M*******n
发帖数: 508 | 1 yeah, it is, the question is how to determine the value of M,
as I understand in macroscopic view, it should be M(DNA)-M(Solvent).
M(solvent) = Density(solvent)* Partial Volume
what's the relationship between partial volume and hydrodynamic volume? |
|
c*****e
发帖数: 238 | 2 First of all, I think the /chi parameter only contains enthalpic interactions,
but the /chi term in the Flory-Huggins free energy contains both enthalpic
and entropic contributions.
Thus from the definition, if the polymer chain is dissolved in its monomer
solvent, /chi parameter is exactly zero. Usually(I guess) people refer to
good solvent as /chi<0, while poor solvent as /chi>0. The thing is that in
experiments, this criterion is usually shifted to shift to some /chi
since usually it is |
|
w********h
发帖数: 12367 | 3 thanks for your theoretical discussion.
according to the original Flory equation,
there is a definition for θ condition and θ temperature for a certain
solvent.
Only at this θ temperature, Rg can be considered as (Rg)θ, which is indeed
the one used for polymer chain in itself.
after Flory's prediction,
[η] was measured for different polymers in corresponding "θ" solvents of
course at θ temperature to get θ result [η]--M^0.5.
when people turned to some oligomer solvents,
they first found when oli |
|
w********h
发帖数: 12367 | 4 good discussion.
I think I need to think more..
as to my original problem,
I think my last post is already close to the "answer" (mine).
only at θ temperature can a polymer chain behaves like it is in itself.
The rest, we need to attribute to Rouse-like behavior, which means draining
effect is not negligible as in Zimm behavior in normal good or θ solvents.
In Colby and Rubinstein's new book,
they mentioned different R---M relationship.
for athermal solvent: R--M^(3/5),
Good solvent: R--M |
|
p*****d
发帖数: 40 | 5 in theta solvents, the interaction between solvent and chains are zero
(repulsion=attraction), that is to say, no interaction between solvents and
chains. then chains should behave the same in bulk as in solution...
that is my understanding~~ |
|
m*******e
发帖数: 119 | 6 MIBK has low surface energy (24 dyne/cm). Toluene is about 28, similar to
xylene. They have meidum boiling points and vapor pressure. Low boiling
point and high vapor pressure allow the solvent to evaporate very quickly,
which may help to reduce crystalization effect in your film. But the problem
is that you might not be able to get nice uniform film due to high
evaporation rate. You can check other solvents that you can find. The
physical properties of the solvents can be found from Belstein da |
|
m*******e
发帖数: 119 | 7 MIBK has low surface energy (24 dyne/cm). Toluene is about 28, similar to
xylene. They have meidum boiling points and vapor pressure. Low boiling
point and high vapor pressure allow the solvent to evaporate very quickly,
which may help to reduce crystalization effect in your film. But the problem
is that you might not be able to get nice uniform film due to high
evaporation rate. You can check other solvents that you can find. The
physical properties of the solvents can be found from Belstein da |
|
f*****n
发帖数: 12 | 8 Solvent surly has a very low Tg. However, if the content of the solvent is
very low, maybe the evaporating rate is reflected on the TGA curves.
The problem about this method or the idea lies 1)if the diffusion
mechanisms of solvent changed at Tg of polymer (lots of results show no
effect at least for water); 2) just as saind the plasticization effect.
Thank your all reply. |
|
l**********g
发帖数: 55 | 9 Given the viscosities and refractive indices of two miscible solvents, and
the volume ratio of the two solvents, how can I calculate the viscosity and
RI of the mixed solvent?
thanks!! |
|
t****1
发帖数: 232 | 10 You could polymerize first in the solvent (not a good solvent for PTFE) and
the polymer MW is controllable. Then spray the polymer solution on the
surface of PTFE and evaporate the solvent. |
|
s****7
发帖数: 1873 | 11 【 以下文字转载自 Chemistry 讨论区 】
发信人: super7 (777), 信区: Chemistry
标 题: 门外汉请教一个胶水化学毒性（甲醛等）的问题，包子答谢！
发信站: BBS 未名空间站 (Tue Jan 7 19:24:35 2014, 美东)
刚搬了家，马上要装修，大冬天又不方便一直开窗。 家里有个强过敏的小孩子。所以
对贴地版的胶水很谨慎。（只能选择胶水粘地板了，房间高度太低决定的，其他非实木
地板
不考虑了）。
有没有同学对于这边胶水有研究的，那些号称安全的真的就安全么？
我刷了一次家，用的油漆也是号称安全的，没有危害的。可是那个味道让我明显感到头
疼等不适，是不是就是里面的甲醛导致的呢？有没有懂行的同学有好的安全品牌推荐呢？
看到下面这个产品不错，不知道Polymer Based Wood Flooring Adhesive 里面Polymer
Based有什么特殊含义表示健康安全性么？
http://www.staufusa.com/index.php/259/smp-960-one-step.html?art
It is ozone and ... 阅读全帖 |
|
发帖数: 1 | 12 http://www.dailymail.co.uk/news/article-1127056/The-real-Slumdo
The real Slumdog Millionaires: Behind the cinema fantasy, mafia gangs are
deliberately crippling children for profit
By ANDREW MALONE FOR THE DAILY MAIL
UPDATED: 12:24 EST, 24 January 2009
View comments
Alone and afraid, Aamir was initially grateful when a ‘kind’ older couple
befriended him on his arrival in Mumbai. This chaotic urban sprawl is now
India’s largest city and home to more than 20 million people. More than
nine mill... 阅读全帖 |
|
O*******d
发帖数: 20343 | 13 The active ingredient in pepper spray is capsaicin, which is a chemical
derived from the fruit of plants in the genus Capsicum, including chilis.
Extraction of oleoresin capsicum (OC) from peppers requires capsicum to be
finely ground, from which capsaicin is then extracted using an organic
solvent such as ethanol. The solvent is then evaporated, and the remaining
waxlike resin is the oleoresin capsaicin.
https://en.wikipedia.org/wiki/Pepper_spray |
|
w********o
发帖数: 10088 | 14 测完了，过了，下班跑了一段高速
上网查了一下，smog test就那么几个tips
1，换机油
2，换spark plug
3，换air filter
4，跑路，让converter充分热起来
5，汽油要加满，有人推荐用87号油，说燃烧快
如果converter实在不给力，可以在油箱汽油剩下一半时加半桶solvent，然后跑完油箱
里的汽油。也有人直接在火花塞那里在车打着的时候加solvent |
|
e********t
发帖数: 9607 | 15 bona traffic不是说了么
Designed specifically for the unique demands of heavy-traffic commercial and
residential hardwood floors, Bona Traffic's advanced formula provides the
ultimate in durability, outperforming any finish in the industry - moisture
cure, solvent-based, oil-modified or other waterborne finishes.
完胜业界任何finishi-moisture cure, solvent-based, oil-modified.... |
|
j*****h
发帖数: 3292 | 16 看来得多刷几遍
http://en.wikipedia.org/wiki/Primer_%28paint%29
Using a primer on wood before painting is mandatory for several reasons.
First of all, wood is very porous and will absorb the solvent from paint,
drying the paint prematurely. Because most paints undergo chemical reactions
during the process of curing (for example, latex and alkyd-based paints
actually polymerize when curing), they depend on water or solvent being
evaporated slowly rather than being absorbed quickly by the underlying
mater... 阅读全帖 |
|
F***Q
发帖数: 6599 | 17 搭车问一下，有人干洗过布沙发吗？那里买solvent? 效果怎么样？
今天请人来看了一下，说他们只能用steam洗，但我沙发的cleaning code是"S"，只能
用solvent来干洗。 |
|
L**P
发帖数: 3792 | 18 有意思,两个东西非常类似,主要成分是石灰石Limestone
Spackling:
Chemical Name Wt%
Limestone 60-100
Ethylene glycol 0.1-1.0
Silica, crystalline 0.1-1.0
Stoddard solvent 0.1-1.0
ALex Caulking:
Chemical Name Wt%
Limestone 40 -70
Ethylene glycol 0.1-1.0
Silica, crystalline 0.1-1.0
Stoddard solvent 0.5-1.5
Titanium dioxide 0.1-1.0
Ammonia 0.1-1.0
Formaldehyde <0.009
Branched and linear phthalates 1-5 我猜这个就是特别的acrylic latex部分高分子
,其实也不是acrylic latex |
|
d******n
发帖数: 12850 | 19 是Oil-Based Polyurethane，这个没有甲醛的吧。请教这个危害主要是来自solvent吗
？是不是solvent挥发完了就好了？
谢谢 |
|
s****7
发帖数: 1873 | 20 【 以下文字转载自 Chemistry 讨论区 】
发信人: super7 (777), 信区: Chemistry
标 题: 门外汉请教一个胶水化学毒性（甲醛等）的问题，包子答谢！
发信站: BBS 未名空间站 (Tue Jan 7 19:24:35 2014, 美东)
刚搬了家，马上要装修，大冬天又不方便一直开窗。 家里有个强过敏的小孩子。所以
对贴地版的胶水很谨慎。（只能选择胶水粘地板了，房间高度太低决定的，其他非实木
地板
不考虑了）。
有没有同学对于这边胶水有研究的，那些号称安全的真的就安全么？
我刷了一次家，用的油漆也是号称安全的，没有危害的。可是那个味道让我明显感到头
疼等不适，是不是就是里面的甲醛导致的呢？有没有懂行的同学有好的安全品牌推荐呢？
看到下面这个产品不错，不知道Polymer Based Wood Flooring Adhesive 里面Polymer
Based有什么特殊含义表示健康安全性么？
http://www.staufusa.com/index.php/259/smp-960-one-step.html?art
It is ozone and ... 阅读全帖 |
|
|
x*****n
发帖数: 101 | 22 谢谢各位热心回答！那请问除了Acetone意外大家知道的在cleanroom里面比较常见的
solvent有哪些是特别需要注意的呢？因为除了Acetone也还会可能用到其他的solvent
，比如IPA，NMP什么的，一时也想不全，所以如果有经验的人能大概说一下需要注意什
么就太感谢了！ |
|
a***h
发帖数: 283 | 23 有相关背景并感兴趣的童鞋，请将你的姓名，工作单位，研究背景/简单履历，email地
址发到我站内邮箱，我会將背景符合者推荐给编辑。
Keywords: solvent deasphalting (SDA) process, solvent recovery using CO2 |
|
l*****r
发帖数: 7130 | 24 From babycenter
http://www.babycenter.com/404_is-it-safe-to-paint-or-be-around-
indoor用的一般都是latex paint，问题不大
Expert Answers
See all Expert Answers
Is it safe to paint or be around paint fumes during pregnancy?
1
Lori Wolfe
Genetic counselor
The answer depends on what type of paint you're using or being exposed to.
Some paint contains ingredients that you should avoid during pregnancy. In
general, paint contains a pigment or dye that's suspended in a liquid to
which thinners, solvents, and drying... 阅读全帖 |
|
c*****r
发帖数: 8227 | 25 关键是这钱会用到哪里？
一言以蔽之：填退休金造成的州赤字的无底洞！“So any money allocated to
schools will merely backfill the teachers' pension fund.”
摘要：
1. 未必增收
As the Analyst cautions, due to huge swings in the investment incomes of top
earners and "the uncertainty of their responses to the rate increases, the
revenues raised by this measure are difficult to estimate."
2. 只拿教育经费开刀
Mr. Brown has threatened to "trigger" $5.9 billion in education cuts if his
initiative fails, but he'd make less than $100 million in other trims.... 阅读全帖 |
|
c*****r
发帖数: 8227 | 26 关键是这钱会用到哪里？
一言以蔽之：填退休金造成的州赤字的无底洞！“So any money allocated to
schools will merely backfill the teachers' pension fund.”
摘要：
1. 未必增收
As the Analyst cautions, due to huge swings in the investment incomes of top
earners and "the uncertainty of their responses to the rate increases, the
revenues raised by this measure are difficult to estimate."
2. 只拿教育经费开刀
Mr. Brown has threatened to "trigger" $5.9 billion in education cuts if his
initiative fails, but he'd make less than $100 million in other trims.... 阅读全帖 |
|
C*******r
发帖数: 10345 | 27 Yes, almost immediately after you arrive home from the range. Clean all the
parts. You need solvent with ammonium for the barrel. I use Sweet 7.62
solvent (5% ammonium). |
|
s****y
发帖数: 939 | 28 I am not sure what is the deposits.
I use bore brush with Hoppe powder solvent--patch with solvent--dry patch--
patch with oil--dry patch; and repeat this.
these deposits just stayed there. |
|
M*******n
发帖数: 1165 | 29 擦了有几次枪了，有个问题一直不能解惑
我用的hoppe 9的solvent和lubricate，说明上是说一遍solvent的patch一遍干patch到
干patch完全干净，我每次都这么过20来遍，干patch还是会有一小点变色，最后实在是
烦了于是直接跳过到下一步了。问下大家都是怎么处理的？ |
|
M*******n
发帖数: 1165 | 30 擦了有几次枪了，有个问题一直不能解惑
我用的hoppe 9的solvent和lubricate，说明上是说一遍solvent的patch一遍干patch到
干patch完全干净，我每次都这么过20来遍，干patch还是会有一小点变色，最后实在是
烦了于是直接跳过到下一步了。问下大家都是怎么处理的？ |
|
|
v*********e
发帖数: 259 | 32 来自主题: GunsAndGears版 - 擦枪这件事 对老手来说是了然于胸， 易如反掌。 可是对新手来说就没那么清楚和容易了。
哪位来介绍一下自己擦枪的心得体会， 也好使新手不走弯路？
我了解了一下， 以下的溶剂经常被用到：
1. Hopper's No. 9 Solvent, 涮洗Bolt， gas-piston, as well as springs
2. Windex or Sweet 762 solvent (5% ammonia), for bore cleaning
3. Shooter's Choice Copper Remover or Breakfree CLP for rust remove
4. baby oil, or gun oil, or breakfree CLP for rust provention and gun
storage.
所知道的就大概这些， 高手们补充吧。。 |
|
n***y
发帖数: 15001 | 33 thinner is solvent....
should be able to solve
the rubber cement...
after all...
rubber cement = natural rubber + solvent... |
|
h*******a
发帖数: 1753 | 34
It's easy to remove the glue built-up on Hurricane 3. Peel off a bit and
then lift up the rest, that is it. No need to rub hard.
We never had the $ to pay for Tenergy. Galaxy Apollo (~$15) and Galaxy Venus
2 (~$10) both work very well for official USATT games. All we do is wet
the blade with a thin layer of organic solvent, either VM&P of Home Depot or
Best Test of Blicker Arts, and place Apollo or Venus 2 on it. Either
Apollo or Venus 2 functions well throughout the weekend tournament. Af... 阅读全帖 |
|
|
l*****e
发帖数: 8596 | 36 wanted an anhydrous solvent with similar polarity and disolving power as MEK
, any suggestion? don't want to distill solvent in my lab..
for disolving polymer resin |
|
k****t
发帖数: 12697 | 37 Tree Sap
"Removing tree sap from a car's finish is a bit more difficult than
removing tar or bird droppings. Incorrectly removing hardened sap can
scratch your paint. I've found that by hand rubbing the sap spots
with mineral spirits, I'm able to easily remove the sap without
damaging the finish. Mineral spirits acts as a solvent to break up
and dissolve the sap.
If there is a large amount of sap on the car, or if the sap has been
left on the finish for an extended period of time, it can be a... 阅读全帖 |
|
c**********a
发帖数: 6 | 38 Magnetic nano catalyst modified by dendrimer has excellent performance.
Magnetic nano catalyst modified by dendrimer has excellent performance: 1.
better stability 2. better solubility, can be dissolved in many organic
solvents 3. higher catalytic activity 4. higher catalytic selectivity. In a
variety of organic solvents, it can catalyze a variety of substance in the
hydroformylation reaction, such as catalytic styrene, 4 - fluoro-styrene,
bromostyrene, etc., in appropriate conditions, conversio... 阅读全帖 |
|
b*****l
发帖数: 3821 | 39 这个里面11楼有些评价：
http://forums.randi.org/showthread.php?t=88831
“The UV spectroscopy is just wrong. The spectrum he presents for ethanol
just is not the UV spectrum of ethanol, period. He then seems to be saying
that the potentised remedies are less absorbent than the solvent. I could
see no data supporting his contention that he could tell different potencies
or different remedies apart.
If in fact what he says is true (that ethanol has significant UV absorbance
at 320nm which is eliminated when th... 阅读全帖 |
|
a**********e
发帖数: 418 | 40 Start With distilled THF as Solvent, Do not use hexanes, lithium halogen
exchange should be done at -78 degree over 30 min. Then add dibromohexane
in THF dropwise at -78, and subsequent warming to rt.
Both Lithium halogen exchange and SN2 reaction (in this case) work better in
a polar solvent. There is no point of using hexanes. Do not use TMEDA which
might result in a deprotonation at the 5 position.
Side reactions: 1. elemination to form 5-bromopenta-1-ene. It is difficult
to avoid 2. dimer |
|
J***y
发帖数: 133 | 41 Any chemistry PhD here can help wiith this problem? How to clear the bench
top and the used glassware? Spray cehmical solvent onto them just like
washing the car using a water gun (surely, solvent gun for the bench top and
glassware). I appreciate your input! |
|
T**y
发帖数: 673 | 42 DMF or DMSO: Very polar and high-boiling solvents that are difficult to
remove. If your product is not dangerously polar, dilute with lots and lots
of water before extracting with a nonpolar solvent. Then thoroughly wash the
organic layer with water.
For 5 mL of DMF or DMSO, use 5 X 10 mL of water during the aqueous wash.
This should remove all of the DMF or DMSO |
|
B******1
发帖数: 9094 | 43 MeOH and Pd/c is a dangerous combination. Better avoid that combo all
together. Switch the solvent to EtOH would reduce the "fire/combustion"
risk dramatically. When doing filtration to remove the used catalyst, make
sure you do NOT make the catalyst super dry and exposed to air.
I agree EtOAc is a much benign solvent for hydrogenation in this respect.
But the speed of hydrogenation therein is very slow compared to using EtOH.
For solubility concerns, a mixture of EtOH/EtOAc seems to work fo |
|
t******t
发帖数: 3045 | 44 If you want to speed up the relaxation, you can use solvents with more
protons(i.e. not the deuterated solvents) or add things like Cr(acac)2. |
|
P******e
发帖数: 129 | 45 LOCATION: New Hampshire
SALARY: Depends on experience
REQUIREMENTS: Min.BS Chemistry with at least 10 years experience in the
lamination of plastic films using solvent and water-based adhesives.
Synthesis and polymer modification experience desired. Must have strong
written and verbal communication skills. Ability to work with people at all
levels.
DESCRIPTION: Person must have a strong background in the formulation
of solvent/water based adhesives. Coating/lamination are performed
usin |
|
s****2
发帖数: 4569 | 46 聚合物 easy to (kind of) "suepending/dissoving" in organic solvents!
wetted by solvents, resin expands in much large volume, better for reaction
to take place.
CPG(control pore glass) is inorganic 载体, it have been used for many many
years, still using for DNA synthesis(at least), 1000A CPG for much longer
DNA(over 100mem) synthesis. |
|
t*******s
发帖数: 16 | 47 用针筒抽的时候有没有选择dry prime并选择solvent？确定solvent没有半夜的时候用
光？如果有很多气泡的话，可能得用
针筒抽好一会。
so far没遇到过你描述的这种情况，一般lost prime都是由于communication造成的，
所以reset之后就一切正常了。
如果以上都不是造成你机器lost prime的原因，可以打开机器右面的门，在打开顶上的
板，看看靠左边1／3附近的电路板
上的指示灯，如果你用的是2795的话，正常情况下应该有4个灯是亮的，至少可以帮助
你判断是不是电路哪里烧了。 |
|
x********e
发帖数: 1064 | 48 International Journal of Pharmaceutics
Volume 43, Issues 1-2, April 1988, Pages 179-186
Solvent selection in the preparation of poly(dl-lactide) microspheres
prepared by the solvent evaporation method
R. BodmeierCorresponding Author Contact Information, a and J.W. McGinitya
Please send the paper to x********[email protected]
Thanks |
|
h**********3
发帖数: 427 | 49 帮忙查一下国内的一篇文章吧，谢谢了：
请发送到h**********[email protected]
Ab initio calculations of vibrational frequencies and structures of ion
pairs of perchlorate. Xuan, Xiao-peng; Xie, You-hai; Zhao, Yang.
School of Chemical and Environmental Sciences, Henan Normal University,
Xinxiang, Peop. Rep. China. Guangpuxue Yu Guangpu Fenxi (2010), 30(9),
2537-2540. Publisher: Beijing Daxue Chubanshe, CODEN: GYGFED ISSN: 1000
-0593. Journal written in Chinese. CAN 153:369826 AN 2010:1137884 ... 阅读全帖 |
|
x****o
发帖数: 60 | 50 What detector? If it's UV, it might be injection solvent (water) disturbance
. You sample solvent might have better compatibility with your mobile phase
for some reason |
|
