"NASA satellite images have revealed that the biosphere is being placed under increasing strain as rising population on a global scale is accompanied by increased consumption of crops and animals per capita."
http://physicsworld.com/blog/2010/12/satellite_reveals_strain_on_ea.html
Wednesday, January 12, 2011
Il satellite Planck per capire le origini dell'Universo
"Da oggi, 11/1/2011 c'è in rete un nuovo tesoro, anzi una vera e propria miniera di tesori. Si tratta del catalogo preliminare dei dati del satellite europeo Planck, un catalogo di dati per astrofisici specialisti, ma che rappresenta un notevole balzo in avanti per la conoscenza del nostro Universo. Ed è solo l'inizio perché il satellite è a metà circa del suo lavoro che terminerà, fondi permettendo fra un paio di anni. Poi ce ne vorranno anche una diecina per pulire e analizzare a fondo la massa enorme di dati che Planck sta trasmettendo."
Tuesday, January 11, 2011
Profiles - Hero of Alexandria
The idea using the power of steam is quite old. A Greek mathematician and engineer who resided in the Ptolemaic Egypt, named Hero, wrote a manuscript describing various devices and ideas of the time. Although it is not sure that Hero was the inventor of these devices, he is credited for the earliest mention of steam power. Hero describes a method to open the doors of a temple with the action of a fire on an altar at the front of the temple. A series of pipes runs between altar and the temple doors: it is the steam created by the fire on the altar and the suitable syste of pipes to open the temple doors.
Figure from http://www.history.rochester.edu/steam/hero/section37.html
This is a page of "THE PNEUMATICS" of HERO OF ALEXANDRIA, from the original greek.
See also http://library.thinkquest.org/C006011/english/sites/steam_first_experiments.php3?v=2
http://en.wikipedia.org/wiki/Hero_of_Alexandria
Figure from http://www.history.rochester.edu/steam/hero/section37.html
This is a page of "THE PNEUMATICS" of HERO OF ALEXANDRIA, from the original greek.
See also http://library.thinkquest.org/C006011/english/sites/steam_first_experiments.php3?v=2
Antikythera mechanism
Antikythera is a Greek island. It is known for being the location of the discovery of the Antikythera mechanism and for the Antikythera wreck, a shipwreck from the 1st or 2nd century BC. It was discovered by sponge divers in the early 1900s. The wreck produced numerous statues and a mechanism, considered as the world's oldest known analog computer.
In October 1900, a team of sponge divers led by Captain Dimitrios Kondos began diving off the coastline of Antikythera island. At that time, divers wore as diving equipment a canvas suit and copper helmet, which allowed them to dive deeper and to stay submerged longer. "The first to lay eyes on the shipwreck 60 metres down was Elias Stadiatos, who quickly signaled to be pulled to the surface. He described the scene as a heap of rotting corpses and horses lying on the sea bed. Thinking the diver had gone mad from too much carbon dioxide in his helmet, Kondos himself dove into the water, soon returning with a bronze arm of a statue." more Wiki.
On 17 May 1902, archaeologist Valerios Stais made the most celebrated find. He was diving to search the area of the wreck and noticed that one of the pieces of rock near him had a gear wheel embedded in it. He found what is now known as the "Antikythera mechanism".
Il meccanismo è un "antichissimo calcolatore per il calendario solare e lunare, le cui ruote dentate potevano riprodurre il rapporto di 254:19 necessario a ricostruire il moto della Luna in rapporto al Sole (la Luna compie 254 rivoluzioni siderali ogni 19 anni solari). L'estrema complessità del congegno era inoltre dovuta al fatto che tale rapporto veniva riprodotto tramite l'utilizzo di una ventina di ruote dentate e di un differenziale, un meccanismo che permetteva di ottenere una rotazione di velocità pari alla somma o alla differenza di due rotazioni date. Il suo scopo era quello di mostrare, oltre ai mesi lunari siderali, anche le lunazioni, ottenute dalla sottrazione del moto solare al moto lunare siderale.Sulla base della sua ricerca, Price concluse che, contrariamente a quanto si era creduto in precedenza, nella Grecia del II secolo a.C. esisteva effettivamente una tradizione di altissima tecnologia." More http://it.wikipedia.org/wiki/Macchina_di_Anticitera and also, a longer discussion, http://en.wikipedia.org/wiki/Antikythera_mechanism
Monday, January 10, 2011
Double-layers and supercapacitors
A double layer (DL), or electrical double layer, is a charge distribution that appears on the surface of an object when it is placed into a liquid. The object might be a solid particle, a gas bubble or a liquid droplet. The double layer is created by two parallel layers of charge, surrounding the object. The first layer is attached to the surface, with a charge either positive or negative. This layer is built by the ions adsorbed* onto the object due to chemical interactions. The second layer is composed of ions attracted to the surface charge via the coulomb force, electrically screening the first layer. This second layer is loosely associated with the object: it is made of free ions which move in the fluid under the influence of electric attraction and thermal motion rather than being firmly anchored. It is thus called the diffuse layer.
DL plays a fundamental role in many real-world systems. For instance, milk exists only because fat droplets are covered with a double layer that prevent their coagulation into butter. DLs exist in practically all heterogeneous fluid-based systems, such as blood, paints, inks, ceramic slurries and cement slurries.
* In general, adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the adsorbent.
More on double-layers at http://en.wikipedia.org/wiki/Double_layer_(interfacial)
http://depts.washington.edu/solgel/pages/courses/MSE_502/Electrostatic_Stabilization.html
DL plays a fundamental role in many real-world systems. For instance, milk exists only because fat droplets are covered with a double layer that prevent their coagulation into butter. DLs exist in practically all heterogeneous fluid-based systems, such as blood, paints, inks, ceramic slurries and cement slurries.
* In general, adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the adsorbent.
More on double-layers at http://en.wikipedia.org/wiki/Double_layer_(interfacial)
http://depts.washington.edu/solgel/pages/courses/MSE_502/Electrostatic_Stabilization.html
An electric double-layer capacitor, also known as supercapacitor, supercondenser, pseudocapacitor, electrochemical double layer capacitor(EDLC), or ultracapacitor, is an electrochemical capacitor with relatively highenergy density, typically on the order of thousands of times greater than anelectrolytic capacitor.
Supercapacitors are able to store about a million times more charges than conventional capacitors. The principle is that of the "double layer". The charge is stored in the so called Helmholtz double layer. When voltage is applied, ions of opposite charge accumulate at the electrodes and the double layer is formed. Its thickness is in the range of several angstroms. Usually, highly porous carbon is used as electrode material, to create a fractal surface. Due to this very high specific electrode surface and the very small distances within the double layer, capacities of several hundreds farads can be achieved. As charge storage is only physical and not chemical, as in the case of batteries.
Some researchers in the US have made the first high-frequency AC supercapacitors containing graphene electrodes. The devices, which are much smaller than conventional capacitors, could be used in applications like computer processing units and other tiny integrated circuits.
Google Earth Engine
Google Earth Engine, mette online mappe e ambientali per la possibilità di analisi e confronti incrociati su deforestazione, desertificazione e risorse idriche. "Un nuovo strumento online per salvaguardare il pianeta. Alla conferenza Onu sul clima di Cancun, in Messico, è stato presentato in questa veste Google Earth Engine, nuova piattaforma targata Mountain View che mette a disposizione della comunità scientifica internazionale 25 anni di dati e immagini satellitari - e gli strumenti per analizzarli."
Dante's portrait by Longfellow
Tuscan, that wanderest through the realms of gloom,With thoughtful pace, and sad, majestic eyes, Stern thoughts and awful from they thoughts arise, Like Farinata from his fiery tomb. Thy sacred song is like the trump of doom;Yet in thy heart what human sympathies,What soft compassion glows...
Henry Wadsworth Longfellow
Dante e l'America, Henry Longfellow
"La presenza di Dante nella cultura americana risale al 1867, quando il poeta Henry Wadsworth Longfellow completò la prima traduzione americana della Divina Commedia", dice Giuliana Fazzion, James Madison University. Longfellow fondò nel 1865 un circolo per la traduzione di Dante nella sua casa a Cambridge, Massachusetts. Altri studiosi collaborarono con Longfellow alla prima intera traduzione della Divina Commedia. Il gruppo di lavori si battezzo “Dante Club” e nel 1881 divenne “The Dante Society of America”.
Saturday, January 8, 2011
Il Caronte di Virgilio
Il post precedente riporta la descrizione di Caronte fatta da Dante nell'Inferno, con la traduzione Longfellow. Chi era Caronte? Nella mitologia, Caronte, figlio di Erebo e Notte, era il traghettatore dell'Ade. Trasportava le anime da una riva all'altra del fiume Acheronte, ma solo se i loro corpi avevano ricevuto i rituali funebri, con un obolo per pagare il viaggio; chi non aveva l'obolo, era costretto vagare tra le nebbie del fiume per cento anni. Si metteva così una moneta nella bocca del defunto prima della sepoltura. Alcuni ricercatori sostengono che il prezzo era di due monete, sistemate sopra gli occhi. Pochissime anime vive son state trasportate da Caronte, tra di loro Enea, Ulisse, Orfeo e Dante.
Caronte viene descritto nell'Eneide da Virgilio al libro VI con le seguenti parole:
Caronte viene descritto nell'Eneide da Virgilio al libro VI con le seguenti parole:
"Portitor has horrendus aquas et flumina servat
terribili squalore Charon, cui plurima mento
canities inculta iacet, stant lumina flamma,
sordidus ex umeris nodo dependet amictus.
Ipse ratem conto subigit velisque ministrat
et ferruginea subvectat corpora cumba,
iam senior, sed cruda deo viridisque senectus."
terribili squalore Charon, cui plurima mento
canities inculta iacet, stant lumina flamma,
sordidus ex umeris nodo dependet amictus.
Ipse ratem conto subigit velisque ministrat
et ferruginea subvectat corpora cumba,
iam senior, sed cruda deo viridisque senectus."
Ecco che Dante segue il suo maestro Virgilio e riprende la figura di Caronte, la barba bianca, gli occhi di fuoco, ma sembra renderlo meno demone e più dannato egli stesso come le anime che traghetta.