The physical chemistry of brewing a decent coffee

I am brazilian, therefore I am addicted to coffee. OK, not all brazilians drink coffee, as not all US Americans play baseball. This does not change the fact that I feel miserable if I have to go out my home in the morning without drinking a large mug of the dark brew (which I drink without additions, including sugar).

I also travel a lot, occasionaly going to places in which coffee is decisively horrible. Recently a former student went through the same problem, and this reminded me of the period in which I lived in Germany.

Not that German coffee is that bad, at least there are places in the world in which coffee is even worse. The problem with German coffee is that if you drink it using a glass, you can see through! For me, this was something like an heresy.

Being myself a scientist, I decided to make experiments. Soon I discovered that the amount of powder didn’t matter. Neither did the roasting level. I tried powders of various provenances, but this didn’t help either. 

Then, one day, I was buying coffee powder at a specialized shop called Tschibo (I had already partially solved my problem, noticing that freshly ground coffee produced better results) when the vendor asked me wether I wanted my powder fein  gemahlen (finely ground) or grob gemahlen (coarsely ground). I asked her what was the difference and she explained to me that the finely ground particles were designed for expresso machines and that if I used it with normal filter, I would get particles going through.

Imediately I realized the solution to my problem, I asked my powder finely ground and confirmed the next day that I was able to brew Brazilian  quality coffee in Germany.

My explanation is the following: in Brazil the griding machines are old, the filters are bad, so many fine particles pass, giving the excellent taste we are used to. In Germany the machines are brand new, the filters are perfect, and hence, only liquid passes. Naturally, having solid particles in suspension the Brazilian coffee becomes opaque.

Of course, according to the scientific method, I would need to further test my hypothesis. I would need to perform a granulometric analysis of the different powders, or verify the solid residues left from evaporation. As my good friend, Eng. Alberto Imoto thaught me, however, in the case of performance-driven research you are entitled to stop the action once you get the desired effect.

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Benjamin Thompson (a.k.a Count Rumford), Julius Robert Meyer

The title reminds of two early heroes of what we know today as thermodynamics. More precisely, the first law of thermodynamics. First I must acknowledge that I only heard about them due to the excellent formation in physics I had at the Instituto de Física da Universidade de Sao Paulo.

Benjamin Thompson was a curious fellow. Born in the United States (better said, in the Massachussets colony), he fought in the American Independence War (at the side of the British), made career in the British Empire (was raised to knighthood) and later went to work for the King of Bavaria (from where his noble title stems, apparently). In other words, he was a sort of a mercenary.

220px-Benjamin_Thompson Benjamin Thompson, 1753 – 1814 (source: wikipedia)

His famous discovery was made while drilling holes in bronze to produce cannons. Everyone who already did this (drill holes in any metal) will agree that the metal piece becomes quite hot. At that time people believed heat was a kind of fluid (a liquid called caloricum) which could be shared by different bodies by flowing.

Thomson devised an experiment to disprove this notion. He placed the drill and the cannon inside water and showed that the water could be brought to boil just by the drilling activity. More than this, he showed that the amount of available heat was practically infinite, depending only on the work done by the drilling activity, and showed that no transformation happened in the material, by comparing the specific heat of the removed material (metal chips) with that of the bronze piece.

He correctly stated, based on this experiment, that mechanical work could be transformed into heat by friction, and it seems that he had the notion that their sum must be conserved, but this was not stated in his work.

Robert Meyer, on the other hand, was a German. He is described in the modern texts as a physician (meaning medic), but one has to remind that at this time all of them were polymaths, so these distinctions we have today made no sense.

GW163H219Robert Meyer, 1814 – 1878 (source: Hmolpedia)

His key experiment was an observation. Working as ship physician in the coast of Java, he noticed that the venous blood of the sailors was less dark than the color he was used to in Germany. This blood was mostly red and only slightly darker than the arterial blood. He correctly assumed that this was a consequence of the different average temperatures in both places, arguing that the body heat is generated by combustion and that more combustion is needed in the cold Germany compared with the hot Java. He also observed (or better, was told by the sailors), that the sea water heated after a storm, and that this was due to agitation (mechanical work). Later he did experiments and came out with a value for the R constant (the mechanical equivalent to heat), and correctly stated the conservation of the sum of heat and mechanical work (the first law). He also published a small brochure in 1851 correctly stating that mechanical work and  heat could be transformed into each other.

He tried to publish his findings in the Ann. Chem. Phys.  in 1841 (two years before Joule) but was ignored. With help of friends he managed to publish a work in the Annals of Chemistry and Pharmacy in 1842. It seems that the problem was that he used philosophical ideas (principally by Immanuel Kant) to justify his physics, bordering metaphysics. His role in thermodynamics was acknowledged only after Helmholtz lectured about him to a group of physicist.

Both characters were complicated persons. Thompson is remembered for his correct interpretation of the drilling experiment, but he also defended very weird theories which were later proven wrong. Meyer was an adept of philosophical thought and obviously designed and interpreted his experiments in the light of these theories (i.e. by preconception), what is today considered frontally wrong in the scientific method. Meyer was also one of Boltzmann’s antagonists, equating his ideas with alchemy (an intended insult, of course).

The important is to realize, however, that both characters relied on observation of physical phenomena to reach their conclusions, something which was very alive in the birth years of thermodynamics, but has been forgotten since then.

I always remind my students not to judge past characters using present day’s moral compass. Thompson and Meyer are products of their respective times and what is contradictory today made perfect sense to them at that time. Their role in the development of thermodynamics, in particular, of the first law, cannot and should not be overlooked.

References:

On Thompson: https://en.wikipedia.org/wiki/Benjamin_Thompson

On Meyer: http://www.eoht.info/page/Robert+Mayer

 

 

How to Lead in a Losing Cause – Lessons from the Real Robert E. Lee

Nice article of Cory Galbraith, showing we should not judge past characters using our present moral standards.

Cory Galbraith

lee

He lost the Civil War but is respected to this day, could control his emotions like nobody else, and kept a pet chicken for companionship.

Robert Edward Lee, the commander of the Confederate army in the U.S. Civil War is said to have never fired a single shot, but was responsible for the deaths of hundreds of thousands of people.

This elusive and misunderstood figure of history, despite being flawed, displayed both humility and a deep appreciation for the unexpected benefits of losing.

Today, these qualities possessed by Lee have much to teach us about leading ourselves, and others, in a world turned upside down.

“We must expect reverses, even defeats. They are sent to teach us wisdom and prudence.”

Lee won the vast majority of his battles, losing ground towards the end of the war. But he understood that with loss comes learning, greater determination, and the ability to…

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The multidisciplinary interplay in materials sciences: can we understand and mimic the nature?

Nature is smart and brilliant. In nature, we can find the best examples on how to biosynthesise a material and use it for several purposes with efficiency. An astonishing case study is the spider silk which is a form protein fibre structurally similar to cellulose and human hair. Looking at the nanoscale, Transmission Electron Microscopy (TEM) analysis performed by Simmons et al. [1] has revealed an intriguing microstructure without any resemblance with typical man’s made materials: the spider silk is composed of small crystallites with sizes around of 30 nm separated by amorphous regions cross-linking those nanocrystals.

This semi-crystalline microstructure is responsible to deliver a unique set of properties which express the complexity and the beauty of such spider fibres. The tensile strength, 1.30 GPa, is in the order of the stainless steels, 1.65 GPa, with its density corresponding to a sixth of the steels [2]. With extreme ductility, these fibres can be stretched almost up to six times of their unloaded length. In terms of structural integrity, the mechanical properties of the spider silks are hold within the temperature range of -40 to 220°C, unlikely relevant for the natural environments. Darwin’s bark spider silk can reach up to 520 MJ/m³ of toughness: at around 10 times higher than Kevlar toughness [3].

Are the metallurgists and material scientists able to invent a material inspired by the semi-crystalline spider silk microstructure and make use of its properties? An interesting multidisciplinary field that, nowadays, has attracted the attention of the scientific community is known as biomimetics.  Consists in how scientists can interpret nature aiming at the design and synthesis of materials and structures by means of mimicking biological process.

In material sciences, the benefits of adopting an interdisciplinary biomimetic approach could bring enormous consequences to the next generation of researchers and engineers. The simple fact that a biological spider silk with mixed amorphous-crystalline microstructure can give birth to a protein-based material with comparable mechanical strength of the human top-steels is an astonishing achievement.

As pointed out in this blog before, superspecialisation has created an entire generation of professionals without any commitment with nature, environment and wellbeing. We need to go back to our roots. To observe nature as scientists and learn with it. To extract the best that nature can give us, and as a result, produce bio-inspired materials with enhanced properties. The triad metals-ceramics-polymers is old fashion and may condemn the creativity of our students for their entire carrers.

[1] SIMMONS, Alexandra H.; MICHAL, Carl A.; JELINSKI, Lynn W. Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk. SCIENCE, p. 84-87, 1996.

[2] SHAO, Zhengzhong; VOLLRATH, Fritz. Suprising strength of silkworm silk. NATURE, 418, 741, 2002.

[3] BLACKLEDGE, Todd; KUNTNER, Matjaz; AGNARSSON, Ingi. Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb spider. Plos one, v. 5, n. 9, p. 1, 2010.

Featured Image: Darwin’s back spider. Credits: BBC London.

How to get rid of pseudoscience?

This post is the English translation of my post “Como se livrar da pseudociência”, published in Portuguese here.

Some months ago I read a post which started like this “Studies show that any post which starts with studies show will be taken seriously by the reader”. This is, of course, a joke (or better, a metajoke), but it is, in some sense also true.

We are flooded with information from multiple sources. Only in Facebook there is a multitude of “so said” science channels. Due to the anarchist nature of internet, anyone can create one of these pages or even a science blog (no pun intended). Worse than that, everyone competes for attention.

Dealing with science one should expect honesty and knowledge of the subject by the ones who create these channels. Unfortunately this is not always the case. In the nonsense search for audience these channels share questionable posts, either by ignorance (in the sense of lack of knowledge) or by ill intention. This is one of the sources of pseudoscience.

There is, however, another source of pseudoscience: ideology driven channels. Fundamentalist religious groups and adepts of conspiracy theories use the internet to gather followers. Ideology and science never worked well together, the ability to question the results is an integral part of the scientific method and this kind of fanatic is unable to proceed with this questioning, so what they generate is always pseudoscience.

But what about the reader? How can he (or she) protect from (or even recognize) pseudoscience? After all, not everybody interested in science has the capability to understand the details and particularities of the scientific method. Also, many of my colleagues refuse to educate the general population and, particularly n Brazil, the poorness of science teaching in the fundamental and intermediate education levels create the proper ground for spreading pseudoscience.

Here are some clues to recognize pseudoscience:

  1. Be suspicious of bombastic contents. Once I read a post which claimed the disk of planet Mars would appear in the sky with the same size as the Moon, this is obviously ridiculously impossible.
  2. Due scientific results are usually published in trustworthy sources: scientific magazines and pages maintained by important universities and research institutes. Published articles usually go through the peer reviewing, a process in which other scientists (usually anonymous) evaluate the work before publishing (but attention, really revolutionary results are usually published in repositories first, therefore before peer reviewing, this does not mean they are less trustworthy). It is always important to read the original source (if possible), the authors of the articles not always understand what they read.
  3. Trust in the science you learned. It is true that really revolutionary results may challenge the view we have from reality at any moment, but Newton’s third law, mass and energy conservation, and the basic chemical reactions in biological organisms will not cease to exist from one day to the other.
  4. True science admits the contradictory, so, get suspicious of any post which claims to defend the absolute truth, without questioning the own result.

I hope this helps.

 

 

What makes a materials scientist tickle?

Back in year 1996 Walter Schütz, in his work “A history of fatigue” told the history on how Gassner in 1941, measuring the fatigue strength of high strength aluminum alloys of the series 7XXX (Al-Zn-Mg), and finding this was not much different from the lower strength, lower cost, alloys of series 2XXX (Al – Cu), warned that if they were used, for example, to build an airplane, this would lead to premature fatigue failures.

This argument is tricky  and seems illogical. Aren’t the alloys of series 7XXX of higher strength compared to alloys 2XXX? And didn’t Gassner find out the fatigue strength was about the same? So why would the fatigue live be smaller if the 7XXX alloys were used?

The explanation for this apparent contradiction is simple. The only possible reason to use a higher strength alloy (especially when it is more expensive) in place of a lower strength one, is to allow higher static stresses. In practice, one is able to reduceaviao-comercial-embraer-175-1334930067222_956x500 the thickness of a sheet, used to build, for example, the fuselage of an airplane. This leads to a lower mass of the structure, which is a good thing for airplanes. The loads acting on the structure, however, are approximately unchanged, since they depend mostly on the overall geometry of the structure. Since stress is the load divided by the cross section area, the material will work at a higher static strength level, and hence this will be inversely proportional to the thickness .

The problem is that the dynamic load (for example, the maximum and the minimum loads in function of time) are also inversely proportional to the reduction in thickness, therefore the difference between the maximum and the minimum stresses, in other words, the stress amplitude will also increase proportionally, leading to a more severe fatigue loading. Therefore fatigue life will be shorter, not because the fatigue strength (the material’s property) decreased, but because the loading became more severe, surpassing the fatigue strength.

This kind of elaborate argument is typical in Materials Science, a similar argument justifies why quenched steels should not be used in the maximum hardness is subject to a hydrogen-rich environment.  Another tricky argument explains also why low stacking fault energy FCC metals present higher strain hardening.

I call this non-linear thinking. A present cause results in an effect as a consequence of a long chain of events, which is not self-evident in principle. As I already wrote, in my opinion the aim of superior education is to prepare the student for this way of thinking.

Non-linear thinking, however, is very common in Materials Science. I believe this is due to the highly interdisciplinary  character of this subject. Of course, other scientific branches are also characterized by interdisciplinarity, but this seems to be more common in Materials Science.

It is this particular way of thinking which motivates the materials scientist. Non-linear thinking is addictive, the first time you get confronted, and understands, one of these long elaborate logical arguments, you will feel the need to learn more of the kind. So, be warned, if you are satisfied with thinking on thing in short cause-effect terms, stay away from Materials Science.