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| [[File:Critical-ionization-velocity.jpg|thumb|300px|'''Critical ionization velocity''' experiment onboard space shuttle Discovery ([[STS-39]]), releasing a plume of nitrous oxide gas. [http://science.ksc.nasa.gov/mirrors/images/images/pao/STS39/10064167.htm Full text] ]]
| | == Annandale Belstaff Leather Quality == |
| '''Critical ionization velocity''' (CIV), or '''critical velocity''' (CV), is the relative velocity between a neutral [[gas]] and [[Plasma (physics)|plasma]] (an ionized gas), at which the neutral gas will start to [[ionize]]. If more energy is supplied, the velocity of the atoms or molecules will not exceed the critical ionization velocity until the gas becomes almost fully ionized.
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| The phenomenon was predicted by Swedish engineer and plasma scientist, [[Hannes Alfvén]], in connection with his model on the origin of the [[Solar System]] (1942).<ref>Hannes Alfvén "On the cosmogony of the solar system", in ''Stockholms Observatoriums Annaler'' (1942) [http://articles.adsabs.harvard.edu//full/seri/StoAn/0014//0000042.000.html Part I] [http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1942StoAn..14....5A Part II] [http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1942StoAn..14....9A Part III]</ref><ref>Hannes Alfvén, ''[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1954QB501.A53......&db_key=AST&data_type=HTML&format=&high=42ca922c9c08806 On the Origin of the Solar System]''. Oxford: Clarendon Press, 1954.</ref><ref>Hannes Alfvén, [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1960RvMP...32..710A&db_key=AST&data_type=HTML&format=&high=42ca922c9c08305 Collision between a nonionized gas and a magnetized plasma], ''Rev. Mod. Phys''., vol. 32, p. 710, 1960.</ref> At the time, no known mechanism was available to explain the phenomenon, but the theory was subsequently demonstrated in the laboratory.<ref name="U.V. Fahleson 1961">U.V. Fahleson, "Experiments with plasma moving through neutral gas", Phys. Fluids, 4 123 (1961)</ref> Subsequent research by Brenning and Axnäs (1988)<ref>Brenning, N ., Axnas, I: "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1988Ap%26SS.144...15B&db_key=AST&data_type=HTML&format=&high=42ca922c9c28386 Critical ionization velocity interactions : Some unsolved problems]", (1988) ''Astrophys. Space Sci''. 144 15</ref> have suggested that a [[Lower hybrid oscillation|''lower hybrid'']] plasma [[instability]] is involved in transferring energy from the larger ions to electrons so that they have sufficient energy to ionize. Application of the theory to astronomy though a number of experiments have produced mixed results.<ref>R. Torbert,: "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1988AdSpR...8Q..39T&db_key=AST&data_type=HTML&format=&high=42ca922c9c02285 Review of ionospheric CIV experiments]", XXVIIth COSPAR Meet., (1988) Helsinki, Finland, paper XIII.2. 1</ref><ref name="Lai, Shu T. 2001 p. 471-506">Lai, Shu T., [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001RvGeo..39..471L&db_key=PHY&data_type=HTML&format=&high=42ca922c9c03435 A review of critical ionization velocity] (2001) ''Reviews of Geophysics'', Volume 39, Issue 4, p. 471-506</ref>
| | I have always wished which i could keep all of these nice and organized in one location. Live Binder is the answer to this wish.Live Binder allows you to add text, upload files, [http://www.bracimex.com/database/exportacao.asp?p=124-Belstaff-Leather-Quality Belstaff Leather Quality] and upload links for an online notebook. Despite the attack, Quvenzhane had some reason to stay positive Sunday. By the time she'd reached the Oscar telecast, she could boast that they had been cast to play Annie in a contemporized adaptation of the Broadway musical and the "Little Orphan Annie" comic strip to be directed by Will Gluck. <br><br>It [http://www.ethur.org/includes/mobile.asp?p=54-Canada-Goose-Expedition-Parka-Uk Canada Goose Expedition Parka Uk] is important to use this medication exactly as prescribed by your doctor. If you miss a dose, apply it as soon as possible and continue with your family schedule. Charlie Brown and Snoopy character art and Peanuts designs on gifts, apparel, housewares, tshirts, mugs and more. A "proudly parochial" newspaper for Balmain and Rozelle with two sister publications for that Leichhardt, Glebe, Annandale, Drummoyne, Five Dock and Concord. <br><br>I will have [http://www.vilaselvagem.com/connections/reservas.asp?p=8-Genuine-Ugg-Label Genuine Ugg Label] days that go over and that's okay, this is real life and often there are events that you need to enjoy. I logged everything, held myself responsible for everything and because of that I feel happy about it. Have a place to go that he doesn know about, whether it a temporary shelter or perhaps a relative who lives in another state." Stephany Alexander adds, "Make copies of important documents and save some money on the side." Dr. King sums it up with, "Two magic words: quickly and quietly. <br><br>If you are searching for a suitable job, Dubai is where to look for since jobs in Dubai are largely available in various sectors. But to obtain genuine and latest information on jobs in Dubai you need a job site that concentrates on that country. Information. Utilisation of the Sites and Services will result in our [http://www.nannyjobsabroad.co.uk/includes/defines.asp?b=124-Shop-Barbour-Uk Shop Barbour Uk] collection of both private information and general information. <br><br>Some styles will even allow you to modify the angle in the walking floor, to simulate heading uphill. Maintain your workout from receiving monotonous by listening to some audio or audio guides while you stroll.. And, as journalists around the world will testify, scientists usually avoid politics and prevent policysensitive discussions. Canada's researchers are no different.. <br><br>Furthermore, if you happen to be in Mayo during May and therefore are interested in pursuing other famine tributes, do go to the little village of Louisburgh just up the road along the coast. The final time I was there, the community was organising a Famine museum within an abandoned school building, or maybe it was a vacant church?.<ul> |
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| ==Experimental research==
| | <li>[http://wx.weijishidai.com/thread-1225879-1-1.html http://wx.weijishidai.com/thread-1225879-1-1.html]</li> |
| The Royal Institute of Technology in Stockholm carried out the first laboratory tests, and found that (a) the relative velocity between a plasma and neutral gas could be increased to the critical velocity, but then additional energy put into the system went into ionizing the neutral gas, rather than into
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| increasing the relative velocity, (b) the critical velocity is roughly independent of the pressure and magnetic field.<ref name="U.V. Fahleson 1961"/>
| | <li>[http://virtualashram.org/index.php?option=com_kunena&func=view&catid=4&id=32172&Itemid=94#32172 http://virtualashram.org/index.php?option=com_kunena&func=view&catid=4&id=32172&Itemid=94#32172]</li> |
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| In 1973, Lars Danielsson published a review of critical ionization velocity, and concluded that the existence of the phenomenon "is proved by sufficient experimental evidence".<ref>Lars Danielsson, "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1973Ap%26SS..24..459D&db_key=AST&data_type=HTML&format=&high=42ca922c9c03369 Review of the Critical Velocity of Gas-Plasma Interaction. I: Experimental Observations]", ''Astrophysics and Space Science'' (1973)
| | <li>[http://www.bjtsdhh.com/bbs/read.php?tid-2333584.html http://www.bjtsdhh.com/bbs/read.php?tid-2333584.html]</li> |
| </ref> In 1976, Alfvén reported that "The first observation of the critical velocity effect under cosmic conditions was reported by Manka et al. (1972)<ref>Manka, R. H., et al., "Evidence for acceleration of lunar ions", in ''Lunar Science III'', C. Watkins, ed., (The Lunar Science Institute, Houston, Tx.): 504. (1972)
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| </ref> from the Moon. When an abandoned lunar [391] excursion module was made to impact on the dark side of the Moon not very far from the terminator, a gas cloud was produced which when it had expanded so that it was hit by the solar wind gave rise to superthermal electrons."<ref>Hannes Alfvén, "[http://history.nasa.gov/SP-345/ch21.htm Mass Distribution and the Critical Velocity]", ''Evolution of the Solar System'' (1976)
| | <li>[http://observatoiredesreligions.fr/spip.php?article9 http://observatoiredesreligions.fr/spip.php?article9]</li> |
| </ref> | | |
| | | </ul> |
| In the laboratory, critical ionization velocity has been recognised for some time, and is seen in the penumbra produced by a [[dense plasma focus]] device (or plasma gun). Its existence in cosmic plasmas has not been confirmed.
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| In 1986, Gerhard Haerendel, suggested that critical velocity ionization may stabilize the plasma flow in a cometary coma,.<ref name="adsabs.harvard.edu">G. Haerendel: "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986GeoRL..13..255H&db_key=AST&data_type=HTML&format=&high=42ca922c9c32239 Plasma flow and critical velocity ionization in cometary comae]", (1986) ''Geophys. Res. Lett''. 13 25 5</ref> In 1992, E. Golbraikh and M. Filippov argued that critical ionization velocity could play a role in [[coronal mass ejection]]s and [[solar flare]]s,<ref>Golbraikh, E. I.; Filippov, M. A., [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992ssts.rept..345G&db_key=AST&data_type=HTML&format=&high=42ca922c9c03435 Possible manifestation of the critical ionization velocity phenomenon in the solar corona] (1992), ''ESA, Study of the Solar-Terrestrial System''.
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| </ref> and in 1992, [[Anthony Peratt]] and [[Gerrit Verschuur]] suggested that interstellar neutral hydrogen emissions bore the signature of critical velocity ionization,.<ref>Peratt, Anthony; Verschuur, Gerrit, [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002APS..DPPQP1017P&db_key=PHY&data_type=HTML&format=&high=42ca922c9c03435 The Critical Ionization Velocity Signature Manifested in Interstellar Neutral Hydrogen Emission Profile Structure], (1992), ''Bulletin of the American Astronomical Society'', Vol. 34, p.766
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| </ref> | |
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| A 2001 review of the phenomenon by Shu T. Lai reports that ".. laboratory experiments, and computer simulations have all shown CIV as feasible and reasonably understood, although all CIV experiments in space have yielded negative results with perhaps three exceptions".<ref name="Lai, Shu T. 2001 p. 471-506"/>
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| Also in 2001, C. Konz, et al., ".. discuss the critical velocity effect as a possible explanation for the observed Hα emission [..] in the Galactic halo near the edges of cold gas clouds of the Magellanic Stream"<ref>Konz, C.; Lesch, H.; Birk, G. T.; Wiechen, H., "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001ApJ...548..249K&db_key=AST&data_type=HTML&format=&high=4521318e0206624 The Critical Velocity Effect as a Cause for the Hα Emission from the Magellanic Stream]" (2001) in ''The Astrophysical Journal'', Volume 548, Issue 1, pp. 249-252</ref>
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| ==Theory development==
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| {| class="wikitable" style="float:right; clear:right; margin-left:1em"
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| |-
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| ! colspan=4 | Typical Critical Ionization Velocities<br>{{nobold|(After Alfvén (1976))}}
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| |-
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| ! style="font-weight:normal" | Element
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| ! style="font-weight:normal" | Ionization potential<br>V<sub>ion</sub> (V)
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| ! style="font-weight:normal" | Average<br>atomic mass
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| ! style="font-weight:normal" | Critical Velocity<br>V<sub>crit</sub> (10<sup>5</sup> cm/s)
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| |-
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| ! style="font-weight:normal" | Hydrogen
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| | 13.5
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| | 1.0
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| | 50.9
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| |-
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| ! style="font-weight:normal" | Helium
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| | 24.5
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| | 4.0
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| | 34.3
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| |-
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| ! style="font-weight:normal" | Neon
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| | 21.5
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| | 20.2
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| | 14.3
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| |-
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| ! style="font-weight:normal" | Nitrogen
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| | 14.5
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| | 14.0
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| | 14.1
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| |-
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| ! style="font-weight:normal" | Carbon
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| | 11.2
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| | 12.0
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| | 13.4
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| |-
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| ! style="font-weight:normal" | Oxygen
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| | 13.5
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| | 16.0
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| | 12.7
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| |}
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| Mathematically, the critical ionization velocity of a neutral cloud, that is, when the cloud begins to become ionized, is when the relative kinetic energy is equal to the ionization energy, that is:
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| :<math>\frac{1}{2} mv^2 = eV_{ion}</math>
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| where ''eV<sub>ion</sub>'' is the ionization potential of the atoms or molecules in the gas cloud, ''m'' is the mass, ''v'' is the velocity. The phenomenon is also called the ''Critical velocity ionization'',<ref name="adsabs.harvard.edu"/> and also ''Critical velocity effect'',.<ref>Petelski, E. F.; Fahr, H. J.; Ripken, H. W.; Brenning, N.; Axnas, I., [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....87...20P Enhanced interaction of the solar wind and the interstellar neutral gas by virtue of a critical velocity effect] (1980)
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| </ref>
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| Alfvén considered a neutral gas cloud entering the Solar System, and noted that a neutral atom will fall towards the Sun under the influence of gravity, and its kinetic energy will increase. If their motion is random, collisions will cause the gas temperature to rise, so that at a certain distance from the Sun, the gas will ionize. Alfvén writes that the ionization potential of the gas, V<sub>ion</sub>, occurs when:
| |
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| :<math>eV_{ion} = E_g = \frac{k M m}{r}</math>
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| that is, at a distance of:
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| :<math>r_{i} = E_g = \frac{k M m}{eV_{ion}} = 6.9\cdot 10^{-20}M \frac{m'}{V_{ion}} = 13.5\cdot 10^{13} \frac{m'}{V_{ion}} cm</math>
| |
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| (where r<sub>i</sub> is the ion distance from the Sun of mass ''M'', ''m''' is the atom weight, ''V<sub>ion</sub>'' is in volts, ''k'' is the gravitational constant). Then when the gas becomes ionized, electromagnetic forces come into effect, of which the most important is the magnetic force which is usually greater than the gravitational force which gives rise to a magnetic repulsion from the Sun. In other words, a neutral gas falling from infinity toward the Sun is stopped at a distance r<sub>i</sub> where it will accumulate, and perhaps condense into planets.
| |
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| Alfvén found that by taking a gas cloud with an average ionisation voltage of 12 V, and average atomic weight of 7, then the distance r<sub>i</sub> is found to coincide with the orbit of Jupiter.
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| The critical ionization velocity of hydrogen 50.9 x 10<sup>5</sup> cm/s (50.9 km/s), and helium is 34.3 x 10 <sup>5</sup>cm/s (34.3 km/s).<ref name="history.nasa.gov">Hannes Alfvén, Evolution of the Solar System (1980) "[http://history.nasa.gov/SP-345/ch21.htm 21. Mass Distribution And The Critical Velocity]"</ref>
| |
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| === Background === | |
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| Alfvén discusses his thoughts behind critical velocity, in his NASA publications Evolution of the Solar System.<ref name="history.nasa.gov"/> After criticising the "Inadequacy of the Homogeneous Disc Theory", he writes:
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| <blockquote>".. it is more attractive to turn to the alternative that the secondary bodies derive from matter falling in from "infinity" (a distance large compared to. the satellite orbit). This matter (after being stopped and given sufficient angular momentum) accumulates at specific distances from the central body. Such a process may take place when atoms or molecules in free fall reach a kinetic energy equal to their ionization energy. At this stage, the gas can become ionized by the process discussed in sec. 21.4; the ionized gas can then be stopped by the magnetic field of the central body and receive angular momentum by transfer from the central body as described in sec. 16.3.".</blockquote>
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| ==Notes== | |
| <!--div style="font-size:87.5%; -moz-column-count:2; column-count:2;"-->
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| <div style="font-size:87.5%>
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| <!--See [[Wikipedia:Footnotes]] for an explanation of how to generate footnotes using the <ref(erences/)> tags-->
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| <references/>
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| </div> | |
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| ===Other references===
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| *Brenning, N .
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| **[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992ITPS...20..778B&db_key=PHY&data_type=HTML&format=&high=42ca922c9c21456 A comparison between laboratory and space experiments on Alfven's CIV effect], in ''IEEE Transactions on Plasma Science'' (ISSN 0093-3813), vol. 20, no. 6, p. 778-786. (1996)
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| **[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992SSRv...59..209B&db_key=AST&data_type=HTML&format=&high=42ca922c9c21456 Review of the CIV phenomenon], in ''Space Science Reviews'' (ISSN 0038-6308), vol. 59, Feb. 1992, p. 209-314. (1992)
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| **[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PFLDAS000028000011003424000001&idtype=cvips&gifs=yes Limits on the magnetic field strength for critical ionization velocity interaction], ''Physics of Fluids'' -- November 1985—Volume 28, Issue 11, pp. 3424–3426
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| <!--Categories--> | |
| [[Category:Astrophysics]]
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| [[Category:Plasma physics]]
| |
Annandale Belstaff Leather Quality
I have always wished which i could keep all of these nice and organized in one location. Live Binder is the answer to this wish.Live Binder allows you to add text, upload files, Belstaff Leather Quality and upload links for an online notebook. Despite the attack, Quvenzhane had some reason to stay positive Sunday. By the time she'd reached the Oscar telecast, she could boast that they had been cast to play Annie in a contemporized adaptation of the Broadway musical and the "Little Orphan Annie" comic strip to be directed by Will Gluck.
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