Gamma ray and Cobble Hill, Brooklyn: Difference between pages

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{{dablink|This article is about Cobble Hill, Brooklyn, for Cobble Hill, British Columbia see [[Cobble Hill, British Columbia]].}}

{{for|the band|Gamma ray (band)}}

'''Cobble Hill''' is a neighborhood in the [[New York City]] [[borough (New York City)|borough]] of [[Brooklyn]], USA. Bordered by [[Atlantic Avenue (New York City)|Atlantic Avenue]] on the north, Hicks Street to the west, Court Street on the east and Degraw Street to the south, Cobble Hill sits adjacent to [[Boerum Hill, Brooklyn|Boerum Hill]] and [[Brooklyn Heights, Brooklyn|Brooklyn Heights]] with [[Carroll Gardens]] to the south. The neighborhood is part of [[Brooklyn Community Board 6]].

{{Nuclear processes|left}}

'''Gamma rays''' or '''gamma-ray photons''' (denoted as [[gamma|γ]]) are forms of [[electromagnetic radiation]] (EMR) or [[photon|light emissions]] of a specific frequency produced from [[atom|sub-atomic]] particle interaction, such as [[electron-positron annihilation]] and [[radioactive decay]]; most are generated from nuclear reactions occurring within the interstellar medium of space.

The area was historically Italian and is centered on two main roads - Court and Smith Street. Family-run shops are Cobble Hill's biggest attraction; Italian meat markets (such as Staubitz Meat Market on Court St.) and old time barber shops mixing with trendy new restaurants. Smith Street is known as Brooklyn's "Restaurant Row" due to the large number of eateries and watering holes that opened on the street during the late 1990s and early 2000s. Cobble Hill Park, at the intersection of Congress and Clinton Streets, was reconstructed in 1989 and reflects the brick and stone character of this tree lined neighborhood. Cobble Hill is also renowned for its private [[Italianate architecture|Italianate style]] [[brownstone]] and brick row houses. Many of these buildings were remodeled according to regulations dictated by the [[New York City Landmarks Preservation Commission]] as the [[gentrification]] of the eastern and southern borders of this designated Historic District took hold.

Gamma rays are generally characterised as EMR having the highest frequency and energy, and also the shortest wavelength, within the [[electromagnetic radiation]] spectrum. Due to their high energy content, they are able to cause serious damage when absorbed by living cells.

== History of Gamma Rays ==

Until the 1970s, Cobble Hill and Carroll Gardens were, together, known as "[[South Brooklyn]]", even though they are in the northwest portion of the modern borough, because they were south of Atlantic Street (now Atlantic Avenue), that being the southern boundary of the City of Brooklyn (now Brooklyn Heights and [[Downtown Brooklyn]]) during part of the 19th century.

Gamma rays were discovered by the French chemist and physicist [[Paul Ulrich Villard]] in 1900, while he was studying [[uranium]]. Working in the chemistry department of the [[École Normale Supérieure|École Normale]] in rue d'Ulm, [[Paris]] with self-constructed equipment, he found that the rays were not bent by a [[magnetic field]].

The neighborhood is served by the [[Bergen Street (IND Culver Line)|Bergen Street]] [[IND Culver Line]] ({{NYCS Culver IND north}}) subway station. This station has an unused lower level; it was in full use in the 1970s for express trains, which were common then because the neighborhoods to the south (such as [[Park Slope]]) were more populous.{{Fact|date=March 2007}}

For a time, it was assumed that gamma rays were particles. The fact that they could be described as rays was demonstrated by the British Physicist [[William Henry Bragg]] in 1910, when he showed that the rays ionized gas in a way similar to [[X-rays]].

In 1914, [[Ernest Rutherford, 1st Baron Rutherford of Nelson|Ernest Rutherford]] and [[Edward Andrade]] showed that gamma rays were a form of electromagnetic radiation by measuring their wavelengths using [[X-ray crystallography|crystal diffraction]]. The measured wavelengths were similar to those of X-rays and are very short, in the range of 10^-11 m to 10^-14 m. It was [[Ernest Rutherford, 1st Baron Rutherford of Nelson|Rutherford]] who coined the name 'gamma rays', after having already named 'alpha' and 'beta' rays; the individual natures of the different rays were unknown at that time.

==Education==

Gamma-ray astronomy did not develop until it was possible to get detectors above all or most of the atmosphere, using balloons or spacecraft. The first gamma-ray telescope, carried into orbit on the Explorer XI satellite in 1961, picked up fewer than 100 cosmic gamma-ray photons. Perhaps the most spectacular discovery in gamma-ray astronomy came in the late 1960s and early 1970s. Detectors on board the [[Vela (satellite)|Vela satellite]] series, originally military satellites, began to record bursts of these rays, not from Earth, but from deep space. <ref>[[NASA]] EM spectrum infopage &ndash; http://imagers.gsfc.nasa.gov/ems/gamma.html</ref>

Gamma rays have the highest frequency and highest amount of energy on the EM spectrum (elctromagnetic spectrum).

There are three schools in Cobble Hill. Public School 29, also known as the John M. Harrigan school, is located on Henry Street and has one of the best records in the city for extracurricular activities. Also, the building which was formerly home to Intermediate School 298 (which closed in 2005 due to poor performance), now containts two 6-12th grade schools with the Brooklyn School for Global Studies occupying the top floor, and the School for International Studies on the bottom floor.

Gamma rays also have the shortest wavelength out of all the waves on the EM spectrum

==PropertiesExternal links==

*[http://www.nycfoto.com/showPage.php?albumID=576 NYCfoto.com Recent photos of Cobble Hill]

===Shielding===

Shielding for gamma rays requires large amounts of mass. The material used for shielding takes into account that gamma rays are better absorbed by materials with high [[atomic number]] and high density. Also, the higher the energy of the gamma rays, the thicker the shielding required. Materials for shielding gamma rays are typically illustrated by the thickness required to reduce the intensity of the gamma rays by one half (the half value layer or HVL). For example, gamma rays that require 1 cm (0.4 inches) of [[lead]] to reduce their intensity by 50% will also have their intensity reduced in half by 6&nbsp;cm (2½&nbsp;inches) of [[concrete]] or 9&nbsp;cm (3½&nbsp;inches) of packed dirt.

{{Brooklyn}}

===Matter interaction===

[[Image:Gamma_Abs_Al.png|300px|thumb|The total absorption coefficient of aluminium (atomic number 13) for gamma rays, plotted versus gamma energy, and the contributions by the three effects. Over most of the energy region shown, the Compton effect dominates.]]

[[Image:Gamma_Abs_Pb.png|300px|thumb|The total absorption coefficient of lead (atomic number 82) for gamma rays, plotted versus gamma energy, and the contributions by the three effects. Here, the photo effect dominates at low energy. Above 5 MeV, pair production starts to dominate]]

[[Category:Brooklyn neighborhoods]]

When a gamma ray passes through matter, the probability for absorption in a thin layer is proportional to the thickness of that layer. This leads to an [[exponential decay|exponential decrease]] of intensity with thickness

:<math>

I(d) = I_0 \cdot e ^{-\mu d}

</math>

Here, &mu; = ''n''&times;&sigma; is the absorption coefficient, measured in cm^&minus;1, ''n'' the number of atoms per cm³ in the material, &sigma; the absorption [[cross section (physics)|cross section]] in cm² and ''d'' the thickness of material in cm.

In passing through matter, gamma radiation ionizes via three main processes: the [[photoelectric effect]], [[Compton scattering]], and [[pair production]].

* '''Photoelectric Effect''': This describes the case in which a gamma photon interacts with and transfers its energy to an atomic electron, ejecting that electron from the atom. The kinetic energy of the resulting photoelectron is equal to the energy of the incident gamma photon minus the binding energy of the electron. The photoelectric effect is the dominant energy transfer mechanism for x-ray and gamma ray photons with energies below 50 keV (thousand [[electronvolt|electron volts]]), but it is much less important at higher energies.

* '''Compton Scattering''': This is an interaction in which an incident gamma photon loses enough energy to an atomic electron to cause its ejection, with the remainder of the original photon's energy being emitted as a new, lower energy gamma photon with an emission direction different from that of the incident gamma photon. The probability of Compton scatter decreases with increasing photon energy. Compton scattering is thought to be the principal absorption mechanism for gamma rays in the intermediate energy range 100 keV to 10 MeV ([[Electronvolt|megaelectronvolts]]), an energy spectrum which includes most gamma radiation present in a nuclear explosion. Compton scattering is relatively independent of the [[atomic number]] of the absorbing material.

* '''Pair Production''': By interaction via the Coulomb force, in the vicinity of the nucleus, the energy of the incident photon is spontaneously converted into the mass of an electron-positron pair. A [[positron]] is the anti-matter equivalent of an electron; it has the same mass as an electron, but it has a positive charge equal in strength to the negative charge of an electron. Energy in excess of the equivalent rest mass of the two particles (1.02 MeV) appears as the kinetic energy of the pair and the recoil nucleus. The positron has a very short lifetime (if immersed in matter) (about 10^-8 seconds). At the end of its [[Range (particle radiation)|range]], it combines with a free electron. The entire mass of these two particles is then converted into two gamma photons of 0.51 MeV energy each.

The secondary electrons (or positrons) produced in any of these three processes frequently have enough energy to produce many [[ionization]]s up to the end of range.

The exponential absorption described above holds, strictly speaking, only for a narrow beam of gamma rays. If a wide beam of gamma rays passes through a thick slab of concrete, the scattering from the sides reduces the absorption.

Gamma rays are often produced alongside other forms of radiation such as alpha or beta. When a nucleus emits an &alpha; or &beta; particle, the [[daughter nucleus]] is sometimes left in an excited state. It can then jump down to a lower level by emitting a gamma ray in much the same way that an atomic electron can jump to a lower level by emitting visible light or [[ultraviolet]] radiation.

[[Image:Cobalt_60.png|thumb|Decay schema of ⁶⁰Co]]

Gamma rays, x-rays, visible [[light]], and UV rays are all forms of [[electromagnetic radiation]]. The only difference is the [[frequency]] and hence the [[energy]] of the [[photon]]s. Gamma rays are the most energetic.

An example of gamma ray production follows.

First ⁶⁰[[cobalt|Co]] decays to excited ⁶⁰[[nickel|Ni]] by [[Beta rays|beta decay]]:

:<math>

{}^{60}\hbox{Co}\;\to\;^{60}\hbox{Ni*}\;+\;e^-\;+\;\overline{\nu}_e.

</math>

Then the ⁶⁰Ni drops down to the ground state (see nuclear [[shell model]]) by emitting two gamma rays in succession:

:<math>

{}^{60}\hbox{Ni*}\;\to\;^{60}\hbox{Ni}\;+\;\gamma.

</math>

Gamma rays of 1.17 MeV and 1.33 MeV are produced.

Another example is the alpha decay of ²⁴¹[[americium|Am]] to form ²³⁷[[neptunium|Np]]; this alpha decay is accompanied by [[gamma]] emission. In some cases, the gamma emission spectrum for a nucleus is quite simple, (eg ⁶⁰Co/⁶⁰Ni) while in other cases, such as with (²⁴¹Am/²³⁷Np and ¹⁹²[[iridium|Ir]]/¹⁹²[[platinum|Pt]]), the gamma emission spectrum is complex, revealing that a series of nuclear energy levels can exist. The fact that an alpha spectrum can have a series of different peaks with different energies reinforces the idea that several nuclear energy levels are possible.

[[Image:Egret_all_sky_gamma_ray_map_from_CGRO_spacecraft.gif|thumb|300px|right|Image of entire sky in 100 MeV or greater gamma rays as seen by the EGRET instrument aboard the [[CGRO]] spacecraft. Bright spots within the galactic plane are [[pulsar]]s while those above and below the plane are thought to be [[quasar]]s.]]

Because a beta decay is accompanied by the emission of a [[neutrino]] which also carries energy away, the beta spectrum does not have sharp lines, but instead is a broad peak. Hence from beta decay alone it is not possible to probe the different energy levels found in the nucleus.

In [[optical]] spectroscopy, it is well known that an entity which emits light can also absorb light at the same [[wavelength]] (photon energy). For instance, a sodium flame can emit yellow light as well as absorb the yellow light from a [[sodium]] vapour lamp. In the case of gamma rays, this can be seen in [[Mössbauer]] spectroscopy. Here, a correction for the energy lost by the recoil of the nucleus is made and the exact conditions for gamma ray absorption through resonance can be attained.

This is similar to the [[Franck-Condon Principle|Franck Condon]] effects seen in optical spectroscopy.

== Uses ==

The powerful nature of gamma rays has made them useful in the sterilization of medical equipment by killing [[bacterium|bacteria]]. They are also used to kill bacteria and insects in foodstuffs, particularly meat, marshmallows, pie, eggs, and vegetables, to maintain freshness.

Due to their tissue penetrating property, gamma rays/X-rays have a wide variety of medical uses such as in [[Computed tomography|CT Scans]] and [[radiation therapy]] (''see [[X-ray]]''). However, as a form of [[ionizing radiation]] they have the ability to effect molecular changes, giving them the potential to cause [[cancer]] when [[DNA]] is affected.

Despite their cancer-causing properties, gamma rays are also used to treat some types of [[cancer]]. In the procedure called [[gamma knife|gamma-knife]] surgery, multiple concentrated beams of gamma rays are directed on the growth in order to kill the cancerous cells. The beams are aimed from different angles to focus the radiation on the growth while minimizing damage to the surrounding tissues.

[[Image:Moon gamma rays egret instrument cgro.jpg|thumb|right|250px|The Moon as seen in [[gamma rays]] by the [[Compton Gamma Ray Observatory]]. Surprisingly, the Moon is actually brighter than the Sun at gamma ray wavelengths.]]

Gamma rays are also used for diagnostic purposes in [[nuclear medicine]]. Several gamma-emitting [[radioisotope]]s are used, one of which is [[technetium]]-99m. When administered to a patient, a [[gamma camera]] can be used to form an image of the radioisotope's distribution by detecting the gamma radiation emitted. Such a technique can be employed to diagnose a wide range of conditions (e.g. spread of cancer to the bones).

Gamma ray detectors are also starting to be used in Pakistan as part of the [[Container Security Initiative]] (CSI). These [[United States dollar|US$]]5 million machines are advertised to scan 30 containers per hour. The objective of this technique is to pre-screen merchant ship containers before they enter U.S. ports.

=== In popular culture ===

* Exposure to gamma rays transformed the scientist Bruce Banner into [[Hulk (comics)|the Incredible Hulk]] in the [[Marvel Comics|Marvel comic]] of the same name; many of the Hulk's villains and allies also attained their superpowers through this method. It is a recurring theme in Marvel stories that mutations caused by gamma radiation often unleash some hidden aspect of the affected person's psyche; for example, the raging Hulk is a manifestation of Banner's repressed emotions and violent tendencies stemming from an abusive childhood. In his ending of the non-canon ''[[Marvel Super Heroes vs. Street Fighter]]'', The Hulk theorizes that gamma radiation caused Blanka's mutations, as they did his. <ref name="Mamend">{{Cite web|title=Mamend: Marvel Super Heroes vs. Street Fighter endings|url=http://www.vazcomics.org/mamend/M/mshvsf_2.htm|accessdate=September 13|accessyear=2006}}</ref>

* In both Gundam [[Gundam Seed|Seed]] and [[Gundam Seed Destiny|Seed Destiny]] gamma ray technology is incorporated in the space cannon G.E.N.E.S.I.S.(Gamma Emission by Nuclear Explosion Stimulate Inducing System); a huge gamma-ray laser canon.

* In [[David Weber|David Weber's]] [[Honorverse]], [[graser]]s are powerful gamma-radiation-powered energy weapons.

* [[Metroids]], creatures in the popular series of the same name, go through a large metamorphosis when exposed to gamma-radiation.

== References ==

# Kelly, K. (2005). ''Radiation may have positive effects on health: study -- Low, chronic doses of gamma radiation had beneficial effects on meadow voles'' University of Toronto

<references/>

== See also ==

*[[Gamma spectroscopy]]

*[[Gamma-ray astronomy]]

*[[Gamma ray burst]]s

*[[Radiation therapy]]

*[[High energy X-rays]]

*[[Food irradiation]]

* [[alpha particles|α (alpha) particles]]

* [[beta particles|β (beta) particles]]

*Types of rays:

** γ (gamma) rays

** [[neutron radiation|n (neutron) rays]]

** [[delta rays|δ (delta) rays]]

** [[epsilon rays|ε (epsilon) rays]]

*[[X-rays]]

== External links ==

*[http://www.rerf.or.jp/eigo/radefx/basickno/whatis.htm Basic reference on several types of radiation]

*[http://www.meds.com/pdq/radio.html Medical-related information on gamma radiation]

*[http://www.cancer.gov/cancertopics/factsheet/Therapy/radiation Radiation Q & A]

*[http://www.gcsechemistry.com/pwav46.htm GCSE information]

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*[http://www.saic.com/products/security/relocatable-vacis/relocatable-vacis-faq.html Radiation facts]

*[http://www.physics.isu.edu/radinf Radiation information]

*[http://www.astro.caltech.edu/~ejb/faq.html Gamma ray bursts]

*[http://nucleardata.nuclear.lu.se/NuclearData/toi/ The Lund/LBNL Nuclear Data Search] - Contains information on gamma-ray energies from isotopes.

{{EMSpectrum}}

[[Category:Electromagnetic spectrum]]

[[Category:Radioactivity]]

[[Category:Synchrotron related techniques]]

[[Category:IARC Group 1 carcinogens]]

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