List of my Publications

Thursday, 29 December 2011

Papin's engine

PAPIN'S STEAM ENGINE, BY  CHARLES A. JOY.
Scientific American, Volume XXXVI., No. 8, February 24, 1877
http://www.gutenberg.org/files/19406/19406-h/19406-h.htm#art60
It is a matter of history that, as early as 1688, Denis Papin, Professor of Physics and Mathematics at the University of Marburg, proposed to substitute steam for powder in the engine invented by Huyghens, and that in 1695 he published a description of several new inventions, in which steam played an important part. The Elector Carl of Hesse-Cassel, was anxious to be free from the annoyances and impositions practised upon his boatmen by the authorities at Münden, and he proposed to avoid that city by constructing a canal connecting the Weser with the river that flowed through Cassel. Much of the work was accomplished, and the half finished line of the canal can be traced even at the present day. Papin was authorized to build a powerful steam pump by which the supply of water was to be regulated. A working model of this pump was completed; and the Elector was on the point of visiting the laboratory to witness its operation, when a fearful explosion frightened the workmen, and afforded an opportunity for enemies to intrigue for the expulsion of Papin from the country. The model was preserved for a long time in Cassel; but at the time of the French invasion, it disappeared, and no trace of it has since been found. In writing about his inventions, Papin says, in 1695: "It would occupy too much space for me to describe in what manner this principle could be applied to removing water from mines, throwing bombs, sailing against the wind, and for many other similar purposes; everyone according to his wants can imagine the constructions that could be made. I cannot, however, refrain from remarking how much preferable this power would be to oars for those whose business calls them to the sea." And further on he says: "The steam cylinders could be employed for a great variety of purposes." One of the cylinders, which was to form a part of the pump, was cast at the foundry in Cassel, and after various vicissitudes has finally become the property of the Historical Museum in that city, where it will be preserved, with jealous care, from any further injury. During the recent exhibition of philosophical instruments in London, this remnant of Papin's invention played an important part, it having been generously loaned by the authorities for that occasion. After the flight of Papin from Germany, the cylinder was used as a receptacle for iron turnings and borings in the royal works; and after the destruction of those works by fire, it came into the possession of Henschel, the founder of one of the most extensive locomotive works in Germany. This man fully appreciated the value of the historical relic; and when I visited him at the works, twenty-five years ago, he pointed out with pride to me the inscription on its side, "Papin's Cylinder," and said that he intended to have it placed upon a solid pedestal near the gate. His grandson has since presented it to the city, and its preservation from destruction or sale is now secured. A copy of the drawing made by Papin of the pump of which this cylinder was to form a part, and which was published in 1695, has recently appeared in Dingler's Journal, and I send it to you, hoping that you will have it engraved and perpetuated in your valuable paper. It is a peculiar combination of Savery's invention and Papin's piston engine, suggested for another purpose, and is a decided improvement on Huyghens' powder engine.


PAPIN'S STEAM ENGINE.

A is the boiler for the generation of the steam, provided with a safety valve (an invention of Papin). On opening the stopcock, C, the steam passes through B into the cylinder, D, and by its expansion drives the plunger, E, against the water contained in the cylinder, D, which is thus forced into the chamber, F, compressing strongly the air, which in turn expels the water through the pipe, G, to the height desired. K is a funnel for the fresh supply of water, and at I and H are valves opening upwards and downwards. After the condensation of the steam in D, a renewed supply of water, through K, forces the plunger, E, to the top of the cylinder, ready for the next action of steam. The strokes of such a pump could not be frequent, and it would not compare very favorably with the wonderful machinery exhibited in Philadelphia last summer; but it contains the germ of the idea, and is worthy of all honor. Having often seen it stated that Papin had invented a steamboat, I resolved during a recent visit to Germany to investigate the matter, and especially to search for the correspondence between Papin and Leibnitz in the library at Hanover. It will be borne in mind that two hundred years ago, on December 4, 1676, Leibnitz was appointed to take charge of the library in Hanover, and that he remained in this position until his death in 1716. He bequeathed his manuscripts to the library; and as he had the habit of writing upon all manner of loose scraps of paper, it has cost much labor to assort and classify them.

On making my application to the librarian to be permitted to see the correspondence between Papin and Leibnitz, my request was at once granted; and a table having been assigned me, I was able to examine these precious relics at my leisure. I was also shown a copy of an original treatise on the steam engine by Papin, which contained numerous marginal notes by Leibnitz. In one place, Leibnitz criticized Papin's method for condensing steam, and makes a drawing on the margin, showing a piston and valve which he thought would be more practical. It is somewhat remarkable that the Germans have not caused a fac-simile of this little volume to be published. After considerable search, I found a copy of the original letter addressed by Papin to Leibnitz in 1707, asking Leibnitz to assist him in obtaining the consent of the Hanoverian Government to navigate the river Weser with a sidewheel steamboat. The letter was dated July 7, 1707, and contained among other interesting passages the following sentence: "The new invention will enable one or two men to accomplish more effect than several hundred oarsmen." It is evident that Leibnitz was deeply impressed by Papin's letter, and he supported the simple and reasonable request contained in it by the following petition addressed to the Councillors of State. This communication from Leibnitz bears two indorsements, one by the clerk of the council, "pro memoria respectfully, in reference to the passage of a ship from the river Fulda into the Weser;" the other is in the handwriting of Leibnitz: "Papin's sidewheel ship." This last indorsement is of great value, as indicating the fact that Papin proposed to apply side wheels for the propulsion of his new invention. The following is a translation of Leibnitz' letter, the original of which I saw in the library:

"Dionysius Papin, Councillor and Physician to his royal highness the Elector of Cassel, also Professor of Mathematics at Marburg, is about to dispatch a vessel of singular construction down the river Weser to Bremen. As he learns that all ships coming from Cassel, or any point on the Fulda, are not permitted to enter the Weser, but are required to unload at Münden, and as he anticipates some difficulty, although those vessels have a different object, his own not being intended for freight, he begs most humbly that a gracious order be granted that his ship may be allowed to pass unmolested through the electoral domain, which petition I most humbly support.

G.W. Leibnitz.

"Hanover, July 13, 1707."

This letter was returned to Leibnitz with the following indorsement:

"The Electoral Councillors have found serious obstacles in the way of granting the above petition, and, without giving their reasons, have directed me to inform you of their decision, and that in consequence the request is not granted by his Electoral Highness.

H. Reiche.

"Hanover, July 25, 1707."

This failure of Papin's petition was the deathblow to his effort to establish steam navigation. A mob of boatmen, who thought they saw in the embryo ship the ruin of their business, attacked the vessel at night and utterly destroyed it. Papin narrowly escaped with his life, and fled to England, where he endured great hardships and poverty, and all traces of him were soon lost, so that it is uncertain in what country he finally died or where he was buried.

This remarkable man was driven out of France on account of his Protestant faith, and found a refuge in Germany; here he was again persecuted on account of the injury that ignorant and jealous people believed his inventions would inflict upon the industries of the country; and when the climax of steam engines for pumping water and propelling ships was reached, the enlightened government of the period "found serious obstacles" in the way of granting him protection, and, without condescending to state what those "objections" were, secretly instigated the mob to make an end of the trouble. It is another instance, unfortunately too often repeated in history, of the mischief men dressed up in a little brief authority can work upon their generation. If Papin had been permitted to navigate the Weser with his ship, and to carry it to London, as was his intention, it is possible that we should have had steamboats one hundred years earlier than they were given to us by Fulton. The plan proposed by Papin was highly impracticable; but a knowledge of what Savery had done in the way of steam machinery, aided by the shrewd suggestions of Leibnitz, combined with the practical assistance of Englishmen, would, no doubt, have enabled him to improve upon his invention until it had obtained sufficient credit to be secure against the misfortune of being totally forgotten. After the lapse of 100 years from the date of Papin's invention, when the first steamboat was put upon the river Rhine, the vessel was fired into by concealed marksmen on shore, and navigation was more dangerous than it is now on the upper waters of the Missouri in times of Indian hostility. It was only after stationing troops along the banks of the river to protect the boatmen that the government, fortunately more enlightened than in the days of Leibnitz, was able to establish steam navigation on a secure footing.

I have thought it worth while to make this contribution to the history of steam navigation, particularly as I have been able to authenticate a portion of it by reference to original documents.

Columbia College, New York city, January, 1877.

Wednesday, 28 December 2011

The searchlight - 1897

In The Project Gutenberg EBook of The Great Round World and What Is Going On In It, Vol. 1, No. 15, February 18, 1897, by Various, http://www.gutenberg.org/files/15325/15325-h/15325-h.htm
we find the following news

"INVENTION AND DISCOVERY.- 1897
A New York newspaper has been making some experiments in signalling ships at night, which, if as successful as it is claimed to be, will be of the greatest service to sailors for all time to come.
Ships have a regular way of talking to one another, by means of flags arranged in certain ways...
There has been one difficulty with the flag-signals, and that has been that they were useless at night. When it became too dark for the flags to be seen, sailors had no other means of communication.
The New York paper claims to have overcome this difficulty.
In saying that ships have no means of communicating with each other, it must not be forgotten that they can use lights and send certain messages with them. But the flag system enables them to say exactly what they wish to, while through the lights they can only show where they are, and call for help in case of accident.
The invention of the searchlight set men thinking, and at last the idea struck one man that if the searchlight were turned on the flags, it ought to be perfectly possible to see them in the darkest night.
A few nights ago two tugs went down to Sandy Hook to try if the experiment would work. To their great delight they found it did answer perfectly. The tugs were stationed about a mile and a half apart, and could read with ease the messages waved across the water.
More experiments will be made, and if on further trial the method is found to be practical, a great advance will have been made in navigation...
This invention is in the nature of a powerful foghorn. It is, however, made somewhat like a musical instrument, so that different tones can be produced by it; and the idea is to have these tones arranged into a signalling code, after the fashion of the flag-signals, so that a conversation can be kept up in a similar way to that done with flags. G.H.R."


Edison's searchlight cart, from the Smitsonian: http://americanhistory.si.edu/edison/ed_d21.htm

Of course, the use of the Morse Code is better. But we have to wait till the Aldis Lamp.
According to the Oxford Dictionary: Aldis lamp, a handheld lamp for signalling in Morse code. Origin:
First World War: named after Arthur C. W. Aldis (1878–1953), its British inventor
The Aldis Lamp is a signal lamp, a visual signaling device for optical communication (typically using Morse code). Modern signal lamps are a focused lamp which can produce a pulse of light.

Moving sand dunes

In several desert areas, the slow motion of sand dunes can be a challenge for modern human activities and a threat for the survival of ancient places or archaeological sites. However, several methods exist for surveying the dune fields and estimate their migration rate. Among these methods, the use of satellite images, in particular of those freely available on the World Wide Web, is a convenient resource for the planning of future human settlements and activities. More at http://arxiv.org/abs/1112.5572


The barchans move. Note the dunes on the tracks.

Centennial Superconductivity

The Japanese Journal of Applied Physics
Volume 51, Number 1, January 2012
 had published the Special Section: Centennial Anniversary of Superconductivity in commemoration of the 50th anniversary of JJAP and the centennial anniversary of superconductivity.

Special Section —Centennial Anniversary of Superconductivity—
Comprehensive Review
Invited Review Papers
Selected Topics in Applied Physics
Rapid Communications
Regular Papers
Semiconductors, dielectrics, and organic materials
Photonics, quantum electronics, optics, and spectroscopy
Spintronics, superconductivity, and strongly correlated materials
Device physics
Nanoscale science and technology
Crystal growth, surfaces, interfaces, thin films, and bulk materials
Plasmas, applied atomic and molecular physics, and applied nuclear physics
Device processing, fabrication and measurement technologies, and instrumentation
Brief Notes

Tuesday, 13 December 2011

Higgs boson

"On Tuesday, physicists at the Large Hadron Collider near Geneva, Switzerland, said that data from two independent experiments had helped them narrow the range of what the mass of the Higgs boson could be. Higgs bosons—if they exist—are created in the giant atom-smashing machine, where they almost instantly decay into other particles. Discovery is based on observing the particles into which they decay.
One experiment, known as Atlas, suggested that the hypothesized Higgs is most likely to have a tiny mass, in the range of 116 to 130 gigaelectronvolts, or GeV. The other experiment pegged mass at 115 to 127 GeV. The experiments were carried out at the European particle physics laboratory CERN near Geneva."
http://online.wsj.com/article/SB10001424052970203430404577096330121408786.html
Wall Street Journal

Thursday, 8 December 2011

Acoustic freezer

Thermoacoustic engines (sometimes called "TA engines") are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices. These two types of thermoacoustics devices can again be divided into two thermodynamic classes, a prime mover (or simply heat engine), and a heat pump. The prime mover creates work using heat, whereas a heat pump creates or moves heat using work. Compared to vapor refrigerators, thermoacoustic refrigerators have no ozone-depleting or toxic coolant and few or no moving parts therefore require no dynamic sealing or lubrication.
More http://en.wikipedia.org/wiki/Thermoacoustic_heat_engine

Wednesday, 23 November 2011

A young Leonardo


A young Leonardo da Vinci - A superposition of images.
See how I processed them at
http://arxiv.org/abs/1111.4654
and also
http://www.technologyreview.com/blog/arxiv/27361/

Friday, 18 November 2011

Turning darkness into light

"Quantum mechanics tells us that the vacuum is not empty but is filled with virtual particles that pop into and out of existence. Normally these particles are hidden from our view, but now a team of physicists has used the electrical equivalent of an ultrafast mirror to convert virtual photons into real electromagnetic radiation. Known as the dynamical Casimir effect, it was first predicted more than 40 years ago. The static Casimir effect ... 1948, involves two perfectly reflecting parallel mirrors that, when placed in a vacuum, will be attracted to one another. This attractive force is caused by the radiation pressure exerted by virtual photons outside the mirrors and the fact that this pressure exceeds the pressure between the mirrors because of the limited number of modes of electromagnetic vibration that are permitted within this gap. In other words, the force results from a mismatch of electromagnetic modes in space. The dynamical effect was proposed by Gerald Moore in 1970 and is caused by a mismatch of modes in time. The phase of an electromagnetic wave goes to zero at the surface of a mirror, if that mirror is a perfect electrical conductor. When the mirror is moved slowly through a vacuum, this zero point can move with the mirror. However, if the mirror is moved at a significant fraction of the speed of light, then the electromagnetic field does not have time to adjust but instead becomes excited and as a result generates real photons. Put another way, the mirror prises virtual photons (always produced in pairs) apart so that instead of rapidly annihilating, the particles are free to remain as real photons."

How to turn darkness into light - physicsworld.com

Thursday, 17 November 2011

Earth's close encounter of asteroids

"After yet another narrow encounter with an asteroid the size of an airship earlier this week, do we need to pay more attention to technology that could protect our planet and its inhabitants from these turbo-charged cosmic fireworks?"
Should Earth's close encounter trigger asteroid avoidance research? | Opinion | The Engineer

Tuesday, 15 November 2011

Leonardo, Genio e Mito

Alla Venaria Reale (Torino) si apre la mostra su Leonardo da Vinci. Il titolo è "Leonardo, il Genio, il Mito".
In esposizione vi è l'autoritratto della Biblioteca Reale e il Codice del Volo.
In una pagina del codice, sotto la scrittura di Leonardo, vi è un ritratto, forse un suo autoritratto da giovane.



Image processing della pagina del codice, A.C. Sparavigna

Monday, 14 November 2011

Dimensions and Dimensional Equations

A discussion on dimensions and their equations. After the theory, several problems are composing the relevant practice. The text is based on the book by Halliday, Resnick, Walker, Fundamentals of Physics, some items from Wikipedia and WolframMathWorld, and problems adapted and translated from a book of mine in Italian.http://www.scribd.com/doc/67888616/Dimensions-and-Dimensional-Equations-Theory-and-Practice

Monday, 31 October 2011

A wave power machine

http://en.wikipedia.org/wiki/Wave_power#Wave_energy_and_wave_energy_flux

"The Pelamis machine consists of a series of semi-submerged cylindrical sections linked by hinged joints. As waves pass along the length of the machine, the sections move relative to one another. The wave-induced motion of the sections is resisted by hydraulic cylinderswhich pump high pressure oil through hydraulic motors via smoothinghydraulic accumulators. The hydraulic motors drive electrical generators to produce electricity.[24] Pelamis Wave Power first tested and grid connected a Pelamis machine in 2004 at the European Marine Energy Center.[25] The first of a second generation of machines, the P2 started grid connected tests off Orkney in 2010, the machine is owned by E.ON.[26]."


Pelamis Wave Energy Converter on site at the European Marine Energy Test Centre (EMEC).
Author P123
Permission (Reusing this file)

Wave energy

"Wave energy is produced when electricity generators are placed on the surface of the ocean. The energy provided is most often used in desalination plants, power plants and water pumps. Energy output is determined by wave height, wave speed, wavelength, and water density. To date there are only a handful of experimental wave generator plants in operation around the world. The articles on this page explore the world of wave energy and its possible applications."
More http://www.alternative-energy-news.info/technology/hydro/wave-power/

Impact of wave energy conversion on marine environment

‘Underwater noise is a global environmental issue that has to be addressed if we are to take advantage of the huge potential of ocean energy,’ said EU commissioner for research, innovation and science Máire Geoghegan-Quinn.
Ireland has one of highest concentrations of wave energy in the world, presenting a significant opportunity to expand its renewable energy portfolio and develop new industry capabilities,’ said Prof Owen Lewis, chief executive officer of SEAI.

Read more:Project assesses impact of wave energy conversion noise | News | The Engineer

Thursday, 27 October 2011

Giant Waterworld Around Naked Eye Star 

Giant Waterworld Confirmed Around Naked Eye Star - Technology Review

"55 Cancri A is a Sun-like star some 40 light years away. It has an apparent magnitude of about 6 and so is visible to the naked eye in the constellation of Cancer.

This star is unusual in that it is just one of a handful that are known to have at least 5 planets. The innermost of these planets--55 Cancri e--was discovered in 2004 and has since had plenty of attention from astronomers. Various groups have observed the the changes in radial velocity that it causes its parent star. This tells them about that it orbits its star every 18 hours and that its mass is about 8 times Earth's or about half Neptune's."

"The innermost planet around 55 Cancri A is almost certainly an exotic waterworld with a radius about twice Earth's, say astronomers"

Tuesday, 18 October 2011

La transizione da liquido isotropo a smettico

La transizione da liquido isotropo a smettico

Amelia Carolina Sparavigna
Dipartimento di Fisica
Politecnico di Torino

Breve discussione della transizione di fase diretta dal liquido isotropo alla mesofase smettica, con osservazioni al microscopio polarizzatore.

I cristalli liquidi sono materiali composti di molecole di forma allungata, come bastoncini, oppure discoidale. Essi sono caratterizzati dalla presenza di mesofasi tra la fase liquida isotropa e quella cristallina. Tipiche mesofasi sono la fase nematica e quella smettica. La fase nematica ha i centri delle molecole che assumono posizioni arbitrarie, mentre gli assi delle molecole tendono a orientarsi nella stessa direzione. Nello smettico, le molecole si dispongono con i loro centri su piani definiti. Gli assi delle molecole hanno una direzione specifica rispetto al piano. Se la direzione è perpendicolare al piano, si dice che la fase è smettica A, se invece l’asse è inclinato, la fase è smettica B. La fase smettica è quindi più ordinata della nematica, ma più disordinata di un cristallo. Vi sono alcuni materiali termotropici in cui la fase nematica non c'è, ma si ha solo una fase smettica. Riscaldando o raffreddando il campione, si passa dalla fase smettica a quella liquido o viceversa, saltando la fase nematica.
Vediamo che cosa si può osservare col microscopo polarizzatore, quando si passa della fase liquida ordinaria, dove le molecole sono disordinate sia in posizione sia in orientamento, nella fase liquido-cristallina. La fase liquida ordinaria è detta “liquido isotropo”. Il cristallo liquido è preparato tra due vetrini e posto, all’interno di un termostato, sotto il microscopio, tra i due filtri polarizzatori. Lo spessore del materiale è di pochi micron. Il campione è riscaldato fino a raggiungere la fase liquida ordinaria. Questa fase, se vista al microscopio con i filtri polarizzatori incrociati, appare come un nero uniforme. L’isotropia ottica del materiale permette l’estinzione completa della luce. Se si raffredda il liquido ed esso passa nella fase nematica, si vedono comparire delle bolle colorate. Dove ci sono le bolle, il materiale è già nematico. Le bolle crescono fino a che tutto il materiale è nematico.

  
Transizione da liquido isotropo, che appare nero nella foto, a nematico, che è colorato. Il cristallo liquido è il 12OBAC (alkyloxybenzoic acid).

Il nematico è otticamente anisotropo. Il materiale modifica la luce che polarizzata dal primo filtro del microscopio. Il secondo non riesce più a estinguere tutta la luce. Il materiale appare colorato per via di fenomeni d’interferenza. Cosa si vede quando si passa del liquido isotropo allo smettico? Dato che ci sono diverse fasi smettiche, quello che si vede dipende dalla fase.

Smettico A
Utilizziamo un oxadiazolo, che ha la transizione diretta dalla fase isotropa a quella smettica. Il materiale ha una fase smettica di tipo A. Al microscopio polarizzatore, questo materiale mostra una  fase caratterizzata da domini a ventaglio (in letteratura si trovano definiti come “fan” oppure  “focal-conic”).


Domini “focal-conic” nella fase smettica.

Aumentando la temperatura, portiamo il campione nella fase liquida isotropa. Il campione diventa nero. Cominciamo a raffreddare lentamente il campione per portarlo nella fase smettica. Nel campo visivo del microscopio appaiono i “batonnets”, che cominciamo a crescere nella fase isotropa.


Batonnets della fase smettica che crescono nella fase isotropa (a sinistra). I domini crescono e si uniscono a formare la tessitura focal-conic.

Questi domini crescono e si uniscono insieme fino a formare la tessitura, ossia l’insieme dei domini osservati al microscopio polarizzatore, della fase smettica. I domini sono in questo caso focal-conic.  

Smettico C
La tessitura vista sopra non è l’unica mostrata dalla fase smettica. Prendiamo un altro materiale, anche lui avente la transizione diretta liquido isotropo - smettico.  Il materiale utilizzato è il 16OBAC della famiglia degli acidi ossibenzoici alchilici (alkyloxybenzoic). Il materiale è cristallino fino a 90 °C e poi passa nella fase smettica C.


A sinistra la fase cristallina del  16OBAC; a destra la fase smettica  osservata in riscaldamento dalla fase cristallina.

Alla temperatura di 131 °C diventa un liquido isotropo, non ha quindi fase nematica. Questo è dovuto al fatto che le molecole sono così lunghe da mantenere l'ordine smettico fino ad alta temperatura, vincendo la tendenza al disordine dovuta all'agitazione termica. In raffreddamento, la fase smettica compare dalla fase isotropa: si osservano delle strutture ramificate che compaiono nel campo nero della cella vista tra polarizzatori incrociati.


Ecco come cresca la fase smettica nella fase isotropa.


La crescita della fase smettica  dalla fase isotopa vista ad un ingrandimento maggiore.


La sequenza mostra l'evoluzione della struttura ramificata, quando si abbassa la temperatura (0.5 gradi al minuto).


E’ interessante notare che la fase smettica che si forma in raffreddamento ha una tessitura differente da quella che si osserva in riscaldamento. La tessitura è di tipo schlieren: poiché la fase è smettica, ci sono solo difetti con carica 1. Possiamo quindi distinguerla dalla fase nematica, che è simile, perché questa ha anche i difetti 1/2.


Fase smettica del 16OBAC che si forma in raffreddamento. La tessitura è di tipo schiere, con i soli difetti con carica 1.


Discussione
Il processo di crescita delle mesofasi dalla fase isotropa è un problema interessante e forse poco studiato ancora [1]. Questo processo ha due fasi, quella di nucleazione e quella di accrescimento. Esse sono state ben studiate per i processi di cristallizzazione dal liquido isotropo. Nella fase di nucleazione succede che, all'interno del liquido si creano dei punti in cui la concentrazione locale è maggiore. Questi punti sono chiamati cluster. Crescendo, si creano dei nuclei che rispecchiano fedelmente l'ordine del cristallo. Sono piccoli cristallini di dimensioni microscopiche.
Anche le mesofasi hanno i loro nuclei. Per quanto riguarda i nematici, di solito si osservano delle piccolissime gocce circolari, che si formano nel liquido isotropo e che poi si uniscono a formare la fase nematica. Anche se il nematico è anisotropo come orientazione, è disordinato come posizione. Immaginiamo le molecole del nematico come dei bastoncini. Quando esse sono nella fase liquida isotropa, i loro centri sono disordinati, come anche le loro direzioni. Al decrescere della temperatura, quando il materiale arriva alla transizione di fase, le molecole possono girare i loro assi lunghi senza doversi spostare. Questo può avvenire nello stesso modo in tutte le direzioni dello spazio. Il nucleo di nematico cresce nel liquido isotropo con una simmetria sferica.
Nello smettico invece, l’ordine locale è molto diverso. Ci sono dei piani microscopici, su cui si devono sistemare i centri delle molecole. Le molecole devono orientarsi ma anche spostare i loro centri per formare i piani. I clusters iniziali possiedono quindi una direzione privilegiata, quella perpendicolare ai piano dello smettico. Ecco quindi che possono comparire i nuclei come batonnets.
E’ molto interessante la crescita dello smettico C, che appare come una struttura ramificata. Sicuramente sono necessari ulteriori studi per determinare meglio le caratteristiche dei nuclei.

Riferimenti

[1] I DierkingC Russell, Universal scaling laws for the anisotropic growth of SmA liquid crystal bâtonnets, Physica B: Condensed Matter, Volume 325, January 2003, Pages 281-286.

Friday, 14 October 2011

Mesophases transitions


An interesting transition is the texture transition inside the nematic phase. We observe in some liquid crystalline compounds a transition from a low-temperature nematic texture which looks like a texture of a smectic phase to a high temperature nematic Schlieren texture. Compounds that have the texture transition are the alkyloxybenzoic acids. Here, you can see a movie of the texture transtion inside the nematic phase of 6OBAC. The sample is heated from the crystal phase. We can see the smectic pahse and then the two following nematic subphases. Click on the image to see the movie.


More details  in my papers:
Texture transitions in binary mixtures of 6OBAC
with compounds of its homologous series
A. Sparavigna;  A. Mello; B. Montrucchio 

Phase Transitions: A Multinational Journal, 1029-0338
Volume 80, Issue 3, 2007, Pages 191 – 201
Abstract 
Texture transitions in the liquid crystalline 
alkyloxybenzoic acid 6OBAC
A. Sparavigna;  A. Mello; B. Montrucchio 
Phase Transitions: A Multinational Journal, 1029-0338
Volume 79Issue 4, 2006, Pages 293 – 303
Abstract 

A new image processing method for enhancing
the detection sensitivity of smooth transitions in liquid crystals

Liquid Crystals, 1366-5855, Volume 24Issue 6, 2001, Pages 841 – 852
Abstract 

novel order transition inside the nematic phase of 
trans -4-hexylcyclohexane-1-carboxylic acid discovered by image processing
Liquid Crystals, 1366-5855, Volume 25Issue 5, 2001, Pages 613 – 620
Abstract 


In the following, three movies show a transition on cooling from the nematic to the smectic phase of an oxadiazole compound. We see a transition from the nemtic to a smectic phase with toric domains.
Clink on images to launch the movies.

  

For more detailsthese are my articles:

Growth of toric domains in mesophases of oxadiazoles
A. Sparavigna;  A. Mello; B. Montrucchio 
Phase Transitions: A Multinational Journal
1029-0338, Volume 81Issue 5, 2008, Pages 471 – 477
Abstract 

Fan-shaped, toric and spherulitic textures of mesomorphic oxadiazoles
A. Sparavigna;  A. Mello; B. Montrucchio 
Phase Transitions: A Multinational Journal
1029-0338, Volume 80Issue 9, 2007, Pages 987 – 998
Abstract 


Amelia Carolina Sparavigna

Saturday, 8 October 2011

Of the Education of an Engineer

"Architecture is a science arising out of many other sciences, and adorned with much and varied learning; by the help of which a judgment is formed of those works which are the result of other arts. Practice and theory  are its parents. Practice is the frequent and continued contemplation of the mode of executing any given work, or of the mere operation of the hands, for the conversion of the material in the best and readiest way. Theory is the result of that reasoning which demonstrates and explains that the material wrought has been so converted as to answer the end proposed. Wherefore the mere practical architect is not able to assign sufficient reasons for the forms he adopts ; and the theoretic architect also fails, grasping the shadow instead of the substance. He who is theoretic as well as practical, is therefore doubly armed; able not only to prove the propriety of his design, but equally so to carry it into execution.
In architecture, as in other arts, two considerations must  be constantly kept in view; namely, the intention, and the matter used to express that intention: but the intention is founded on a conviction that the matter wrought will fully suit the purpose; he, therefore, who is not familiar with both branches of the art, has no pretension to the title of architect. An architect should be ingenious, and apt in the acquisition of knowledge. Deficient in either of these qualities, he cannot be a perfect master.
He should be a good writer, a skillful draftsman, versed in geometry and optics, expert at figures, acquainted with history, informed on the principles of natural and moral philosophy, somewhat of a musician, not ignorant of the sciences both of law and physics, nor of the motions, laws, and relations to each other, of the heavenly bodies. By means of the first named acquirement, he is to commit to writing his observations and experience, in order to assist his memory. Drawing is employed in representing the forms of his designs. Geometry affords much aid to the architect: to it he owes the use of the right line and circle, the level and the square; whereby his delineations of buildings on plane surfaces are greatly facilitated. The science of optics enables him to introduce with judgment the requisite quantity of light, according to the aspect. Arithmetic estimates the cost, and aids in the measurement of the works; this, assisted by the laws of geometry, determines those abstruse questions, wherein the different proportions of some parts to others are involved. Unless acquainted with history, he will be unable to account for the use of many ornaments which he may have occasion to introduce. ...
Many other matters of history have a connexion with architecture, and prove the necessity of its professors being well versed in it. Moral philosophy will teach the architect  to be above meanness in his dealings, and to avoid arrogance: it will make him just, compliant and faithful to his employer ; and what is of the highest importance, it will prevent avarice gaining an ascendancy over him: for he should not be occupied with the thoughts of filling his coffers, nor with the desire of grasping every thing in the shape of gain, but, by the gravity of his manners, and a good character, should be careful to preserve his dignity. In these respects we see the importance of moral philosophy; for such are her precepts. That branch of philosophy which the Greeks call phusiologia, or the doctrine of physics, is necessary to him in the solution of various problems; as for instance, in the conduct of water, whose natural force, in its meandering and expansion over flat countries, is often such as to require restraints, which none know how to apply, but those who are acquainted with the laws of nature: nor, indeed, unless grounded in the first principles of physics, can he study with profit the works of Ctesibius, Archimedes, and many other authors who have written on the subject.
Music assists him in the use of harmonic and mathematical proportion. It is, moreover, absolutely necessary in adjusting the force of the balistae, catapultae, and scorpions...
Astronomy instructs him in the points of the heavens, the laws of the celestial bodies, the equinoxes, solstices, and courses of the stars; all of which should be well understood, in the construction and proportions of clocks. Since, therefore, this art is founded upon and adorned with so many different sciences, I am of opinion that those who have not, from their early youth, gradually climbed up to the summit, cannot, without presumption, call themselves masters of it. Perhaps, to the uninformed, it may appear unaccountable that a man should be able to retain in his memory such a variety of learning ; but the close alliance with each other, of the different branches of science, will explain the difficulty. For as a body is composed of various concordant members, so does the whole circle of learning consist in one harmonious system. Wherefore those, who from an early age are initiated in the different branches of learning, have a facility in acquiring some knowledge of all, from their common connexion with each other...
For in such a variety of matters, it cannot be supposed that the same person can arrive at excellence in each, since to be aware of their several niceties and  bearings, cannot fall within his power. We see how few of those who profess a particular art arrive at perfection in it, so as to distinguish themselves: hence, if but few of those practising an individual art, obtain lasting fame, how should the architect, who is required to have a knowledge of so many, be deficient in none of them, and even excel those who have professed any one
exclusively. ...
I beseech you, O Caesar, and those who read this my work, to pardon and overlook grammatical errors; for I write neither as an accomplished philosopher, an eloquent rhetorician, nor an expert grammarian, but as an architect: in respect, however, of my art and its principles, I will lay down rules which may serve as an authority to those who build, as well as to those who are already somewhat acquainted with the science."

From "The Architecture", by Marcus Vitruvius Pollio

Friday, 7 October 2011

Solid angle

A Lecture on Solid Angle, by Ben Kravitz
http://www.stanford.edu/~bkravitz/research/solidangle.pdf
"In order to talk about solid angles, we fi rst need to talk about projections. There are lots of diff erent kinds of projections, some of which you already know. We should begin with a very simple defi nition of what a projection is, and then we'll get more complex as we go along. A projection is the transformation of points and lines in one plane onto another plane by connecting corresponding points on the two planes with parallel lines".

Wednesday, 5 October 2011

Theory and practice

From the post
Teaching: Theory or practice? by Marcus Wilson Aug 07

"What’s clear is that many teachers take the view that theory is the opposite of practice. Since, in teaching, it is clearly the practice that matters (since it’s what the students experience) this leads to the conclusion that theory is irrelevant and there is no benefit in engaging with it. ... The fallacy is the implicit assumption that theory and practice are unconnected. (I mean, you don’t have experimental physicists and theoretical physicists working in complete isolation from each other, so why expect that with teaching?) What you believe about student learning will influence the way you teach, whether you formally acknowledge it or not. That’s become clear for me as I think about my teaching practice. I have my own ‘beliefs’, or my own models, call them ‘theories’, of how students learn, and these influence how I teach."

Read the post at
http://sciblogs.co.nz/physics-stop/2011/08/07/teaching-theory-or-practice/

Friday, 30 September 2011

Speed of neutrino and cosmic consequences

Let me report a part of the discussion on the speed of neutrinos by Wikipedia
"In September 2011 the OPERA collaboration released calculations showing velocities of 17-GeV and 28-GeV neutrinos exceeding the speed of light in their experiments. The authors write, "Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly." This result had not been detected by previous experiments, and lies in contrast to several others. For instance, photons and neutrinos from SN 1987A were observed to have an agreement in transit time to about 1 part in 450 million, with even this difference being accounted for by light being impeded by the material of the star early in its journey. The OPERA results, in contrast, suggested that neutrinos were traveling faster than light by a factor of 1 in 40,000, i.e. that neutrino speed is 1.0000248(28) c. Had neutrinos from SN 1987A (a supernova, approximately 168,000 light-years from Earth, http://en.wikipedia.org/wiki/SN_1987A) traveled faster than light by this factor, they would have arrived at Earth several years before the photons; this was not observed to be the case. However, neutrinos from the supernova had orders of magnitude less energy than the neutrinos observed in the OPERA experiment, as the authors point out."

Friday, 23 September 2011

Neutrino: fast and furious

Here the news of the day! Neutrinos are faster than light!
http://www.guardian.co.uk/science/2011/sep/23/faster-light-neutrinos
"Scientists at the Opera (Oscillation Project with Emulsion-tRacking Apparatus) experiment in Gran Sasso, Italy, found that beams of neutrinos sent to its detectors from Cern, 730km away in Geneva, arrived earlier than they should have."

Thursday, 22 September 2011

Coherers as “energy catalyzers”

Coherers as “energy catalyzers”
Amelia Carolina Sparavigna
Dipartimento di Fisica,
Politecnico di Torino, Torino, Italy

Abstract: A device defined as an “energy catalyzer”, able to give thermal energy at the expense of electric energy, has aroused a great popular interest. In fact, the confidence on this device does not allow its discussion. Some known features are intriguing, which can therefore become the starting point for a discussion on old coherers and the Branly effect. We could define the coherers as a sort of “energy catalyzers”.

------------

On Wednesday September 21, 2011, from the news of RAI, the Italian broadcaster, I learned that a new device for energy production was on the way for industrial developments. I had not immediately realized the features of this device, but I memorized the fact that it was based on water, nickel powders and current, that I saw sparkling in the video clip.  After searching on the Web, I found that the announced device was the energy catalyzer, E-Cat, under patent request by its inventor, Andrea Rossi. The development of prototypes was due to the work of Rossi and Sergio Focardi, University of Bologna. It seems that they have announced a device able of producing more than 10 kilowatts of heat power, while only consuming a fraction of that. "On January 14, 2011, they gave the Worlds' first public demonstration of a nickel-hydrogen fusion reactor capable of producing a few kilowatts of thermal energy. At its peak, it is capable of generating 15,000 watts with just 400 watts input required. In a following test the same output was achieved but with only 80 watts of continual input" [1]. The item is also reporting that the inventor prefers to invoke a catalyzer process, not to a cold fusion. There are so many Web pages on the E-Cat, that it is impossible to list them, but an exhaustive one is the corresponding Wikipedia item [2]. It is there that we can find the reference to the patent [3], which is about a "method and apparatus for carrying out a highly efficient exothermal reaction between nickel atoms and hydrogen atoms, in a tube, preferably, though not exclusively made of a metal, filled by a nickel powder and heated to a high temperature preferably, though not necessarily, from 150 to 5000°C, by injecting hydrogen into said metal tube said nickel powder being pressurized, preferably, though not necessarily, to a pressure from 2 to 20 bars ".

The confidence on this device does not allow its discussion. And in fact, the aim of my paper is not a discussion on E-Cat, but on what the poor information on it suggested me. Some features of the device attracted my interest: they are the metal powders, the high temperatures and the sparks of electricity. In fact I read recently about all these things together in a old book published in 1904, entitled Elements of Physics, by Fernando Sanford,  professor at the Stanford University, one of the members of the group of scientists who came there to create the  pioneer faculty in 1891. In [4], I discussed the experiments of Sanford on the electric photography and the fact that, several years after in 1939, the fringes around the electrically photographed objects had been rediscovered by Semyon Kirlian. Of course the book written by Sanford is quite old, but, in my opinion, it has to be appreciated due to the fact that it is based on the description of experiments. The book is then quite interesting from the point of view of experimental physics and for its history. A chapter is devoted to electric radiation and electric waves. Let us remember that Fernando Sanford was talking of experiments, which, at his times were revolutionizing physics and technology. Reading the book we learn that a new device was used in laboratories, the Coherer (see Fig.1).  Let me report the Laboratory Exercise 119 of the book.

"Take a glass tube of about a centimeter bore and six or eight centimeters long, fit the ends with corks through which copper wires can be passed, and fill the tube between the corks with brass or iron filings. Thrust copper wires through the corks and into the iron filings until their ends are one or two centimeters apart. Connect these wires in circuit with one or more voltaic cells and a tolerably sensitive galvanometer. The resistance of the filings to the passage of a current should be so great that the galvanometer is slightly, if at all, deflected. Bring an electric machine near, and pass sparks from one discharging knob into one of the wires which enter the tube. The resistance should fall so that the galvanometer is deflected through nearly 90°.  This instrument is called a Coherer. The passage of the electric discharge into the small metallic particles in the tube apparently causes them to cling together so that they make better electric contact than before.  After your coherer has become sensitive enough to allow the passage of a suitable current, increase its resistance again by tapping gently on the glass and causing the particles to separate. Then move the electric machine to a distance of a few feet from the coherer and turn the handle and cause sparks to pass between the discharging knobs of the machine. If your coherer has been properly adjusted, the galvanometer will be deflected again, showing that the resistance of the coherer has been again diminished. By a little care in the adjustment, and by using a sensitive galvanometer, the coherer will respond to a spark at a distance of several yards. ... The Coherer described above is similar to the receiver used in "wireless telegraphy." The Coherer is connected between a battery and a telegraph sounder, and is attached to a long wire or other conductor suspended at some height. A similar conductor is suspended at the sending station, and is connected with the spark gap of the electric machine or induction coil. The oscillations in the receiving conductor are accordingly partly due to resonance, and they are sufficient to lower the resistance of the coherer so that a signal can be made through it. An automatic tapper jars the particles apart, so that the signal is momentary unless the instrument is sensitized by another spark. "


Fig.1. The Coherer in the book written by F. Sanford.

The device described by Sanford is a radio signal detector used in the receivers of wireless telegraphy at the beginning of the twentieth century. The coherer was invented, around 1890, by Édouard Branly [5]. As Sanford is telling, it consisted of a tube or capsule containing two electrodes spaced a small distance apart, with metal filings between them. It works because of the "Branly effect". To have this effect, it is necessary a thin resistive layer between the grains, to have an initial high resistance. The effect is not observed with noble metal grains, cleaned from any surface contaminant [6]. Therefore, the coherer works because the metal particles cling together, that is, cohere after being subjected to the radio frequency electricity. This provokes a reduction in the coherer's electrical resistance, which is persistent after the radio signal. To receive another signal, the device needs a de-coherer mechanism, able to tap the coherer, mechanically disturbing the particles and resetting them to the high resistance state. As Wikipedia [5] is telling "Coherence of particles by radio waves is an obscure phenomenon that is not well understood even today", but several recent experiments with metal particles seem to confirm that particles cohere by a micro-weld phenomenon, caused by radio frequency electricity fluxing across the small contact area between particles. This phenomenon is probably involving a tunnelling of charge carriers across an imperfect junction between conductors, as deeply discussed in Ref.6. In fact, in this reference the author is proposing to relate the Branly effect to the induced tunnelling effect first described by François Bardou and Dominique Boosé, asserting then that the effect is mainly governed by an electrical tunnel effect [7].

In the work published in 2001 [7], Bardou and Boosé theoretically proposed that the tunnelling probability of a particle through a potential barrier could be enhanced by striking the particle when the centroid of its wave packet is reflecting on the barrier. This is applied to Branly effect as discussed in [6] in the following way. “In a granular metallic medium microscopic grains are electrically isolated one from the other by a metal oxide nanometric layer ... When a voltage is applied to the medium, electrons are accelerated and they do reflect on the potential barriers. At the time of the reflection, these electrons can be kicked forward or backward by the short electromagnetic pulses present in the external electromagnetic field. … The enhanced transmission induced by the momentum transfer produces an increased electrical current, that for some events become large enough to permit a local heating in the metal grains thanks to the Joule effect. Eventually a welding of the grains can occur and when a percolation path has formed the electrical resistance of the medium drops down going from an exponential dependence on the applied voltage to a linear one”. Reference 6 is also reporting that Auerbach demonstrated in 1898 that a coherer could be made conducting by an acoustic excitation in the audible range of the spectrum. According to [6], this means that acoustical waves, by giving vibrations to tunnel barriers between the metallic grains, could be responsible of an induced tunnelling.

Let us also consider the recent experiments with particle coherers by Falcon et al. [8]. They reported on observations of the electrical transport within a chain of metallic beads, which were slightly oxidised.  As the applied current is increased, a transition from an insulating to a conductive state is observed. The authors are proposing that the transition comes from an electro-thermal coupling, at the micro-contacts between each bead. Due to these contacts, the current flows through them, generating a high local heating. This heating increases the local contact areas, enhancing the conduction.  This current-induced temperature rise, up to 1050°C, results in the micro-soldering of the contact points, even for low voltages.

If we define an “energy catalyzer” as a device able to produce change in, or transform energy, the coherer acts in such a manner, where the catalyst is an electromagnetic pulse. Let us hope that as soon as possible, an open report on E-Cat is published, in order to understand the role of hydrogen in it.  In this device, is any tunnelling present? Is it there a tunnelling able to give a fusion of nickel and hydrogen to have copper in a proton capture as told in [9]? Is there any kicking mechanism? What we find in [9] is that the paper is just reporting the results “obtained with a process and apparatus not described here (in [9]) in detail and protected by patent in 90 countries, consisting of a system whose heat output is up to hundred times the electric energy input. As a consequence, the principle of the conservation of energy ensures that processes involving other energy forms are occurring in our apparatus”. And in the conservation of energy we trust.

 References
1. http://peswiki.com/index.php/Directory:Andrea_A._Rossi_Cold_Fusion_Generator
2. http://en.wikipedia.org/wiki/Energy_Catalyzer
3. http://www.wipo.int/pctdb/en/wo.jsp?IA=IT2008000532&DISPLAY=DESC
4. A.C. Sparavigna, Fernando Sanford and the "Kirlian effect", arXiv:1105.1266v1 [physics.pop-ph], http://arxiv.org/ftp/arxiv/papers/1105/1105.1266.pdf
5. http://en.wikipedia.org/wiki/Coherer
6. C. Hirlimann, Understanding the Branly effect, arXiv:cond-mat/0703495v1 [cond-mat.mtrl-sci], http://arxiv.org/ftp/cond-mat/papers/0703/0703495.pdf
7. D. Boosé and F. Bardou, A quantum evaporation effect, Europhys. Lett., 53, 1-7 (2001).
8.  E. Falcon, B. Castaing, and M. Creyssels,  Nonlinear electrical conductivity in a 1D granular medium, The European Physical Journal B, 38,  475-483 (2004)
9. S. Focardi and A. Rossi, A new energy source from nuclear fusion, http://www.lenr-canr.org/acrobat/FocardiSanewenergy.pdf