Diffusion is the net movement of molecules or atoms from a region of high concentration (or high chemical potential) to a region of low concentration (or low chemical potential). This is also referred to as the movement of a substance down a concentration gradient. A gradient is the change in the value of a quantity (e.g., concentration, pressure, temperature) with the change in another variable (usually distance). For example, a change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, and a change in temperature over a distance is a called a temperature gradient.
The word diffusion is derived from the Latin word, "diffundere", which means "to spread out" (if a substance is “spreading out”, it is moving from an area of high concentration to an area of low concentration). A distinguishing feature of diffusion is that it results in mixing or mass transport, without requiring bulk motion (bulk flow). Thus, diffusion should not be confused with convection, or advection, which are other transport phenomena that utilize bulk motion to move particles from one place to another.
Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration. Once the concentrations are equal the molecules continue to move, but since there is no concentration gradient the process of molecular diffusion has ceased and is instead governed by the process of self-diffusion, originating from the random motion of the molecules. The result of diffusion is a gradual mixing of material such that the distribution of molecules is uniform. Since the molecules are still in motion, but an equilibrium has been established, the end result of molecular diffusion is called a "dynamic equilibrium". In a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing.
In historical linguistics, lexical diffusion is both a phenomenon and a theory. The phenomenon is that by which a phoneme is modified in a subset of the lexicon, and spreads gradually to other lexical items. For example, in English, /uː/ has changed to /ʊ/ in good and hood but not in food; some dialects have it in hoof and/or roof but others do not; in flood and blood it happened early enough that the words were affected by the change of /ʊ/ to /ʌ/, which is now no longer productive.
The related theory, proposed by William Wang in 1969, is that all sound changes originate in a single word or a small group of words and then spread to other words with a similar phonological make-up, but may not spread to all words in which they potentially could apply. The theory of lexical diffusion stands in contrast to the Neogrammarian hypothesis that a given sound change applies simultaneously to all words in which its context is found.
Mainstream historical linguists reject Wang's hypothesis, continuing to adhere to Neogrammarian exceptionlessness. For example, Pulleyblank regards the theoretical formulation of lexical diffusion as presented by Hsieh in Wang 1977 as “so manifestly at odds with any realistic picture of how dialects are inter-related and how innovations spread spatially through a language as to make them totally untenable” (1982: 408).
Against may refer to:
Against is the seventh studio album by the Brazilian metal band Sepultura, released in 1998 through Roadrunner Records. It is the band's first release with new frontman Derrick Green, who replaced group founder Max Cavalera in 1997.
The album shows strong elements of world music. It also uses elements of several other genres including hardcore punk, crossover thrash, groove metal, death metal, experimental metal, alternative metal and nu metal.
Like Roots that preceded it, the album has a variety of guest musicians and incorporates tribal influences – Japanese percussion elements are added with the assistance of Japanese taiko group Kodo.
The songs "Against", "Choke" and "Tribus" were released as singles, with a music video accompanying "Choke". The video featured footage from the Barulho Contra Fome (Noise Against Hunger) concert that was the first gig of the Against tour. This performance included guest appearances from the Xavantes tribe, who had featured on Roots (as documented in the "Choke" video) as well as Mike Patton, Jason Newsted, Carlinhos Brown, original Sepultura guitarist Jairo Guedz and Coffin Joe (whose "blessing" of the band performed during this concert turned up as a B-side entitled "Prenúncio" on the Tribus EP).
Against (styled as AgainST) is a Crossover thrash band formed in 2006 by singer-songwriter Dan Clements, original Suicidal Tendencies members Grant Estes, Louiche Mayorga and Amery Smith and former No Mercy vocalist Kevin Guercio.
In 2006 Louiche Mayorga started a compilation album project with another bands from Venice, California. Just a few days later he met by chance with Grant Estes and Amery Smith, he told them about the project and they instantaneously accepted to join it. Mayorga recorded some tapes and sent them to Dan Clements (Excel founding member and frontman) who called him that same night to form new band together. With the line-up complete, the band was called Against. In May 2006 they made two shows at "The Good Hurt Club" in Venice, both concerts were benefits to help launch the compilation album Welcome 2 Venice (disc which continues the previous compilation released in 1985 with songs by their original bands). At the time of going to the studio Mayorga recruited Kevin Guercio (original No Mercy singer) as a second vocalist for the group. They recorded two tracks for Welcome 2 Venice: "Camarillo" (with Clements) and "Roll the Dice" (with Guercio). The entire recording, release and distribution was conducted by Louiche Mayorga's independent label "Built On An Ounce". After the release of the album there were rumors about a possible Excel reunion, however Clements said he had no intentions of reforming the band and did not want anyone to take Against as a return of the group.
Here we go with this again
You know the odds are against us now
You know they'll always tell you that they're your
friend
Until you finally need them
There's always something that you'll never know
But will always keep burning
Your blood is boiling but never will show
Unless they give you a reason
You've broken ties so many lies
Some scars will never cease to show
Face your choices, pay the price
And they won't break us
You've made the wrong choices for too long
Now it's time for my redemption
With the world as my witness
They'll never break us
The storm is coming, it's closing in
You know the odds are against us now
The water's rising, you better learn to swim
It's just a matter of time
Nobody's coming, they don't know you're here
Now there's nowhere for you to run
That sinking feeling, I can smell your fear
Your time is up tonight
You've broken ties so many lies
Some scars will never cease to show
Face your choices, pay the price
And they won't break us
You've made the wrong choices for too long
Now it's time for my redemption
With the world as my witness
They'll never break us
Here we go with this again
You know the odds are against us now
You know they'll always tell you that they're your
friend
Until you finally need them
You've broken ties so many lies
Some scars will never cease to show
Face your choices, pay the price
And they won't break us
You've made the wrong choices for too long
Now it's time for my redemption
With the world as my witness
They'll never break us
You've broken ties so many lies
Some scars will never cease to show
Face your choices, pay the price
And they won't break us
You've made the wrong choices for too long
Now it's time for my redemption
With the world as my witness