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| The '''gray''' (symbol: Gy) is the [[SI derived unit]] of [[absorbed dose]], [[Specific energy|specific energy (imparted)]], and of [[Kerma (physics)|kerma]]. Such energies are typically associated with [[ionizing radiation]] such as [[X-rays]] or [[gamma particles]] or with other [[nuclear particles]]. It is defined as the absorption of one [[joule]] of such [[energy]] by one [[kilogram]] of [[matter]].<ref>{{cite web
| | To regain normal cycling piles achieve this by maintaining certain level of hormones and suppressing the point of other hormones to achieve the result. If a woman wants to have a quick pregnancy, it's always handy to have an inexpensive ovulation test kit. Getting blood to flow can be difficult when a woman is pregnant and by not moving your legs enough, you can get blood clots, which can be deadly. These vitamins are especially equipped to provide your body, and baby, with the nutrients they need to get off to a head start. To make it clear once more, you did not know you had Lyme while you were pregnant. <br><br>Some women get it right away, without even trying it. However, there are some uterine malformations that can affect your ability to get pregnant and to maintain the embryon long enough to give birth to the baby. If there is any drawback to the Pregnancy Miracle ebook, it's that it contains so much information, that some readers may find it a bit overwhelming. Diet is another way many believe birth gender can be controlled. Douching may be used to prevent infection caused by bacteria in or around the women vagina, but it also toxic to the sperm and affect the cervical mucus, therefore women who try to get pregnant should avoid douching all together. <br><br>To have a girl, therefore, couples should have sex not too close to ovulation - 3 to 5 days before ovulation. progress, or worse yet stop the sperm from reaching the egg completely. Acupuncture balances the stage of hormones in your body which is incredibly critical for a woman to turn into a mother. Use techniques like meditation, breathing exercises, and yoga. a) In men, it causes low levels of testosterone resulting of small size ****, cryptorchism leading to infertility because of no sperm during ejaculation. <br><br>The cleansing program, followed by optimal nutrition and vitamins supplementation, may enhance your fertility. ' Diet - Each partners ought to eat properly-balanced meals, including meals eminent in anti-oxidants (vegatables and fruits) and iron (poultry and meat). It also doesn't take that much time to find out your best day to get pregnant. It was an interesting spiritual cleansing and as with all spiritual journeys, it just might have worked if there is enough belief. And your chances of conceiving a baby girl will have improved to 90 - 98%. <br><br>In fact the baby continues to gain fat at the rate of half an ounce each and every day. Folic acid supplements are some of the best supplements that you can take when trying to conceive. Method 1 – Determining how to ‘read’ Cervical Fluid as a sign of the Best Time To Get Pregnant. If you've put off pregnancy schedule because of work or relationship concerns or because you simply weren't ready or tried but not "lucky" so to say, and you delay it until late 30's or even at 40's There's no denying your odds of getting pregnant are now far lower than at 20's. My oldest daughter had some issues in high school with her joints and she was unable to do some of her cheer leading moves because of it, but for the most part she was and is functioning normally.<br><br>When you beloved this article as well as you would want to receive more details concerning [http://www.quebec-1759.info/ how to get pregnant on the pill] i implore you to check out our web page. |
| | url = http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf
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| | title = The International System of Units (SI)
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| | publisher = Bureau International des Poids et Mesures ([[BIPM]])
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| | accessdate = 2010-01-31 }}</ref> Unlike the pre-1971 [[roentgen (unit)|roentgen]], the gray has always been defined independently for any target material. The same beam of 1 roentgen would impart more grays to biological tissue than it does to air. The gray is sometimes used to measure beam kerma, in which case the reference target material must be defined explicitly, usually dry air at standard temperature and pressure.
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| The gray was named after the British physicist [[Louis Harold Gray]], a pioneer in the field of measurement of radium radiation and X-rays and their effects on living tissue,<ref>{{cite web
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| |url = http://www.lhgraytrust.org/lhgraybiography.html
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| |title = Rays instead of scalpels
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| |publisher = LH Gray Memorial Trust
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| |year = 2002
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| |accessdate = 2012-05-15}}</ref> and was adopted as part of [[International System of Units|SI]] by the [[General Conference on Weights and Measures|15th CGPM]] in 1975. The SI unit is similar to the traditional [[cgs]] unit, the [[Rad (unit)|rad]] (equivalent to 0.01 Gy), which remains common in industry in the United States, while "strongly discouraged" in the style guide for U.S. [[National Institute of Standards and Technology]] authors.<ref>{{cite web |url=http://physics.nist.gov/Pubs/SP811/sec05.html#5.2 |title=NIST Guide to SI Units - Units temporarily accepted for use with the SI}}</ref>
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| ==Definition==
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| One ''gray'' is the absorption of one [[joule]] of energy, in the form of [[ionizing radiation]], per [[kilogram]] of [[matter]].
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| :<math>1 \ \mathrm{Gy} = 1\ \frac{\mathrm{J}}{\mathrm{kg}}= 1\ \frac{\mathrm{m}^2}{\mathrm{s}^{2}}</math>
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| The gray was defined in 1975 in honour of [[Louis Harold Gray]] (1905–1965) who, in 1940, first proposed a similar concept, "that amount of neutron radiation which produces an increment of energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one [[Roentgen (unit)|röntgen]] of radiation".<ref name="Gupta2009">{{cite book|last=Gupta|first=S. V. |title=Units of Measurement: Past, Present and Future : International System of Units|url=http://books.google.com/books?id=pHiKycrLmEQC&pg=PA144|accessdate=2012-05-14|date=2009-11-19|publisher=Springer|isbn=978-3-642-00737-8|page=144|chapter=Louis Harold Gray}}</ref>
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| {{SI unit lowercase|Louis Harold Gray|gray|Gy}} the SI unit description should read '...the first letter of its symbol is upper case (Gy) after the number or value or by itself, not in a sentence.'
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| ==Biological risk==
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| [[File:SI Radiation dose units.png|thumb|400px|Graphic showing relationship of SI radiation dose units]]
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| The gray measures the absorbed energy of radiation, but the biological effects vary by the type and energy of the radiation and the organism and tissues involved. This is expressed by the [[sievert]], which has the same dimensions as the gray, but is a measure of the potential for damage to human tissue.<ref>{{cite web
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| |url = http://www.mpoweruk.com/conversion_table.htm
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| |title = Conversion Table: Energy
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| |accessdate = 2012-05-15
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| |publisher = Battery and Energy Technologies
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| |work = Electropedia}}</ref> It is related to the gray by weighting factors which are fully described in the articles on [[equivalent dose]] and [[Effective dose (radiation)|effective dose]].
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| For X-rays and gamma rays the gray is numerically the same value when expressed as the [[sievert]] (Sv), but for [[alpha particles]] one gray is equivalent to twenty [[sievert]]s because of the radiation weighting factor that is applied. To avoid any risk of confusion between the [[absorbed dose]] (by matter) and the [[equivalent dose]] (by biological tissues), one must use the corresponding special units; ''gray'' is used instead of the joule per kilogram for absorbed dose and the ''sievert'' instead of the joule per kilogram for the equivalent dose.
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| ==Effect on the body==
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| A whole-body exposure to 5 or more gray of high-energy radiation at one time usually leads to death within 14 days. This dosage represents 375 joules for a 75 kg adult (equivalent to the chemical energy in 20 mg of sugar). Since gray are such large amounts of radiation, medical use of radiation is typically measured in milligray (mGy).{{Citation needed|date=August 2013}}
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| As experienced from follow-up after [[radiation therapy]], [[epilation]] may occur on any hair-bearing skin exposed to doses above 1 Gy. Hair loss may be permanent with a single dose of 10 Gy, but if the dose is fractionated permanent hair loss may not occur until dose exceeds 45 Gy. The [[salivary gland]]s and [[tear gland]]s have a radiation tolerance of about 30 Gy in 2 Gy fractions, a dose which is exceeded by most radical head and neck cancer treatments, potentially causing dryness. Dry mouth ([[xerostomia]]) and dry eyes ([[xerophthalmia]]) can become irritating long-term problems and severely reduce the patient's [[Quality of life (Medical)|quality of life]]. Similarly, [[sweat glands]] in treated skin (such as the [[armpit]]) tend to stop working, and the naturally moist [[vaginal mucosa]] is often dry following pelvic irradiation.{{Citation needed|date=August 2013}}
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| A dose of 8 Gy or more to the [[ovaries]] generally causes permanent [[female infertility]].<ref>Chapter on Amenorrhea in: {{cite book |author=Bradshaw, Karen D.; Schorge, John O.; Schaffer, Joseph; Lisa M. Halvorson; Hoffman, Barbara G. |title=Williams' Gynecology |publisher=McGraw-Hill Professional |location= |year=2008 |pages= |isbn=0-07-147257-6 |oclc= |doi= |accessdate=}}</ref>
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| ==Dose by source==
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| In [[radiation therapy]], the amount of radiation varies depending on the type and stage of cancer being treated. For curative cases, the typical dose for a solid epithelial tumor ranges from 60 to 80 Gy, while lymphomas are treated with 20 to 40 Gy. Preventive (adjuvant) doses are typically around 45–60 Gy in 1.8–2 Gy fractions (for breast, head, and neck cancers).
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| The average radiation dose from an abdominal X-ray is 0.7 mGy, that from an abdominal [[X-ray computed tomography|CT scan]] is 8.0 mGy, that from a pelvic CT scan is 6 mGy, and that from a selective CT scan of the abdomen and the pelvis is 14 mGy. <ref>http://www.xrayrisk.com/calculator/calculator.php</ref>
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| ==Leading up to the gray==
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| The adoption of the gray by the [[General Conference on Weights and Measures|15th CGPM]] in 1975 as the unit of measure of the absorption of [[ionising radiation]], [[Specific energy|specific energy absorption]], and of [[Kerma (physics)|kerma]] in 1975<ref>{{SIBrochure8th|page = 157}}</ref> was the culmination of over half a century of work, both in the understanding of the nature of ionising radiation and in the refinement of measuring techniques. | |
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| [[Wilhelm Röntgen]] first discovered [[X-ray]]s on November 8, 1895 and within a few years they were being used to examine broken bones. One of the earliest techniques of measuring the intensity of X-rays was to measure their ionisation potential in air. Initially various countries developed their own standards, but in order to promote international cooperation, the First International Congress of Radiology (ICR) which met in London in 1925 proposed a separate body to consider units of measure. This body, the [[International Commission on Radiation Units and Measurements]] (ICRU),<ref>Originally known as the International X-ray Unit Committee</ref> came into being at the Second ICR in Stockholm in 1928 under the chairmanship [[Manne Siegbahn]]<ref>{{cite journal|last=Siegbahn|first=Manne|coauthors=et al|title=Recommendations of the International X-ray Unit Committee|journal=Radiology|date=October 1929|volume=13|issue=4|pages=372–373|doi=10.1148/13.4.372|url=http://radiology.rsna.org/content/13/4/372.full.pdf|accessdate=2012-05-20}}
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| </ref><ref>
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| {{cite web
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| |title = About ICRU - History
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| |url = http://www.icru.org/index.php?option=com_content&task=view&id=25&Itemid=63
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| |publisher = International Commission on Radiation Units & Measures
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| |accessdate = 2012-05-20}}
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| </ref><ref> | |
| The host country nominated the chairman of the early ICRU meetings</ref>
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| and at their first meeting proposed that one unit X-ray dose should be defined as the quantity of X-rays that would produce one [[Statcoulomb|esu]] of charge in one [[cubic centimetre]] of dry air at 0 [[°C]] and a [[standard pressure|standard atmosphere]]. This unit was named the roentgen in honour of Röntgen who had died five years previously. At the 1937 meeting of the ICRU, this definition was extended to apply to [[gamma radiation]] as well as X-rays.<ref name=GM>{{cite conference
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| |title = Dosimetry in Europe and the USSR
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| |first1 = JH
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| |last1 = Guill
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| |first2 =John
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| |last2 = Moteff
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| |page = 64
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| |url = http://books.google.co.uk/books?id=czTi4G6-Hq8C&pg=PA63&lpg=PA63&dq=roentgen+redefinition&source=bl&ots=Ha5UORUMvK&sig=2InfcxgNMCdnKBsJw9JMWDmrn0Y&hl=de&sa=X&ei=X3CyT7-ENabP4QTA0dyLCQ&ved=0CGMQ6AEwBA#v=onepage&q=roentgen%20redefinition&f=false
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| |conference = Symposium on Radiation Effects and Dosimetry - Third Pacific Area Meeting American Society for Testing Materials, October 1959, San Francisco, 12–16 October 1959
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| |publisher = ASTM International
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| |booktitle = Third Pacific Area Meeting Papers - Materials in Nuclear Applications - American Society Technical Publication No 276
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| |lccn = 60-14734
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| |location = Baltimore
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| |date = June 1960
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| |accessdate = 2012-05-15}}</ref> This technique, although appropriate for the technology of the day, had the disadvantage that it was not a direct measure of either the intensity of X-rays or of their absorption, but rather was a measurement of the effect of the X-rays in a specific circumstance.<ref name=Lovell4>{{cite book
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| |url =http://books.google.de/books?id=lK48AAAAIAAJ&pg=PA56&lpg=PA56&dq=roentgen+defined&source=bl&ots=DGneAMV5Ea&sig=a4ra-zQGp4-49WMn1sxb_IU0YA8&hl=de&sa=X&ei=AlmyT6KAOpPT4QT8soyOCQ&ved=0CHYQ6AEwCQ#v=onepage&q=roentgen%20defined&f=false
| |
| |title = An introduction to Radiation Dosimetry
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| |first1 = S
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| |last1 = Lovell
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| |year = 1979
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| |chapter = 4 - Dosimetric quantities and units
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| |pages = 52–64
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| |isbn = 0 521 22436 5
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| |publisher = Cambridge University Press
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| |location = Cambridge, United Kingdom
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| |accessdate = 2012-05-15}}</ref>
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| In 1940, Gray, who had been studying the effect of neutron damage on human tissue, together with [[William Valentine Mayneord|Mayneord]] and Read published a paper in which a unit of measure, dubbed the "''gram roentgen''" (symbol: gr) defined as "that amount of neutron radiation which produces an increment in energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one roentgen of radiation"<ref name="Gupta2009"/> was proposed. This unit was found to be equivalent to 88 ergs in air. In 1953 the ICRU recommended the [[rad (unit)|rad]], equal to 100 erg/g as the new unit of measure of absorbed radiation. The rad was expressed in coherent cgs units.<ref name=GM/>
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| In the late 1950s the ICRU was invited by the CGPM to join other scientific bodies to work with the [[International Committee for Weights and Measures]] (CIPM) in the development of a system of units that could be used consistently over many disciplines. This body, initially known as the "Commission for the System of Units" (renamed in 1964 as the "Consultative Committee for Units") was responsible overseeing the development of the [[International System of Units]] (SI).<ref>{{cite web
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| |url = http://www.bipm.org/en/committees/cc/ccu/
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| |title = CCU: Consultative Committee for Units
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| |publisher = [[International Bureau of Weights and Measures]] (BIPM)
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| |accessdate = 2012-05-18}}</ref> At the same time it was becoming increasingly obvious that the definition of the roentgen was unsound and many calls were made for its redefinition. In 1962 it was redefined.<ref>{{cite book
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| |url = http://books.google.co.uk/books?id=IEhJpyEBKYIC&pg=PA554&lpg=PA554&dq=roentgen+1925+1937+1962+ionisation&source=bl&ots=ZKipzcuUUn&sig=l0kKmjEJ6Fud-rBDvsTnY8AVChg&hl=en&sa=X&ei=acG2T_b1G8TFtAbVsJGaCA&sqi=2&ved=0CE8Q6AEwAw#v=onepage&q=roentgen%201925%201937%201962%20ionisation&f=false
| |
| |title = The Dental Assistant
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| |first1 = Pauline C
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| |last1 = Anderson
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| |first2 = Alice E
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| |last2 = Pendleton
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| |edition = 7th
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| |isbn = 0-7668-1113-1
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| |publisher = Delmar
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| |location = Albany, NY
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| |chapter = 14 Dental Radiography
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| |page = 554}}</ref> The definition of the roentgen had the advantage over the gray of being simpler to measure, but the gray is independent of the primary ionising radiation<ref name=Lovell3>{{cite book
| |
| |url =http://books.google.de/books?id=lK48AAAAIAAJ&pg=PA56&lpg=PA56&dq=roentgen+defined&source=bl&ots=DGneAMV5Ea&sig=a4ra-zQGp4-49WMn1sxb_IU0YA8&hl=de&sa=X&ei=AlmyT6KAOpPT4QT8soyOCQ&ved=0CHYQ6AEwCQ#v=onepage&q=roentgen%20defined&f=false
| |
| |title = An introduction to Radiation Dosimetry
| |
| |first1 = S
| |
| |last1 = Lovell
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| |year = 1979
| |
| |chapter = 3. The effects of ionizing radiation on matter in bulk
| |
| |pages = 43–51
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| |isbn = 0 521 22436 5
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| |publisher = Cambridge University Press
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| |location = Cambridge, United Kingdom
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| |accessdate = 2012-05-15}}</ref>
| |
| | |
| The CCU decided to define the SI unit of absorbed radiation in terms of energy per unit mass, which in MKS units was J/kg. This was confirmed in 1975 by 15th GCPM and the unit was named the "gray" in honour of Hal Gray who had died in 1965. The gray was exactly equal to 100 rad.
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| ==See also==
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| * [[Dose area product]] (Gy·cm<sup>2</sup>)
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| * [[International System of Units]] base units
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| * [[Orders of magnitude (radiation)]]
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| * [[Rad (unit)]]
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| * [[Roentgen equivalent man]]
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| * [[SI derived unit]]
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| * [[Sievert]], SI derived unit of dose equivalent radiation
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| | |
| == Notes and references ==
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| {{Reflist|2}}
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| {{SI units}}
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| {{DEFAULTSORT:Gray (Unit)}}
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| [[Category:SI derived units]]
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| [[Category:Nuclear physics]]
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| [[Category:Units of radiation dose]]
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| [[Category:Radioactivity]]
| |
To regain normal cycling piles achieve this by maintaining certain level of hormones and suppressing the point of other hormones to achieve the result. If a woman wants to have a quick pregnancy, it's always handy to have an inexpensive ovulation test kit. Getting blood to flow can be difficult when a woman is pregnant and by not moving your legs enough, you can get blood clots, which can be deadly. These vitamins are especially equipped to provide your body, and baby, with the nutrients they need to get off to a head start. To make it clear once more, you did not know you had Lyme while you were pregnant.
Some women get it right away, without even trying it. However, there are some uterine malformations that can affect your ability to get pregnant and to maintain the embryon long enough to give birth to the baby. If there is any drawback to the Pregnancy Miracle ebook, it's that it contains so much information, that some readers may find it a bit overwhelming. Diet is another way many believe birth gender can be controlled. Douching may be used to prevent infection caused by bacteria in or around the women vagina, but it also toxic to the sperm and affect the cervical mucus, therefore women who try to get pregnant should avoid douching all together.
To have a girl, therefore, couples should have sex not too close to ovulation - 3 to 5 days before ovulation. progress, or worse yet stop the sperm from reaching the egg completely. Acupuncture balances the stage of hormones in your body which is incredibly critical for a woman to turn into a mother. Use techniques like meditation, breathing exercises, and yoga. a) In men, it causes low levels of testosterone resulting of small size ****, cryptorchism leading to infertility because of no sperm during ejaculation.
The cleansing program, followed by optimal nutrition and vitamins supplementation, may enhance your fertility. ' Diet - Each partners ought to eat properly-balanced meals, including meals eminent in anti-oxidants (vegatables and fruits) and iron (poultry and meat). It also doesn't take that much time to find out your best day to get pregnant. It was an interesting spiritual cleansing and as with all spiritual journeys, it just might have worked if there is enough belief. And your chances of conceiving a baby girl will have improved to 90 - 98%.
In fact the baby continues to gain fat at the rate of half an ounce each and every day. Folic acid supplements are some of the best supplements that you can take when trying to conceive. Method 1 – Determining how to ‘read’ Cervical Fluid as a sign of the Best Time To Get Pregnant. If you've put off pregnancy schedule because of work or relationship concerns or because you simply weren't ready or tried but not "lucky" so to say, and you delay it until late 30's or even at 40's There's no denying your odds of getting pregnant are now far lower than at 20's. My oldest daughter had some issues in high school with her joints and she was unable to do some of her cheer leading moves because of it, but for the most part she was and is functioning normally.
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