Group items tagged

Solution to DeathTouch Problem......

Original implementation Integrating 2D Mouse Emulation with 3D Manipulation for Visualizations on a Multi-Touch Table -- project built on top of VisLink, check video !!

Researchers developed a new imaging method that can measure cell mass using two beams of light, offering new insight into the much-debated problem of whether cells grow at a constant rate or exponentially. They found that mammalian cells show clear exponential growth only during the G2 phase of the cell cycle. This information has great implications not only for basic biology, but also for diagnostics, drug development and tissue engineering.

nice article ... though the colouring used seems a lit awkward to me ...

I know, it is not a new concept, but apparently the guys from BMW put some money into it to make is series-proof. Could we - in principle - put something like that onto a spacecraft to solve thermal and energy problems at the same time?

That's really amazing. The problem is: driving drunk, too fast or without stopping at red traffic lights are the first causes of traffic fatalities, and finding a solution is really important... But those guys want to read our minds to see if there are

ZetaGrid is a platform independent grid system that uses idle CPU cycles from participating computers. Problem: The ZetaGrid activities must come to a final end! Now all services are down and this domain will be closed soon. The official last update note

This is an article on the problems of defining a scientific term. Or better how people can argue when trying to agree on a definition. Rather funny than important

So far only in german: A guy has on 10% of the usual brain mass. But lives without big problems. The study should be published in LANCET.

nice application for mac users to use Bibdesk integrated into MS word ... still have some problems with the template file but hope to solve this soon ....

Hmm it seems that we should really push this project forward...

luca please check it out ... anything new we did not know? // TSe: it is about the old problem of the free will - when I talked about that you all killed me.

5 espressos a day is good, 7+ may cause addiction, with 170 on a single day you might have a problem...

The latest from Schmidt / Lipson / Eureqa. A significant improvement over their previous work is that now "The algorithm selects between multiple candidate models by designing experiments to make their predictions disagree."

Good to solve the Landing problem!!!! No skew due to perspective and gimballed by definition

Very very nice idea! Unfortunately samples show they still have quite some work to do on the image processing side... which is interesting because there are very good open-source solutions for stitching.

Theoretized 80 years ago was Breit-Wheeler pair production in which two photons result in an electron-positron pair (via a virtual electron). It is a relatively simple Feynmann diagram, but the problem is/was how to produce in practice a high energy photon-photon collider... The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light. The next stage of the experiment involves a tiny gold can called a hohlraum (German for 'empty room'). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars. They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can. Now this is a good experiment... :)

True, but isnt it E2=(pc)^2 + (m0c^2)^2 such that for photons E\propto{pc} and for mass E\propto{mc^2}. I agree it will take a lot of energy, but this assumes that that wont be the problem at least. The question therefore is whether the mass flow of the photon rocket (fuel consumed to create photons, eg fission/fusion) is higher/lower than the mass flow for e-p creation. You are probably right that the low e-p cross-section will favour direct use of photons to create low thrust for long periods of time, but with significant power available the ISP might be higher for e-p pair creation.

In essence the equation tells you that for photons with zero rest mass m0 all the energy will be converted to momentum of the particles. If you want to accelerate e-p then you first spend part of the energy on creating them (~511 keV each) and you can only use the remaining energy to accelerate them. In this case the equation gives you a lower particle momentum which leads to lower thrust (even when assuming 100% acceleration efficiency). ISP is a tricky concept in this case because there are different definitions which clash in the relativistic context (due to the concept of mass flow). R. Tinder gets to a I_SP = c (speed of light) for a photon rocket (using the relativistic mass of the photons) which is the maximum possible relativistic I_SP: http://goo.gl/Zz5gyC .

he new SR-72 will use a turbine-based combined cycle (TBCC) that will employ the turbine engine at lower speeds, and use a scramjet at higher speeds. A scramjet engine is designed to operate at hypersonic velocities by compressing the air through a carefully designed inlet, but needs to be traveling supersonic before it is practical to begin with. So far research projects from NASA, the Air Force and other Pentagon entities have not been able to solve the problem of transitioning from the subsonic flight regime, through hypersonic flight with a single aircraft. Same problem as Reaction Engines is trying to solve, so I am not sure whether they actually cracked it. In any case, nice pictures. Not sure why the exhaust color is purple in color. Its not running on Argon I believe.

Weird article. Intermediate thruster stage (Ramjet) is missing. Scramjet has supersonic combustion and a normal turbine delivers subsonic flows. Even with afterburner - the Scramjet inlet would decelerate the flow down to subsonic velocity with "normal" subsonic combustion. The only thing I can imagine is that the Scramjet stage is bi-functional and covers both, subsonic and supersonic combustion. But the article doesn't say anything about it.

enjoy ....

ok, but if we first have to define consciousness before starting dealing with any physics, isn't a large pause looming ahead, proposed by the author?

I kind of subscribe to Tononi's information theory approach to consciousness: http://www.biolbull.org/content/215/3/216.full And of course the watered down wikipedia version for whoever lacks the patience to read the whole treatise http://en.wikipedia.org/wiki/Integrated_information_theory

An exhaustive overview of all possible advanced rocket concepts, eg.. "As an example, consider a photon rocket with its launching mass, say, 1000 ton moving with a constant acceleration a =0.1 g=0.98 m/s2. The flux of photons with E γ=0.5 MeV needed to produce this acceleration is ~1027/s, which corresponds to the efflux power of 1014 W and the rate of annihilation events N'a~5×1026 s−1 [47]. This annihilation rate in ambiplasma l -l ann corresponds to the value of current ~108 A and linear density N ~2×1018 m−1 thus any hope for non-relativistic relative velocity of electrons and positrons in ambiplasma is groundless." And also, even if it would work, then one of the major issues is going to be heat dispersal: "For example, if the temperature of radiator is chosen T=1500 K, the emitting area should be not less than 1000 m2 for Pb=1 GW, not less than 1 km2 for Pb=1 TW, and ~100 km2 for Pb=100 TW, assuming ε=0.5 and δ=0.2. Lower temperature would require even larger radiator area to maintain the outer temperature of the engine section stable for a given thermal power of the reactor."

The problem is not achieving a high energy density, that we can already do with nuclear fission, the question however is how to confine or harness this power with relatively high efficiency, low waste heat and at not too crazy specific mass. I see magnetic confinement as a possibility, yet still decades away and also an all-or-nothing method as we cannot easily scale this up from a test experiment to a full-scale system. It might be possible to extract power from such a plasma, but definitely well below breakeven so an additional power supply is needed. The fission fragments circumvent these issues by a more brute force approach, thereby wasting a lot of energy for sure but at the end probably providing more ISP and thrust.

Sure. However, the annihilation based photon rocket concept unifies almost all relevant drawbacks if we speak about solar system scales, making itself obsolete...it is just an academic testcase.

This paper, answers a long-standing open problem in the programming languages community: is it possible to smear paint on the wall without creating valid Perl?

Do you have problems remembering things? Maybe you should switch your font?