The shield of Captain America

posted by @ulaulaman #physics #chemistry #superhero #CaptainAmerica

After the releasing of the movie Captain America: The first Avenger in 2011 by Paramount Picture, Suveen N. Mathaudhu, the Program Manager responsible for Synthesis and Processing of Materials at the U.S. Army Research Office in Durham, NC, written a brief article, The Making of Captain America's Shield (pdf), where he try to understand if today we have the ability to construct the Captain America's shield. Thanks to Lynne Robinson⁽¹⁾ and the Avengers movie, Mathaudhu and his little review returned to the attention of people.
First of all we try to resume the story of the Cap's shield. The first comics shield was a triangular shield but starting from Captain America Comics #2 (april 1941), Cap was equipped by the most famous circular shield:

A concavo-convex metal disc approximately 0.76 m in diameter, it is virtually indestructible and has remained his most constant shield over the decades.

Following Captain America #255 (march 1981), the shield was presented to Rogers by president Franklin Roosevelt⁽⁶⁾.

It is created by the scientist Myron MacLain during some experiments with vibranium, an extraterrestrial metal introduced in Fantastic Four #53 with the ability to absorb vibrations⁽⁶⁾. A useful utilization of the vibranium was made by Thor in Avengers #68 in order to contain the explosion of Ultron-6⁽⁵⁾.

During the same saga (started on Avengers #66), MacLain presented for the first time the adamantium⁽⁶⁾. This metal was created (or founded) by MacLain some years after the creation of Cap's shield: this last was made by an alloy of vibranium and steel with an unkown catalyst; so MacLain try to reproduce that experiment and he accidentaly created adamantium, like the same metallurgist telled in Captain America #303.

The Graham Bell's tetrahedronal shed

posted by @ulaulaman Thanks to @fadesingh #geometry #chemistry #math

Tony Smith realized an interesting shed that it seems inspired by the tetrahedron, a particular polyhedron, but following Tropolism, this idea was just used by Alexander Graham Bell:

The tetrahedron is in general a polyhedron constituted by four triangular sides. Now, if we describe every vertices of every sides with the vector $(x_i, y_i, z_i)$, where $i = 1, \cdots, 4$, then the volume of the tetrahedron is given by: \[V = \frac{1}{3!} \begin{vmatrix} x_1 & y_1 & z_1 & 1\\ x_2 & y_2 & z_2 & 1\\ x_3 & y_3 & z_3 & 1\\ x_4 & y_4 & z_4 & 1 \end{vmatrix}\] And if the tetrahedron is regular, we can relate in one beutiful formula, the volume $V$, the area $\Delta$ of the triangles and the radius $R$ of the sphere outside the tetrahedron (or the circumsphere)^{(1, *)} \[6RV = \Delta^2\] The regulartetrahedron is also the platonic solid $P_5$

(...) with four polyhedron vertices, six polyhedron edges, and four equivalent equilateral triangular faces.

His symmetries are a bit complex, with 12 rotational symmetries, and the tetrahedral group is isomorphic with the symmetric group $S_4$, i.e. the group of all permutations of 4 elements.

The tetrahedron is also the basic idea to the Four corner project, developed by the artist David Barr in 1976, with the idea to realize a Erth-size tetrahedron in order to span our planet.
Finally we can find tetrahedron also in chemistry: methane, xenon tetroxide, perchlorate ion, sulfate ion, phosphate ion and others.
It's also interesting observe that also water presents a structure like a tetrahedron, but in this case isn't a regular polyhedron. In particular:

The most common arrangement of liquid water molecules is tetrahedral with two hydrogen atoms covalently attached to oxygen and two attached by hydrogen bonds. Since the hydrogen bonds vary in length many of these water molecules are not symmetrical and form transient irregular tetrahedra between their four associated hydrogen atoms.^{(2, 3)}

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(1) MathWorld: Weisstein, Eric W. Tetrahedron; Jackson, Frank and Weisstein, Eric W. Regular Tetrahedron
(2) Wikipedia: Tetrahedral molecular geometry
(3) P. E. Mason and J. W. Brady (2007). "Tetrahedrality" and the Relationship between Collective Structure and Radial Distribution Functions in Liquid Water. J. Phys. Chem. B 111 (20): 5669–5679

This is water

posted by @ulaulaman thanks to @archivioDFW

This comics watercolor is drawned by Davide Osenda, a computer engineer and cartoonists. His first comics is about mathematics, the italian graphic novel L'ultima lezione a Gottinga (The last lesson in Gottinga), about Cantor and the mathematics of transfinite numbers. Now it seems that he's working to a comics inspired by This is water, a speech by David Foster Wallace. So I propose you the audio of that speech:

The science behind tears

posted by @ulaulaman about #chemistry #comics #tears

From the collaboration between the National Cartoonists' Society and the Center for Cartoon Studies, it is born the first issue of the first volume of the on-line magazine The Cartoon Crier. The tabloid is a collection of the saddest strips and cartoons from a lot of great cartoonists. In particular there is also a science comics, Lacrimal studies 101 by Jon Chad, from the Fizzmont institute of rad science⁽¹⁾.

The structure of the comic is like the series of stories named A Goofy Look At... and Goofy as a famous hystoric persons drawned in particular by Hector Adolfo de Urtiága, one of the cartoonists of the Jaime Diaz's studios.
But stop to write about comics and start with science, in particular about the three type of tears that our eyes can produce: basal, reflex and emotional.

Basal tears are produced by our eyes constantly to keep them moist. These tears contain glucose, mucin, lysozyme, lactoferrin, lipocaln, potassium and sodium

Reflex tears are produced when an irritant either physical (a poke in the eye) or chemical (onion fumes) agitates an eye!!

About the emotional tears⁽²⁾ I find, instead, an interesting paper published last year on Science⁽³⁾. First of all there is the composition:

Tears are drops of liquid produced by the lacrimal, accessory lacrimal, and Meibomian glands, which contain proteins, enzymes, lipids, metabolites, electrolytes, and traces of drugs. In mice, tears contain a chemosignal or pheromone. Because the chemical makeup of human emotional tears differs from that of reflexive eye-protective tears, we hypothesized that human tears may similarly convey a chemosignal.

The research team, in order to test their hypothesis, choses a group of women between 30 and 31 years and has occurred the effect of their tears on various groups of men. For various types of emotions and tears were used different groups of donors (each group had an average age 30 years old) and after the samples are submitted to the attention of different groups of men (mean ages of groups were between 28 and 29 years old). First of all, we must note that the first test has been necessary to understand if the tears had some odor able to distinguish them than, for example, a saline solution. After determining that the tears do not have characteristic odors, they went ahead quietly with the actual experiment that aimed to test one of the two hypotheses under consideration, i.e. either that tears contain chemical signals related to the context of sadness in which they were produced, or that human tears, such as those of the mice, are capable of signaling information related to the behavior sociosexual.
We can summarize the results with the following paragraph from the abstract:

We found that merely sniffing negative-emotion–related odorless tears obtained from women donors induced reductions in sexual appeal attributed by men to pictures of women's faces. Moreover, after sniffing such tears, men experienced reduced self-rated sexual arousal, reduced physiological measures of arousal, and reduced levels of testosterone. Finally, functional magnetic resonance imaging revealed that sniffing women's tears selectively reduced activity in brain substrates of sexual arousal in men.

The results, of course, carry with them a series of questions, such as which are the substances inside the tears responsible for this type of response, or if such signals is restricted to emotional tears, or if we can still find the same effect even in the tears of men than women.
It's also interesting to note what is not said in the paper, namely that this kind of research can provide the best information to more effectively convey a certain kind of commercial messages. Discover something about ourselves, like in this case, presents a downside: it can trivially be used against us. However I think that the beauty of the world around us is equal to similar risks, especially if certain findings are not closed to the rooms of the researchers and donors.

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(1) A fake institute where we talk about REAL science!
(2) About emotional tears, I translate you a breaf quote from an italian pdf about tears:

This last type of tears [the emotional tears] contains very high percentages of manganese and some hormones including prolactin

(3) Gelstein, S., Yeshurun, Y., Rozenkrantz, L., Shushan, S., Frumin, I., Roth, Y., & Sobel, N. (2011). Human Tears Contain a Chemosignal Science, 331 (6014), 226-230 DOI: 10.1126/science.1198331 (4) Other links about research: Christine Dell'Amore for National Geographic and Janelle Weaver for Scientific American

Video abstract: Experimental demo of an invisibility cloak

a post by @ulaulaman via @NJPhysics

A little video about the paper Experimental demonstration of a broadband array of invisibility cloaks in the visible frequency range by V N Smolyaninova, I I Smolyaninov and H K Ermer

Weighted towel

a good #towelday by @ulaulaman

The primary object of the present invention is to provide a simple and safe means to secure a beach towel or blanket to the ground in the wind. A second objectis to make the invention easily carried. One embodiment offers an attached for holding wallet, clothing, etc. while swimming. These objects and will become apparent from the drawings, the description givev herein and appended claims.
In all embodiments the anchoring means is provided by a weighted cord sewnall around the perimeter of the material. Thus this invention could comprise a beach towel or a blanket or a mat. Metal weights are first inserted into a woven cord. The ends are scaled. Such weighted are available commercially. The weighted cord is then sewn into a hem along the perimeter of the material.

Arthur Dent thanks!

From the patent number 4634618 by Keith B. Greer et al (1987) ...
And a good towel day!

David Merritt and June Barrow-Green at Milano

The next Monday (28/05/2012) will be a great day for science in Italy. Indeed the astrophysicist David Merritt and the mathematician June Barrow-Green will be at Milano for two distinct talks.
Merritt will be at the Osservatorio Astronomico di Brera for the following talk:

Relativistic Dynamics at the Centers of Galaxies (h 14:00)

Encounters between stars and stellar remnants at the centers of galaxies drive many important processes, including generation of gravitational waves via extreme-mass-ratio inspirals (EMRIs). The fact that these encounters take place near a supermassive black hole (SMBH) turns out to be important for two reasons: (1) The orbital motion is quasi-Keplerian, so that correlations are maintained for much longer than in purely random encounters. (2) Relativity affects the motion, through mechanisms like precession of the periapse and frame-dragging. The interplay between these processes is just now beginning to be understood, based on N-body simulations that contain a post-Newtonian representation of relativistic dynamics. A key result is that relativity can be important even for orbits that extend outward to a substantial fraction of the SMBH influence radius, by destroying the long-term correlations that would otherwise drive the evolution. I will discuss this work and its implications for the EMRI problem, for experimental tests of theories of gravity, and for the long-term evolution of SMBHs and galactic nuclei.⁽¹⁾

And June Barrow-Green will be at Mathematics Department "Federigo Enriques" with the talk Poincaré and the three body problem.⁽²⁾ (h 16:30)
The problem was stated by Poincaré in 1890 with the following quotation:

I consider three masses, the first very large, the second small but finite, the third infinitely small; I assume that the first two each describe a circle around their common centre of gravity and that the third moves in the plane of these circles. An example would be the case of a small planet perturbed by Jupiter, if the eccentricity of Jupiter and the inclination of the orbits are disregarded.⁽³⁾

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(1) From inSPIRE I found the following paper, Towards relativistic orbit fitting of Galactic center stars and pulsars (arXiv), that seems about the subject of the thalk.
(2) From the introduction of Oscar II's prize competition and the error in Poincaré's memoir on the three body problem by June Barrow-Green:

In the autumn of 1890 Henri Poincaré's memoir on the three body problem was published in the journal Acta Mathematica as the winning entry in the international prize competition sponsored by Oscar II, King of Sweden and Norway, to mark his 60th birthday on January 21, 1889. Today, Poincaré's published memoir is renowned for containing the first mathematical description of chaotic behavior in a dynamical system. Correspondence preserved at the Institut Mittag-Leffler reveals that the competition was beleaguered by difficulties throughout. In particular, it has emerged that only weeks before the prize-winning memoir was due to be published, Poincaré discovered an error in his work which forced him to make very substantial changes. Indeed it was only as a result of correcting the error that he discovered the existence of what today are known as homoclinic points. This paper is an account of the troubled history of the competition together with an explanation of the error in Poincaré's memoir.

(3) Quotation extracted from Poincaré and the Three Body Problem