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| [[Image:Monodisperse Collection.jpg|thumb|A uniform (monodisperse) collection]]
| | "Why does my computer keep freezing up?" I was asked by a lot of individuals the cause of their computer freeze difficulties. And I am fed up with spending much time in answering the question time plus time again. This post is to tell you the real cause of your PC Freezes.<br><br>We all recognize which the registry is the critical component of the Windows running system because it shops all information regarding the Dll files, programs found on the computer and system settings. However, because days by, it is actually unavoidable that you may encounter registry issue due to a huge amount of invalid, useless and unwelcome entries.<br><br>So what if you look for whenever we compare registry products. Many of the registry products available now, have extremely similar attributes. The primary ones which you should be seeking are these.<br><br>The 1328 error is a common problem caused by a system being unable to correctly procedure different updates for the program or Microsoft Office. If you have this error, it commonly signifies which a computer is either unable to read the actual update file or the computer has problems with all the settings it's utilizing to run. To fix this problem, we first want to change / fix any issues which a computer has with its update files, and then repair any of the issues which the system can have.<br><br>In a word, to accelerate windows XP, Vista startup, it's very important to disable some startup items and clean and optimize the registry. We can follow the procedures above to disable unwanted programs. To optimize the registry, I suggest you use a [http://bestregistrycleanerfix.com/tune-up-utilities tuneup utilities] software. Because it is actually very risky for we to edit the registry by oneself.<br><br>You should additionally see with it which it is easy to download and install. You must avoid those treatments which will require you a especially complicated set of instructions. Furthermore, you need to no longer require any different system requirements.<br><br>Perfect Optimizer is a wise Registry Product, updates consistently plus has lots of attributes. Despite its price, there are which the update are certainly useful. They provide a lot of support via telephone, send and forums. You might wish to go and visit the free trial to check it out for yourself.<br><br>A system and registry cleaner could be downloaded from the web. It's effortless to use plus the process refuses to take lengthy. All it does is scan plus then when it finds mistakes, it usually fix and clean those mistakes. An error free registry can protect the computer from mistakes and give we a slow PC fix. |
| [[Image:Polydisperse Collection.jpg|thumb|A non-uniform (polydisperse) collection]]
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| In [[physical chemistry|physical]] and [[organic chemistry]], the '''dispersity''' is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called '''uniform''' if the objects have the same size, shape, or mass. A sample of objects that have an inconsistent size, shape and mass distribution is called '''non-uniform'''. The objects can be in any form of [[Dispersion (chemistry)|chemical dispersion]], such as particles in a [[colloid]], droplets in a cloud,<ref>{{Cite doi|10.1088/1748-9326/4/1/015002}}</ref> crystals in a rock,<ref>{{cite journal
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| |url=http://wwwdsa.uqac.ca/~mhiggins/am_min_2000.pdf
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| |title= Measurement of crystal size distributions
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| |last= Higgins
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| |first= Michael D.
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| |journal= American Mineralogist
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| |volume=85
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| |year=2000
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| |pages=1105–1116}}</ref>
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| or polymer molecules in a solvent.<ref>{{Cite doi|10.1021/j100847a053}}</ref> Polymers can possess a distribution of [[molecular mass]]; particles often possess a wide distribution of size, surface area and mass; and thin films can possess a varied distribution of film thickness.{{Citation needed|date=February 2012}}
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| [[IUPAC]] has [[deprecation|deprecated]] the use of the term ''polydispersity index'' having replaced it with the term ''dispersity'', represented by the symbol ''Đ'' (pronounced D-stroke<ref name=Stepto/>) which can refer to either molecular mass or degree of polymerization. It can be calculated using the equation ''Đ''<sub>M</sub> = ''M''<sub>w</sub>/''M''<sub>n</sub>, where ''M''<sub>w</sub> is the weight-average molar mass and ''M''<sub>n</sub> is the number-average molar mass. It can also be calculated according to degree of polymerization, where ''Đ''<sub>X</sub> = ''X''<sub>w</sub>/''X''<sub>n</sub>, where ''X''<sub>w</sub> is the weight-average degree of polymerization and ''X''<sub>n</sub> is the number-average degree of polymerization. In certain limiting cases where ''Đ''<sub>M</sub> = ''Đ''<sub>X</sub>, it is simply referred to as ''Đ''. IUPAC has also deprecated the terms ''monodisperse'', which is considered to be self-contradictory, and ''polydisperse'', which is considered redundant, preferring the terms ''uniform'' and ''non-uniform'' instead.<ref name=Stepto>Stepto, R. F. T.; Gilbert, R. G.; Hess, M.; Jenkins, A. D.; Jones, R. G.; Kratochvíl P. (2009). "[http://media.iupac.org/publications/pac/2009/pdf/8102x0351.pdf Dispersity in Polymer Science]" ''Pure Appl. Chem.'' '''81''' (2): 351–353. DOI:10.1351/PAC-REC-08-05-02.</ref>
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| ==Overview==
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| {{Quote box
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| |title = IUPAC definition
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| |quote = <big>''Đ''<sub>M</sub> = ''M''<sub>w</sub>/''M''<sub>n</sub></big><br/>where ''M''<sub>w</sub> is the weight-average molar mass and<br/>''M''<sub>n</sub> is the number-average molar mass.
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| |source = [http://www.iupac.org/publications/pac/81/2/0351/ ''Pure Appl. Chem.'', '''2009''', 81(2), 351-353]
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| |align = right
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| }}
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| A uniform [[polymer]] (formerly described as a monodisperse polymer) is composed of molecules of the same mass.<ref>{{cite web
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| |url=http://goldbook.iupac.org/M04012.html
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| |title= monodisperse polymer (See: uniform polymer)
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| |work= IUPAC Gold Book
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| |publisher= International Union of Pure and Applied Chemistry
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| |accessdate=25 January 2012}}</ref> Natural polymers are typically uniform.<ref>{{ cite book
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| |last1 = Brown
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| |first1 = William H.
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| |last2 = Foote
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| |first2 = Christopher S.
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| |last3 = Iverson
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| |first3 = Brent L.
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| |last4 = Anslyn
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| |first4 = Eric V.
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| |url = http://books.google.ca/books?id=rxRHzOS-3xoC&pg=PT1193
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| |title = Organic chemistry
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| |edition = 6
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| |publisher = Cengage Learning
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| |year = 2012
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| |isbn = 978-0-8400-5498-2
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| |page = 1161 }}</ref> Synthetic uniform polymer chains can be made by processes such as [[anionic]] polymerization, a method using an anionic [[catalyst]] to produce chains that are similar in length. This technique is also known as [[living polymerization]]. It is used commercially for the production of [[block copolymer]]s. Uniform collections can be easily created through the use of template-based synthesis, a common method of synthesis in [[nanotechnology]].{{Citation needed|date=February 2012}}
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| A polymer material is denoted by the term non-uniform (formerly 'polydisperse') if its chain lengths vary over a wide range of molecular masses. This is characteristic of man-made polymers.[http://www.chemicool.com/definition/polydisperse.html]. [[Natural organic matter]] produced by the decomposition of plants and wood debris in soils ([[humic substances]]) also has a pronounced non-uniform character. It is the case of [[humic acid]]s and [[fulvic acid]]s, natural [[polyelectrolyte]] substances having respectively higher and lower molecular masses. A rather different meaning of polydispersity index is explained in the article [[Dynamic light scattering]] (cumulant method subheading). In this sense, the PDI values are in the range from 0 to 1.
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| The dispersity (''Đ'', formerly known as '''polydispersity index''', '''PDI''', or heterogeneity index), is a measure of the distribution of [[molecular mass]] in a given [[polymer]] sample. The dispersity calculated is the [[weight average molecular weight]] (<math> M_w </math>) divided by the [[number average molecular weight]] (<math> M_n </math>). It indicates the distribution of individual [[molecular mass]]es in a batch of [[polymer]]s. The dispersity has a value equal to or greater than 1, but as the polymer chains approach uniform chain length, ''Đ'' approaches unity (1).<ref>Peter Atkins and Julio De Paula, ''Atkins' Physical Chemistry'', 9th edition (Oxford University Press, 2010, ISBN 978-0-19-954337-3)</ref> For some natural polymers, ''Đ'' is almost taken as unity.
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| The dispersity from polymerization is often denoted as ''Đ'' <math> = M_w/M_n</math>,
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| where <math> M_w </math> is the [[weight average molecular weight]] and <math> M_n </math> is the [[number average molecular weight]]. <math> M_n </math> is more sensitive to molecules of low molecular mass, while <math> M_w </math> is more sensitive to molecules of high molecular mass.
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| == Effect of polymerization mechanism ==
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| Typical dispersities vary based on the mechanism of polymerization and can be affected by a variety of reaction conditions. In synthetic polymers, it can vary greatly due to [[reactant]] ratio, how close the [[polymerization]] went to completion, etc. For typical addition [[polymerization]], ''Đ'' can range around 10 to 20. For typical step polymerization, most probable values of ''Đ'' are around 2 —[[Carothers' equation]] limits ''Đ'' to values of 2 and below.
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| [[Living polymerization]], a special case of addition polymerization, leads to values very close to 1. Such is the case also in biological polymers, where the dispersity can be very close or equal to 1, indicating only one length of polymer is present.
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| ==Determination methods ==
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| * [[Gel permeation chromatography]] (also known as [[size exclusion chromatography]])
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| * [[Light scattering]] measurements such as [[dynamic light scattering]]
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| * Direct measurement via [[mass spectrometry]] using [[MALDI]] or [[ESI-MS]]
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| ==References==
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| {{reflist}}
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| ==External links==
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| *[http://openlearn.open.ac.uk/mod/resource/view.php?id=196629 Polymer structure]
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| [[Category:Copolymers]]
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| [[Category:Polymer chemistry]]
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| [[ru:Дисперсность]]
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"Why does my computer keep freezing up?" I was asked by a lot of individuals the cause of their computer freeze difficulties. And I am fed up with spending much time in answering the question time plus time again. This post is to tell you the real cause of your PC Freezes.
We all recognize which the registry is the critical component of the Windows running system because it shops all information regarding the Dll files, programs found on the computer and system settings. However, because days by, it is actually unavoidable that you may encounter registry issue due to a huge amount of invalid, useless and unwelcome entries.
So what if you look for whenever we compare registry products. Many of the registry products available now, have extremely similar attributes. The primary ones which you should be seeking are these.
The 1328 error is a common problem caused by a system being unable to correctly procedure different updates for the program or Microsoft Office. If you have this error, it commonly signifies which a computer is either unable to read the actual update file or the computer has problems with all the settings it's utilizing to run. To fix this problem, we first want to change / fix any issues which a computer has with its update files, and then repair any of the issues which the system can have.
In a word, to accelerate windows XP, Vista startup, it's very important to disable some startup items and clean and optimize the registry. We can follow the procedures above to disable unwanted programs. To optimize the registry, I suggest you use a tuneup utilities software. Because it is actually very risky for we to edit the registry by oneself.
You should additionally see with it which it is easy to download and install. You must avoid those treatments which will require you a especially complicated set of instructions. Furthermore, you need to no longer require any different system requirements.
Perfect Optimizer is a wise Registry Product, updates consistently plus has lots of attributes. Despite its price, there are which the update are certainly useful. They provide a lot of support via telephone, send and forums. You might wish to go and visit the free trial to check it out for yourself.
A system and registry cleaner could be downloaded from the web. It's effortless to use plus the process refuses to take lengthy. All it does is scan plus then when it finds mistakes, it usually fix and clean those mistakes. An error free registry can protect the computer from mistakes and give we a slow PC fix.