Apple offers no definition of the nonlinearity - or loosely speaking, gamma - that is intrinsic in QuickDraw. But the combination of a default QuickDraw lookup table and a standard monitor causes luminance to represent the 1.8-power of the R, G, and B values presented to QuickDraw. It is wrongly believed that Macintosh computers use monitors whose transfer function is different from the rest of the industry. The unconventional QuickDraw handling of nonlinearity is the root of this misconception.

The luminance generated by a physical device is generally not a linear function of the applied signal. A conventional CRT has a power-law response to voltage: luminance produced at the face of the display is approximately proportional to the applied voltage raised to the 2.5 power. The numerical value of the exponent of this power function is colloquially known as gamma. This nonlinearity must be compensated in order to achieve correct reproduction of luminance.

The RadWare matrix formats are very simple, just direct-access, unformatted integers, one record per row of 4096 channels. These integers can be either 2 Bytes per channel (for the .mat format) or 4 Bytes per channel (for the .spn / .m4b format). A standard matrix (.mat) file is 4096*4096*2 bytes, with one unformatted direct-access record of 8192 bytes per row. Subroutine rmat in src/libsutil/util.c reads such a file, but it's very simple to write.

In a video system, luminance of each of the linear-light red, green, and blue (tristimulus) components is transformed to a nonlinear video signal by gamma correction, which is universally done at the camera. The Rec. 709 transfer function takes linear-light tristimulus value (here L) to a nonlinear component (here E'), for example, voltage in a video system: The linear segment near black minimizes the effect of sensor noise in practical cameras and scanners. Here is a graph of the Rec.

Gamma ray bursts (GRBs for short) are intense and short (approximately 0.1-100 seconds long) bursts of gamma-ray radiation that occur all over the sky approximately once per day at very large distances from Earth. Gamma rays are very energetic photons (E>10^5 eV), which represent the most extreme portion of the electromagnetic spectrum (ranging from radio waves at the lowest energies through visible optical light at higher energies, to gamma rays at the highest energies).

Yes. We'd like to thank all our loyal Mac users for their patience above and beyond the call, and are overjoyed to announce that the game was released for the Mac on 15th March this year. (You can even buy the game right here on the Starship Titanic Online Shop. To reward your long wait, there's a special offer only with the Mac version: a FREE Official Strategy Guide Book). During the development of the Mac version, we took quite a bit of flak for the delay. Here's Douglas's response.

The naming system for gamma ray bursts is very simple: "GRB yymmdd". For exmaple, a gamma ray burst which occured on July 4, 1999 is called GRB 990704. If there is more than one gamma ray burst on the same day, the letter a, b, c, etc. are added to the name (for example, the second gamma ray burst on July 4, 1999 is called GRB 990704b).

Up until the 1990s and the launch of the Compton Gamma Ray Observatory (CGRO; see next question) there was a heated debate in the astronomical community about the source of, and distance to gamma ray bursts. One group claimed that gamma ray bursts occur in our own galaxy (the Milky Way), while others claimed that they occur in very distant galaxies.

Based on almost 30 years of observing gamma ray bursts, we now think that on average there is one gamma ray burst per day somewhere in the Universe. However, recent developments in the study of gamma ray bursts indicates that the true number of these events may be 500 times larger. This means that we only see one out of every 500 gamma ray bursts.

Gamma ray bursts are detected by satellites orbiting the Earth and travelling through the Solar system. They can only be detected from space because the Earth's atmosphere absorbs gamma rays and therefore we cannot observe them from the ground. The first gamma ray bursts were detected by the Vela satellites, which were launched in the 1960s to ensure compliance with the Nuclear Test Ban Treaty.

The study of several thousand bursts has shown that there are two main classes of gamma ray bursts: those shorter than 2 seconds, and those longer than 2 seconds. In addition, it was found that the short bursts release more of their energy in very energetic gamma rays relative to the longer bursts. Therefore the terminology that is used to describe the two classes is "short and hard" and "long and soft". All of all bursts that have been studied in detail so far are "long and soft".

In principal every gamma ray burst is followed by an afterglow. However, we do not always see these afterglows for several reasons. First, prior to 1997 and the launch of the BeppoSAX satellite (see question 15) it was impossible to find the position of gamma ray burst accurately enough to detect the afterglow. Second, even after 1997 the afterglows from some gamma ray bursts are too faint to detect from Earth.

There are many popular level and scientific articles about gamma ray bursts. For popular level discussion of gamma ray bursts try looking for articles in Scientific American. Scientific articles can be found on the astro-ph preprint server and ADS.

The Gamma Knife Perfexion? precisely focuses 192 beams of gamma radiation on a specific target area of the brain, with each beam originating from a slightly different point. Highly sophisticated computer software is used to determine the size, location and shape of the area to be treated. Only at the point where all 192 beams cross is enough radiation delivered to affect the diseased tissue, while sparing surrounding tissue.

This noninvasive technology treats patients with abnormalities that are located within the brain or that are too close to delicate structures and blood vessels (though it is most effective on targets less than four centimeters in size). Almost a third of all the patients treated with the Gamma Knife since 1968 have sought relief from blood vessel problems (i.e. AVMs). Nearly two-thirds were treated for brain tumors, including cancer, glial tumors and rarer types of tumors.

The individual beams of gamma radiation are not strong enough to damage any tissue as they travel through the skull to the treatment site. At the site, the beams join together pecisely to act in the same way a surgical "knife" would to treat the abnormality.

Both Macintosh and Windows versions of the Helper are available. You can also retrieve customer files with a Mac. Back to Top

It is now thought that the "long and soft" gamma ray burts come from the collapse of massive stars, while the "short and hard" bursts come from the merger of binary systems. This result comes from computer simulations which show that the merger of neutron star or black hole binaries occurs much faster than the collapse of the iron core of a massive star.

The distribution of several thousand bursts which were detected primarily by the Burst And Transient Source Experiment (BATSE) on CGRO is uniform across the sky. This means that there is no prefered direction from which we detect more gamma ray bursts. This distribution was the first indication that gamma ray bursts occur in bery distant galaxies and not in our own galaxy.

Gamma ray bursts release extremely large amount of energy - approximately 10^52 ergs (or 10^45 joules), with the most extreme bursts releasing up to 10^54 ergs. This is the equivalent of turning a star like the Sun into pure energy (using Einstein's famous equation E=mc^2).

In the first years of gamma ray burst research there were more proposed sources (or progenitors) for gamma ray bursts than the actual number of gamma ray bursts detected! However, ever since it was determined that gamma ray bursts occur at very large distances (and therefore release huge amounts of energy) the list of proposed progenitors shrunk into two main classes: very massive stars, and binary (2 star) systems composed of neutron stars or black holes.

The first step in the detection of afterglows is always the detection of a new gamma ray burst by a satellite such as the IPN, BeppoSAX, and HETE-II (see qeustion 4). The information from the satellite is quickly sent down to Earth and is distributed to gamma ray burst astronomers by email, pagers, and cellular phones. When astronomers get the information, they observe the part of the sky where the gamma ray burst occured, and look for an object which fades quickly.

The twinkling of radio waves from afterglows (see question 23) has shown that afterglows start very small (about the size of the Earth's orbit around the Sun), and then expand and become larger than the Solar system.

It is precise. Its effects on surrounding brain and other critical neural and vascular structures are minimized. It is safe - the design of the Department of Neurosurgery's Gamma Knife unit meets the rigorous standards for safety and efficacy set by the U.S. Nuclear Regulatory commission and patients do not face the risks associated with open-skull procedures or general anesthesia. The Gamma Knife Perfexion is also highly effective - its success rate is unprecedented.

Some servers have no facility for this; you may be able to adjust your monitor to correct somewhat. Later versions of XFree86 allow these server options: gamma f set gamma value (0.1 < f < 10.0) Default: 1.0 -rgamma f set gamma value for red phase -ggamma f set gamma value for green phase -bgamma f set gamma value for blue phase

High Dynamic Range images are scene-referred. This means that an HDR image stores the values of light as captured by the camera. Unlike output-referred jpeg files produced by cameras, HDR images are not pre-processed for the purpose of a pleasant display on monitors. The values of an HDR image remain proportional to light, i.e. they are linear values. So, the gamma for an HDR image would be just 1, which is the same as to say that they do not have a gamma.

outlined above, gamma correction in video effectively codes into a perceptually uniform domain. In video, a 0.45-power function is applied at the camera, as shown in the top row of this diagram: Synthetic computer graphics calculates the interaction of light and objects. These interactions are in the physical domain, and must be calculated in linear-light values.

On the industrial model, there is a set of Advanced picture settings. Go to the Picture menu, turn Advanced on, and then hit the down-arrow. In the subsequent menu you can adjust quite a few parameters, including select from a few gamma settings.