Posts 2017

Pattern formation in thermal convection

In the mid of December, I attended the annual meeting of the international polymer processing society held in Mexico. Honestly speaking, I am not quite keen about this society meeting, but this time I was the organizer of polymer rheology session. As the organizer, I must be at the conference room, at least during my session. For such a task, I booked the flight and the hotel earlier and kept my schedule during the conference. However, the other organizers (we have 3 professors for the session including myself) did not come, and even the keynote lecturers did not come either! I was suggested by the other organizers to deliver a keynote lecture. But I declined the offer as I am the organizer, and I recommend the other person. But this guy did not come... There are several cancelled talks as well, and the attendee seemed escaping from the conference room to the beach. Indeed, it was a great place, as seen in the photo below.

Even in such a chaotic conference, in general, Japanese professors are sobriety. They did not skip their own talks (of course) and stayed in the room for discussion. The photo below is the situation at the conference dinner. They all are busy professors and it is rather difficult to catch them in Japan. It was a great chance to chat with them about various topics including small talks for the situation in each university. It would be also somewhat funny to see Japanese professors tend to attend the talks by the other Japanese professors. The situation might be a sought of roll-call ;-> Nevertheless, because they often deliver review talks for their recent results in international conferences, it is a good chance to catch up the situation.

Concerning the topic in the title, I found an interesting article from Tokyo Metropolitan here. When a liquid is placed between two parallel plates with different temperatures, vortex formation induced by the thermal convection is observed. In this specific study, they observed such pattern formations for various liquids. To me, very interesting one is the mixture of two silicon oils with different viscosity. As the chemistry is identical, the liquids seem miscible, and the viscosity becomes just in between the viscosities for the original liquids. Then, intuitively the pattern would be just according to the viscosity. However, they found that the pattern formation is affected further complicated manner by the mixing.

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/12/IMG_0213.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/12/IMG_0227.jpg
https://www.nature.com/articles/s41598-017-13409-w

Original publication: 2017-12-24 23:30:56
Source: https://rheology.jp/nagoya/2017/12/pattern-formation-in-thermal-convection/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Freezing Bubble

These weeks our students are busy for the thesis and for the preparation to attend to the coming IWEAYR meeting in Jeju. Joining the event is a challenge, in particular for undergrads since that is their first opportunity to present their works outside. To go for it, they have to make the abstract, slides, poster and talk, all in English. The situation is certainly stressful. Meanwhile, for the master course students, now they are well-experienced. Indeed, I am happy to see that they are making the things effectually, clearly demonstrating their progress.

The news from our group is that Ankita Pandey, the post-doc researcher, has left our group by many reasons. This situation may push our group back to quite domestic situations, as we do not have foreigner in our group at this time being. For instance, it may not necessary to write this blog entry in English. But I have found that there are some readers of this blog outside Japan as well...

During the days, I have found this interesting article. Just see the video below.
https://youtu.be/X_laL3Nucec

Links
https://www.sciencenews.org/article/how-freezing-soap-bubble-turns-it-snow-globe

Original publication: 2017-12-12 10:38:10
Source: https://rheology.jp/nagoya/2017/12/freezing-bubble/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Polymers mitigate vortex formations

The recent great news for our group is that Mr Hirayama has been awarded by the Japanese Society of Polymer Processing for his research on the solidification of Nylons. Among several prize winners, Mr Hirayama was chosen as the special choice of the Chairman of Western Japan Branch of the society. That means, his study is the best among the papers in the autumn meeting of the society. I have had several nice feedbacks from the other professors on his research, in which he has shown, for the first time I believe, that some Nylons solidify even with zero crystallinity owing to the hydrogen bonding. Nevertheless, he deserves the prize. Take a look at his blog entry for this issue.

For myself, I was invited to the award ceremony for the Nikkei global environmental technology awards 2017, for which the highest award has been given to the Sumitomo Rubber Industry. As I was involved in The Commendation for Science and Technology by MEXT, I have been being collaborated with SRI, and for this occasion they kindly invited me to share the delights. I greatly appreciate their kind consideration.

A nice paper has come out from the group in Okinawa directed by Prof. Amy Shen for the effects of polymers on the vortex formation in liquids. In our daily life, liquids with relatively low viscosity like water do not flow with laminar flows, in which the flow behavior completely depends on the viscosity. Rather, such liquids are exposed to turbulent flows, in which the eddy viscosity dominates the situation. The eddies dissipate energy much further than the viscous damping of the liquid. Polymers, some surfactants and micro-bubbles are known to reduce the eddy viscosity. The mechanism has been thought that those materials can suppress the eddy formation. The team in Okinawa clearly demonstrates that the polymers mitigate the vortex formation in their liquid.

Links
http://rheology.jp/nagoya/2017/11/%e6%88%90%e5%bd%a2%e5%8a%a0%e5%b7%a5%e5%ad%a6%e4%bc%9a%e3%81%a7%e3%83%9d%e3%82%b9%e3%82%bf%e3%83%bc%e8%b3%9e%e3%82%92%e3%81%84%e3%81%9f%e3%81%a0%e3%81%8d%e3%81%be%e3%81%97%e3%81%9f%ef%bc%81/
http://www.nikkei-events.jp/chikyu-kankyo/
http://rheology.jp/nagoya/2017/04/receiving-the-commendation-by-the-minister-of-education-culture-sports-science-and-technology/
https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.041039

Original publication: 2017-12-03 23:32:17
Source: https://rheology.jp/nagoya/2017/12/polymers-mitigate-vortex-formations/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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成形加工学会でポスター賞をいただきました！

こんにちは、M２の学生の平山です。

先日行われた成形加工学会でポスター賞をもらったので報告です！

先日と言っても学会は先月末に行われたので、ざっと一ヶ月くらい期間が空いています。

というのも、この記念品の盾が特注だった為、来るのに期間が空いてしまったのです。
首をながーくしながら待っていたら昨日、研究室に届きこの報告を書いている次第です。

成形加工学会は初めての参加だったので、少し緊張もしましたが多くの先生方にも意見をいただくことが出来て良かったです。

やはりこういう賞はいただけると嬉しいもので、この盾も大事にしたいと思います。

今回の受賞はひとえに自分だけの結果では無く研究室の先生方含めメンバー皆さんのおかげだと思っています。
再び、このような賞がもらえるよう（もう卒業が迫っていますが...）頑張っていきたいと思います！

ありがとうございました！

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/11/DSC_1250-min.jpg

Original publication: 2017-11-30 08:30:58
Source: https://rheology.jp/nagoya/2017/11/%e6%88%90%e5%bd%a2%e5%8a%a0%e5%b7%a5%e5%ad%a6%e4%bc%9a%e3%81%a7%e3%83%9d%e3%82%b9%e3%82%bf%e3%83%bc%e8%b3%9e%e3%82%92%e3%81%84%e3%81%9f%e3%81%a0%e3%81%8d%e3%81%be%e3%81%97%e3%81%9f%ef%bc%81/
Categories: {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'from-students', 'label': 'From Students'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

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Liquid drops levitate on liquid surfaces

In the last week I listened the training course for ventilators, I attended the editorial board meeting for a textbook on polymer science in Tokyo, I managed the entrance examination for foreign students of our graduate school, I discussed with industrial people in Kobe, and I made an invited lecture in Osaka. And even Saturday I was in the office to manage the computer cluster, which has to be shut-down owing to the electric down on Sunday.

Exhausting..

Great video from Professor McKinley's group shown below. The paper is here

Links
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/thermal-delay-of-drop-coalescence/CB55985D6ADC2251BA5EA94C8021C18F

Original publication: 2017-11-18 23:01:31
Source: https://rheology.jp/nagoya/2017/11/liquid-drops-levitate-on-liquid-surfaces/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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ER and MR may return to the stage

In the last week, I shuttled back and forth to Tokyo twice. One of the opportunities was for the meeting related to SIP project, in which my due is to develop a coarse-grained simulation scheme for thermoset polymers, on the basis of the multi-chain slip-spring method. The other event was the lecture in the gel group in the Japanese polymer society on the rheology of gelation. The latter was dedicated to introduce the Chambon-Winter method for the gelation. Professor Urayama should give this talk because he is the famous rheologist doing gels and network polymers. But he was busy at that day and I was a cover for him. However, I found Prof. Sakai in the venue! It was somewhat embarrassing for me to make the lecture on gel rheology in front of him...

During the events, I got an interesting news for MR fluid. At the Tokyo motor show 2017, the Akebono brake company displays the new break system with Magneto-rheological fluids. Magneto-rheological fluids are liquids that changes the viscosity according to the magnetic field intensity. The use of such a fluid to the break system seems several advantages to the conventional solid breaks. For instance, fluid is not worn down, and it dissipates the heat of friction. The material itself seems not new. Indeed, there were lots of research projects for electro and magneto rheological fluids 20 years back, even in the private sector. I heard that applications to motor-cars have been attempted even in the past. However, at that time, conventional combustion systems dominated the market. In the conventional systems, ER and MR systems are practically difficult owing to the electric systems equipped with low power supply. Now, the situation is changing into EV, in which high electric power supply is available and may be used for ER and MR, as well as the driving system.

The rise of EV may induce the return of ER and MR...

Links
http://www.jst.go.jp/sip/k03.html
http://main.spsj.or.jp/c12/gyoji/gels.php
https://www.hyokadb.jim.kit.ac.jp/profile/ja.c532efa723328619cd482617b6a862d3.html
http://www.tetrapod.t.u-tokyo.ac.jp/sakai-tei/TetraNet/Top.html
http://www.akebono-brake.com/static/news/2017/10/17/ne20171017_01.html

Original publication: 2017-11-12 23:37:53
Source: https://rheology.jp/nagoya/2017/11/er-and-mr-may-return-to-the-stage/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Bone and viscoelasticity

Even after the discussion meeting of Japanese society of rheology, I have been being busy. In particular, I am stressed by the situation of the journal of the Japanese society of rheology. For the coming issue, currently we do not have sufficient amount of manuscripts, and we are afraid that the issue may not be publishable. Owing to this situation, I wrote a manuscript on the molecular description of viscosity growth curve under fast shear. I have already published several papers on the molecular mechanism of stress overshoot. This time, I focus the stress undershoot following the overshoot. The undershoot has come into fashion recently owing to the development of experimental technology. Nevertheless, I made some simulations, analyzed the results, and wrote the manuscript in a short period. Because the study was initiated by Professor Marrucci and Professor Ianniruberto in Italy, I have sent the manuscript to them to have their approval for co-authoring. Now the manuscript is under their evaluation, and hopefully the manuscript is going to be submitted in time. Such a quick manuscript writing is a kind of training.

Apart from the manuscript mentioned above, I made several 1-hour lectures during the period on different topics for each; basic rheology, simulation of polymer dynamics, basics of coarse-graining simulations, and rheology of polymers. These are of course related to each other and there are some overlaps. Indeed, the significant issue for all the topics is the relaxation. For viscoelastic relaxation, I have found an interesting video shown below. I did not know that bone is viscoelastic.

https://www.youtube.com/watch?v=BxP-G4LuQMo

Original publication: 2017-11-02 23:45:37
Source: https://rheology.jp/nagoya/2017/11/bone-and-viscoelasticity/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Polymers for Watches

Last week we had the discussion meeting of the Society of Rheology, Japan, in Niigata. There were many interesting talks but I saw some problems in the computational rheology session, which I organized. It seems that the session does not fit the situation. There exist some people doing computational researches, but they prefer submitting their papers to the sessions that discuss the target of the computation rather than the computational methods. The audience as well. I have to discuss this matter with the other members. Apart from the management of the session, I attended the board meeting and the editorial office meeting because I am in charge of the editor-in-chief of the journal of the society. The main issue this time is the installation of web-submitting system to our journal. Nowadays, most of the scientific journals collect the papers via web-system. Reviewing and editing of the papers are also managed via the system. But currently our journal does not have such a system so that the process is rather bothering, and indeed, not standard. Now I am investigating possible web-systems.

The society meeting was from Tuesday to Thursday, and the board meetings were Tuesday and Thursday. Very unfortunately, I had the meeting of the department heads in Nagoya on Wednesday. Thus, I got back and forth between Niigata and Nagoya on the day. I got in trains for 8 hours in total... But it was nice to finish up some papers and presentations in the Shinkansen.

During my train riding, I got this interesting article on the usage of plastics for luxurious watches. This article includes a nice introduction of the basics of polymeric materials, as well as the specific use of polymers in watches. In particular, I did not know about the wide use of Bakelite. The use of plastics for date disks by Seiko, and the use of PTFE by Rolex are also interesting. Carbon fibers and Carbon nano-tubes seem also in use, maybe for their impression as cutting-edge materials.

Links
http://quillandpad.com/2017/10/08/focus-technology-plastics-watches-likely-see/

Original publication: 2017-10-22 23:46:47
Source: https://rheology.jp/nagoya/2017/10/polymers-for-watches/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Talk in science cafe

On Oct 11th, I was invited to deliver a talk on theology in the Aichi Science Cafe, which is a series of talks by the researchers in the university in this region. This year 15 talks are planned in total, and all of the talks will be in October and November. The topics are widely distributed, and categorized into several themes, which are astrophysics, advanced manufacturing, medical science, biology, and science in general. Although my talk (on rheology) was arranged in the advanced manufacturing, I did not know this arrangement and actually my talk was mostly on basis of rheology and not that related to manufacturing. Nevertheless, I do not believe that the audience cares about the categorization.

The venue was a drinking bar located in Sakae-area with around 20 seating capacity. I was afraid that the place may be empty. But fortunately, there were more than 15 people came up to the talk. I made the talk without any equations to focus fun of rheology with various funny stories, which include for example the youtube presented in my blog. I also performed demonstrative experiments including the egg drop onto the alpha gel. The number of audience was appropriate for the demonstrations that were virtually experienced by all the people there.

Overall, I enjoyed the event owing to the satisfactory reactions from the audience. It was a happy surprise to see a woman who came up to the event with her children motivated my book on rheology.

Links
https://aichi-science.jp/
http://rheology.jp/nagoya/wp-content/uploads/2017/10/IMG_0078.jpg
http://www.bokumo.jp/
https://www.amazon.co.jp/%E3%81%8A%E3%82%82%E3%81%97%E3%82%8D%E3%83%AC%E3%82%AA%E3%83%AD%E3%82%B8%E3%83%BC-%E2%80%95%E3%81%A9%E3%82%8D%E3%81%A9%E3%82%8D%E3%80%81%E3%81%90%E3%81%AB%E3%82%83%E3%81%90%E3%81%AB%E3%82%83%E7%89%A9%E8%B3%AA%E3%81%AE%E7%A7%91%E5%AD%A6-%E7%9F%A5%E3%82%8A%E3%81%9F%E3%81%84-%E3%82%B5%E3%82%A4%E3%82%A8%E3%83%B3%E3%82%B9-%E5%A2%97%E6%B8%95/dp/4774143103

Original publication: 2017-10-15 16:36:29
Source: https://rheology.jp/nagoya/2017/10/talk-in-science-cafe/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}

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粘弾性とは何か

粘弾性とはどのような性質なのでしょうか．粘弾性は，粘性と弾性の両方を併せ持つ性質，と言われることがありますが，この説明は正確ではありません．（例えば塑性でも粘性と弾性の両方を示します．）

粘弾性は，「分子の熱運動による緩和が応力の緩和として観測される現象」です．図１のように，階段状のひずみを与える実験（「応力緩和実験」と呼びます）を行うと系は平衡状態から外れた非平衡状態となり，分子の熱運動によって時間とともに平衡状態に戻っていきます．この様子が応力の時間変化として観測できると，時間とともに応力が減衰します．これが粘弾性です．変形開始直後の挙動は弾性ですが，時間を経るに従って徐々に粘性を示すように見えるので，粘弾性と呼ばれます．

図１　変形後の緩和現象

上記の緩和現象はどのように記述されるでしょうか．以下のような仮定のもとでは指数関数で表すことができます．仮定１：加える変形の大きさ（ひずみ）と，励起される分子の数は比例する．　仮定２：励起している成分の数と応力は比例する．　仮定３：各分子は独立に緩和する．　励起した分子の数を$[A*]$，平衡状態（励起される前の状態）にある分子の数を$[A]$とします．仮定３に基づけば，A*からAへの遷移は一次の反応速度式で書くことができます．つまり$[A*]\rightarrow[A]$ です．反応速度定数を$k$とすれば，$d[A*]/dt = -k[A*]$となりますので，$[A*]=[A*]_0 \exp(-kt)$となります．$[A*]_0$は$t=0$のときの$[A*]$です．ここで仮定２をつかって，$[A*]_0=\gamma[A*]_{00}$と書くことにします．$\gamma$は与えた歪みの大きさです．また，$k$は時間の逆数ですから，$\tau=1/k$とすれば，$[A*]=\gamma[A*]_{00} \exp(-t/\tau)$となります．最後に仮定１を使って，$\sigma\propto[A*]$とし，また$\sigma=G\gamma$とすると，$\sigma(t)/\gamma=G\exp(-kt)$となります．$\sigma(t)/\gamma=G(t)$と定義しますと（これを緩和弾性率といいますが）$G(t)=G\exp(-kt)$が得られます．

緩和の様子を模式的に図２に示しました．緩和が単一指数関数で書かれることはあまり多くありません．AからA*に至る緩和のルートが単一ではないことが多いためです．それぞれの緩和ルートが独立であると仮定すると，緩和挙動は指数関数の線形和として$G(t)=\sum_i G_i \exp(-t/\tau_i)$のように書くことができます．

粘弾性は「緩和弾性率」で評価し，「緩和スペクトル」で定量化します．$G(t)=\sum_i G_i \exp(-t/\tau_i)$のパラメーターGitiは「緩和強度」，「緩和時間」と呼ばれます．ひとまとめにして「緩和スペクトル」と呼ばれます．（正確には，緩和時間の分布を連続化したときの強度分布が緩和スペクトルです．）

図２　応力緩和実験と緩和弾性率

緩和スペクトルには分子や構造の熱運動を知る手がかりになる情報がたくさん含まれています．例えばtiのうちで最も大きなもの（tiは慣例で長いものから順に番号をつけるのでt1）は「最長緩和時間」と呼ばれ，系に含まれる最も遅い運動を特徴付ける時間です．均一系であれば，分子の重心が分子の広がりと同程度の距離を熱運動で移動するのに必要な時間に相当します．

しかし，緩和スペクトル$\{G_i,\tau_i\}$そのものを決めることには意味はありません．図２の緩和関数を指数関数でフィッティングする問題はill-posedです．つまり，唯一解を持たない問題です．したがって，$G_i$や$\tau_i$そのものではなく，緩和の概形を定量化するために，統計量を評価します．表１に示すように，分子量分布との対応で考えると分かりやすいでしょう．これらの量は，別に述べる動的粘弾性試験を行うと，作図で容易に評価することができます．

表１　緩和時間分布と分子量分布：統計量の対応

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/10/RELAXATION.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/10/VISC.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/10/Table_moldisp.jpg

Original publication: 2017-10-07 15:34:19
Source: https://rheology.jp/nagoya/2017/10/%e7%b2%98%e5%bc%be%e6%80%a7%e3%81%a8%e3%81%af%e4%bd%95%e3%81%8b/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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レオロジー的な物質の分類

理想的な固体，理想的な液体：

応力をひずみや歪み速度の関数として調べることで，物質の振る舞いをレオロジー的に特徴付けていきます．このとき，理想的な固体，理想的な液体の振る舞いを手がかりにして考えていきます．まず理想的な固体は，フック弾性体と呼ばれるもので，応力とひずみが比例関係にあるものです（高校までに習ったバネの伸びと力の関係を思い出してください）．比例係数Gを弾性率（正確にはせん断弾性率）と呼びます．単位はPaです．一方，理想的な液体はニュートン流体と呼ばれるもので，応力と歪み速度が比例関係にあるものです（こちらはバネと違って大学でも学科によっては習いません）．比例係数を粘度と呼び，単位はPas（パスカルセカンド）になります．

レオロジー的な物質の分類：

上記の理想的な固体と理想的な液体をある種の極限として，それらの間に様々なレオロジー挙動があります．下の図は英国レオロジー学会がNatureに出した分類です（Nature 1942 v149-3790, p702）．上下二段がありますが，上段は一定の応力のもとでのひずみの時間変化を示しています．破線は応力をゼロにした後の挙動を示します．（元の論文では文字の定義が違っており，このNatureの論文ではσをひずみとして使っています．）下段は右３つとそれ以外で違っており，右３つについては定常状態での応力に対するひずみの変化です．（元の論文では応力はS，ひずみはσで横軸/縦軸に書かれています．）残りの６つは，定常状態での応力に対するひずみ速度の変化です．

図 レオロジー的物質の分類

図でフック弾性はどこにあるでしょうか？まず物質を変形させた時，流れてしまう(Flow)か，弾性変形するだけで流れないか(Elastic deformation)で右と左に分かれます（ここでいう“流れる”，とは，変形させる力を取り除いた時に物質の形状がもとに戻ろうとしないことを言います）．フック弾性は流れないので左側をたどると，理想的(Ideal)か，そうでないか(Non-ideal)を訊かれます．理想的な固体は力を取り除くと瞬時にひずみがゼロになります（つまり変形が瞬時にもとに戻ります）．理想的でないものは，外力に対する応答に遅れがあったり，完全には戻らなかったりします．理想的な固体のうちで，さらに応力とひずみが比例関係にあるものがフック弾性体（つまり左端）というわけです．

ニュートン流体はどうでしょう．流れるもの（右側）をたどると，粘性(Viscous)と塑性(Plastic)に分かれています．塑性とは，ある一定以上のちからを加えた時に流れる性質です．よってニュートン流体は右の粘性を選びます．さらにニュートン粘性（Newtonian：粘度がせん断速度や時間に依存しない）か，それ以外(Non-Newtonian)かを選ぶと，右端がニュートン流体となります．

フック弾性体を含め左３つは固体（流れない物質），ニュートン流体を含め右３つは液体（流れる物質），真ん中３つは塑性体（物質で決まる，ある一定の力よりも弱い力を加えたときは固体，それより大きな力を加えたときは液体）です．食品，化粧品，その他身の回りの物質が，どのカテゴリーに入るか，考えてみてください．

Links
https://www.nature.com/nature/journal/v149/n3790/pdf/149702a0.pdf
http://rheology.jp/nagoya/wp-content/uploads/2017/10/reoroji.jpeg

Original publication: 2017-10-06 23:19:18
Source: https://rheology.jp/nagoya/2017/10/%e3%83%ac%e3%82%aa%e3%83%ad%e3%82%b8%e3%83%bc%e7%9a%84%e3%81%aa%e7%89%a9%e8%b3%aa%e3%81%ae%e5%88%86%e9%a1%9e/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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レオロジーを学ぶ準備：変形と応力

レオロジーでは物質の変形と応力の関係を議論します．

変形は多様で任意性があり，本来は２階のテンソルで表す量です．ここでは液体や等方的な固体を扱うものとして，せん断変形と一軸伸長変形だけを考えます．（この２つの変形を知っておけばレオロジーの論文の９割以上は読めます．）

図１　一軸伸長変形（左）とせん断変形（右）

図１にそれぞれの変形を示します．中央の立方体を変形させたとき，左側のように伸ばすのが一軸伸長，右側のようにずらすのがせん断変形です．変形量を表すひずみの定義も示しています．変形が変わるとひずみの定義がかわることに注意が必要です．また．ひずみに関する材料力学の定義とレオロジーの定義は違います．変形量が小さければどちらも同じですが，大変形する場合はレオロジーの定義でないと正しく評価できません．なお，ひずみには単位はありません．

変形を与えるには物質に外力を与える必要があります．応力は，この変形に必要な外力と，評価にかかる面から定義される２階のテンソルです．図２には伸長応力とせん断応力を示します．応力は力を面積で割っているので，その単位はN/m$^2$となり．これをPa（パスカル）といって圧力と同じになります．

図２　一軸伸長応力（左）とせん断応力（右）

上記２で定義された変形量（ひずみ）と応力の関係から，弾性率と粘度が定義されます．

まず弾性率ですが，応力をひずみで割ったものとして定義します．伸長変形の場合であれば$E=\sigma_E/\epsilon$，せん断変形の場合であれば$G=\sigma_{xy}/\gamma$です．いずれもバネのばね定数に相当するものと考えればわかりやすいと思います．単位は応力と同じくPa（パスカル）となります．なお，同じ物質であっても変形様式が違うので値が違います．非圧縮性の物質では（かつ変形が小さければ）$E=3G$となります．なお，$E$はヤング率，$G$はせん断弾性率あるいは剛性率と呼ばれます．弾性率は，応力が変形量に比例する場合に意味をもつ量です．変形量が小さければどのような固体でも応力は変形量に比例します．このように応力が変形量に比例する物質をフック弾性体と呼びます．しかし多くの物質は，大変形になると図３のように破壊したり降伏したりします．このような非線形の挙動を扱う場合は，弾性率はあまり便利ではありません．なお，液体では弾性率は０となります．

次に粘度ですが，応力をひずみ速度で割ったものとして定義します．伸長変形の場合であれば$\eta_E=\sigma_E/\dot{\epsilon}$，せん断変形の場合であれば$\eta=\sigma_{xy}/\dot{\gamma}$です．ここで$\dot{\epsilon}$と$\dot{\gamma}$は，$\epsilon$と$\gamma$の時間微分（変化率）を表します．単位はPas（パスカルセカンド）となります．弾性率と同じく，同じ物質であっても変形様式が違えば値が違います．非圧縮性の物質では（かつ変形速度が小さければ）$\eta_E=3\eta$となります．変形速度が小さければどのような液体でも応力は変形量に比例します．このように応力が変形速度に比例する物質をニュートン流体と呼びます．しかし大変形速度になると図３のように応力が非線形に振舞います．このような物質は非ニュートン流体と呼ばれます．なお，固体は流動しないため，流動速度がゼロとなりますので，粘度は無限大となります

図３　弾性率（左）と粘度（右）

上記の弾性率と粘度の定義は，定常状態でのものであることに注意が必要です．すなわち，弾性率での議論では，ひずみを与えたのちに十分に長時間経過したときの応力が図３の縦軸です．粘度の議論では，ひずみ速度が一定の流動を十分に長時間与えた時に観察される応力が図３の縦軸です．

弾性率や粘度のデータを見るときは，身近な物質の値を知っておくと感覚的な理解ができます．弾性率ですが，人間の骨が$10^{10}$Pa，人間の肉は$10^5$Paと大雑把に覚えておくとよいと思います．また粘度については常温の水が1mPasです．

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/10/図1.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/10/図２.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/10/図３.jpg

Original publication: 2017-10-06 22:33:49
Source: https://rheology.jp/nagoya/2017/10/%e3%83%ac%e3%82%aa%e3%83%ad%e3%82%b8%e3%83%bc%e3%82%92%e5%ad%a6%e3%81%b6%e6%ba%96%e5%82%99%ef%bc%9a%e5%a4%89%e5%bd%a2%e3%81%a8%e5%bf%9c%e5%8a%9b/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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レオロジーとはなにか？

レオロジー（rheology）は物質の流動と変形を科学する学問です．似たような分野に流体力学と材料力学があります．流体力学と材料力学では理想的な液体（流体），理想的な固体が，複雑な境界条件のもとで複雑な流動や変形を受けた時にどのように振る舞うかを考えます．これに対してレオロジーでは，液体と固体の中間にあるような性質を示す物質（高分子液体を始めとする，いわゆるソフトマターのほとんどすべて）が，単純な境界条件と理想的な流動や変形を受けた時にどのように振る舞うかを考えます．食品やコスメ品，塗料のような製品ではユーザーの使い心地に直接関係します．またプラスチックの成形加工のように化学工学的なプロセス設計でも重要です．このような現象論的レオロジーはレオロジーの黎明期には盛んに研究され論文も多数ありましたが，現在では研究論文が出版されることは稀です．しかし工学的には非常に有用かつ重要であり，パラメーター特許にも使われます．

レオロジーにはまた別の側面として，物質内部のダイナミクスを見るためのプローブとしての役割があります．物質が流れるということは分子の位置が動いていることです．よって，レオロジーが系内部の分子運動を何らかの形で反映することは直感的に理解できると思います．ここでは，レオロジーは緩和現象として捉えます．すなわち，力学的な変形によって系に摂動を与えて平衡状態からずらし，そこから如何にして平衡に戻るかを観察します．近年，レオロジー関連の学術的な学会発表や論文は大半が分子論的レオロジーに関するものです．何らかの構造解析とレオロジー測定を組み合わせることによって，系の構造とダイナミクスの関係を明らかにすることを目的としています．

上記の２つの面は，ほとんど別の学問といってよいほど，別物と捉えるべきだと増渕は考えています．最初の面は流体力学からの延長線上にあって，機械や化学工学の分野で重要です．一方で２番目の面は分光学の一種と捉えるべきもので，系の中のミクロなダイナミクスを解析するための道具としてソフトマター物理学や高分子科学で重要です．どちらに重点を置くかによって学ぶ内容は異なります．講演会やセミナーに出席される場合や，教科書を選ぶ場合は，どちらに興味があるのかをはっきりさせると良いでしょう．

増渕がレオロジーの講演や講義をお引き受けする場合は，上記のどちらがよいかを必ずお尋ねします．両方話してくれ，といわれると，焦点がボケるので大変困ります．

Original publication: 2017-10-06 21:54:58
Source: https://rheology.jp/nagoya/2017/10/%e3%83%ac%e3%82%aa%e3%83%ad%e3%82%b8%e3%83%bc%e3%81%a8%e3%81%af%e3%81%aa%e3%81%ab%e3%81%8b%ef%bc%9f/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Rheology for Traffic Safety

Very interesting movie below, in which a nice application of rheology to safety is demonstrated.

https://www.youtube.com/watch?v=2fng6gCjl58

This is actually the application of shear thickening liquids, for which the viscosity increases with increasing shear rate. The famous application is d3o and mainly for sports. The other famous example is the STF for military usage.

Several years back, I was told by a researcher that shear thickening property is not that useful in comparison to shear thinning property. But nowadays it seems not.

Links
https://www.d3o.com/
http://science.howstuffworks.com/liquid-body-armor1.htm

Original publication: 2017-09-17 17:33:24
Source: https://rheology.jp/nagoya/2017/09/rheology-for-traffic-safety/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

────────────────────────

Rheology of Cats

It is pity that I did not recognize the importance of this study (see page 17), which has received The 2017 Ig Nobel Prize.

Below is the ceremony, but almost nothing for the research was presented.
http://www.improbable.com/ig/2017/

The video linked to the paper would be sufficient to demonstrate the fun of this study.
https://www.youtube.com/watch?v=pX4yK4yG3pE

Nevertheless, the paper itself is excellent to convey the concept of Deborah number. I will put this cat rheology story into my rheology lecture course.

Links
http://www.rheology.org/sor/publications/rheology_b/RB2014Jul.pdf
http://www.improbable.com/ig/2017/

Original publication: 2017-09-17 16:20:25
Source: https://rheology.jp/nagoya/2017/09/rheology-of-cats/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

────────────────────────

Coarse-graining and collision detection

In the last weeks, I was almost fully occupied by many things including the entrance examination of our graduate school and some conferences. In the conferences, I was made three invited talks in different topics, which were distributed from very basic polymer science for beginners to an advanced (rather maniac) topic on polymer dynamics. In between, at the middle of the topic distribution and also at the middle of the conferences, I delivered the talk on modeling and simulations of polymer dynamics. For the modeling, the key issue is coarse-graining, in which several atoms in the system are bundled into one calculation element. By this strategy, we can largely reduce the calculation costs.

In the talk on polymer dynamics, I used this movie to demonstrate the advantage of coarse-graining strategy for the reduction of calculation costs. The reduction is actually made by the collision detection. As shown in the movie, in the screen, the fighter and the enemies are drawn in a fine picture. But the collision detection between obstacles is made between the outward squares, neglecting the fine structures. This collision detection allows us to enlarge the calculation interval (delta t) for the numerical integration. If we have to consider the collision between fine architectures, the calculation interval is limited to attain that the moving distance (in delta t) of obstacles must be smaller than the characteristic length of the fine structure.

In short, what I am making is to create a new trick for smart collision detection between polymers... The movie is my favorite and thanks for the creator.

Links
http://www.nicovideo.jp/watch/sm27704255

Original publication: 2017-09-09 23:30:43
Source: https://rheology.jp/nagoya/2017/09/coarse-graining-and-collision-detection/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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予稿や卒論等を書くとき

日本語の文章を書くときの内容なので日本語のエントリーです．

増渕の個人的な経験で恐縮ですが，高校までの国語がなまじ得意な人は，大学で理系の文章を書くときに苦労することがあるように感じます．高校の現代文で問題に出るような文章は，わかりづらく書いてあるものです．（わかりやすいと読解力を問えないから．）そういう文章をたくさん読ませられれば，そういう難解な文章が格調高いような気がして，自分が作文するときも真似します．さらに，その真似した結果として，作文や読書感想文で良い点を取ってしまうと，成功体験となり，その後もそういう文章を書くようになります．ところが，理系の論文やレポートで書くべき文章は，わかりやすさが一番です．相手の読解力によらず正しく読んでもらえるように書く必要があります．

高校までの国語ではあまり教わらないような気がする，わかりやすい文章を書く技術，について，
このサイトに感銘を受けました．科学技術文を書くときは８−１０はあまり関係ないかもしれない．また，５も状況によるかもしれない．けれどもそのほかについては完全に同意します．

Links
http://hajimeteweb.jp/column/web_writing/vol2.php

Original publication: 2017-08-21 23:03:41
Source: https://rheology.jp/nagoya/2017/08/%e4%ba%88%e7%a8%bf%e3%82%84%e5%8d%92%e8%ab%96%e7%ad%89%e3%82%92%e6%9b%b8%e3%81%8f%e3%81%a8%e3%81%8d/
Categories: {'domain': 'category', 'nicename': 'to-students', 'label': 'To Students'}

────────────────────────

レオロジー物理工学特論2017前期

本科目においては成績は以下のようになりました．
A　20名
B　 2名
C　 2名

今回の課題はレオロジーに関する論文を読んで内容についてレポートしていただくものでした．レポートを提出された方で，増渕から応答した方はすべて合格となっています．面白い論文もいくつか報告していただきました．基本はA判定ですが，レオロジーの役割について記述が不十分なものはB判定としました．C判定はレオロジーについて述べていない論文を提出された方や，論文の読み込みに問題があった方で，再提出をお願いしたものです．S判定がないのは，Sについては数の縛りがあるためです（全体の１割程度に留めないといけない）．今回の受講者数では２名ないし3名だけしかSがつけられないことになります．A判定のなかでも甲乙ありましたが，２−３名だけを選ぶのは困難でしたので今回は出しませんでした．

Original publication: 2017-08-18 10:07:52
Source: https://rheology.jp/nagoya/2017/08/%e3%83%ac%e3%82%aa%e3%83%ad%e3%82%b8%e3%83%bc%e7%89%a9%e7%90%86%e5%b7%a5%e5%ad%a6%e7%89%b9%e8%ab%962017%e5%89%8d%e6%9c%9f/
Categories: {'domain': 'category', 'nicename': 'lectures', 'label': 'Lectures'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

────────────────────────

線形代数１（2017前期）

表題の科目の成績です．

受講者数６１名
S　9　名
A　24　名
B　14　名
C　8　名
F　5　名
欠席　１名

Fの方は，相当おまけしましたが，それでも６０点に達しなかったものです．計算間違いの他に基本的な理解に問題があります．十分復習してください．また，3月に再試験となり，再試験に合格すれば来年度再履修の必要はありません．再試験の対象者は自ら申請しないと再試験を受けられません．案内があるはずですが，ご注意ください．

Cの方はかなりオマケした結果，ようやく通っています．Fの方々と同様に復習が必要だと考えてください．

B以上の方々は概ね問題ないと思います．単なる計算ミスで点数を落としている勿体無い答案もかなりありました．しかしその一方で，B以上の答案の中でも，基本的な事柄の理解が疑われるものがいくつかありました．例えば行列の計算を通常の文字式の計算と混同しているもの（行列Aを分母にもってくるような書き方や，行列なのに数字の１と足し算するような書き方）．配点の都合上Sになっている人の回答にもそういうのがありました．

線形代数は後期に２もありますし，その後も種々の科目で使います．つまづきがないようにお願いします．

追記：欠席の方は病欠だったとのことで追試験を実施しましたが再度欠席されました．このかたは3月の再試験対象とはなりませんので来年再履修してください．

追記２：授業評価アンケートの結果がきました．増渕に対する受講生の評価も示します．
いずれも，４から１の４段階評価で，４が良い評価です．（）の中は，４から１を答えた受講生の数です．
＊担当教員の熱意や工夫を感じたか（35:14:2:0）スコア3.7
＊意見等を伝えたり質問する機会はあったか（22:20:8:1）スコア3.2
＊教材，教授法は適切だったか（24:25:2:0）スコア3.4
それぞれ全学教養科目の数学の平均は3.2，2.8，3.1，なので，合格点だと自画自賛します．

Original publication: 2017-08-02 18:50:30
Source: https://rheology.jp/nagoya/2017/08/%e7%b7%9a%e5%bd%a2%e4%bb%a3%e6%95%b0%ef%bc%91%ef%bc%882017%e5%89%8d%e6%9c%9f%ef%bc%89/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'lectures', 'label': 'Lectures'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'to-students', 'label': 'To Students'}

────────────────────────

応用物性（2017前期）

表題の講義の成績分布です．

全受講登録者数　５６名
S 2　名
A 1　名
B 6　名
C 8　名
F 0　名
欠席　３９　名

この講義は今期からの受け持ちで新しく立ち上げました．4年前期の選択ですから割合好きなことができますので，土井先生のSoftMatter Physicsの内容をやりました．とはいえ，当該の本でもっとも重要なOnsager's Principleは教えておりません．平衡論をやるのがやっとでダイナミクスに到達できなかったためです．

よって，内容はほとんど統計力学のソフトマターへの応用に終始したものでした．登録者が多いのに欠席が多いのは途中で興味なくなった方々でしょう．講義のやり方に工夫の余地があるのかもしれません．

Original publication: 2017-08-02 11:34:54
Source: https://rheology.jp/nagoya/2017/08/%e5%bf%9c%e7%94%a8%e7%89%a9%e6%80%a7%ef%bc%882017%e5%89%8d%e6%9c%9f%ef%bc%89/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'lectures', 'label': 'Lectures'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'to-students', 'label': 'To Students'}

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Brownian? non-Brownian?

Because I am in charge of the editor for the journal of society of rheology, japan, these days I have made the proofreading for the coming issue, which includes 4-5 papers. Of course the contents of each paper have been approved, so that what I have to do is to find and correct some minor errors... They are very minor errors and maybe not that important for the readers. But it would be a matter of cheapness, for example, if the style of bibliography in the list of reference is not consistent with each other.

Nothing related to my journal but I have found
this article interesting because it might be something like astro-rheology.
One of the important aspects of rheology is to probe the Brownian motion of molecules (by means of mechanical spectroscopy).　In this sense, Brownian motion is deeply related to rheology. The issue in the linked article is for discrimination of signals with respect to the Brownian motion; if the signal obtained from space is not just due to Brownian motion, the signal might represent some living organisms.
But, I am wondering if there exist any specific criteria to distinguish the signal of life from the Brownian signal, which may include diffusive, sub-diffusive, drifts,... etc.

Links
http://online.liebertpub.com/doi/10.1089/ast.2016.1616

Original publication: 2017-07-30 15:57:53
Source: https://rheology.jp/nagoya/2017/07/brownian-non-brownian/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Slimy Car Accident

https://youtu.be/4kX6LztfNAM

From last May, in addition to the position in Nagoya University, I am in charge of the full professor in Yamagata University. Last week I went to Yonezawa for the job. In Yonezawa, I organized the meeting to celebrate Professor Takimoto's 60th birthday, and it was quite fun with many friends.

During the trip to Yonezawa, I found an interesting rheological news. The Oregon State Police Dept has reported the car accident in which slimy liquids from a large amount of hug fishes were splashed on the load. As I posted before, the liquid is quite stubborn. There is an interesting document on this matter.

Links
https://twitter.com/ORStatePolice/status/885597812980711424
http://rheology.jp/nagoya/2017/02/slimes-for-difence/
http://www.southernfriedscience.com/your-car-has-just-been-crushed-by-hagfish-frequently-asked-questions/

Original publication: 2017-07-16 22:12:02
Source: https://rheology.jp/nagoya/2017/07/slimy-car-accident/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Estimation of mechanical properties of Spiderman's webs

Last week, I had a lecture for the Rouse model and I derived the G(t) for the continuum limit. In the talk, I used eigenfunction expansion, and mentioned the relation between the technique and JPEG format, the latter is widely used image format in which the image quality is controlled via the truncation of the expansion. See this page for the very nice example.

By the way, This article is fun for reading. Actually, the Young's modulus for the material used as Spiderman's webs is discussed. It would be a nice practice for students as a topic for basic mechanics.

For silks of spiders and worms, people sometimes misunderstand their production process. For instance, the Spiderman spews out the fiber from his wrist. The famous Japanese monster, Mosra, also spews his fiber out. But the insects do not spew it out, but the fibers are pulled out from the spinneret, by the motion of insects. Watch this movie. The silkworm attaches the end of the fiber and pulls the fiber out from his body.

One of my students in my Tokyo period, Mr Moriya, published three papers on the spinning of silkworms. Amazingly, he made these works during his Master course, even though he had the great help from Prof. Asakura and his colleagues.

• M. Moriya, F. Roschzttardtz, Y. Nakahara, H. Saito, Y. Masubuchi, T. Asakura, "Rheological Properties of Native Silk Fibroins from Domestic and Wild Silkworms, and Flow Analysis in Each Spinneret by a Finite Element Method", Biomacromolecules, 10, 929–935, (2009).

• M. Moriya, K. Ohgo, Y. Masubuchi, D. P. Knight and T. Asakura, “Micro-computerized tomographic observation of the spinning apparatus in Bombyx mori silkworms”, Polymer 49(26), 5665-5669 (2008).

• M. Moriya, K. Ohgo, Y. Masubuchi, T. Asakura, “Flow analysis of aqueous solution of silk fibroin in the spinneret of Bombyx mori silkworm by combination of viscosity measurement and finite element method calculation”, POLYMER 49(4), 952-956 (2008).

Links
http://www.math.kobe-u.ac.jp/~yamaguti/en/anime.html
https://www.wired.com/story/spider-man-homecoming-web-physics/
https://www.youtube.com/watch?v=UtHjDRVRM_Y
http://pubs.acs.org/doi/abs/10.1021/bm801442g%40proofing
http://www.sciencedirect.com/science/article/pii/S0032386108009129
http://www.sciencedirect.com/science/article/pii/S003238610701186X

Original publication: 2017-07-09 19:58:22
Source: https://rheology.jp/nagoya/2017/07/estimation-of-mechanical-properties-of-spidermans-webs/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Einstein's soft-matter physics

In my course of rheology conveyed to the graduate course students, I had a class dedicated to basics of Brownian motion and derivation of the Einstein's equation for the diffusion. At that occasion, I noticed that some students did not know about the great contributions by Einstein for soft-matter physics. This article would be nice to see the contributions. I wish to add the other paper on the Einstein's relation for viscosity of suspensions, which is certainly important for pigment inks for example. Nevertheless, the article lists 4 things and 2 of them are related to soft-matter physics.

Links
http://news.nationalgeographic.com/2017/06/einstein-relativity-lasers-solar-genius-science/
http://onlinelibrary.wiley.com/doi/10.1002/andp.19063240204/abstract;jsessionid=3FBEC011C45E236E453B6502000EBD86.f04t02?systemMessage=Wiley+Online+Library+will+be+unavailable+on+Saturday+01st+July+from+03.00-09.00+EDT+and+on+Sunday+2nd+July+03.00-06.00+EDT+for+essential+maintenance.++Apologies+for+the+inconvenience.

Original publication: 2017-07-01 22:45:56
Source: https://rheology.jp/nagoya/2017/07/einsteins-soft-matter-physics/
Categories: {'domain': 'category', 'nicename': 'lecture-note', 'label': 'Lecture Note'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Analysis of Brownian Motion of DNA

https://www.youtube.com/watch?v=DRyMLJJ9Sow&feature=youtu.be

I found this paper very interesting. From my phD study, Brownian motion of DNA molecules has been observed via fluorescent microscope, and typical observed behavior of DNA is as shown above. (This movie was taken by Mr Sato who graduated form my group when I was in Tokyo University of Agriculture and Technology.) Just following the standard procedure, I have analyzed the motion in terms of mean-square-displacement, and conformational relaxations.

The research proposes a new method for the analysis in the long time regime, in which the dynamics is usually regarded as normal diffusion whereas the authors extracted sub-modes deviating from the normal diffusion.

The authors kindly provide their code for the analysis. It seems worth trying.

Links
http://dx.doi.org/10.1038/ncomms15675

Original publication: 2017-06-17 21:21:16
Source: https://rheology.jp/nagoya/2017/06/analysis-of-brownian-motion-of-dna/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'post_format', 'nicename': 'post-format-video', 'label': '動画'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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"Coffee ring" for liquid crystals

An interesting article for the topic above.

As shown in the photo above, when a drop of coffee is put on a substrate, after the drying process the drop exhibits a ring pattern. This phenomenon has been of course well-known in our daily life, and has been discussed in the soft-matter community. The pioneering work for this issue is the paper by Deegan. He explained the phenomena by the evaporation-induced flow in the droplet. The evaporation rate of the liquid is much faster at the edge of the droplet than that at the center. This difference in evaporation rate generates a liquid flow from the center to the edge. Consequently, the particles are pushed by this flow and concentrate at the edge.

The new study coming out has revealed that the coffee ring phenomenon mentioned above exhibits a variety of pattern formations in relation to the liquid crystalline phases and anisotropic frictions. The study would be of industrial importance for painting processes, for example.

Links
https://www.sciencedaily.com/releases/2017/05/170530154306.htm
https://www.nature.com/nature/journal/v389/n6653/abs/389827a0.html

Original publication: 2017-06-04 12:47:51
Source: https://rheology.jp/nagoya/2017/06/coffee-ring-for-liquid-crystals/
Categories: {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Poster award to Mr Isoda

In the annual meeting of the society of rheology, Japan, Mr Isoda won the best presentation award for his poster on the stability of liquid films in foams. Honestly, I was afraid that his study may not be highly appreciated in the specific meeting, because his study is not directly related to rheology. Indeed, he theoretically describes the disjoining pressure between two facing liquid surfaces, where charged surfactants are attached to, and some oppositely-charged polyelectrolytes are dispersed in between. At this time being, his theory is for the equilibrium and not for the dynamics. However, disjoining pressure is related to stability of foams and may affect the lifetime of the foam, and such effects may be detectable in a rheological measurement something like this. Actually, Mr Asai is attempting this direction for his thesis.

Nevertheless, I appreciate the fellows who correctly evaluate his study. And, of course, congratulation to Mr Isoda for his success. I am happy to see that his efforts has been rewarded somehow.

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/05/52a885a5a40ca34231095fa8f734b5f4_s.jpg
http://rheology.jp/nagoya/2017/05/%e3%83%9d%e3%82%b9%e3%82%bf%e3%83%bc%e8%b3%9e%e3%81%a8%e3%81%a3%e3%81%9f%e3%81%9e%ef%bc%81/
https://www.jstage.jst.go.jp/article/rheology/43/3_4/43_71/_article

Original publication: 2017-05-24 08:03:47
Source: https://rheology.jp/nagoya/2017/05/poster-award-to-mr-isoda/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

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ポスター賞とったぞ！

修士2年の磯田です。

2017年5月18、19日に京都大学 宇治キャンパスで行われた日本レオロジー学会第44年会に参加して、Best presentation賞（ポスター賞）をいただきました。

副賞で学会名入りボールペンも頂きました。Jet Streamの良いやつです。

今回、受賞できたのは、周りの人から意見をたくさん頂けたからだと思っています。

今回の発表でも貴重な意見を貰えたので、研究に反映させてもっと面白くて、楽しい研究ができるように努力していきます。

皆様、今後ともご指導ご鞭撻のほど、よろしくお願いします。

Links
http://www.srj.or.jp/yoteihyou.html

Original publication: 2017-05-22 17:10:15
Source: https://rheology.jp/nagoya/2017/05/%e3%83%9d%e3%82%b9%e3%82%bf%e3%83%bc%e8%b3%9e%e3%81%a8%e3%81%a3%e3%81%9f%e3%81%9e%ef%bc%81/
Categories: {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'from-students', 'label': 'From Students'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

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Thrombelastography

An interesting article for clotting of human blood, I have found.

I can imagine that clotting (solidification) of blood has significant effects on surgeries and other medical operations. But I did not know how people quantify it. According to the article above, medical people make rheological measurements so-called thrombelastography. Because I did not know the term “thrombelastography”, I made google and found this quite informative website with nice videos.

As mentioned above, the measurement is a kind of dynamic viscoelastic measurement, and conceptually very similar to the Chambon-Winter method for detecting the gelation. Namely, an oscillatory shear deformation is applied to the sample, and the stress is measured. However, the way to evaluate the clotting ability is of huge difference. The main reason of difference is, to me, the necessity for quick evaluation as possible for the case of medical usage. Indeed, the paper mentioned above is for the development of new evaluation method for thrombelastograph to attain further swift evaluation than the conventional one.

For polymer rheology, the methodology has been mostly established, and the fundamentals have to be followed as possible. But for some materials that exhibits time-dependent behaviors and/or strong sample-individualisms, just like blood, something new is of necessity.

Links
https://scicasts.com/channels/clinical-research/2111-in-vitro-diagnostics/12566-novel-test-of-clotting-ability-accurately-predicts-need-for-transfusion-in-trauma-patients/
https://www.haemonetics.com/products/devices/surgical-and-diagnostic-devices/teg-5000

Original publication: 2017-05-19 23:30:22
Source: https://rheology.jp/nagoya/2017/05/thrombelastography/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Shear thinning of chocolate (?)

This article reports shear thinning data of a chocolate melt. This article is a nice review for the rheology of chocolates and it mentions that melting chocolates exhibit plastic behaviors with yield stress. This page is also nice to present the physics and chemistry of chocolate, and it schematically shows the flow curve of chocolates with yielding.

So my question is that chocolates are shear thinning liquids (pseudo-plastic), or plastic?

Links
http://www.azom.com/article.aspx?ArticleID=13829
http://www.scielo.br/pdf/cta/v30n4/v30n4a02.pdf
https://chem-is-you.blogspot.jp/2013/02/the-chemistry-of-chocolate.html

Original publication: 2017-05-14 23:07:43
Source: https://rheology.jp/nagoya/2017/05/shear-thinning-of-chocolate/
Categories: {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Viscoelasticity of brain correlates with its functionality?

I have found an interesting article on the subject above. See this page. According to this study, the viscoelasticity of hippocampus, which is the part of brain, correlates with the memory skill of human.

In my lecture course of rheology, viscoelasticity is of course one of the important topics, and an explanation of viscoelasticity is that, the materials property showing relaxation of modulus and retardation of viscosity. For some people, relaxation and retardation are not familiar. In such a case, handy examples are helpful. For instance, when we attempt to commemorate a series of random numbers, the memory eventually goes away (see forgetting curve). This phenomena is actually a kind of relaxation. Indeed, a viscoelastic material has a memory of deformation within a certain characteristic time so-called relaxation time.

Nevertheless, in my rheology course, I just have forgetting phenomena as an analogy of viscoelasticity, and I did not mean any physical correlation between them. On the other hand, very interestingly, the new study above exhibits the real physical correlation. I will add this story to my list of rheological fun stories.

Links
https://news.illinois.edu/blog/view/6367/493856
https://en.wikipedia.org/wiki/Forgetting_curve

Original publication: 2017-05-07 21:33:17
Source: https://rheology.jp/nagoya/2017/05/viscoelasticity-of-brain-correlates-its-functionality/
Categories: {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Labo visiting day (29/04/2017)

Today we had the labo visiting day which is the opportunity for the students who wish to come to the graduate school. The event this year is something special because it is the first visiting event for the Department of Materials Physics which has been newly established this April.

As the department head, I was wondering if a sufficient number of students would come to the event or not. Indeed, I was afraid that the announcement for this event might not be circulated well. In particular, our website (http://www.mp.pse.nagoya-u.ac.jp/) did not appear in Google for a while due to unknown reasons. Meanwhile, I was also afraid that the event site may not be large enough, if a great number of students come there. This thought is for the undergrads in our school of engineering. Due to the modification in organization of our school, the students have to take a look at the other laboratories to submit their application to the entrance examination to the graduate school. They have to submit the list of preference for the laboratories and they need some info for the laboratories coming from the other departments.

Nevertheless, the number of students attending the event was just. There were around 100 students in the room including over 20 outsiders.

In the event, some explanations for the entrance examination were given followed by the short presentations from the PI's who direct the laboratories in the Dept. of Applied Physics and the Dept. of Materials Physics. These talks were just in time, although I was afraid that some presentations might exceed the given time slot. It is not in the case. As the department head, I really appreciate the cooperation of the speakers.

After the presentations, the labo visiting tour took place. The students were offered the opportunities to visit two laboratories. The choice is not easy from 18 laboratories in which a large variety of research projects are being made. To our group, only 4 students came. In particular, only one student chose our group as the 1st preference. (The rest came to the group as their 2nd choice.) Hmmm, my presentation to introduce our group may not good enough to attract the students. And, I know well that my group is very much different from the other groups and the research topics may seem somewhat chemistry or biology like.

Nevertheless, I was impressed (and very much pleased) by the fact that, the student (for whom our group was the 1st choice) has read this blog(!!!!) Of course the blog-reading is nothing helpful for the entrance examination, but I felt rewarded...

Finally, I thank the help from the labo members for the event and thank again for the coming of the visitors.

If somebody missed the event and wish to visit our group, just write me to set an appropriate schedule for a private labo visit. Such a request is more than welcome.

Links
http://masubuchi.jp

Original publication: 2017-04-29 22:05:59
Source: https://rheology.jp/nagoya/2017/04/labo-visiting-day-29042017/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'category', 'nicename': 'to-students', 'label': 'To Students'}

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Receiving the commendation by the Minister of Education, Culture, Sports, Science and Technology

On Apr 17th, 2017, I went to the Ministry of Education, Culture, Sports, Science and Technology to receive The Commendation for Science and Technology, for "Advanced Tire Development through Coordinated Utilization of SPring-8, J-PARC and the K Computer" in collaboration with the researchers in the Sumitomo Rubber Industry, and Prof Shinohara in the University of Tokyo. The prize is the development of rubber materials, which is used for motor-tires. Take a look at the articles by the Sumitomo Rubber (in Japanese, and in English).

Honestly speaking, my contribution to the project is not that large, and actually, I just suggested a few ideas for the simulation of rubbers by the K Computer. The team directed by Dr Kishimoto in the Sumitomo Rubber made the most of the things, and they just kindly add me to the receiver of the prize. I must appreciate their very kind consideration.

Nevertheless, soft-matter physics contributes to our life, even though one may think of the soft-materials such like rubbers as the research target of chemistry...

Links
http://www.srigroup.co.jp/newsrelease/2017/sri/2017_046.html
http://www.srigroup.co.jp/english/news/2017/2017_046.html

Original publication: 2017-04-22 22:26:41
Source: https://rheology.jp/nagoya/2017/04/receiving-the-commendation-by-the-minister-of-education-culture-sports-science-and-technology/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

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Subtraction of a scientific paper

There has been announced the subtraction of the paper in which the behavior of polymers under fast shear deformations is discussed.
http://pubs.acs.org/doi/abs/10.1021/acsmacrolett.7b00171

As mentioned in the article above, their first paper appeared in ACS MacroLetter.
http://pubs.acs.org/doi/abs/10.1021/mz500260h
This specific paper had a great impact for the description of polymer dynamics in entangled states. In the conventional view, under fast shear deformations, the origin of stress is orientation given that the shear rate is lower than the reciprocal Rouse time. On the contrary, their study demonstrates that the stress is from polymer stretching rather than the orientation. Because they used the generic bead-spring model (so-called Kremer-Grest model) and they performed the simulation via the established code (LAMMPS), their study appeared somewhat convincing, and thus, the paper was published in the journal of a high-impact factor.

But, it should be emphasized that, apart from the conventional theory (that might be possibly not 100% perfect), their simulation results are inconsistent with the earlier experimental results for the stress-optical relationship. We made a publication for this issue.
http://pubs.acs.org/doi/abs/10.1021/mz500627r
Even before the publication of the paper (subtracted one), I heard that some researchers in my network evaluated the manuscript as the reviewers (for the other journal rather than ACS Macro Letter), and they did not recommend publication. Nevertheless, the topic was hot and some attempts were made. For instance, Professor Likhtman traced their study (just before his tragic accident) and published the paper in which the results with full consistency with the experimental results.
http://pubs.acs.org/doi/abs/10.1021/acsmacrolett.5b00708
We made a very similar study as well.
https://www.jstage.jst.go.jp/article/rheology/44/1/44_65/_article/-char/ja/

What I was impressed is that, after the accumulation of the studies in which the result of the first paper was suspected, the authors have decided to retract the paper. This decision is not only for that specific paper, but also for the related papers which is based on the result of the first paper. I greatly appreciate their decision that clarifies the situation and eliminate possibilities for further confusion. Their behavior is highly admirable. It might be thought that the subtraction is somewhat embarrassing, and it may damage their reputation. But I believe that it is not in the case.

Original publication: 2017-04-16 21:11:38
Source: https://rheology.jp/nagoya/2017/04/subtraction-of-a-scientific-paper/
Categories: {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}

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Ankita won the best poster prize from the European Rheology Community

We have received the great news for Dr Ankita Pandey who won the best poster prize at the Annual European Rheology meeting. Take a look at the award certificate that has been sent from her mobile phone.

Her poster was on "Coarse-Grained Simulations for Entangled Star Polymer Melts" and co-authored by myself, and presented at Annual European Rheology Conference 2017 in Copenhagen.

The study is the part of our research project for the development of simulation methods for high-performance materials for motor-cars and aviation industries. I pushed her to make the presentation in the conference because we have to continuously exhibit our activities to convince the funding agency, which is also watched by the government and the tax-payers. Due to the time constraint, the accumulated results by the conference were not that sufficient, even though the study itself deserved the presentation. (Indeed, her results were scarcely entangled stars rather than well-entangled stars.) Observing the situation before the conference, I did not expect the prize and actually it is beyond my expectation.

Nevertheless, I appreciate the consideration from the European colleagues, and of course, congratulations to Ankita!!

Original publication: 2017-04-07 23:49:25
Source: https://rheology.jp/nagoya/2017/04/ankita-won-the-best-poster-prize-from-the-european-rheology-community/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

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Mechanism of swimming for active matter in viscoelastic medium (Prof. Komura's theory)

Prof. Komura and his colleagues in Tokyo Metropolitan University has published the theoretical study for active matters swimming in viscoelastic medium.

Japanese article:
http://news.mynavi.jp/news/2017/03/30/142/

Original paper (in English):
http://journals.jps.jp/doi/10.7566/JPSJ.86.043801

Original publication: 2017-04-02 11:42:54
Source: https://rheology.jp/nagoya/2017/04/mechanism-of-swimming-for-active-matter-in-viscoelastic-medium-prof-komuras-theory/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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IWEAYR-12th 学会発表

2017年 2/8〜2/11に開催された学会IWEAYR-12thに増渕研究室から研究員二人、M1三人、B4二人の計七人で参加してきました。

学会の思い出を夏目の視点からお伝えします。
IWEAYRは東アジアの若年のレオロジストのための学会です。今年の開催場所はタイのパタヤです。パタヤはリゾート地として有名で、多くの観光客が集まります。今回の会場のホテルも、目の前に壮大な海が広がるまさにリゾートホテルでした。

⬆️会場のホテルと同期の久世くん

学会は主な行事はポスタープレゼン発表、ポスター発表、エクスカーション(遠足)の三つです。
それぞれについて書いていこうと思います。

・ポスタープレゼン発表
ポスタープレゼン発表は5分間の口答発表です。後にあるポスター発表を見に来ていただくための宣伝をするような感じです。
初めての学会発表、しかも英語でということもあり、とても緊張しました。
先生方や先輩方に何回も発表を見ていただいた甲斐があり、なんとか無事に終えることができました。
また、他の学生さんの発表も聞き自分の発表の至らなさを実感しました。

⬆️ポスタープレゼン発表の会場

・ポスター発表
ポスター発表は30分の持ち時間で自分の研究を詳しく発表する機会です。
僕はタイの女性教授から英語で質問攻めされ、とても焦りました。
言いたいことをうまく伝えられたかはわかりませんが、初めての人と英語で話すという貴重な機会を得られて良かったです。

・エクスカーション(遠足)
学会の参加者全員でバスに乗って、Nong Nooch Tropical Botanical Gardenという動物園と植物園を組み合わせたような野外施設に行ってきました。
この野外施設では、間近でトラや象を見ることができたり、様々な植物が飾られていたりしました。

 ⬆️ 象

⬆️ サボテン

敷地はとても広く、僕たちは小型バスで移動しながらの観光となりました。
最後には、タイのダンスや象のショーを間近で見ることができました。
残念であったのがグループアクティビティがなかったことです。せっかくの国際学会であるのにほとんど他国の学生さんと交流できなかったことが心残りです。

二年後のIWEAYRは名古屋で開催されるそうです。その時僕はM2で、学会の運営をすべき立場であるので英語でのコミュニケーション能力を高めないといけないなと感じました。

今回の学会は僕にとって初めての学会で、しかも国際学会ということで学会に出るまでの準備がとても大変でした。
ですが、初めての経験になることがとても多く、楽しかったです。

今回の学会発表にあたりご協力をいただきました多くの方々に御礼申し上げます。本当にありがとうございました。
来年の韓国でのIWEAYR-13thにも出られるよう、この一年研究を頑張っていきたいと思います。

以上、夏目でした。

Links
http://www.sci.src.ku.ac.th/iweayr12/index.html
http://rheology.jp/nagoya/wp-content/uploads/2017/03/2017-02-08-15.24.01.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/03/2017-02-09-19.53.35.jpg
http://www.nongnoochtropicalgarden.com
http://rheology.jp/nagoya/wp-content/uploads/2017/03/2017-02-10-16.20.03-e1490674317826.jpg
http://rheology.jp/nagoya/wp-content/uploads/2017/03/2017-02-10-14.19.43.jpg

Original publication: 2017-03-28 13:48:29
Source: https://rheology.jp/nagoya/2017/03/iweayr-12th-%e5%ad%a6%e4%bc%9a%e7%99%ba%e8%a1%a8/
Categories: {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'from-students', 'label': 'From Students'}

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Some requests for student positions

I have received some e-mail messages from some students who have interests in the position of research student and/or graduate student in our group. From communications with those students, I have been aware that some basic things should be shown on our website. This document is written for such a purpose.

For students who are interested in Ph.D. candidate positions, it should be noticed that Japanese Ph.D. students are not paid from laboratories. It means that they have to survive by themselves, and usually their parents have to pay their living costs. The situation is very different from that in Europe, the US, and China, in which generally Ph.D. students are paid from the supervisor.

There are some scholarship programs, but no guarantee. Apart from the life cost, the tuition fee is necessary as well, although the universities have a waiver and discount of the fee according to the economic situation of the student. On the other hand, the research money is, of course, paid from my research budget.

Some details for the admission are available here.

For students who wish to come to our group for the master course, in addition to the economic issues mentioned above, be aware of the entrance examination. The students in my group are in the Engineering school, and in the Department of Materials Physics, not in the polymer/chemistry department. Due to this situation, the subjects for the entrance exam for the master course is basically physics heading like quantum physics, electromagnetics, applied math, stat phys, etc, although the exam is somewhat different from that for Japanese students and the situations of foreign applicants would be considered.

Most of the cases, foreign students come to our Department as a research student in October for the preparation of the exam and take the exam in November. Then they will be the master course students from April if they pass the exam.

The other possible way to our group is to get to the Ph.D. course, rather than the master course. For such a case, as long as the research project during the Ph.D. course fits our direction, the entrance exam is not too much difficult, in general.

For students in the physics-related field, the subjects in our group may seem something chemistry and/or bio-related topics. They may be funny and/or even stupid. But you can enjoy it. I graduated from the Applied Physics Department and started studies for rheology and soft-matters in my undergrad project, and I found lots of fun.

For further information, please write to me.

Links
http://www.engg.nagoya-u.ac.jp/en/admissions/admissions.html
http://masubuchi.jp/

Original publication: 2017-03-25 22:14:22
Source: https://rheology.jp/nagoya/2017/03/some-requests-for-student-positions/
Categories: {'domain': 'category', 'nicename': 'to-students', 'label': 'To Students'}

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Hearing temperature?

Very interesting article in which they discuss the difference of sounds made by water with different temperatures. From the movie, I can hear the difference. The given explanation is the difference of water viscosity... Hmmm... Watch the video, and try it.

http://video.dailymail.co.uk/video/mol/2017/03/10/1348777916341402017/640x360_MP4_1348777916341402017.mp4

Take a look at the article here as well.

Links
http://www.dailymail.co.uk/sciencetech/article-4297086/Hot-cold-water-make-different-noises.html

Original publication: 2017-03-11 23:52:03
Source: https://rheology.jp/nagoya/2017/03/hearing-temperature/
Categories: {'domain': 'post_format', 'nicename': 'post-format-video', 'label': '動画'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

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Ketchup From a Bottle

On March 3rd 2017, I was invited to deliver a talk on very basic rheology for the group of people mostly from Japanese cosmetic industry. As usual, there was virtually no Q&A at the end of the session. This situation is quite normal for Japanese people who have been trained to be quiet as possible during the lecture. So, I have to find another way to have their feedbacks. My favorite way is to see the number of people sleeping in the lecture room. The sleeping during lectures is another characteristics for Japanese who have been trained to stay there up to the end. Nevertheless, I found very few sleepers, so that my lecture there should be fair, I believe.

My talk there was mostly for Non-Newtonian fluids like shear-thinning fluids, shear-thickening fluids, plastic bodies and viscoelastic fluids.
Relating to this topic, I have found a nice article from NewYork Times; "How to Get Ketchup From a Bottle Without the Wait, Watery Goo and Splatter"

And, the video embedded in the article is very nice, in a sense that, the ideas of Newtonian and Non-Newtonian fluids are excellently presented. I put the link below. This video is really great and I have learned a lot for the way of conveying the idea of rheology.

https://youtu.be/KB43fM_ozKQ

Links
https://www.nytimes.com/2017/02/13/us/ketchup-bottle-pour.html?_r=0

Original publication: 2017-03-04 23:45:43
Source: https://rheology.jp/nagoya/2017/03/ketchup-from-a-bottle/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'post_format', 'nicename': 'post-format-video', 'label': '動画'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

────────────────────────

Slimes for defence

https://youtu.be/F8aVgSIDJjM

Take a look at the video above. I found this video from this article, in which possibilities of slimes from hagfishes as a protection of solders are discussed.

Links
https://qz.com/909157/slime-eels-or-hagfish-have-inspired-new-materials-designed-to-protect-soldiers-in-combat/

Original publication: 2017-02-25 21:22:43
Source: https://rheology.jp/nagoya/2017/02/slimes-for-difence/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'post_format', 'nicename': 'post-format-video', 'label': '動画'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

────────────────────────

Photos from IWEAYR-12

All the students and post-doc members joined the 12th International Workshop for East Asian Young Rheologysis in Thailand. The event has been organized by the research groups in which the topics are related to rheology.

From the organizer, I have received the kind message with weblinks for the photo taken in the event. In particular, the FaceBook page exhibits a lot of nice photos for our labo members.

https://www.facebook.com/PolymerTechKUSRC/

Reports from the labo members will appear, hopefully soon, I expect.

Original publication: 2017-02-19 20:28:29
Source: https://rheology.jp/nagoya/2017/02/photos-from-iweayr-12/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}

────────────────────────

Rheology of Flog's Saliva

https://www.youtube.com/watch?v=IubFs-PtzhM

Take a look at the very interesting video above. In particular, I am very much interested in the flow-curve of saliva that is available in this paper.
To me, this flow-curve is quite exceptional.

There are many shear-thinning fluids for which the viscosity decreases with increasing shear rate. For instance, mayo is such a fluid. If mayo is put on a dish and the deformation rate is low, mayo keeps its shape and not that flowing. On the other hand, if mayo is stirred in a bin and the deformation rate is high, it is less viscous than honey, for example. Such a material behavior is so-called shear-thinning.

The flog saliva is a shear thinning fluid. But the shear-thinning property is unusual. The viscosity drastically changes in a narrow range of shear rate. Both sides of this critical shear rate window, the viscosity does not depend on shear rate.

Very interesting. I like this study much, in particular due to the fact that they collected amount of flog's saliva for the measurements...

Links
http://rsif.royalsocietypublishing.org/content/14/127/20160764

Original publication: 2017-02-04 23:45:09
Source: https://rheology.jp/nagoya/2017/02/rheology-of-flogs-saliva/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}, {'domain': 'category', 'nicename': 'rheology', 'label': 'Rheology'}

────────────────────────

The 6th international symposium of GMAP and LPIC

I was invited to Yonezawa for the conference above (program). I came to Yonezawa last week as well, and such frequent trip to Yonezawa is rare. This time, the event was hosted by GMAP center headed by Prof. Ito who is famous for polymer processing, and by LPIC headed by Prof. Furukawa who is well-known for 3D printing of polymers. They have had huge fundings, and owing to such financial situations they have organized the series of conferences in these years. To me, the event was real international one, in a sense that there were many researchers participated from outside. (In some cases, international conferences in Japan are not really internationalized. For example, I saw a situation in which all the people in the room were Japanese, even though they were supposed to speak in English ;-> )

The city was fully covered with snow as shown in the photo above, just as of the last week, although the weather was not that freezing.

The conference was for 2days from Jan 27th to 28th. But I had the class for polymer physics in 27th morning, I could not attend the sessions in Day1. Skipping sessions in conferences is not a correct way, in particular if you are paid. But I have to put my priority to the class rather than the conference outside. After the class I rushed into subway and take trains to attend the banquet, which is important for networking. (Even more important than the sessions, sometimes.)

Day2 morning I made my talk which was for 1 hour. As I mentioned earlier, 1 hour talk is difficult in general to hold attention from the attendee. Actually, I think I did not fully succeeded, in particular for the later half of my talk dedicated to some detailed discussions for extensional rheology. But I think it succeeded at least partly, because some foreign professors who do not make rheology made questions after the talk.

A good thing for me was to see Prof. Atarashi, Okayama University, who graduated from Prof. Keiji Tanaka's laboraotry, and who is a friend of Prof. Amamoto. He told me that he is interested in my blog-posts(!) That is a sort of happy pressure to me, and I should make more posts on funny stories on rheology...

(As usual) I appreciate the kind invitation from the organizers.

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/01/16110822_804412763029866_1419238893189857280_n.jpg
http://ngap.yz.yamagata-u.ac.jp/event2017.html
https://www.researchgate.net/profile/Hiroshi_Ito7
https://www.researchgate.net/profile/Hidemitsu_Furukawa
http://soran.cc.okayama-u.ac.jp/view?l=en&u=6e24dd9a78d8744f74506e4da22f6611&n=atarashi&sm=name&sl=en&sp=1

Original publication: 2017-01-28 23:35:07
Source: https://rheology.jp/nagoya/2017/01/the-6th-international-symposium-of-gmap-and-lpic/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'post_format', 'nicename': 'post-format-image', 'label': '画像'}

────────────────────────

International Workshop in Yonezawa

On Jan 18, 2017, I have organized the international workshop for soft-matter simulations in Yamagata University, Yonezawa, Japan. The photo above is the scenery of the campus. According to the local professors, they enjoyed rather dry weather until the last week but a huge amount of snow suddenly came up, and now the view is something spectacular. Because I started my academic career there, I know the situation and it is somewhat nostalgic. But of course the real life there is not always enjoyable, due to laborious snow removing activities, for example.

Nevertheless, the workshop itself was successful. For the recording purpose, the program is shown below. All the speakers are invited and no poster session took place due to time constraint.

13:00-13:30 Tomonori Koda (Yamagata Univ): Interface between substrate and liquid crystal of hard repulsive molecules

13:30-14:00 Masato Makino (Yamagata Univ): Dynamics of the Propeller-Like Particles in Simple Shear Flow and Rotating Electric Field

14:00-14:30 Sathith K Sukumaran (Yamagata Univ): Structure of Entanglements in Polymer Blends

14:30-15:00 Jun-ichi Takimoto (Yamagata Univ): Rotation of polymers under fast shear

15:00-15:15 Break

15:15-15:45 Takahiro Murashima (Tohoku Univ): Multiscale simulation of polymer flow developed for K computer

15:45-16:15 Yuichi Masubuchi (Nagoya Univ): Molecular mechanism of strain hardening revealed by multi-chain slip-link simulations

16:15-17:00 Giuseppe Milano (Keynote Lecture, Univ Salerno): Exploring nanomaterials with multiscale simulations for interface and interphase engineering

On the days before and after the conference, I was with Prof. Milano for intensified discussions for possible collaborations. Actually we started the collaboration for merging the simulation techniques developed in both sides, a few years ago, but the activity has been paused, partly due to my relocation to Nagoya, for example. Now we wish to restart it, but of course it depends on the situations, mainly for the budget and human resources.

I greatly appreciate the contributions from the speakers and the attendees.

Links
http://rheology.jp/nagoya/wp-content/uploads/2017/01/Yonezawa2017Jan.jpg

Original publication: 2017-01-21 23:01:45
Source: https://rheology.jp/nagoya/2017/01/international-workshop-in-yonezawa/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'conference-activity', 'label': 'Conference'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}

────────────────────────

Molecular Dynamics Simulations for Resolving Scaling Laws of Polyethylene Melts

The new paper has come out from the collaboration with Prof. Takahashi in AIST and Prof. Yasuoka in Keio Univ.

K. Z. Takahashi, R. Nishimura, K. Yasuoka and Y. Masubuchi, “Molecular Dynamics Simulations for Resolving Scaling Laws of Polyethylene Melts”, Polymers, 9(1), 24 (2017). http://www.mdpi.com/2073-4360/9/1/24

This specific study was almost completely made in Keio Univ. when Prof. Takahashi was a post-doc researcher and Mr Nishimura was a student of Prof. Yasuoka's group. At the beginning, I suggested making a quantitative comparison between atomistic polymer models and coarse-grained bead-spring polymer models. Although such a comparison is demanded to attain multi-scale simulations of polymers, there seem few systematic studies. Nevertheless, we are still working towards such a direction. In this paper Prof. Takahashi reported the behavior of polyethyrene constructed by a united-atom model. We appreciate the comments from the reviewers who mentioned the value of this study as a benchmark of polymer simulation using utited-atom models. My contribution is not great and just for the way of analysis and discussion.

I appreciate the efforts by Prof. Takahashi and Mr. Nishimura on this paper. Meanwhile, this is a memorial paper for me by a specific reason. Prof. Yasuoka was my labo-mate in Dept. Applied Physics in Nagoya Univ and we got our phD in the same year. He has made large scale molecular simulations, mainly for small molecules. Actually, his thesis was on the nucleation of liquids from vapor phase. On the other hand, I have made coarse-grained modeling of polymers and my thesis was DNA motion in gels. We have been good friends with each other but no collaboration paper in the past. Thus, this paper is the first paper in which both of our names are in the list of authors. I am more than happy to have it.

Links
http://www.mdpi.com/2073-4360/9/1/24

Original publication: 2017-01-14 23:56:53
Source: https://rheology.jp/nagoya/2017/01/molecular-dynamics-simulations-for-resolving-scaling-laws-of-polyethylene-melts/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'paper', 'label': 'Paper'}

────────────────────────

Extensional Step Strain Rate Experiments on an Entangled Polymer Solution

A research paper based on the collaboration with Australian professors has been published.
http://pubs.acs.org/doi/abs/10.1021/acs.macromol.6b00823

In this research, the elongational behavior of entangled polymers was investigated. The topic is something very typical for non-linear rheology of polymers. Indeed, there have been lots of attempts for this issue. The problem in this specific paper is the material behavior under two-step elongational flows. Namely, the polymeric liquid was stretched under a certain elongational rate until a pre-determined stretching time, and then, the stretch rate was increased with a stepwise manner. The purpose is to extract the polymer dynamics under the transition between different non-linear but steady states. The experimental part was made by the research group in Monash University, and I joined the project to simulate the behavior by my multi-chain slip-link model. Interestingly, the experimental results cannot be reproduced by any theoretical models including my simulations. I cannot specify the reason and actually this experimental dataset is very difficult in many aspects. Consequently, the discussion is not satisfactory, mainly due to the failure of the models that are expected to depict molecular pictures...

Professor Sridhar who kindly invited me to this project, has retired last year. I heard that his research group has been dissolved. For such an event, I have ambivalent feelings. For one side, of course, the retirement of great researcher and the loss of his active group are sad news for the society. On the other hand, the new vacancy is necessary for younger researchers who might explore completely new directions.

Nevertheless,I thank the Australian professors for letting me join this project.

Links
http://pubs.acs.org/doi/abs/10.1021/acs.macromol.6b00823

Original publication: 2017-01-07 23:05:59
Source: https://rheology.jp/nagoya/2017/01/extensional-step-strain-rate-experiments-on-an-entangled-polymer-solution/
Categories: {'domain': 'category', 'nicename': 'activity', 'label': 'Activity'}, {'domain': 'category', 'nicename': 'life', 'label': 'LifeLog'}, {'domain': 'category', 'nicename': 'paper', 'label': 'Paper'}

────────────────────────

Happy New Year 2017

This year, 2017, is the year of birds (roosters) in the oriental zodiac. We wish you all a good flying. I believe our group will fly right.

Links
http://rheology.jp/nagoya/wp-content/uploads/2016/12/NY2017.jpg

Original publication: 2017-01-01 00:03:51
Source: https://rheology.jp/nagoya/2017/01/happy-new-year-2017/
Categories: {'domain': 'category', 'nicename': 'micellaneous', 'label': 'Micellaneous'}