A gamma ray, or gamma radiation, is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their strong penetration of matter. Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts to 8 megaelectronvolts, corresponding to the typical energy levels in nuclei with reasonably long lifetimes; the energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy. Very-high-energy gamma rays in the 100–1000 teraelectronvolt range have been observed from sources such as the Cygnus X-3 microquasar. Natural sources of gamma rays originating on Earth are as a result of radioactive decay and secondary radiation from atmospheric interactions with cosmic ray particles.
However, there are other rare natural sources, such as terrestrial gamma-ray flashes, which produce gamma rays from electron action upon the nucleus. Notable artificial sources of gamma rays include fission, such as that which occurs in nuclear reactors, high energy physics experiments, such as neutral pion decay and nuclear fusion. Gamma rays and X-rays are both electromagnetic radiation, since they overlap in the electromagnetic spectrum, the terminology varies between scientific disciplines. In some fields of physics, they are distinguished by their origin: Gamma rays are created by nuclear decay, while in the case of X-rays, the origin is outside the nucleus. In astrophysics, gamma rays are conventionally defined as having photon energies above 100 keV and are the subject of gamma ray astronomy, while radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy; this convention stems from the early man-made X-rays, which had energies only up to 100 keV, whereas many gamma rays could go to higher energies.
A large fraction of astronomical gamma rays are screened by Earth's atmosphere. Gamma rays are thus biologically hazardous. Due to their high penetration power, they can damage internal organs. Unlike alpha and beta rays, they pass through the body and thus pose a formidable radiation protection challenge, requiring shielding made from dense materials such as lead or concrete; the first gamma ray source to be discovered was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Villard knew that his described radiation was more powerful than described types of rays from radium, which included beta rays, first noted as "radioactivity" by Henri Becquerel in 1896, alpha rays, discovered as a less penetrating form of radiation by Rutherford, in 1899. However, Villard did not consider naming them as a different fundamental type.
In 1903, Villard's radiation was recognized as being of a type fundamentally different from named rays by Ernest Rutherford, who named Villard's rays "gamma rays" by analogy with the beta and alpha rays that Rutherford had differentiated in 1899. The "rays" emitted by radioactive elements were named in order of their power to penetrate various materials, using the first three letters of the Greek alphabet: alpha rays as the least penetrating, followed by beta rays, followed by gamma rays as the most penetrating. Rutherford noted that gamma rays were not deflected by a magnetic field, another property making them unlike alpha and beta rays. Gamma rays were first thought to be particles like alpha and beta rays. Rutherford believed that they might be fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, proving that they were electromagnetic radiation. Rutherford and his co-worker Edward Andrade measured the wavelengths of gamma rays from radium, found that they were similar to X-rays, but with shorter wavelengths and higher frequency.
This was recognized as giving them more energy per photon, as soon as the latter term became accepted. A gamma decay was understood to emit a gamma photon. Natural sources of gamma rays on Earth include gamma decay from occurring radioisotopes such as potassium-40, as a secondary radiation from various atmospheric interactions with cosmic ray particles; some rare terrestrial natural sources that produce gamma rays that are not of a nuclear origin, are lightning strikes and terrestrial gamma-ray flashes, which produce high energy emissions from natural high-energy voltages. Gamma rays are produced by a number of astronomical processes in which high-energy electrons are produced; such electrons produce secondary gamma rays by the mechanisms of bremsstrahlung, inverse Compton scattering and synchrotron radiation. A large fraction of such astronomical gamma rays are screened by Earth's atmosphere. Notable artificial sources of gamma rays include fission, such as occurs in nuclear reactors, as well as high energy physics experiments, such as neutral pion decay and nuclear fusion.
A sample of gamma ray-emitting material
In molecular biology, the protein family Dispanin is another name for Interferon-induced transmembrane protein. This refers to a family of protein domains which have a specific formation, or in other words, topology containing two alpha helices in within the cell membrane which are called two transmembrane proteins; this includes proteins such as CD225. The function of this protein family is to inhibit cell invasion of many harmful, pathogenic viruses, such as HIV. Henceforth, they are being intensively studied in the hope of drug discovery, they mediate the immune response by interferons. Dispanins have a wide range of functions within the organism, it has a role to play in oncogenesis and germ cell development ( as well as cell adhesion and cell signalling. In particular, IFITMs prevent HIV infection by preventing the virus from entering the host cell, it does this by S-palmitoylation, a process where fatty acids are added to an amino acid named cysteine. The process is of huge interest in research.
Through studying Dispanin, it is hoped that its antiviral properties can be exploited, distributed in the form of medicines and vaccines. Additionally, a type of dispanin, IFITM5, is expressed in cells; this is due to the important role dispanins play in strengthening the bone by bone mineralization. This protein family has two transmembrane helices; the precise crystal structure remains to be elucidated. The sequences across a vast array of organisms, from bacteria to high level eukaryotes all contain the similar sequence motifs; this motif has been shown to undergo post-translational modification through S-palmitoylation. This is important since it increases hydrophobicity, increases its anti-viral properties. Dispanins in eukaryotes and bacteria have high sequence similarities and share several conserved sequence motifs indication a common evolutionary ancestor. There are a number of human genes which encode for Dispanin proteins, they are as listed below: IFITM: IFITM1, IFITM2, IFITM3, IFITM4 PRRT2 AC023157 AL160276 AC068580 DSPC2 TMEM233 TMEM90A TMEM90B TMEM91 TUSC5
"Lilly, Do You Want to Know a Secret?" is the pilot episode of the Disney Channel sitcom series Hannah Montana. It was written by Gary Dontzig, Steven Peterman, Michael Poryes, it aired on March 24, 2006. The episode title is a reference to The Beatles song "Do You Want to Know a Secret?". The episode starts with teen pop sensation Hannah Montana —, Miley Stewart — and her father Robby Ray Stewart singing the song "This Is The Life" in preparation for a sold out concert in Los Angeles the next day. After she reluctantly gives her older brother Jackson two tickets for him and a girl he is trying to ask out to the concert, Miley's best friend, unaware of her dual identity and a big fan of Hannah, calls to announce that she is "incoming in 20 seconds". Miley puts a blue jacket over her Hannah clothes. Lilly says she has two tickets for herself and Miley to the concert; as Miley is Hannah, she has to decline, to protect her secret, she says she wants to spend quality time with her brother. Lilly tries to force her to come but Miley doesn't agree.
Miley's other best friend, Oliver Oken somewhat stalks her. Before the episode ended, Lilly keeps her secret, it is in the following episode, "Miley Get Your Gum," that we learn Hannah Montana has been around for 2 years when we are first introduced to her. Oliver says, "Well there goes 2 years of my life," when Miley shows that she's Hannah Montana. Miley Cyrus as Miley Stewart/Hannah Montana Emily Osment as Lilly Truscott Mitchel Musso as Oliver Oken Jason Earles as Jackson Stewart Billy Ray Cyrus as Robby Stewart Corbin Bleu as Johnny Collins Shanica Knowles as Amber Addison Anna Maria Perez de Tagle as Ashley DeWitt Matt Winston as Fermine Derek Basco as an MTB host Every Hannah Montana episode title references a song. Jackson's line of "When you got it, flaunt it" references a song from The Producers. Cyrus received the script for the pilot, before auditioning for Hannah Montana for 6–7 months changing her father's plans to cut an album, do a tour, retire. Creators Poryes, Rich Correll and Barry O'Brien looked in Los Angeles and New York for someone to play Hannah, but couldn't find anyone.
Cyrus sent in an audition tape, but while the creators were impressed, they were not convinced, leery of putting the show in the hands of a 12-year-old with no acting experience. As they looked fruitlessly for an actor to portray Hannah for one year, they decided to look at Cyrus again; the decision was between a 16-year-old with lots of sitcom experience. The room was evenly split on who should play Hannah, Marsh made the decision to go with Cyrus. Garry Marsh's exact quote was "We pride ourselves not just on creating great television, but on creating stars. So, after consulting with everyone involved, I'm ready to pull the trigger on Miley." On the day the pilot was shot, the show was to star a girl named Chloe. According to Billy Ray Cyrus, when the writers heard him calling his daughter Miley, who at that time was still called Destiny, they changed their minds and said "Everything Chloe is Miley." The Disney Channel used three Hannah Montana music videos to promote the series in the weeks leading up to its debut.
The music videos used were "Best of Both Worlds", "Who Said" and "This is the Life". David Cornelius of DVDTalk.com felt that "Lilly, Do You Want to Know a Secret?" was awkward and that it overused musical interludes, due to it being the pilot episode. An ultimatedisney.com review felt that the pilot was "coincidence-riddled." "Lilly, Do You Want to Know a Secret?" had the highest-rated series premiere on a kids network in seven years, scoring 5.4 million viewers. It was the highest ratings for a Disney Channel series. Lilly, Do You Want to Know a Secret? on IMDb "Lilly, Do You Want to Know a Secret?" at TV.com