Re : @Chemist

I take your point. Re-painting a plimsoll line is a serious breach of maritime law ( I think ) and must surely void any insurance.

Re : Generalists - top down or bottom up makes a difference

Agree entirely. An inordinate amount of time can be spent refuting a poor idea by a someone who is ignorant of the basic principles of an area. The recent 'discussions' in The Reg. about siphons being a notable example

Re : Check out Bernoulli's Equation

Bernoulli's equation for a siphon includes a term for gravity.

Siphons do NOT work in zero-g

Bernoulli's equ. for max. height of siphon is h=P/pg P=external pressure, g= acc. due to gravity, p=fluid density

Re : If freezing is the problem then....

I think the freezing problem was caused by the solid so-called methane hydrates (clathrates actually) that form at low-ish temperatures and high pressures when methane is in contact with water.

Re : Brazil?

What has re-painting the Plimsoll line got to do with the depth of water the ship was working in ?

It shows how heavily it's loaded - that's all

Re : hmmm x-rays, you say?

Gamma are higher frequency than x-rays although there can be considerable overlap

Re : Hot fridges

I think STB and many of the rest of us know how fridges work. The essential problem is that their waste heat is low-grade and limited and it would require extensive modifications merely to boost the temp. of the input water to a heating system by a small amount. This heat in any case adds to the warmth of the house (most of the year). In the case of industrial scale warehouse freezing units or office block air-conditioning units recovery of waste heat could potentially be much more effective

The underground problem is unfortunately similar - although the commuters swelter the temperature is actually quite low and removing the heat in a useful manner would be quite involved and inefficient.

Far better as suggested above is to remove the necessity by not having as much waste heat to begin with if this is feasible.

Re : Surely...

Are you suggesting a new government should renege on debts as well ??

Re : evolutionarily speaking they sat around talking and playing with children

I've never heard such an ill-informed rant

We have the physiology of hunter-gathers from thousands of years ago. They all had hard lives with low calorie intakes and considerable daily exercise.

Re : BMI?

It's not hokum -it works quite well for a large population - however it's poor as an indicator for individuals.

Treat it as a heuristic - if BMI suggests you have a problem you really need to use a better method to see if you have.

Re : cold vacuum

Don't want to be pedantic but what you are really measuring in a vacuum is the temperature of the thermometer which will be some balance of what it radiates v. what it absorbs

@cs94njw

The difference between a synthesised stretch of DNA and somehow managing to make a viable, simple bacteria is absolutely GIGANTIC.

A moderately good analogy is that of having a program code that describes in detail how to build an entire computer (from atoms and molecules) but not yet having the computer to run it on.

The major step forward with is the is the knowledge that the new DNA is the only DNA in the cell and that all functions are being managed by it after the cells have been cycled a number of times

Re : Designed?

You are correct but at the same time the knowledge of how to change the individual genes within a genome is routinely used already and has been for years. I can remember years (25 ?) ago a team in the lab downstairs synthesised the insulin gene. All that's happened here is that for the first time the entire genetic sequence of an organism has been synthesised. With the usual hybrid approach a modified gene is inserted by various techniques into the genome of an existing bacteria or yeast. This kind of happens at random and only some cells will be viable or useful. With this new technique a new sequence can placed in the exact position required.

An analogy would be : take 1 million copies of a program - insert at random a new sequence of code - by chance some versions will still run but not run the new code whilst MAYBE the odd one will execute the new sequence. This new technique is more akin to writing the source again and incorporating the new code correctly.

HOWEVER in the case of organisms the code is the easy bit. Synthesising an 'empty' cell to put your new genome into would be many orders of magnitude more difficult.

The 'empty' cell needs a membrane with associated proteins, and protein complexes to transcribe the new genome into fresh proteins, generate energy, and LOTS of other things. As an example in more complex cells there are enzymes called topoisomerases which are needed to keep the vast length of DNA from getting well and truly knotted.

A DNA sequence on it's own is impotent.

Re : would you think of the children (and the elderly) → #

TOO OLD !!

Tell that to my 87 year-old mother-in-law who shops on-line, banks, types up/sends minutes for University of the 3rd Age, e-mails, etc.

All this on LINUX by the way

"What have you lot got against DAB?"

1) Unnecessary i.e. wasteful

2) Unwanted - very definitely most people don't want to lose FM - although many don't even know that is going to happen yet

3) All those car radios that will need changing or naff adaptors

4) Unfair - why the hell should most people have to pay for something they already have

.

5) I've just been walking in the hills with my 15 year old Roberts FM radio which weights nothing and is ~8cm * 3cm * 1cm and uses 1 AAA NiMH battery that lasts ~12 hours on one charge. Where the heck am I going to replace that ?

In the Alps....

many villages are essentially motorized traffic-free and rely on electric vehicles like golf-buggies or small milkfloats. They solve the problem with small cowbells attached to the front. The small undulations in the road do the rest.

Re : depressing

You think energy is going to be FREE ?!

Re : Not just atmospheric pressure

I think we need to clarify some terms.

"driven by" - to my mind that means the thermodynamics of the situation and that is the energy derived from potential energy - in this case gravity

An 'atmospheric' pressure is necessary for the mechanism to work but it doesn't contribute to the overall energy change. There are a number of factors - height of hump, boiling point of liquid, atm. pressure, temperature, width of pipe, end of pipe in or out of bottom reservoir that modify the behaviour of the system but only gravity drives it.

The limiting height for the hump is that the shorter limb is less than ~10m in the case of water

Re : Actually..

No it wouldn't necessarily - the column is being held there by air pressure.

In the case of a siphon with wide tubes AND the long tube not being under the surface of the bottom reservoir THEN air could potentially enter and break the siphon. That could well be related to surface tension.

There area number of mechanistic reasons for a siphon NOT working but the driving force is just gravity

Re : True, but not vapour point

You may have noticed that I never mention zero atmospheric pressure. The vapour pressure is important however - the 'weight' ( actually pressure = weight/area ) of liquid in both legs is resisted by the outside pressure until a point is reached with a hump that's too high (~10m with water at normal atmospheric pressure) when the liquid pressure cannot be balanced by atm. pressure and a vapour bubble forms at the point of lowest pressure - the top of the hump. This is exactly the same as a barometer - if you tried to siphon mercury ( don't suck !) the hump would only work up to ~1m at normal atm. pressure.

As I mention above the system would work with a high-boiling liquid and a low 'hump' at very low atmospheric pressures

Re : Re: shame

All the more reason for Linux - 1 DVD can be loaded onto hundreds or thousands of computers

Re : Shame

If you know enough to upgrade to a newer version of Windows you can upgrade to Linux as or more easily.

Mind 256 MB is not going to get you stunning performance.

Re : 24 years to get to here → #

"its *fairly* easy to make *lots* of copies of a component molecule"

I'm glad you qualified it with 'fairly'

Re : 64-bit

I used to handle data-sets of ~2 million rows every few months - not worth setting-up a data base as the set was always rapidly cut down to a few thousand for further processing by applying a few limits. Of course, Excel was useless for this size, and in any case most work was done on a Linux workstation (dual Xeon). The program of choice was JMP partly due to it's ability to handle huge sets but also to rapidly isolate sub-sets for further analysis.

(The speed of the database that handled the original data was an issue as was the speed of download of the data so it was quicker to download the whole dataset and process it locally . The limits necessary to cut down the dataset had to be generated by intuition and often required a few iterations to get right so again interrogating the slow back-end database wasn't the best approach)

Re : And in a Passat too!

We've got Park Assist in our Touran although the model just came with it - we'd never have paid specifically for it.

Never used it or indeed plan to. The front and aft sensors can be useful for tight situations though.

Re : Hmm, unusable??

FUD pure and extremely simple. I'm sure you spend hours p**sing about though

Never written a driver in my (Linux) life except for my home-built hardware.

Why would I NEED to buy software ??

Re : Dual boot?

"What do old people know about computers" Er, I think they invented them

Re : Water in a vacuum

Separate the thermodynamics from the mechanism

Gravity drives the thermodynamics - the potential energy lost is the product of the mass of liquid moved and the height difference between the reservoirs.

The mechanism requires that the 'hump' over which the liquid has to climb is such that the liquid will not form a vapour bubble at the highest point - this point will depend on the atmospheric pressure. With a high-boiling liquid and a low hump the 'outside' pressure could be quite low. Practically this would require the entire app. to be a partial vaccum chamber

In a normal environment, of course, atmospheric pressure is related to gravity.

Re : How to write a Linux virus in 5 easy steps

1) It's a trojan approach not a virus - no one is claiming Linux is immune to trojans

2) I can't get it to work sensibly -the downloaded program which has to be a script not an executable ( I used one of mine off my webserver which is set world executable ) is saved in tmp but after e-mailing the executable desktop link to self the icon is automatically set not executable and any attempt to click on it gives a warning message and indeed the text of the command.You'd have to click to accept that you trust the program at this point to launch it and set it executable This under KDE/OpenSUSE 11.2

Re : Might not hurt to do a math check

Certainly burning 114g of octane will yield 352 g CO2 and 162 g water but as I mentioned already liquid water is in equilibrium with vapour so outputting 'more' isn't going to make any difference to the average level

Re : Nope

I think electrochemical cells used for this probably use extremely expensive Nafion superacid membranes to separate the anode/cathode compartments. The feedstock, which I'm guessing would be water with something like suphuric acid, and I think would need to be pretty pure. Certainly not raw sea-water as this would generate chlorine gas.

Just an organic chemist so may be way off on this.

By the way the energy efficiency of electrolysis is ~~50-70%

Re: Propane is very similar to methane chemically

That's like saying wood is chemically similar to sugar. What do you put in your coffee.

The trick unfortunately is getting the 3 carbon atoms to join together

Re : Other Greenhouse Gasses?

I think the point about water vapour is that it's broadly in equilibrium with the massive amount of liquid water that's around naturally whereas increasing CO2 from 300 ppm to 450 ppm or whatever is a large change.

(There's certainly a lot around naturally where I live at the moment)

Re : settled?

"True science is never settled" - there may be an elephant of truth in that but it would take something truly amazing to change the laws of thermodynamics or 'get below' absolute zero or not get the exact same amount of energy out of burning a mole of butane or step out of a window without artificial aids and NOT plummet to the ground.

There's always something further to learn but even the totally different gravitational theory in General Relativity still approximates to Newton's gravity for calculation purposes under most everyday circumstances (GPS time corrections being the most recent and widely used exception)

On the subject of climate change raised above I can only say that the simple physics of the sun's heat being increasingly retained by increased carbon dioxide has to be correct. The contention is what happens to that heat - does it lead to a corresponding increase in temperatures?

(I've no great love for Frank Skinner's comedy but as a (retired) scientist there are many more things that offend me )

Re : Why only four digits?

I have a UBS debit card for our Swiss current account that can have a variable number of digits - we use more than 4. I've never tried it in a UK ATM though, but it works in all Swiss chip+pin readers that I've tried.

Re : RE: @Anonymous Coward

Sounds just like a Windows update to me !

Re : @Chemist "GPS satellites don't run in geostationary orbits"

It wouldn't !

WAAS only issues corrections to GPS data - it depends on conventional GPS

@MeRp

"I'd say that is pretty damning to the idea that GPS satellites not running in Geostationary orbits..."

You might say it but you'd be wrong ! GPS satellites are NOT in geostationary orbit - they make 2 orbits a day - this can be seen on many receivers

They have to track all over the globe and be as far apart as possible AFAIK for the best fix. Geostationary satellites are in an equatorial orbit and, er, stationary. If they were stationary the same satellites would always be visible to the receiver which they are not.

The data this dead satellite provides is just augmentation data to improve the accuracy of the real system.

There's even a little animation at http://upload.wikimedia.org/wikipedia/commons/9/9c/ConstellationGPS.gif

@AC

GPS systems can be augmented by many means including terrestrial and satellite sources - the Galaxy satellite was just one such source, however, it is not a primary GPS source and normal GPS receivers don't use augmentation signals.

@AC

GPS satellites do NOT run in geostationary orbits

To quote from YOUR source !

The global coverage for each system is generally achieved by a constellation of 20–30 Medium Earth Orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but use orbit inclinations of >50° and orbital periods of roughly twelve hours (height 20,000 km / 12,500 miles).