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15 August 2008 - 08:52 AMHey folks. I am wondering if I can borrow some of that wonderful brain stuff that is in abundance here
I am going to be building a Lighter Then Air structure for a project I am working on. I need to be able to control the lift generated by the gas, without dumping the gas.
The concept I have come up with is something along the lines of the following.
The idea is that the inner bladder can contain a cheap lift gas like Hydrogen. the while the outer envelope is filled with a cheap inert gas like Nitrogen (is there a more appropriate gas I could use here?).
In full lift, the outer envelope is completely unpressurised, allowing the inner bladder to expand to it's full size.
To decrease lift, increase pressure of the inert gas to collapse inner bladder.
No loss of lift gas.
Outer envelope cheaper to manufacture as it does not have to contain small molecule gases. (Laminated rip stop nylon should suffice?)
Inner bladder is Aluminized Polyester ("Mylar" rebranded name). It is cheap, and commonly available.
Inner bladder needs minimal structural strength as it is not pressurized. Bladder is larger then the envelope so even if outside pressure drops, the ripstop provides the mechanical strength, not the Mylar.
Modular. Add as many as you require.
The inert gas in the envelope should help offset concerns about the flammability of the hydrogen.
Lastly, I was hoping that an envelope containing the inert gas under pressure would help to contain or reduce losses of the lift gas. Modern containment systems for Hydrogen generally have a 5% loss per year, and I wanted to reduce that to 1% and the most.
Would a system like this work?
How much pressure would be needed to cut the lift in half?
Is there a better system out there?
05 November 2007 - 12:05 PMIf I had a 1,000 meter tall tube that was perfectly isolated thermally, and I proceeded to fill that tube with gaseous ammonia at -28 degrees C.
Given a dry adiabatic lapse rate of 10 degrees C per 1000 meters and boiling point of Ammonia at -33 degrees C.
Would the Ammonia condense on the tube surface on its journey up the tube?
If it did, I could collect a constant stream of condensed ammonia from a thermally isolated process, correct?
This seems wrong on so many levels , so I would like to know what I am missing. (I suspect something to do with the vapor pressure)
29 May 2006 - 06:13 AMI am not even certain how to phrase the question as I do not have a physics background, but here goes anyway.
I have been struggling for a very long time to understand the wave/particle properties of matter without referring to that bad thing called mathematics.
As any physicist knows, without the math, true understanding is unlikely, but I am a very visual person and need to see things in my head to truly grasp them.
To start with. The electron in "Orbit" around an nucleus actually exists at every point in it's possible orbit. If we were to measure and locate the electron, it would be found at some point in it's orbit, and the likelihood of it being in one particular place would be based on probabilities.
Is it possible that this represents the multi-verse in a microcosm? That all of the possible multi-verses exist at that one conjunction, and only when we force the outcome (by measuring or observing) do we move along a specific "Path" while all other multi-verses (created from that particular junction) go off in their own?
If this is the way things are, then all "Wave" properties would seem to come from the congruence of the multi-verses, and all particles would represent the choices (chances) our particular verse has made to get to where we are.
If this were true, then I could finally imagine a solution to the double slit experiment that has so bothered me. Until measured (and forcing our verse along a particular path) the traveling electron (or photon) travels all possible paths of all the multi-verses, creating a wave like effect. These possible paths, since they all exist at one time, can even interfere/interact with each other. If the electron/photon is measured at the slit before it travels through, it can no longer interact with other possibilities of itself, and can not create an interference pattern on the other side. If it is measured as it strikes the far wall only, then it will have had the opportunity to interact with it's other possible outcomes, and an interference pattern is created.
While it is nice that this allows me to visualize a tidy solution to the double slit experiment without resorting to math, is the concept way out to lunch?
25 May 2006 - 08:50 AMScientists at Duke and Rutgers universities have developed a mathematical framework they say will enable astronomers to test a new five-dimensional theory of gravity that competes with Einstein's General Theory of Relativity.
Charles R. Keeton of Rutgers and Arlie O. Petters of Duke base their work on a recent theory called the type II Randall-Sundrum braneworld gravity model. The theory holds that the visible universe is a membrane (hence "braneworld") embedded within a larger universe, much like a strand of filmy seaweed floating in the ocean.
The "braneworld universe" has five dimensions -- four spatial dimensions plus time -- compared with the four dimensions -- three spatial, plus time -- laid out in the General Theory of Relativity.
The framework Keeton and Petters developed predicts certain cosmological effects that, if observed, should help scientists validate the braneworld theory. The observations, they said, should be possible with satellites scheduled to launch in the next few years.
If the braneworld theory proves to be true, "this would upset the applecart," Petters said. "It would confirm that there is a fourth dimension to space, which would create a philosophical shift in our understanding of the natural world."
The scientists' findings appeared May 24, 2006, in the online edition of the journal Physical Review D. Keeton is an astronomy and physics professor at Rutgers, and Petters is a mathematics and physics professor at Duke. Their research is funded by the National Science Foundation.
The Randall-Sundrum braneworld model -- named for its originators, physicists Lisa Randall of Harvard University and Raman Sundrum of Johns Hopkins University -- provides a mathematical description of how gravity shapes the universe that differs from the description offered by the General Theory of Relativity.
Keeton and Petters focused on one particular gravitational consequence of the braneworld theory that distinguishes it from Einstein's theory.
The braneworld theory predicts that relatively small "black holes" created in the early universe have survived to the present. The black holes, with mass similar to a tiny asteroid, would be part of the "dark matter" in the universe. As the name suggests, dark matter does not emit or reflect light, but does exert a gravitational force.
The General Theory of Relativity, on the other hand, predicts that such primordial black holes no longer exist, as they would have evaporated by now.
"When we estimated how far braneworld black holes might be from Earth, we were surprised to find that the nearest ones would lie well inside Pluto's orbit," Keeton said.
Petters added, "If braneworld black holes form even 1 percent of the dark matter in our part of the galaxy -- a cautious assumption -- there should be several thousand braneworld black holes in our solar system."
But do braneworld black holes really exist -- and therefore stand as evidence for the 5-D braneworld theory?
The scientists showed that it should be possible to answer this question by observing the effects that braneworld black holes would exert on electromagnetic radiation traveling to Earth from other galaxies. Any such radiation passing near a black hole will be acted upon by the object's tremendous gravitational forces -- an effect called "gravitational lensing."
"A good place to look for gravitational lensing by braneworld black holes is in bursts of gamma rays coming to Earth," Keeton said. These gamma-ray bursts are thought to be produced by enormous explosions throughout the universe. Such bursts from outer space were discovered inadvertently by the U.S. Air Force in the 1960s.
Keeton and Petters calculated that braneworld black holes would impede the gamma rays in the same way a rock in a pond obstructs passing ripples. The rock produces an "interference pattern" in its wake in which some ripple peaks are higher, some troughs are deeper, and some peaks and troughs cancel each other out. The interference pattern bears the signature of the characteristics of both the rock and the water.
Similarly, a braneworld black hole would produce an interference pattern in a passing burst of gamma rays as they travel to Earth, said Keeton and Petters. The scientists predicted the resulting bright and dark "fringes" in the interference pattern, which they said provides a means of inferring characteristics of braneworld black holes and, in turn, of space and time.
"We discovered that the signature of a fourth dimension of space appears in the interference patterns," Petters said. "This extra spatial dimension creates a contraction between the fringes compared to what you'd get in General Relativity."
Petters and Keeton said it should be possible to measure the predicted gamma-ray fringe patterns using the Gamma-ray Large Area Space Telescope, which is scheduled to be launched on a spacecraft in August 2007. The telescope is a joint effort between NASA, the U.S. Department of Energy, and institutions in France, Germany, Japan, Italy and Sweden.
The scientists said their prediction would apply to all braneworld black holes, whether in our solar system or beyond.
"If the braneworld theory is correct," they said, "there should be many, many more braneworld black holes throughout the universe, each carrying the signature of a fourth dimension of space."
Source: Duke University
18 May 2006 - 09:52 AMBy Patricia Reaney
LONDON (Reuters) - Scientists have reached a landmark point in one of the world's most important scientific projects by sequencing the last chromosome in the Human Genome, the so-called "book of life".
Chromosome 1 contains nearly twice as many genes as the average chromosome and makes up eight percent of the human genetic code.
It is packed with 3,141 genes and linked to 350 illnesses including cancer, Alzheimer's and Parkinson's disease.
"This achievement effectively closes the book on an important volume of the Human Genome Project," said Dr Simon Gregory who headed the sequencing project at the Sanger Institute in England.
The project was started in 1990 to identify the genes and DNA sequences that provide a blueprint for human beings.
Chromosome 1 is the biggest and contains, per chromosome, the greatest number of genes.
"Therefore it is the region of the genome to which the greatest number of diseases have been localized," added Gregory, from Duke University in the United States.
The sequence of chromosome 1, which is published online by the journal Nature, took a team of 150 British and American scientists 10 years to complete.
Researchers around the world will be able to mine the data to improve diagnostics and treatments for cancers, autism, mental disorders and other illnesses.
Chromosomes, which are found in the nucleus of a cell, are thread-like structures that contain genes which determine the characteristics of an individual.
The human genome has an estimated 20,000 to 25,000 genes. The sequencing of chromosome 1 has led to the identification of more than 1,000 new genes.
"We are moving into the next phase which will be working out what the genes do and how they interact," Gregory told Reuters.
The genetic map of chromosome 1 has already been used to identify a gene for a common form of cleft lip and palate. It will also improve understanding of what processes lead to genetic diversity in populations, according to Gregory.
Each chromosome is made up of a molecule of DNA in the shape of a double helix which is composed of four chemical bases represented by the letters A (adenine), T (thymine), G (guanine) and C (cytosine). The arrangement, or sequence, of the letters determines the cell's genetic code.
The scientists also identified 4,500 new SNPs -- single nucleotide polymorphisms -- which are the variations in human DNA that make people unique.
SNPs contain clues about why some people are susceptible to diseases like cancer or malaria, the best way to diagnose and treat them and how they will respond to drugs.