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Benvenuti in queste pagine dedicate a scienza, storia ed arte. Amelia Carolina Sparavigna, Torino

Saturday, January 8, 2011

Charon the demon

Ed ecco verso noi venir per nave un vecchio, bianco per antico pelo,
gridando: <<Guai a voi, anime prave! Non isperate mai veder lo cielo:
i' vegno per menarvi a l'altra riva ne le tenebre etterne, in caldo e 'n gelo.
E tu che se' costi`, anima viva, partiti da cotesti che son morti>>.
Ma poi che vide ch'io non mi partiva, disse: <<Per altra via, per altri porti
verrai a piaggia, non qui, per passare: piu` lieve legno convien che ti porti>>.
E 'l duca lui: <<Caron, non ti crucciare: vuolsi cosi` cola` dove si puote
cio` che si vuole, e piu` non dimandare>>. Quinci fuor quete le lanose gote
al nocchier de la livida palude, che 'ntorno a li occhi avea di fiamme rote.
Ma quell'anime, ch'eran lasse e nude, cangiar colore e dibattero i denti,
ratto che 'nteser le parole crude. ...
Caron dimonio, con occhi di bragia, loro accennando, tutte le raccoglie;
batte col remo qualunque s'adagia.



And lo! towards us coming in a boat an old man, hoary with the hair of eld, crying:
"Woe unto you, ye souls depraved! Hope nevermore to look upon the heavens; I come to lead you to the other shore, to the eternal shades in heat and frost. And thou, that yonder standest, living soul, withdraw thee from these people, who are dead!"
But when he saw that I did not withdraw, he said: "By other ways, by other ports thou to the shore shalt come, not here, for passage; a lighter vessel needs must carry thee." And unto him the Guide: "Vex thee not, Charon; it is so willed there where is power to do that which is willed; and farther question not." Thereat were quieted the fleecy cheeks of him the ferryman of the livid fen, who round about his eyes had wheels of flame.
But all those souls who weary were and naked their colour changed and gnashed their teeth together, as soon as they had heard those cruel words...
Charon the demon, with the eyes of glede, beckoning to them, collects them all together, beats with his oar whoever lags behind.

(traduzione Longfellow)

Fluorescence test for water quality

"A team of engineers and scientists are developing a device that measures water’s fluorescence in order to detect harmful microbes and chemicals... Water, like other substances, can absorb certain wavelengths of electromagnetic radiation and then emit it at a different wavelength, a process known as fluorescence.
Bridgeman’s technology identifies where radiation absorbed and emitted at specific wavelengths creates high intensity fluorescence, indicating that water pollutants are present."
Item by Stephen Harris, http://www.theengineer.co.uk/1006706.article?cmpid=TE01P&cmptype=newsletter&cmpdate=070111&email=true

Coronary stent

Most balloon angioplasty procedures include the insertion of tiny cylindrical wire mesh structures, called cardiovascular stents*, into the artery to prevent the elastic recoil that follows arterial dilatation. The scaffolding characteristics of the stent provide strength to the artery wall. However, vascular injury during stent deployment and/or recognition of the stent as a foreign material triggers neointimal hyperplasia, causing re-closure of the artery. A recent advancement to counteract restenosis is to employ drug-eluting stents to locally deliver immunosuppressant andantiproliferative drugs.  Furthermore,  auxetic (negative Poisson's ratio) stent structures were proposed that exhibits high circumferential strength in its expanded configuration and low flexural rigidity in its crimped configuration. 


*A stent is an artificial tubular structure inserted into a natural passage/conduit to prevent, or counteract, a localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow access for surgery.
See also http://en.wikipedia.org/wiki/Coronary_stent


Note the structure of the two stents. Stretching the tube corresponds in increasing the diameter. This image has been obtained after elaboration of the original one: Zwei Stents von schräg vorne mit Zentimetermaß. Ort der Aufnahme: Baden-Baden, Deutschland, Frank C. Müller.

Angioplastica coronarica

"L’angioplastica consente di ristabilire il flusso del sangue al cuore, riaprendo le coronarie ristrette per la presenza di placche aterosclerotiche, senza bisogno di aprire lo sterno con un intervento chirurgico, come si fa nei by-pass, ma arrivando direttamente ai vasi ostruiti risalendo lungo un’arteria perforata attraverso la pelle."..."A metà degli anni ottanta si pensò di inserire nell’arteria, di solito dopo averla dilatata col palloncino, un cilindro cavo formato da una retina metallica che si apriva impedendo che il vaso si restringesse di nuovo. Questo strumento, che viene lasciato in quella posizione al termine della procedura, è detto stent". ..."A metà degli anni novanta nascono i cosiddetti stent medicati, retine metalliche identiche alle precedenti ma ricoperte di un farmaco che viene rilasciato apoco a poco e che riduce la proliferazione delle cellule responsabili del restringimento all’interno del canale."

Auxetics, that is Negative Poisson's ratio materials

"Poisson's ratio, also called the Poisson coefficient, is the ratio of transverse contraction strain to longitudinal extension strain in a stretched bar. Since most common materials become thinner in cross section when stretched, Poisson's ratio for them is positive. The reason is that inter-atomic bonds realign with deformation. Stretching of normal honeycomb, shown on the right, illustrates the concept. Normal polymer foams or cellular solids, above left, have a positive Poisson's ratio. Re-entrant polymer foams developed in our laboratory, above right, have a negative Poisson's ratio." by Rod Lakes
http://silver.neep.wisc.edu/~lakes/Poisson.html



Auxetics are materials that have a negative Poisson's ratio. When stretched, they become thicker perpendicular to the applied force. Auxetic materials can be created from particular structures of macroscopic matter. Such materials are expected to have mechanical properties such as high energy absorption and fracture resistance. Auxetics may be useful in applications such as body armor, packing material, knee and elbow pads, robust shock absorbing material, and sponge mops. The term auxetic derives from a Greek word  which means "that which tends to increase", This terminology was coined by  Ken Evans of the University of Exeter.

Self-Organization of Helical Assemblies

"Organisms in nature can assemble themselves into highly functioning structures. Understanding the unique architectural principles that prompt this self-organization offers important clues into economical ways of solving complex material and design challenges."

Scientists explore nature’s designs

"A Harvard physical chemist Joanna Aizenberg acquired a passionate curiosity about — of all things — sponges. She particularly liked the ones made of glass, whose apparent fragility belied the fact that they could withstand terrific pressure in the deep sea"
More http://news.harvard.edu/gazette/story/2008/12/scientists-explore-nature%E2%80%99s-designs/
"To illustrate the kind of work done at her laboratory, Aizenberg focused on Venus’ Flower Basket, a milky-looking undulant sponge shaped like a tapering tube... native to the deep ocean, thriving in cold, crushing pressures a thousand feet below the surface... Venus’ Flower Basket is an intriguing package. At 500 million years old, it’s very low on the evolutionary tree. But its layered superstructure of glass illustrates how strong nature makes things, and with what apparent ease."

Sponges and glass fibers

The Venus' Flower Basket, or Euplectella aspergillum, is a deep ocean sponge. In traditional Asian cultures, this particular sponge, in the dry state, was given as a wedding gift. The reason is that this sponge is the house for a couple of small shrimp. The shrimp inside of the basket clean it, and in return, the basket provides food  by trapping it in its fiberglass-like strands, and then releasing it into the body of the sponge for the shrimp. The sponge  is also bioluminescent.
The glassy fibers that attach the sponge to the ocean floor,  are of interest to fiber optics researchers. The sponge extracts silicic acid from seawater and converts it into silica, then forms it into an elaborate skeleton of glass fibers. Other sponges  can also produce glass biologically. The current manufacturing process for optical fibers requires high temperatures and produces a brittle fiber. A low-temperature process for creating and arranging such fibers, inspired by sponges, could offer more control over the optical properties of the fibers.
More http://en.wikipedia.org/wiki/Venus'_Flower_Basket

Friday, January 7, 2011

Buddha - Thailandia


Bronzo laccato e dorato, Thailandia, XVII-XVIII sec.

Anche questa statua è esposta nella collezione del Museo d'Arte Orientale dedicata alla Thailandia.

Buddha - Tibet


Museo Arte Orientale, Buddha Shakyamuni, Rame dorato e pigmento azzurro, Tibet centrale, XIII sec.

Il Museo d'Arte Orientale di Torino ha una sezione dedicata alla regione Himalaiana, ricca di reperti provenienti dal Tibet. Buddha Shakyamuni siede nella posizione del loto. La spalla destra scoperta, un sottile panneggio ricade sulla sinistra dopo aver fasciato il busto. Il collo ha le tre pieghe di bellezza. Busto slanciato e spalle larghe e arrotondate. Viso ovale che si allarga in alto nella fronte spaziosa. Gli occhi si estendono verso le tempie con le palpebre abbassate a caratterizzare uno sguardo interiore. Questa immagine del Buddha venne creata per un monastero Tibetano, anche se risente della tradizione della scultura nepalese, nella fusione in rame e la ricca doratura al mercurio.


Museo Arte Orientale, Buddha del Paradiso d'Oriente, Fusione in rame con tracce di oro freddo, Tibet centrale, XIV secolo

La statua mostra il Buddha del Paradiso d'Oriente nel momento della tentazione del Buddha Shakyamuni da parte di Mara e la sua incrollabile decisione di raggiungere l'Illuminazione. Il Budha siede su una doppia corolla di loto culminante in un filare di perle, con la mano sinistra nell'atteggiamento della meditazione e con la mano destra che sfiora il suolo nel gesto che chiama la Terra a testimone del diritto maturato in infinite vite precedenti.