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Interesting Items...

Here is the sting cell story, as the link i gave seems flaky. The item is spoilt somewhat by the qualifier up to.

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Nematocysts (stinging cells) of Portuguese Man o' War (Physalia physalis, 100x), coastal Charleston, SC.
Credit: Image courtesy of Southeast Regional Taxonomic Center​


By using an electronic ultra-high-speed camera, researchers have characterized the explosive discharge of stinging jellyfish nematocytes and show that this event represents one of the fastest cellular processes in nature. The research is reported by Thomas Holstein of the University of Heidelberg and his colleagues in Current Biology.

Nematocysts (also known as cnidocysts) of jellyfish and other cnidarians are giant exocytotic organelles of the stinging cells used for prey capture and defense. These miniature cellular weapons contain a cocktail of hemolytic and neurotoxic poisons, making some cnidarians the most venomous animals known. Injection of the toxins requires an effective release mechanism that breaks the physical barrier of the prey's outer-surface tissue. It was known already that a high pressure (15 MPa) drives nematocyst discharge, and that stylets can penetrate even thick crustacean shells. However, neither the kinetics nor the forces involved were known, simply because discharge is so fast that it had not been previously resolved by conventional high-speed imaging.

To clarify these issues, the researchers studied nematocyst discharge with an electronic framing-streak camera at a framing rate of 1,430,000 frames per second. They show discharge kinetics of nematocysts in Hydra to be as short as 700 nanoseconds, creating an acceleration of up to 5,410,000 g. The researchers calculate that although the accelerated mass is very small (~1 nanogram), a pressure generated at the site of impact is more than 7 GPa, which is in the range of that generated by some bullets, and sufficient to penetrate the cuticle of crustacean prey. The researchers propose that the high speed of discharge is caused by the release of energy stored in the stretched configuration of the collagen-polymer of the nematocyst capsule wall. This ingenious solution allows the cellular process of vesicle exocytosis to release kinetic energy in the nanosecond range by a powerful molecular spring mechanism.
 
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Re. Braking. (I'm late to the party as I've been away for a week)
I drove BMW i3 recently and by design the regenerative braking is at the 'top' of the throttle pedal, not on the brake. It was a little odd at first but it does mean you can drive the car without having to change pedals except to actually kill the last couple of mph. It was a system I'd be quite happy with.
Leaving the car in gear with your foot on the brake while waiting is going to become more common, certainly with autos. We now have auto stop/start on both cars as standard because emission regs are pushing it that way and it works by stopping the engine when stationary with your foot on the brake. When you lift off the brake the engine starts and the car starts to move as normal. If you put it in neutral (actually anywhere other than D) the engine restarts. I'm actually trying to retrain SWMBO to not keep putting it in neutral and applying the handbrake at every traffic light - partly for the environment, partly as it's wearing out the selector and handbrake linkages, and partly because when the lights change she's never ready to go!
 
Another feature on some automatics is the "hold" feature. When stopping at traffic lights, etc. Pressing the brake slightly when stopped will hold the brakes on, the driver can then lift foot of the peddle and the brakes stay on. They are released by either pushing the brake pedal again or pressing the accelerator. Unfortunately for the guy behind, the brake lights stay on. Sorry BH that's becoming an unfortunate fact of life now.
I'm sure the manufacturers would listen, in this case Mercedes, if you complained


Sent from my iPad using Tapatalk
 
The hold feature in mine thankfully doesn't keep the brake lights on; it's a manual though
 
Stop start: naff idea, best switched off, as it saves so little fuel but greatly damages the starter motor and battery. Should be compulsory for dirty diesels, though

Hill start: hit and miss, sometimes it works, sometimes not. On an auto it is dead easy to jump from foot brake to accelerator anyway.

Brake lights: get over it, it isn't the end of the world.
 
Mike0001 said:
Stop start: naff idea, best switched off, as it saves so little fuel but greatly damages the starter motor and battery. Should be compulsory for dirty diesels, though

Hill start: hit and miss, sometimes it works, sometimes not. On an auto it is dead easy to jump from foot brake to accelerator anyway.

Brake lights: get over it, it isn't the end of the world.
Click to expand...

Unfortunately the stop/start defaults to on each time you start the car, so it requires remembering. I do tend to switch it off if I remember as it's a pain at roundabouts when you often stop for just a second or few before jumping into a passing space - doing that from a dead engine is ... unsettling.

If I'm doing a hill start in an auto I use my left foot to hold the brake pedal down then move my right to the throttle. Simples.

One other thing on the BMW i3 is that it lights the brake lamps when using significant regenerative braking - ie, more deceleration than you'd get from an ice car when lifting off the throttle.
 
MikeSh said:
If I'm doing a hill start in an auto I use my left foot to hold the brake pedal down then move my right to the throttle. Simples.
Click to expand...
The approved technique for driving automatics is to use the left foot on the brake anyway. This is especially the case with torque-converter autos, where the drive is never really disengaged and any inclination to forward movement needs moderating with the brake.
 
Black Hole said:
The approved technique for driving automatics is to use the left foot on the brake anyway. This is especially the case with torque-converter autos, where the drive is never really disengaged and any inclination to forward movement needs moderating with the brake.
Click to expand...
Approved? I hope not. If you never drive stick-shift that's fine, but if you drive both it can get interesting. I know some people can do it but I tried it once and never have again. (You just need to think about how your left foot is 'programmed'.)
It could actually be dangerous too. My wife (auto only licence) started to teach her son to drive on her car using left foot to brake. He had trouble stopping until they realised that her instruction to brake didn't specifically mention backing off the accelerator as well.

As to torque convertors the only time they creep is at low/no speed with the engine idling, so you just use your right foot to 'moderate' the motion. The only time I've had to use significant force to hold an auto was one that had a poorly set up engine with a ferocious amount of fast idle when cold - it was scary to drive until the choke backed off.
 
MikeSh said:
Approved? I hope not. If you never drive stick-shift that's fine, but if you drive both it can get interesting. I know some people can do it but I tried it once and never have again. (You just need to think about how your left foot is 'programmed'.)
Click to expand...
I have no problem with my left-foot being programmed to operate the clutch when driving a manual(*), to do nothing when driving an automatic or to operate the brake when karting.

(*) I assume that is what you meant by stick-shift. I didn't know you were American.
 
I must confess to doing a stoppy in an automatic work van after a few days driving a manual instead by rapidly depressing what I thought was the clutch pedal. :eek:

So I guess part of the programming is conditioned by the context of sitting in my manual car or an automatic van or a kart.
 
Mike0001 said:
Approved by whom?
Click to expand...
Are you not aware of standard training for automatic transmission vehicles?

MikeSh said:
Approved? I hope not. If you never drive stick-shift that's fine, but if you drive both it can get interesting. I know some people can do it but I tried it once and never have again. (You just need to think about how your left foot is 'programmed'.)
Click to expand...
Nonetheless it is - I didn't say everybody does it that way, but even if you don't it is as well to know about it. I rarely drive an automatic, and when I do the only reprogramming I try to cope with is not to dip the clutch when braking (which tends to result in an emergency stop).

MikeSh said:
It could actually be dangerous too. My wife (auto only licence) started to teach her son to drive on her car using left foot to brake. He had trouble stopping until they realised that her instruction to brake didn't specifically mention backing off the accelerator as well.
Click to expand...
That is the fault of the instructor not the student.

MikeSh said:
As to torque convertors the only time they creep is at low/no speed with the engine idling, so you just use your right foot to 'moderate' the motion. The only time I've had to use significant force to hold an auto was one that had a poorly set up engine with a ferocious amount of fast idle when cold - it was scary to drive until the choke backed off.
Click to expand...
There have been many accidents caused by an automatic not being under proper control, regardless of whether it was perfectly adjusted, because of the lack of correct training.
 
Not to mention thinking your foot is on the brake when it's actually on the accelerator. In a proper car, it doesn't usually lead to massive damage because the left foot is on the clutch limiting the amount of energy transmitted from engine to wheels. In a toy automatic car, the harder the person pushes the 'brake pedal' in their vain attempt to stop, the more damage that is done to the car and whatever eventually stops it.
 
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