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PhD Candidate in polymer chemistry and physics Research Institute of Material Science, South China University of Technology, Guangzhou, P. R. China Please visit my page at www.andrewsun.net or subscribe my FriendFeed at http://feeds2.feedburner.com/AndrewSun-Friendfeed.
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- February 9, 2010
- 10:40 AM
- 1,694 views
关于Strain-Rate Frequency Superposition的看法
by Andrew Sun in Notes on Research Papers
Brian M. Erwin, Simon A. Rogers, Michel Cloitre, & Dimitris Vlassopoulos (2010). Examining the validity of strain-rate frequency superposition when measuring the linear viscoelastic properties of soft materials Journal of Rheology, 54 (2), 187-195
Strain-Rate Frequency Superposition（SRFS）的文章会不会如雨后春笋般暴发我不清楚。有很多我很不以为然的东西都莫名其妙地暴发过了，教训就是千万别跟文章上写的东西较真。
SRFS是H. Wyss等人（D. Weitz小组）发表在PRL 98:238303上的工作，是在胶体玻璃等许多软物质上发现的可叠加现象。做流变的朋友应该多多少少也留意到这项研究了。其他组后续跟踪的不少。我也算是跟踪了一下，文章还没出炉。所以我在这里要谈谈看法。
这东西如果不是一个很花俏的废物，那就是重大发现的开端。现在看来像前者多一点。
给定PRL那篇文章，起码要有以下的疑问：
PRL那篇文章是说，SRFS在很多软物质材料体系上都有，甚至按照我理解H. Wyss的意思，只要一个软物质在dynamic strain sweep下出现典型如右图的行为，就一定符合SRFS（详见SRFS的介绍网页）。这到底有什么物理上的根据？最终到底满足什么条件的材料就会有，不满足就没有？
左图的数学关系，已经在许多实验中证实了，如果考虑粘度和松弛时间等价，它其实就是广义宾汉流体的方程。而SRFS的数学关系，是要把左图的稳态剪切速率gamma-dot换成振荡剪切速率幅度gamma-dot-zero。这又是什么道理？
dynamic strain sweep下大应变区的G”斜率绝对值其实是等于广义宾汉流体里面那个幂ν的，这个已经从数学上证明了。MCT和SGR理论也都各自导出了这一关系。如果上述SRFS的各方面都成立，那么SRFS下G”在低频区的斜率，也要等于ν，而且水平平移因子a同应变速率幅度gamma-dot-zero之间的幂率关系，指数也要等于ν。也就是说，这个ν冥冥中统治了软物质世界！如果你不给出一个统治软物质世界的模型来解释这个ν，我情愿相信这是巧合。
PRL这篇文章出来之后，感兴趣的人很多。我好像记得Nature的Journal Club都赞扬过，只是我一时找不回原文了。后续跟踪的文章发表在Soft Matter、Phys. Rev. E、J. Phys. Chem. B等等上面，档次都不算低。在这些文章里，SRFS仅仅是一部分内容而不是全部，也仅仅是描述一下现象，至于其意义，都是照抄PRL的观点，也没有提出过什么质疑。尤其是在不同测试下的幂率指数之间的相等关系，有很多报道硬是说“大致成立”，审稿人竟也得过且过。让我非常不爽的是，这些幂率指数，全是通过实验数据的拟合而获得的。做过实验的都知道，这样的拟合，你多取一个点少取一个点，结果会不一样。因此我认为要同时给出拟合的标准差。有好几篇论文，想去讨论那个指数随实验体系组成的变化，但又没有同时给出拟合的标准误差数据。从文章上看那数值只变化了一点点，作者也坦言是“appears to increase slightly”。既然是appears to，既然是slightly，你不给出error [...]... Read more »
Brian M. Erwin, Simon A. Rogers, Michel Cloitre, & Dimitris Vlassopoulos. (2010) Examining the validity of strain-rate frequency superposition when measuring the linear viscoelastic properties of soft materials. Journal of Rheology, 54(2), 187-195. info:/
- February 24, 2009
- 08:30 PM
- 1,409 views
Please provide me with more information
by Andrew Sun in On The Road
First things first, I believe that it’s normal and should be highly appreciated that criticism becomes the major voices from the west as China starts to get into their eyes. This will not last long, and this is why the nation should appreciate them more. But it seems quite not the case, critiques are much less than what I have expected, and China still have been incapable to pay enough attention and consideration to the critiques that have come out. For individuals like me, they have freedom to form their own points, based on “facts” they can collect from news. Sometimes however, it is the lack of factual information that set us into confusion.
In the Feb. 19 issue of Nature is this editorial titled Collective responsibilities1, which provided invaluable opinions that can surely help China overcome its hurdle toward scientific independence. But it mentioned something I failed to find more information of:
The spread in China of unproven stem-cell therapies for conditions such as epilepsy and spinal cord injuries has left the nation’s health authorities concerned.
and,
The Chinese authorities, however, tend to have an aversion to congregations— especially those such as the Falun Gong, which they believe pose a threat to the country’s stability. So the Ministry of Civil Affairs keeps a tight hold on who is allowed to organize in any formal sense. As a result, China’s stem-cell hopefuls must go through the slow process of planning and applying to become a ‘level 2’ society.
According to my knowledge of English, the as a result implies a causal relationship.
So are there some scandals about the Chinese authority’s misconducts on the stem cell research community? Is there a Chinese stem cell organization once being pressed down by the Ministry of Civil Affairs? This is ironical that I who live in China have to ask people who are not about whether something did happened in China. But I assume you understand this. I have already tried Google.com, but with no success. So I am asking you to provide me more information about this issue. If you ever heard of such kind of news, please tell me. You can just tell me “yes there seem to be once when I heard that … but I forget the detail”…
Or, this is a piece of news that first comes out from an Editorial article, which I believe is not appropriate. Editorial should not serve for news breaking itself.
1 Nature (2009). Collective responsibilities Nature, 457 (7232), 935-935 DOI: 10.1038/457935a... Read more »
Nature. (2009) Collective responsibilities. Nature, 457(7232), 935-935. DOI: 10.1038/457935a
- February 13, 2009
- 07:19 AM
- 1,395 views
Liquid Mirrors
by Andrew Sun in On The Road
Liquid Mirror Telescope
The first time I heard that liquid mirrors worth studying was from a Nature‘s News & Views article. Rotating liquid that creates a parabolic surface enables human to conceive about really big telescopes that have to be built on the moon. The Nature article praised the use of ionic liquid, liquid with ’nearly zero’ vapor pressure, for liquid mirror support, because in the moon the working environment is vacuum. And it is also cold there, so the liquid mirror should also melt at as low a temperature as possible.
Then it started to seem that all researching or manufacturing efforts on reflective liquid droplets were for the future, exciting, lunar application, at least for me, who only heard of these things from the moon fantasy. Afterward I kept being informed by various science news agents of the same moon fantasy (NewScientist, NASA, the MIT based Technology Reviews, etc.), although I also knew more that liquid mirror for telescope is not new. NASA has one – a 3-meter Liquid Mirror Telescope (LMT) for tracking orbital debris:
Image from the NASA Orbital Debris Program Office
The liquid used in this ‘Earth version’ is mercury. The man in the photo was not committing suicide because the surface of mercury was covered by a layer of oxide which prevent the mercury to evaporate. But this is not likely to work on the moon where the pressure is much lower and things are much more ready to evaporate. So it can be said that ionic liquid have saved the crazy idea of lunar liquid mirror telescope, and will realize an ongoing lunar liquid mirror telescope project.
An Ancient Project
The legend of Archimedes’s weapon
The idea of “mobile” curved mirror is not new, although there have been many debates on the historical existence of the mirrors as “weapons of mass destruction” in ancient Greece implemented by Archimede – the Death Ray, in which multiple mirrors were arranged to concentrate the sun light and set the enemy in fire. Not only is it theoretically doubtful, but experimentally, an MIT group also indicated that the effect of this kind of weapon was exaggerated. The experiment was only able to set a small fire on one ship at half the distance described in the legend, and that fire was quickly extincted. Some authors even suspected the translation of the ancient Greek word πυρεια referring the very object used as weapon in the concerned war as mirrors. However, knowledge of the concentrating effect of curvature on a mirror seems to have indeed established early. No matter the legend of the Death Ray was true or not, at least there must have been someone conceiving many normal-scale plain mirrors to assemble a large-scale, ‘mobile’, curved reflective surface.
Stories in Smaller Scales
And this seems to have been realized in a much smaller scale recently. Researchers from different universities cooperated to assemble tiny hexagonal mirrors along the interface between an oil droplet and the surrounding water bath, thus created a liquid mirror droplet. The tiny mirrors are actually hydrophilic, transparent silicon platelets 8 μm in diameter and 1μm thick, fabricated by lithography. Each platelet is then covered by gold on one side (hydrophilic). When the mirror platelets was injected into the oil droplet submerged in water bath, the platelets gradually migrated to the water/oil interface with the gold side facing toward the oil phase, forming a curved reflective surface. Moreover, the researchers were able to alter the curvature of the droplet by electrowetting method, making the focus length of the liquid mirror tunable.
Tunable liquid mirror. Langmuir ASAP Article. Permission obtained from Rightslink
This work’s perspective differs quite largely from the above mentioned large scale lunar project, in that suspending droplets with enhanced boundary optical properties are also a promising step toward tunable optofluidic devices for cell, microparticle, and even nanoparticle manipulation in a really small scale world.
Robin D. Rogers (2007). Materials science: Reflections on ionic liquids Nature, 447 (7147), 917-918 DOI: 10.1038/447917a
A.S. Papadogiannis, N.S. Papadogianni, A. Carabelas, S. Tsitomeneas, P. Kyraggelos, T.G. Chondros (2008). The Mirror Weapon in Archimedes Era Proceedings of EUCOMES 08, 29-36 DOI: 10.1007/978-1-4020-8915-2_4
D. L. Simms (1991). Galen on Archimedes: Burning Mirror or Burning Pitch? Technology and Culture, 32 (1), 91-96
Michael A. Bucaro, Paul R. Kolodner, J. Ashley Taylor, Alex Sidorenko, Joanna Aizenberg, Tom N. Krupenkin (2008). Tunable Liquid Optics: Electrowetting-Controlled Liquid Mirrors Based on Self-Assembled Janus Tiles Langmuir DOI: 10.1021/la803537v... Read more »
Robin D. Rogers. (2007) Materials science: Reflections on ionic liquids. Nature, 447(7147), 917-918. DOI: 10.1038/447917a
A.S. Papadogiannis, N.S. Papadogianni, A. Carabelas, S. Tsitomeneas, P. Kyraggelos, & T.G. Chondros. (2008) The Mirror Weapon in Archimedes Era . Proceedings of EUCOMES 08, 29-36. DOI: 10.1007/978-1-4020-8915-2_4
D. L. Simms. (1991) Galen on Archimedes: Burning Mirror or Burning Pitch?. Technology and Culture, 32(1), 91-96. DOI: http://www.jstor.org/stable/3106011
Michael A. Bucaro, Paul R. Kolodner, J. Ashley Taylor, Alex Sidorenko, Joanna Aizenberg, & Tom N. Krupenkin. (2008) Tunable Liquid Optics: Electrowetting-Controlled Liquid Mirrors Based on Self-Assembled Janus Tiles. Langmuir, 2147483647. DOI: 10.1021/la803537v
- February 6, 2010
- 10:27 AM
- 1,307 views
非年顿流体用于艺术品保护（哥写的不是综述）
by Andrew Sun in Notes on Research Papers
Siano, S., & Salimbeni, R. (2010). Advances in Laser Cleaning of Artwork and Objects of Historical Interest: The Optimized Pulse Duration Approach Accounts of Chemical Research DOI: 10.1021/ar900190f
Carretti, E., Grassi, S., Cossalter, M., Natali, I., Caminati, G., Weiss, R., Baglioni, P., & Dei, L. (2009). Poly(vinyl alcohol)−Borate Hydro/Cosolvent Gels: [...]... Read more »
Siano, S., & Salimbeni, R. (2010) Advances in Laser Cleaning of Artwork and Objects of Historical Interest: The Optimized Pulse Duration Approach. Accounts of Chemical Research, 2147483647. DOI: 10.1021/ar900190f
Carretti, E., Grassi, S., Cossalter, M., Natali, I., Caminati, G., Weiss, R., Baglioni, P., & Dei, L. (2009) Poly(vinyl alcohol)−Borate Hydro/Cosolvent Gels: Viscoelastic Properties, Solubilizing Power, and Application to Art Conservation . Langmuir, 25(15), 8656-8662. DOI: 10.1021/la804306w
- February 21, 2010
- 08:38 AM
- 1,244 views
GM Whitesides的TED演讲
by Andrew Sun in Notes on Research Papers
George M. WhitesidesH-index第一名的人，好像还保持了几年。07年的数据是151。仅仅因为这个他每年诺奖呼声都很高，没得奖估计是他做得太杂。
我是不喜欢从“学霸”这种角度去解释人为什么牛的，因为一方面我个人没有获得什么证据支持这一论点，另一方面这样去解释所有的牛人对于自己变牛没有帮助。用“黑暗”来解释别人牛，其实是草根的做法，因为他们其实是在解释自己为何菜，且多数只是心理安慰或者阿q精神。很多人认为精英和草根是一对对立概念，我认为精英跟阿q才是一对对立概念。
所以我愿意认为GM Whitesides是名副其实的牛，只有这么认为，你才有了解他分析他学习他的前提。想通过分析别人如何成为学霸如何耍手段如何潜规则也不是不可以，但是这条途径非常难以获得信息，人很难知道别人背后的事情。所以你越这么想越认为自己的人生已经暗淡，生出类似“谁叫你生在中国”之类的感叹，没真正遇到黑暗降临你头上之前，已经自己自动圆满了人生。想来想去，这种做法很脑残。
最近刚写过一点申请书的内容，虽然是抱着锻炼的心态但也觉得十分受教育（主要属于挫折教育）。所以，看看GM Whitesides怎么解释自己的研究不是拍脑袋而是很重大，可以提高自己形成研究思路的水平。就好像我妈整天说的：“瞧瞧人家！啧啧……”。
演讲里所介绍的工作，代表文章是发在Anal. Chem.上的文章：
Martinez, A., Phillips, S., Whitesides, G., & Carrilho, E. (2010). Diagnostics for the Developing World: Microfluidic Paper-Based Analytical Devices Analytical Chemistry, 82 (1), 3-10 DOI: 10.1021/ac9013989
Anal. Chem.的Pod Cast也介绍了这个工作。... Read more »
Martinez, A., Phillips, S., Whitesides, G., & Carrilho, E. (2010) Diagnostics for the Developing World: Microfluidic Paper-Based Analytical Devices. Analytical Chemistry, 82(1), 3-10. DOI: 10.1021/ac9013989
- February 23, 2009
- 03:10 PM
- 1,213 views
Latest report of adaptive synthetic surfaces
by Andrew Sun in On The Road
A dung beetle’s never too dirty. From Wikipedia.org
The biological concept of adaptation has sneaked into synthetic materials research. I was informed of this by a report on Adv. Mater.1 describing an adaptive non-adhesive surface. The report cited further for us a review on Prog. Polym. Sci.2 summing up the advances in fabricating smart surfaces by designing and synthesizing polymer brushes.
Yes. We have got encouraging advances in synthetic and fabricating skills, as evidenced by numerous reports on delicate yet strange structures on every issues of high impact chemistry journals, without, however, knowing the practical uses of them.
And ‘chemistry that really works’ cannot be easily achieved by conceiving such exciting concepts as ‘an adapting non-living thing’, ‘a smart nonintellectual being’, etc. In the particular case of non-adhesive surface, which we wish can be equally non-adhesive both in air and in water solutions, as the report on Adv. Mater. has excellently reviewed, even the smartest, most adaptive design by human failed. Adaptive surfaces for this purpose has been tried to achieved by grating amphiphilic polymers so that, the hydrophobic segments swell when placed in air, while the hydrophilic segments swell when place in aqueous solution, both cases being unfavorable for adhesion. However, the real products are not smart enough, they adapt too slow due to the slow motion of polymer chains. Softening the polymer surface make the surface sticky too due to increased contact area, which is favorable to adhesion.
When confronting such difficulties, we often turn to biomimetics too late. Soil animals which survive in varying humidity in soils have their solution to prevent soil adhesion on their skins, which are commonly a triple combination of cuticles with different smooth appearances, liquid secretion, and electrical charges. Although like in most cases, the structure-function relationship here is complex, we can well be satisfied by merely clumsy mimicking of its mechanism. Close-packed monodispersed silica nanpoarticles as the artistic ‘cuticles’ on dung beetles, or responsive stretching polymer chains as the ‘secretion’ behavior may be, perhaps, clumsy, but it seemed to work perfectly microscopically — the report1 only test the adhesiveness of the so-synthesized surface by atomic forced microscopy, that is at an atomic scale.
But we have a positive experience in the relation between atomic and macroscopic effects in terms of adhesive properties. The well known gecko foot mimic was also first tested by atomic forced microscopy in the Nature article by H. Lee et al.3, and lately demonstrated by Zhonglin Wang macroscopically4 with similar molecular design. I look forward to a macroscopic test for this non-adhesive counterpart.
1 Roman Sheparovych, Mikhail Motornov, Sergiy Minko (2009). Low Adhesive Surfaces that Adapt to Changing Environments Advanced Materials DOI: 10.1002/adma.200802449
2 I LUZINOV, S MINKO, V TSUKRUK (2004). Adaptive and responsive surfaces through controlled reorganization of interfacial polymer layers Progress in Polymer Science, 29 (7), 635-698 DOI: 10.1016/j.progpolymsci.2004.03.001
3 Haeshin Lee, Bruce P. Lee, Phillip B. Messersmith (2007). A reversible wet/dry adhesive inspired by mussels and geckos Nature, 448 (7151), 338-341 DOI: 10.1038/nature05968
4 L. Qu, L. Dai, M. Stone, Z. Xia, Z. L. Wang (2008). Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off Science, 322 (5899), 238-242 DOI: 10.1126/science.1159503... Read more »
Roman Sheparovych, Mikhail Motornov, & Sergiy Minko. (2009) Low Adhesive Surfaces that Adapt to Changing Environments. Advanced Materials. DOI: 10.1002/adma.200802449
I LUZINOV, S MINKO, & V TSUKRUK. (2004) Adaptive and responsive surfaces through controlled reorganization of interfacial polymer layers. Progress in Polymer Science, 29(7), 635-698. DOI: 10.1016/j.progpolymsci.2004.03.001
Haeshin Lee, Bruce P. Lee, & Phillip B. Messersmith. (2007) A reversible wet/dry adhesive inspired by mussels and geckos. Nature, 448(7151), 338-341. DOI: 10.1038/nature05968
L. Qu, L. Dai, M. Stone, Z. Xia, & Z. L. Wang. (2008) Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off. Science, 322(5899), 238-242. DOI: 10.1126/science.1159503
- February 17, 2009
- 07:19 AM
- 1,171 views
Man-Made but Living Systems - Bio Besides Mimetics and Inspirations
by Andrew Sun in On The Road
According to Wikipedia.org which though is not often desirable, the meaning of the word biomimetics does not include the direct utilization of the functional part of living structures. We have found lotus leaves superhydrophobic. But biomimetically we didn’t directly grow lotus crops for water-repelling coatings, nor did we try to culture similar layer from lotus tissue. Rather, we got ‘inspired’ and started ‘mimicking’ the structure by purely artificial technologies we are familiar with. Similar situation is in computer science—obviously we didn’t try to clone some people exclusively for intellectual production, leaving us a comfortable yet improving future without necessity to think over anything complex. Rather, we turn to silicon-based computers and only wish these computers can become smarter by mimicking the logical structure of brain—what the cyberneticists are doing. There seems to be a far future perspective of biomimetics where we will have learned how all the living things work in the planet. At that time we will be alright living without any other living things because they are no longer mysterious or fascinating. Or in other words, at that time we will never fear of the extinction of living things because they are no longer Nature’s monopoly; we can create all living things from bottom up.
However, today’s reality does not seem to allow such an biomimetic optimism. Although some structural tricks have been played by scientists, we are still generally helpless in front of the core mechanism of life. Currently we have learned very little from Nature as we estimate, and our biomimetic products are essentially nonliving. While the genius of Natural gifts are extincting at a much faster way than human can catch up, we now still need to rely on living things in many crucial aspects of life besides foods.
Energy source of the matrix in the movie Matrix. From Jason Kurtz’s website.
Whereas biomimetics wishes us to rely less on ecology, with little real success, another idea wishes us to rely more, by exploring the nature and finding new living species that may potentially work for human. The logic is somewhat similar to ‘to grow crops of lotus for water-repelling coating’, but practically this kind of research focus primarily on biofuels, agricultural technology (e.g. mix planting), etc. Although this kind of idea can still be ethically scary if pushed to some extreme (remember the energy producing units in the movie Matrix), it still sounds better than a biomimetic claim that we will kill all fauna and flora when we have known them all (at least in Matrix we still have human).
Shewanella. From http://www.ornl.gov.
And sometimes this kind of research is also seen in materials science. A group of Japanese scientists recently published a paper1 on Angew. Chem. Int. Ed. describing a electrically conductive bacterial network under some artificial manipulation—a man-made material that functions only when it’s living. The featured bacterium is called Shewanella, which is known capable to recognize and transfer electrons to Fe(III) oxide surfaces2. The researchers found that, although individual cells are electrically
insulated from the others, addition of semiconducting Fe2O3 colloidal particles to the bacterial culture resulted in a continuous film that is found electrically conductive, provided the food for the bacteria, lactate, is sufficient. It is proved that the conductivity of the film is the result of bacteria, not the added Fe2O3 colloids, because pure this colloids were found electrically isolate. The authors said in the paper that this finding is relevant to “designing and fabricating bioanode materials for microbial fuel cells”.
This paper reminded me another earlier one3 published on Adv. Mater., where cells were added to a solution of polymer which is modified with cell recepters, resulting a bio-crosslinked hydrogel. The sol-to-gel transition was characterized by rheological method implying some mechanical properties of the so-formed hydrogel. This cell-croslinking hydrogel was further found reversible—it flows when sheared, and gels again when allowed to stand for a while. This property is important for injectable gel drugs that allow the drug can pass through the syringe while can stay at one place after injection, curing specifically the lesion site. What if we can inject some living cell amendment instead?! And, considering also the former electrical bacteria, what if we can inject some living electronic devices into our bodies where they keep functioning so long as our bodies provide them nutrients for living?
That may be a totally different scene from what biomimetics provides.
1 Ryuhei Nakamura, Fumiyoshi Kai, Akihiro Okamoto, Greg J. Newton, Kazuhito Hashimoto (2009). Self-Constructed Electrically Conductive Bacterial Networks Angewandte Chemie International Edition, 48 (3), 508-511 DOI: 10.1002/anie.200804750
2 Gemma Reguera, Kevin D. McCarthy, Teena Mehta, Julie S. Nicoll, Mark T. Tuominen, Derek R. Lovley (2005). Extracellular electron transfer via microbial nanowires Nature, 435 (7045), 1098-1101 DOI: 10.1038/nature03661
3 K.Y. Lee, H.J. Kong, R.G. Larson, D.J. Mooney (2003). Hydrogel Formation via Cell Crosslinking Advanced Materials, 15 (21), 1828-1832 DOI: 10.1002/adma.200305406... Read more »
Ryuhei Nakamura, Fumiyoshi Kai, Akihiro Okamoto, Greg J. Newton, & Kazuhito Hashimoto. (2009) Self-Constructed Electrically Conductive Bacterial Networks. Angewandte Chemie International Edition, 48(3), 508-511. DOI: 10.1002/anie.200804750
Gemma Reguera, Kevin D. McCarthy, Teena Mehta, Julie S. Nicoll, Mark T. Tuominen, & Derek R. Lovley. (2005) Extracellular electron transfer via microbial nanowires. Nature, 435(7045), 1098-1101. DOI: 10.1038/nature03661
K.Y. Lee, H.J. Kong, R.G. Larson, & D.J. Mooney. (2003) Hydrogel Formation via Cell Crosslinking. Advanced Materials, 15(21), 1828-1832. DOI: 10.1002/adma.200305406
- August 18, 2009
- 11:47 PM
- 1,159 views
对付完收件箱、Google Reader，谁是一下个？
by Andrew Sun in Notes on Research Papers
我是Web 2.0时代进入研究生学习阶段的。我需要各路信息聚集到我的本地，而不是我主动去跑路去找信息。看文献是研究生学习给我生活增加的众多必要事务之一，我很自然希望文献信息自动送过来。在那时，许多期刊都提供邮件提醒功能，我订了一堆高分子期刊的邮件提醒。几乎每周的inbox都有一堆TOC需要消灭掉。对付inbox成了一个新奇的心理负担。
不久，越来越多的期刊支持RSS Feed了，Google Reader慢慢占去了我原本花在Gmail上的一半时间。同时，随着我的知识面和兴趣面越来越广，我关注的期刊也越来越五花八门。每天GReader上的条目动辄几百，极力提高脑筋转速，减少眨眼频率，提高大拇指敲空格的速度，争取在最短的时间内把几百个论文题目过掉！
时间久了，是有提高的。不知不觉我眼睛只扫一次，就只会看到几个术语，近乎下意识地判断感不感兴趣，条件反射地决定按v还是按空格。有两种情况值得我多花几秒钟时间重看一个条目。一是看到熟悉的keyword了，二是虽然keyword不熟悉，但突然警醒这个词最近出现频率狂高，说明是研究热点，需要了解一下。有的期刊的RSS feed附了Graphical Abstract，这种情况下我可能连标题都不看，只看图。尽管扫视速度已经到了极限，但还是经常无法看完所有的条目，只能忍痛点一下mark all as read……
不光是扫Google Reader必须一目千行，看一个PDF文件也非常考验鼠标滚轮。很多文章的abstract只说做了啥，不说啥结果，往往需要你“刷刷”马上滚到Conclusion部分。有的文章Conclusion只是报实验数据，看了白看，有的文章是Communication没有Conclusion，于是又要“刷刷”翻到Introduction的末尾后看往前找“In the present/this paper/study, we…”的类似字眼。这样的遭遇多了，就深感差劲的撰文基本功有多么令人生恶。令人头痛的还有古老的论文，那时候的论文没有现在这么结构化，有时还必须看。另一种快速了解文章工作的就是把文章的所有图看一遍，看了图就知道同时知道你做了什么实验，有什么结果。所有结果了解了之后往往不用看我也知道能有什么结论了。总之，被逼从Introduction的第一个字读起是最令人泄气的情况，需要极力避免。我追求的是以最快的速度斃掉尽可能多的PDF。
看了Science的这篇Review我才知道，以上描述种种种行为特征有一个很好听的名词——战略式阅读（Strategic Reading）。这篇文章还有两个绝妙的比喻。一是把快速看文献的行为比喻成打CS：
Now, as scientists search and browse, they are making queries and selecting information in much tighter iterations and with many different kinds of objectives in mind, almost as if they were playing a fast-paced video game. They sweep through resources, changing [...]... Read more »
Renear, A., & Palmer, C. (2009) Strategic Reading, Ontologies, and the Future of Scientific Publishing. Science, 325(5942), 828-832. DOI: 10.1126/science.1157784
- February 12, 2009
- 12:58 PM
- 1,124 views
Snake Robot
by Andrew Sun in On The Road
A review on snake-inspired robot design was published on the IOP journal, Bioinspirations and Biomimetics, 2009 ,4, 021001. DOI: 10.1088/1748-3182/4/2/021001. The introduction paragraphs of the review described several advantages of snake-like robot compared with other types of design, which is quite interesting to read. But I did not go into the detail of the review. There are images of various design of snake robots in this paper. And this reminds me to search some videos in Youtube.com. It seems that these robots don’t just move like snakes. They also moves like worms, or something not seen in nature.
This video shows many motions of a snake-like robot. I’ve never seen a real snake climb up a tree, like that!
And this is one of the few snake-like robots that really move like a snake.
This poor little worm was stuck on the wall for minutes.
James K Hopkins, Brent W Spranklin, Satyandra K Gupta (2009). A survey of snake-inspired robot designs Bioinspiration & Biomimetics, 4 (2) DOI: 10.1088/1748-3182/4/2/021001... Read more »
James K Hopkins, Brent W Spranklin, & Satyandra K Gupta. (2009) A survey of snake-inspired robot designs. Bioinspiration , 4(2), 21001. DOI: 10.1088/1748-3182/4/2/021001
- February 14, 2010
- 12:42 PM
- 1,124 views
答Science记者问之后：文化管制的必要性
by Andrew Sun in Notes on Research Papers
Stone, R., & Xin, H. (2010). Google Plots Exit Strategy As China Shores Up ‘Great Firewall’ Science, 327 (5964), 402-403 DOI: 10.1126/science.327.5964.402-a
Science记者郝炘曾通过邮件问过我关于谷歌退出中国事件的看法，最终文章是Google Plots Exit Strategy As China Shores Up ‘Great Firewall’，里面没有引用我说的话。文章引用了饶毅先生的话，他还在博客里展开他的观点，虽然我没有抓住文章的智慧，但通读全文也没有哪些特别反对的地方。
当时郝炘问我的问题是很具体的，对于谷歌退出中国的看法，所以我的回答也没有扯到“网络管制”这个问题上面。想来我跟此文也算有缘，于是跟着饶先生也谈网络管制。
我的一个基本见解是，网络管制有其合理性。因为中国的文化体系和状况，还没有强大到能够理直气状地抵挡外来袭击的地步。
为什么说我们的文化还不够强大？因为，不管如何学习外国先进的东西，也总要讨论“保留什么”“保留多少”的问题。现在，我们对“学习”已经讲得太多做得太多，但对“保留什么”“保留多少”这方面问题仍然莫衷一是。这说明虽然改革开放三十年以来政局稳定，国力不断增强，创造了很多奇迹，但是在文化还没形成凝聚力，还没有形成方向。我们还不清楚我们赖以作为中国人的东西是什么，我们万变不离其宗的宗是什么，因此才怕变。
一种文化要发达到一定程度，它才可以自圆其说。现在我们在很多问题上还没法自圆其说，不够完善，那只能说还有待探索。但很不幸，信息时代来了，有一个唯一的超级大国，它的文化已经发展到了能自圆其说的高级形态。这对于所有发展中国家来说都是一种文化险境。也许很多朋友看到的是在美国的“民主”、“人权”话语攻击下，很多落后民族的国家政权显得如此固步自封，他们的说辞是如此的老套而又无法自圆其说。其实这是各族文化发展阶段不相当的缘故。虽然有的政权的确犯过罪，像萨达姆政权，但反过来去亲美则更加不符合伊拉克人民的福祉。所以，不干涉别人内政，并不是什么表面文章，而是有利于文化多样性，有害于美国独大的一种实际主张。美国目前正在趁着自己在政治文化上的先进性，抓紧推销美国模式，希望世界按美国人舒服的方向发展。而发展中国家也有一部分人认为，既然一个完善的东西摆在了面前，为什么不直接拿来用。
文化发展不完善的另一个特点是国民缺乏文化自信，尤其是面对另一个完善的外国文化的时候。现在，美国所自豪的一切，中国人都不知道为什么学或者为什么不学。如果好就得学，那要学的几乎是全部，但事实上中国人并不同意全盘西化。西方有很多有很深的文化渊源，中国人会觉得别扭。但中国人又不敢承认自己觉得别扭——这么好的东西你如果感觉别扭，那就是你的劣根性，那就是因为你是劣等民族所以不适合高级文化。这种扯淡实际上存在于很多中国人的潜意识中，体现的其实就是文化上的不自信。但如果你说不一定好就得学，那么到底学哪些？学多少？怎么学？原则是什么？这些我们都不清楚，因为我们不知道我们自己的梦，别人已经实现了的梦对我们也就失去了参考价值。现在如果说美国人喜欢某事，中国人敢说咱不喜欢吗？尤其是在明明美国得益于这件事，而中国受此事拖累的情况下——中国人敢说，改变不只有一种方向吗？假如中国人已经清楚自己是谁，梦在何方，那就有能力免疫各种纷扰，但现在并不是如此，外在的纷扰的负面效应就非常大。
美国政府有一个部门叫Bureau of International Information Programs（IIP），我不知道中文怎么翻译，Wikipedia上对这一部门的介绍如下：
The Bureau of International Information Programs (IIP) is the principal international strategic communications service for the foreign affairs community. IIP designs, [...]... Read more »
Stone, R., & Xin, H. (2010) Google Plots Exit Strategy As China Shores Up 'Great Firewall'. Science, 327(5964), 402-403. DOI: 10.1126/science.327.5964.402-a
- March 7, 2009
- 04:00 AM
- 1,118 views
Is science a must for human being?
by Andrew Sun in On The Road
A Thesis published on Nature Nanotechnology1 shown that public acceptance of nanotechnology, and also generally any new technologies, depend not on the knowledgeablility of those technologies but former religious status of the public.
Strength of religious beliefs is negatively related to support for funding of nanotechnology. Religious apprehensions that developed earlier, in response to biotechnology, served as a template for reactions to nanotechnology. People for whom religion was not very important were more supportive of funding for nanotechnology. Once more, knowledge of nanotechnology had little influence.
Originally, science and religion work separately on human’s spiritual world and do not conflict. The reason why they conflict in the real world seems to be that scientists need to get funding from the public, where science and religion must interact. So scientific research is not a purely personal hobby today, it depends on the taxpayers and therefore is part of the governmental motivation. So why does a government need science? Because nations in the modern time have realized the importance of science and technology to the economical, military and political power, right? That’s why science exist.
But I never hear that religion, or the religious loyalty of its people, plays a role in a nation’s power. Religion still exists only because we humans are born to be religious. Religion exists as long as human beings exist.
So how about science?
Einstein had the following paragraph in his letters:
The development of Western science has been based on two great achievements，the invention of the formal logical system (in Euclidean geometry) by the Greek philosophers，and the discovery of the possibility of finding out causal relationships by systematic experiment (at the Renaissance). In my opinion one need not be astonished that the Chinese sages did not make these steps. The astonishing thing is that these discoveries were made at all.
So, as I agree with, at least Chinese sages did not make these steps. So we are not born to have these two capabilities science bases on. So science does not exists as long as human beings exist.
What do you think?
1 Chris Toumey (2009). Hearts and minds and nanotechnology Nature Nanotechnology, 4 (3), 136-137 DOI: 10.1038/nnano.2009.16... Read more »
Chris Toumey. (2009) Hearts and minds and nanotechnology. Nature Nanotechnology, 4(3), 136-137. DOI: 10.1038/nnano.2009.16
- February 9, 2010
- 07:19 AM
- 1,062 views
地震预测和人生预测
by Andrew Sun in Notes on Research Papers
Robinson, A. (2010). No crystal ball for natural disasters Nature, 463 (7278), 160-160 DOI: 10.1038/463160a
Megadisasters: The Science of Predicting the Next Catastrophe
Nature书评作者在评论这本书的时候，主要站在一个悲观的立场。他说：
Without an understandig of what happens underground, forecasting is inevitably hit-and-miss.
评论中还回顾了中国建国后地震预测的几件事情，选用了2008年北川地震的照片。但是据书评作者介绍，书的作者的态度是比较乐观的：
“At worst, earthquakes are part of a chaotic system, so long-term predictions will always fail,” notes Diacu. By contrast, he points out, short-term warnings [...]... Read more »
Robinson, A. (2010) No crystal ball for natural disasters. Nature, 463(7278), 160-160. DOI: 10.1038/463160a
- May 31, 2010
- 02:19 PM
- 1,057 views
玻璃还是凝胶——从纠结到调侃
by Andrew Sun in Notes on Research Papers
Ruzicka, B., Zulian, L., Zaccarelli, E., Angelini, R., Sztucki, M., Moussaïd, A., & Ruocco, G. (2010). Competing Interactions in Arrested States of Colloidal Clays Physical Review Letters, 104 (8) DOI: 10.1103/PhysRevLett.104.085701
玻璃化转变是《Science》期刊提出目前亟待解决的125个重要的科学难题之一。自从发现胶体粒子悬浮液体积分数不断增加的过程，会发生跟过冷液体温度不断降低的过程类似的玻璃化转变，胶体玻璃（colloidal glass）的非平衡物理研究是近来的热点.因为比起过冷液体来说，胶体玻璃实验简单可控。在玻璃化转变理论的一般预测越来越多地在胶体体系中都得到印证之后，现在好像大家都去研究胶体体系了。
最接近理论的模型是轻度多分散的硬球胶体，例如PMMA球或者PS球。因为玻璃化转变比较完善的理论MCT就是基于硬球的，至多进行一些表面修饰来调控粒子间作用力。但是实验领域的人更有兴致改换胶体性质，用不硬的（微凝胶）或者非球体的（Laponite）体系来做实验。我就是上了Laponite的贼船。
永远悬在Laponite胶体玻璃这一块研究之上的“达摩克利斯之剑”就是：Laponite是玻璃（glass）还是凝胶（gel）——即导致Laponite分散液进入非遍历态的相互作用力是排斥还是吸引力——都还没搞清楚。如果都不是玻璃，那还谈什么玻璃化转变？
Laponite粒子分散在水中，整体带负电荷。因此粒子间有静电排斥力，于是Laponite确实有成为玻璃的理论空间。但是这个排斥力的作用范围要受到水中离子强度的影响。由于自由离子的静电屏蔽作用，静电排斥力的作用距离会随离子强度的增大而减小，直至它竞争不过吸引力。这个吸引力可能来自范德华力，也可以来自粒子上带的正电荷。Laponite粒子虽然总体带负电，但是除了两面带大量负电荷之外，边缘带有少量正电荷。这个静电吸引力比起范德华力来讲更可观。总之这样的话，Laponite形成的就是粒子间相互吸引聚合形成的凝胶。学界长期纠结的是，具体离子强度到达多少是玻璃，达到多少是玻璃。Laponite的相图也被重画了N遍。
实验上我还看不到谁直接去区分粒子间是吸引还是排斥力，基本上都是用间接的方法，从侧面去确定体系处于凝胶还是玻璃结构。各种实验方法都有局限性，而且往往都是那种导致逻辑隐患的局限性。不同实验方法的结果又不可比，没办法通过多种实验方法来完善一个结论。Laponite的实验结果也确实能够用MCT玻璃化理论来描述，描述得多了大家都觉得Laponite就是玻璃了。其实这些符合MCT预测的实验，都不全面。因此就算MCT能描述得很好，也只能说Laponite体系的某些局部具有MCT的特征。所以，关于Laponite是玻璃还是凝胶的说法，一直延续至今。
从我看文献的感受来讲，我发现“内心希望”Laponite是玻璃的人越来越多。毕竟现在玻璃是凝胶态物理的热门。最近我导师给我看的一篇paper（PRL 2010, 104, 085701），让我感觉，这帮人渐渐已经不关注问题的解决了，反而想把这问题变成一个常炒常新的话题。没事调侃一下也能发paper，反正你说较真的话也没谁有本事较真出个结果，发文章干脆越来越随便，毕竟colloidal glass的热门度放在那里。
PRL的这篇文章说，基于吸引力的凝胶，加水之后，能保持水归水，凝胶归凝胶的两相，因为形成凝胶的粒子间为吸引力，后来加的水不能打破已经形成的凝胶结果；相反，基于排斥力的玻璃，加水之后能够稀释成液态，因为粒子间无非是堆积在原有体积限制之内而已，加了水之后能扩散。这一基本说理，原本就不可靠，因为这个实验现象并不能反过来说明体系是基于排斥力还是吸引力，只能说明这种相互作用力是可逆的。
令我和我导师都很困惑的是，PRL具体给出的实验结果还有很明显的问题。PRL说，浓度1.5%的Laponite是凝胶，因为加同样体积水之后，原体积的凝胶不会受影响；但浓度为3%的Laponite是玻璃，加同样体积的水之后，就把样品稀释成（1.5%）液体了。这样说来，1.5%的Laponite到底是凝胶还是玻璃呢？文章作者除了给出以上实验的宏观照片之外，只做了SAXS这一种测试，而且并没有做1.5%的样品，结果也说明不了作者想下的结论。也就是说，这篇PRL是靠几张数码相机照片得以发表的。
比起以往试图分清Laponite是凝胶还是玻璃的论文来看，这篇PRL对体系离子强度的实验控制也太粗略了。不管是支持Gel还是Glass观点，一个共识是盐浓度（静电屏敝作用）是控制这两种机理的关键因素。因此各个不同实验室报道的盐浓度控制方法就很重要，尤其如果文章的目的就是要纠结Gel和Glass的区别的话。即使用纯水来分散Laponite，体系的盐浓度就很可能处于Gel的区域了，更何况很多实验室还特意加NaOH去把pH调到10（包括PRL那篇文章的作者）。实验时添加多少盐，跟实际盐浓度是两回事。之前有人甚至用透析的方法来控制实际盐浓度，这样报道的盐浓度就比较符合实际，接下来关于Gel还是Glass的讨论才有意义。这篇PRL想要讨论Gel or glass话题，却不去纠结这个问题，显得很没基础。
靠照片来说明问题，能发Adv. Mater.或者ACS Nano是正常的，但是能发Physical Review系列期刊，感觉不可思议。... Read more »
Ruzicka, B., Zulian, L., Zaccarelli, E., Angelini, R., Sztucki, M., Moussaïd, A., & Ruocco, G. (2010) Competing Interactions in Arrested States of Colloidal Clays. Physical Review Letters, 104(8). DOI: 10.1103/PhysRevLett.104.085701
- January 3, 2010
- 09:05 AM
- 1,041 views
球球载药药——饶了我吧！
by Andrew Sun in Notes on Research Papers
做合成的哥们，把东西做成球状吧——任何东西。1）空心的叫capsule，澳大利亚的Frank Caruso凭此牛了。好几年前我就看过Caruso就在Adv. Mater.发Mini Review，还有照片，挺帅一小伙儿，但看来看去觉得——这idea好老啊，心想省省吧。结果他狂发ACIE至今。2）做成Janus的，现在也有好几种常规的方法了。3）如果实心的话，那就响应性的吧。记住：不管是哪种，一定要是nano的，掺点荧光药打到老鼠里面，做个共聚焦，呯！——ACIE。
把东西做成球，说drug delivery的，至今还小够得上Langmuir呢。一般我看到比较老的idea的文章我会跳过不看，但是看到把东西做成球，还要drug delivery的，我就要痛苦地跳过不看。
ScienceWatch.com给牛人做专访的问题是固定的：
Why do you think your paper is highly cited?
Does it describe a new discovery, methodology, or synthesis of knowledge?
Would you summarize the significance of your paper in layman’s terms?
How did you become involved in this research and were any particular problems encountered along the way?
Where do you see your research [...]... Read more »
HE, C., KIM, S., & LEE, D. (2008) In situ gelling stimuli-sensitive block copolymer hydrogels for drug delivery. Journal of Controlled Release, 127(3), 189-207. DOI: 10.1016/j.jconrel.2008.01.005
- April 5, 2010
- 04:10 AM
- 1,038 views
为环保，别离婚。
by Andrew Sun in Notes on Research Papers
Liu, J. (2010). China’s Road to Sustainability Science, 328 (5974), 50-50 DOI: 10.1126/science.1186234
这期Science的Policy Forum有一篇讲到了中国的环境问题和可持续发展。大话题没有什么新意，但里面有些信息比较有趣。
中国政府在近三十年来十分注重环保，但有的措施的结果并不符合期望。
例如在干旱风沙地区大量植树，使得土壤仅有的少量水分被树吸光了，反而加剧了土壤风化。所以越植树越沙尘暴。前几天我还看到一行国家领导人在北京一个全是沙的地方植树……
又例如，旨在控制人口的计划生育政策，本来应该能减少资源的开采程度。但实际上，独生子女的增多，家庭规模变小了。以前一家人叔叔婶婶什么的都一起住，资源的使用是比较高效的。现在基本上一对夫妻就是一个家庭，实际上家庭数量的增加，又大大增加了资源浪费。再加上离婚率升高，很多人单身，一个人就是一个家，还有好多人包二奶三奶，一个人有好几个家……
所以作者在文中建议中国政府为了环保事业而控制离婚率，并提倡尽量所有家人都住在一起，以提高资源的使用效率。
现在很多浪漫主义，不食人间烟火的无知少年在跟什么“低碳生活”的时尚风，所有“低碳生活”的时尚活动一律色调年轻，语言俏皮，旨在吸引年轻人——即又无知又有钱的人群——的加入。其实，他们只是玩玩。如果来真的，为了他们所青睐的“低碳”、“乐活”、那种新亮干净简洁现代的意象，叫他们不许过二人世界，结婚后跟公公婆婆住，他们绝对不同意。他们喜欢的只是挂着“低碳”羊头的后工业时代浪费式时尚狗肉。实际上越老土的东西越低碳。原始社会最低碳。... Read more »
Liu, J. (2010) China's Road to Sustainability. Science, 328(5974), 50-50. DOI: 10.1126/science.1186234
- March 4, 2010
- 11:34 AM
- 1,018 views
凝胶化过程的非线性粘弹性
by Andrew Sun in Notes on Research Papers
熟悉溶液-凝胶转变（sol-gel transition）的朋友应该知道渝渗（percolation）理论。流变学上，H. Winter从高分子凝胶的实验提出的临界凝胶指数也“众”所周知：
至于指数n与渝渗理论的分形指数df之间的关系则要考虑高分子链的排除体积、分子量分布等问题，用得比较多的是M. Muthukumar的关系式：
我们课题组之前在也做了一些这方面的工作。
渝渗理论把凝胶化看成一种相变，还基于这样一个基本现象：在凝胶化初期，样品中发生局部交联而形成团簇，溶液的零切粘度不断增大，在临界点之前发散，说明形成了无限网络，失去流动性；临界点后体系显示非零的平衡模量，并随着网络的继续完善而不断增大，形成凝胶。我导师曾经猜想，在临界点附近，不管是之前还是之后，体系的非牛顿性会非常大，显示出较明显的非线性粘弹性，而在初期的溶液状态，体系是牛顿流体；在后期的完善凝胶状态，体系是虎克弹性体，两种情况的非线粘弹性粘弹性都不明显。也就是说不光可以用H. Winter的线性粘弹性方法找到临界凝胶点，还可以通过非线性的流变实验方法来定义临界凝胶点，具体就是当时刚热门起来的所谓LAOS。可是，我在聚丙烯酸/铁(III)凝胶体系上花了一年时间，都没做出这样的结果来。我采用的主要是M. Wilhelm提的Fourier变换流变学的方法，我的结果是在Winter凝胶点前后，I3/1单调增加，没有什么最大值。而且数据很烂，很难做到适合发表的程度。
其实，实验时不得不采用的大幅形变，把样品形成的网络结构都破坏了，出来的结果都不是那个凝胶了，而是网络破坏之后的流体，所以用LAOS无法证实我导师的猜想。想来，LAOS也许只适合去研究“破坏什么东西”的过程或体系（非平衡态），不适合去研究“形成了什么东西”的过程或体系（平衡态），因此后来我和放弃了这个实验，转而做别的去了。现在非线性流变学方面的热点转到屈服流体上，可能也是因为上述原因。
这两天看到Rheol. Acta上的一篇文章：
Andrade, R., Azevedo, A., Musampa, R., & Maia, J. (2010). Thermo-rheological behavior of model protein–polysaccharide mixtures Rheologica Acta DOI: 10.1007/s00397-010-0431-3
做的是多糖/蛋白体系热致凝胶化，倒是使用了一下LAOS，做了凝胶化过程的I3/1 vs γ0图，结果是凝胶化点前后，曲线按形状可明显分为两堆（见下图），凝胶化之前的体系非线性粘弹性比凝胶化之后大得多。我相信这些结果也是反映的也是网络已被破坏后结果，对凝胶网络的形成过程没有什么参考作用。
顺便说明一下，上图是我使用Engauge Digitizer软件从文章的PDF文件移植出来的数据，用Origin重新作的图。Engauge Digitizer的功能是从静态的图片文件格式的坐标曲线中抓取数据，重新生成数据文件的软件。做流变学研究，经常要理论和实验两边跑。经常要拿他人发表的数据按照重新代入新的方程来运算。用这个软件，就可以从PDF文章截下坐标图，转化成数据文章，进行进一步的运算了。这是开源软件，免费的，在此推荐一下。
也就是说LAOS这个东西如果要做，目前暂时还具体体系具体分析。凝胶化方面，没有什么理论支持。按渝渗理论猜想出来的东西是不存在的，或者如果像Muthukumar那样，严格地推导一下大幅形变场下的行为，会有什么有意义的结果？
Rheol. Acta这篇文章还提到了Hyun等人曾经报道的I3/1 vs γ0的初始斜率问题（log-log图下），线形高分子体系斜率为2，支化体系斜率小于2。Rheol. Acta这篇文章的初始斜率为1.4，按Hyun的观点，那就是一个非常支化的体系。这又让我动了心思：既然LAOS做的是网络破坏后的体系，那么，没形成网络前，是“破坏”不出来“支化结构的”；只有网络形成后，“破坏”的结果才会是一种支化结构的混合物。如果用I3/1 vs γ0的初始斜率来表征，那么凝胶点附件，斜率应该从突降，在该处就能定义一个非线性的临界点了。结果是不是这样呢？我用Rheol. Acta这篇文章的数据试了一下，发现它做的斜率也没有什么规律，勉强说也是“突增”，而且并不发生在Winter凝胶点附近。又没戏！
所以再次说明yield stress fluid为什么火！人家起码有个SGR理论比较好用的。... Read more »
Andrade, R., Azevedo, A., Musampa, R., & Maia, J. (2010) Thermo-rheological behavior of model protein–polysaccharide mixtures. Rheologica Acta. DOI: 10.1007/s00397-010-0431-3
- August 4, 2009
- 11:41 AM
- 984 views
No one added their test on oxidative NaH to ResearchBlogging.org?
by Andrew Sun in On The Road
I have been busy setting up the Chinese language version of ResearchBlogging.org. To explain how research blogging can be meaningful and important to the Chinese bloggers I have to provide several points and examples in an introductory webpage.
One of the best example is the recent blogging review on a NaH catalyzed oxidation reaction published on JACS1. The unexpected property of this reagent stirred up a number of synthetic chemists who repeated it and reported on their blogs. Chemistry World even reported this reviewing action from the blogosphere. This event best exemplified the role blogs can play in the “post-peer review” process — peer review on a published research work, during especially controversies in the academic community.
If ResearchBlogging.org — a Web 2.0 tool to syndicate research blog posts into tagged, searchable, RSS-feeding, and DOI-linked network — has gained supports from major chemistry blogs, this oxidative NaH events must have some records in it. However, I did a search in ResearchBlogging.org for that JACS paper but no blog post was related. Blogs I know which wrote about this paper — Totally Synthetic, Carbon Based Curiosities and PeterMR’s blog did not use ResearchBlogging.org to spread the discussion. My post here may be the first on ResearchBlogging.org linked with the controversial JACS paper.
These blogs may not need to use ResearchBlogging.org since they have had enough visits and comments as were shown under their posts. Indeed, they, not and well without ResearchBlogging.org, led and accelerated this discussion. However, ResearchBlogging.org and its readers may lose an opportunity to join this discussion. After all, Web 2.0 is about the effect of collective behavior of unknown contributors, instead of led, concentrated effect by several famous individuals. Though the latter may still be important, but more interesting is the former, which ResearchBlogging.org seeks to promote.
As a blogger you may care no other’s view and be as independent as possible among the WWW, but as a researcher you have to be the opposite, and only in this case ResearchBlogging.org can be helpful and attractive to you.
1 Wang, X., Zhang, B., & Wang, D. (2009). Reductive and Transition-Metal-Free: Oxidation of Secondary Alcohols by Sodium Hydride Journal of the American Chemical Society DOI: 10.1021/ja904224y
... Read more »
Wang, X., Zhang, B., & Wang, D. (2009) Reductive and Transition-Metal-Free: Oxidation of Secondary Alcohols by Sodium Hydride. Journal of the American Chemical Society, 2147483647. DOI: 10.1021/ja904224y
- December 26, 2009
- 04:00 AM
- 969 views
Topology的迷思
by Andrew Sun in Notes on Research Papers
我大三的时候（那是多么遥远的时代啊），上组织工程课的老师曾经在课上布置一条作业，让我们回去查阅理解一下常常出现在生物材料文献中的“拓扑结构”是什么意思，下一堂课请同学讲一下。我记得当时有一个女生查阅了关于拓扑学的内容，介绍了作为数学分支的拓扑学如何跟几何学有所区别。她讲得还算清楚完整。我讲的就是：“其实说白了就是形状，材料里面的形状问题都不是真正的拓扑学问题，只是借用了这个词。”我记得当时老师也没有最后给我们下什么结论，只是告诉我们将来要注意这个问题。
这件事我一直记得，所以在看到Nature Chemistry上这篇散文的时候，觉得感同身受。这几年随着超分子化学和生物化学在化学研究领域变热，形貌问题渐渐变得重要，需要讨论形貌的时候越来越多。于是，化学家为了这一经常讨论的对象更加学术化，挪用了数学术语“拓扑”。而实际上正如我在大三时期讲的那样，化学里面的形貌问题都仅仅只有几何学意义，完全没有拓扑学意义。在Nature Chemistry这篇散文中举过两个例子。一个就是，蛋白质折叠的空间结构常被称为所谓“拓扑结构”，但几乎所有蛋白质的拓扑结构都跟一条直线是等价的，因为它们都可以连续变化为一条直线。同样，讨论紫外吸收光谱的“拓扑结构”，也没有拓扑学意义。
故意堆砌不必要的术语以故作高深应该是十分庸俗的行为，不应该出现在学界中。为什么化学家们要不当地使用topology这个词呢？散文作者的猜测是：希望化学研究变得更有数学基础。这也许反映了化学家潜意识中的尴尬。化学不如物理学那样有数学基础，使得它不能像研究物理学那样趣味盎然。而事实上也的确，化学中涉及“拓扑结构”较多的方面，倒真的有较多的物理学家介入，例如蛋白质折叠问题，高分子物理、液晶等等。但是，仅仅使用“拓扑”这个词，并不能使化学进入拓扑学。使用“拓扑”一词，并不是实质性进展。探索存在于化学中的拓扑学，才是真正的进展，到那时，你想不用“拓扑”这个词都不行。
Francl, M. (2009). Stretching topology Nature Chemistry, 1 (5), 334-335 DOI: 10.1038/nchem.302... Read more »
Francl, M. (2009) Stretching topology. Nature Chemistry, 1(5), 334-335. DOI: 10.1038/nchem.302
- January 3, 2010
- 01:02 PM
- 965 views
界面流变学？做条毛！
by Andrew Sun in Notes on Research Papers
现在是有一些人做界面流变学的。就是研究2D的单层的东西的流变学。我没有具体去了解过大家都用什么仪器设计，但大概印象就是这东西难，DIY程度很高，精度要求高，涨落影响大。
如果我将来的事业要继续做流变学研究，我要寻思着一些新方向了。照我的短浅认识，现在流变学的新东西一个是在额外的场下的流变学，就是边剪切边小角散射，边加电场磁场等等，目的不言而喻；一个是微流变学，就是加粒子进去通过粒子运动得到局部信息，粒子的运动测量方法包括动态光散射和显微镜人工追踪粒子，这个方法的好处是什么我还不太明白，可能是灵敏度吧；第三就是界面流变学。
为什么流变学还能继续研究下去呢？因为这种方法特别适合研究软物质的非均相体系和非平衡过程。现在物理方面非平衡、非线性、非均相都比较火嘛，有物理学家参与，才有好的科学。以上是我幼稚的个人看法。这也可以解释界面流变学为什么值得研究。
照我的理解，界面流变学的实验难度之一是专门获得界面的信息，而排除各相本身性质的干扰。但是由于界面上的东西少，相里面的东西多，相里面的东西的贡献总是非常大，界面上东西的贡献在跟误差范围差不多，导致困难。具体现在报道的界面流变学研究是怎么解决这个问题的？我没有专门了解过。AR-G2已经有这附件了。而我这两天碰到这篇PRE，做得也很漂亮。
作者在AFM探针上粘一条毛（玻纤啦），然后伸到水里去。探针部分在空气里，毛的一部分浸在了水里。本来，在空气里，空气阻力很小，做AFM好做。但是在水里，由于阻力大，探针的阻尼衰减不可忽略，就不好做。粘条毛，把探针留在空气里，就解决了这个问题。毛插到水里，由于水在动，毛就要动。这是布朗运动，因此符合Langevin方程。如果毛是垂直插入水里的，基本上就只有一种振动模式，用一维的Langevin方程搞定。通过Langevin方程的描述，可以得到磨擦系数ξ。ξ与浸没的深度h有关。通过算一条与流动方向平行的圆柱体的Navier-Stokes方程可以知道ξ与粘度的关系，搞定。作者测出来的水的粘度和glycerol水溶液粘度都准，文章里所有图都很漂亮。
流变仪厂商们一向都很注意留意流变学研究发展，很快就把一些新方法所需要的仪器设计纳入到他们推出的新附件或者新仪器当中。他们是通过跟这些研究的作者合作达到这一目的的。如果你的此类研究被仪器厂商比如说TA瞄上了，那就发财了。今后大家都买TA的流变仪，都看着TA的说明书做实验，因此都引你的文章。你的文章不光靠数据库搜索被引，还靠TA卖仪器被引。如果牛，还不光TA，其他厂也会学着做。哇……
这篇PRL是香港科技大学Tong Penger课题组发的，第一作者倒是中山大学的。是交换生吗？值得向这位同学学习！
同时，让我好兴奋的是，我也就是这几天才开始看非平衡统计力学，结果没看几章书，就能看懂以前我看不懂的文章了，觉得非常受鼓舞！
Xiaomin Xiong, Shuo Guo, Zuli Xu, Ping Sheng, & Penger Tong1 (2009). Development of an atomic-force-microscope-based hanging-fiber rheometer for interfacial microrheology Physical Review E, 80 : 10.1103/PhysRevE.80.061604... Read more »
Xiaomin Xiong, Shuo Guo, Zuli Xu, Ping Sheng, & Penger Tong1. (2009) Development of an atomic-force-microscope-based hanging-fiber rheometer for interfacial microrheology. Physical Review E, 61604. info:/10.1103/PhysRevE.80.061604
- August 9, 2009
- 01:50 PM
- 963 views
评Adv. Polym. Sci.上几篇跟Cyclodextrin有关的Review
by Andrew Sun in Notes on Research Papers
Adv. Polym. Sci.在网上预先放出了四篇Reviews：
Cyclodextrin Inclusion Polymers Forming Hydrogels
Functional Cyclodextrin Polyrotaxanes for Drug Delivery
Recognition of Monomers and Polymers 1 by Cyclodextrins
Polymerization of Included Monomers and Behaviour of Resulting Polymers
我本科恰好就是做环糊精与聚合物的Polyrotaxane课题的，对所有这些Review涉及到的工作都很熟翻。看到这几个人09年还在Adv. Polym. Sci.上发Review，实在有些话想说。
第一篇Review是Jun Li，现在在新加坡。他是在日本跟A. Harada造环糊精套高分子发了Nature的。结果A. Harada之后不玩这个了，他到了新加坡还玩这个，一直玩到现在。我05、06年做硕士课题的时候就已经感觉到，环糊精套高分子成点强度很差的触变性凝胶，实在难以成什么气候。我特意看了看这篇09年的论文，发现还是老的东西整理一下，炒冷饭。
A. Harada是一个有一定思维活力的人。我注意过他后续的其他一些论文，尤其是后来赶上的超分子聚合物的早班车。其实他抓住的不多，只抓环糊精，不再抓住高分子，因此能够及时跳开一度让人着迷的环糊精-聚合物“分子项链”。但是我隐约感觉到Jun Li去Harada那里读博是去错了地方，虽然凭着一篇Nature和好几篇其他高档paper为他后来在新加坡找到了一个好位置。为什么还是说去错了地方呢？因为他在博士期间进行的工作是一种脱离经典理论，天马行空式的研究。发一两篇Nature当然很好，但是谈到今后几十年独当一面进行研究的个人事业，没有属于自己的理论靠山，是很难走出自己的路的。在科学界，永远常青的是基本科学问题和迫切的人类问题。就基本科学问题而言，永远是理论领域和实验领域的“双城记”。在这两个领域中玩得转，才能长期保住自己的饭碗。以我老板为例，他在八十年代初，日本读博时的研究课题是经典的高分子溶液相平衡问题，而且是老一代的Flory理论。因此他有着作为一个那个时代高分子科学家基本的理论素养，能够从一种高度去看待研究课题，这种高度就是牢记本学科基本未解决问题，用这一问题来评判所有新研究方向的高度。没有在理论和实验中争扎过的话，是无法在茫茫的眼花瞭乱的新paper中抓住主线，形成自己的方向和饭碗的。
但是话虽如此，第三篇Review的作者Wenz，几乎与A. Harada开始同时发现环糊精与聚合物的IC，很早就不如后者出名了，但却一直靠吃老本混到今天，他之前甚至还在Chem. Rev.发过Review，自己却没做过什么工作。真不知道这些人的学术名声是怎么保持的。
第二篇Review的Yui，倒是一个科研上的正面例子。他进入环糊精-聚合物这一领域是比较迟的了，但他甫一进入就方向明确——智能给药体系。在经过一段时期不断地改换功能团发类似文章打发一堆学生毕业之后，终于更进了一步，将原本只是花哨的idea和concept scheme的超分子给药材料做到了细胞实验上，总之获得了可以发paper的结果。算是完完全全把一件事情做完了。我老板说过一句我很受用的话：想到点什么不难，难的是切切实实地把想到的东西成功地做出来。
至于第四篇的作者Ritter，据我得到的信息是他没怎么进入到环糊精-聚合物这一块来。他最早是做rotaxane的，也可能不局限于环糊精主体。后续他还做什么就不清楚了。这次的review主要也是对于小分子客体包结物的某种性质——可聚合性——的综述而已。
环糊精与聚合物形成的超分子体系，原本具有很fundanmental的理论意义，例如它给出了一种调节主链刚度的方法，可以从柔性链一直调整到棒状链；同时，在链上滑动的环，很容易让我们联想起de Gennes的reptation model和Doi-Edwards的tube-like chains。这些工作都没人做。也许像我老板所说的，现在没人关心高分子物理，没人关心“链”的问题了。
Gerhard Wenz (2009). Inclusion Polymers Advances in Polymer Science, 222 DOI: 10.1007/978-3-642-01410-9... Read more »
Gerhard Wenz. (2009) Inclusion Polymers. Advances in Polymer Science. DOI: 10.1007/978-3-642-01410-9
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