.

What does anyone else think?
Do you become more immune to the visual assualt and clutter if that's your regular store?

9

Chemistry / Why is the smell of fish so persistant?

« on: 18/04/2011 23:35:59 »

If you've cooked fish at home then the smell can linger mildly for days. If they serve (especially deep fried) fish in the restaurant at work, and I wear a particularly fluffy cotton shirt the smell lingers in the shirt all afternoon until I can get home and wash the shirt.

What makes the smell of fish so persistant compared to other (cooked) foods?

10

Physiology & Medicine / How does the brain "direct" dreams?

« on: 13/03/2011 13:50:23 »

I've been not-so-well recently [:-'(], and been spending more time in bed sleeping ... and dreaming.

I had one particular dream which raised two questions...


I was dreaming a sequence which could have come from an Aussie soap-opera (not that I've seen one for over a decade). There was an open-top 'pick-up truck' with a guy and a girl flirting in the back seat, a couple of slightly older guys in the front seats, one of whom was driving. I wasn't personally there (not as a first-person) but was watching the story be told as in a film/TV drama. My viewpoint jumped around, from watching the drama on the back seat, to the driver's-eye view looking forward to the view of the driver's face as seen from the front-passenger's corner of the windscreen - just like a film/TV production.

Question 1: I can imagine that historically people might have dreamt of being a "fly on the wall" (as well as first-person dreams)... but dreaming from all those changing viewpoints - is that a modern thing which mostly has only happened since we experience this way of looking at the world in film and TV?

In the dream, what started out as a relaxed/friendly drive along open roads gradually became more tense as the driver, without saying anything, became increasingly tense/agitated and began to drive progressively more aggressively as the road narrowed through a village and became more twisty and there were pedestrians and young children at the sides of the road (with no pavement)... which somewhat miraclously we avoided hitting. From the driver's perspective we then see 20-30 yards ahead of us a mother and maybe 7 yr old child and the child suddenly screams and points at us (the truck) ... then the my viewpoint jumps to the child's perspective and we see a tree fallen across the road that our truck is about to hit. And the dream ends/I wake up.

I found this business of the reaction of the child (a character in the dream) to a danger before the nature of that hazard has been seen directly by the person doing the dreaming intriguing.

Question 2: When the brain is dreaming, does it make up everything 'on the fly' as you dream it, or is part of the brain 'planning ahead' or 'looking forward' in the dream?


Do you know of any formal research/results in this area?
Have you experienced similar happenings in your own dreams?

11

General Science / What's the best way to convey small sizes for a general-public audience?

« on: 23/12/2010 11:16:11 »

I was just reading this story: http://www.bbc.co.uk/news/uk-scotland-glasgow-west-12063975  about a very small "Christmas card" produced by a nanotechnology group in Glasgow.

The story says: "The image, which measures 200x290 micro-metres, features a Christmas tree and is etched on a tiny piece of glass."

They then trot out, by way of explanation "To put that into some sort of perspective, a micro-metre is a millionth of a metre; the width of a human hair is about 100 micro-metres."


This seems terribly abstract.

Why couldn't they have just said that the card "measured 0.2 x 0.3 millimetres"? (Or, if they're afraid of decimals, "one-fifth of a millimetre by one-third of a millimetre"?)

Is it that expressing the size in millimetres sounds less impressive, that they're deliberately trying to educate the public about units of "micrometres", or do you think it's just a case of not thinking?


Human hair varies between fine and thick (perhaps 50µm to 130µm), but 0.1mm is about right. Also a typical piece of 90gsm office paper is pretty much 0.1mm thick.
You can visualise millimetres, you can imagine basic fractions of millimetres.


I'd argue that paper is a better reference (than hair) as we commonly experience a wad of paper and have some feel for what several sheets stack up to. Although most of us have hair on our head, it's not really very easy to appreciate how thick or thin it is - or how wide a "ribbon" of say twenty hairs laid side by side would be.


What does everyone else think?

12

Physiology & Medicine / Why does "fresh air" relieve feelings of nausea?

« on: 14/05/2010 22:28:03 »

Another question on nausea:

Cool dry "fresh" air relieves feelings of nausea.
Hot wet air (like in a shower-room) makes it far worse.  Why?

Why does having a stuffy nose, or holding your nose closed exacerbate pre-existing feelings of nausea? Is this related to the humidity effect?

What's going on physically or phsyiologically?
Is there some evolutionary explanation too?


Thanks,

Andrew

13

Physiology & Medicine / Body-temperature affects colour-perception: is this widespread/documented?

« on: 31/10/2009 15:05:41 »

Hi,

I've been suffering from a flu-like virus thing the past few days. I've long observed that when I am ill and have a raised body-temperature, my colour-perception is subtly affected and my room or environment seems more yellowy-greeny than usual.

Do other people experience the same thing?
Is the colour-shift in the same direction for everyone?

Is it documented in the medical literature?

What's the physical origin?
Is it that the three colour-sensors in the eye have a differential change of 'gain' (or sensitivity) with temperature?

14

General Science / What is the problem with re-freezing previously-frozen food?

« on: 07/07/2009 21:36:59 »

Food-books / programmes and food-packaging frequently warns against re-freezing previously-frozen food. Examples include New Zealand lamb, and some fish, which are sold refridgerated but have been previously frozen. The packaging on some foods which are sold frozen (including some ready meals) warn against allowing the product to thaw then re-freezing.

Why is this such a big no-no?


What if I bought something refridgerated intending to use it the following day, but put it too near the top/back of my fridge and it froze overnight. Surely the product won't be more harmful the next day than if it had merely been refridgerated at 5C overnight?

I'm guessing the rule is a simplification, but am interested to know what's behind it - as I suspect the warnings have also attracted some additional urban myths.

15

Plant Sciences, Zoology & Evolution / What animals made these footprints in the snow?

« on: 13/02/2009 20:06:18 »

Any idea what kind of animal left these footprints?

The prints are almost exactly 45cm (18 inches) from print-centre to print-centre along the walk.
The individual prints are approximately 6-7cm (2.5 inches) wide.

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The prints do go over the wall in the distance (the wall is about 9 metres away).

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The boring answer would be a fox, but to me (not being very familiar with foxes) they seem rather large and well-spaced for this explanation.
This is to the south of Cambridge, UK.

16

Plant Sciences, Zoology & Evolution / Do you know what this plant is?

« on: 03/11/2008 00:04:47 »

Do you know what this plant is? (Photos taken in June)

Growing in my previous garden, in Surrey, near Gatwick.

Is it native to the UK? It looks most unlike anything else I've seen.

Note the leaves on the stem growing all at right-angles to each other.
Note the branching of the stalks from the flower/buds.

17

General Science / What is happening (scientifically) when shoes are polished to make them shiny?

« on: 05/10/2008 00:38:35 »

A Saturday chore, but what's actually going on with the "polishing on" "polishing off" etc?

You apply the (waxy) polish with one brush and the shoes go matt. Leave them to stand for a few minutes then "polish off" with the second brush and they come up shiny. What's actually happening?

18

Technology / How did they put the top on this bridge?

« on: 28/09/2008 13:32:02 »

Since moving to Cambridge in August, I've been watching them build this bridge on the new Addenbrookes access-road.

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As at 25 Aug.

I'm fairly sure the triangular concrete bits were cast in-situ using wooden frames.

19

Plant Sciences, Zoology & Evolution / Can you identify this garden bug?

« on: 28/09/2008 13:10:10 »

Photographed on Aug 30th 2008, in Surrey.

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While I know lots about physics and electronics, I am embarrassingly clueless when it comes to biology and things you find in the garden.

So what is this rather fearsome looking creature? (the body is probably about 3cm long)

And what does it do with the vicious pointy bits at the rear end?

20

Radio Show & Podcast Feedback / Archimedes - crips advert of years ago

« on: 11/06/2008 23:52:59 »

Many years ago (early 1990's I guess) there used to be an advert on the commercial radio stations that went like this:

(read it with a northern-ish accent, and "bath" to rhyme with "Kath")

'Ere I am, in my bath, for purely gastronomic reasons to do with Walker's Crisps.
The bath, after all, is where the great mathematician Archimedes discovered his famous principle - that is
(spoken very quickly) "the apparent loss in weight of a body immersed in liquid is equal to the weight of the displaced liquid"
Awww - if Archimedes could work that out in the bath, then I'm sure I can discover why it is that Walker's crisps always taste so good.

'Owever, I've been 'ere for three days now, and all I've discovered so far is that bathwater makes yer crisps soggy.


(fades out) 'ello Mr Ducky

I'll never forget Archimedes principle!

It'd be a laugh if you could get your hands on a copy of the radio advert. But I suspect licensing stuff would prevent you from playing it :-(