MyCity :: Fizika

Fizi�ari prona�li novu subatomsku �esticu

nobody@mycity.rs (Rogi) — Fri, 07 Jul 2017 09:40:09 +0100

Fizi�ari koji rade na Velikom hadronskom sudara�u objavili su da su prona�li novu subatomsku �esticu sa dva �armantna kvarka za koju se nadaju da bi mogla da objasni klju�nu silu koja povezuje materiju.

Re� je o �estici barion �ije se postojanje teorijski dugo pretpostavljalo, ali do sada nije eksperimentalno potvr�ena.

Barioni su subatomske �estice sastavljeni od kvarkova, a najpoznatiji barioni su protoni i neutroni. Kvarkovi su jo� manje �estice i ima ih �est tipova podeljenih u lake i te�ke. Fizi�ari su kvarkovima dali zaista neobi�na imena � gore (up), dole (down), stranost (strange), �arm (charm), dno (bottom) i vrh (top).

Laki su gornji i donji kvarkovi, a te�ki �udni, �armantni, vr�ni i dubinski. Barioni su jedna od vrsta hadrona, odnosno �estica sastavljenih od kvarkova.

Novoprona�ena �estica se sastoji od dva �armantna kvarka i jednog gornjeg kvarka i upe�atljvo za ovu �esticu je �to se sastoji od dva te�ka kvarka.

Po�to postoji �est vrsta kvarkova, teorijski su mogu�e mnoge kombinacije, ali svi do sad opa�eni barioni imaju najvi�e jedan te�ak kvark.

Fizi�ar sa Oksforda Gaj Vilkinson, koji je u�estvovao u eksperimentu, rekao je da je u Velikom hadronskom sudara�u na deli� sekunde stvoren barion nazvan "Xi cc".

Izvor i nastavak: [Link mogu videti samo ulogovani korisnici]

Fantasti�no otkri�e srpskih fizi�ara

nobody@mycity.rs (Recoba20) — Mon, 11 Mar 2013 00:55:15 +0100

Mo�e li se predvideti koji po�etni uslovi rezultiraju da tri tela orbitiraju jedna oko drugih na periodi�an na�in? U prvih 300 godina otkako je problem tri tela definisan, samo su tri familije re�enja otkirvene. Nedavno, dva doma�a fizi�ara su otkrila jo� 13 novih familija. Ovo je pravi podvig u matemati�koj fizici, prenosi presti�ni nau�ni magazin Science, i mogao bi zna�ajno da pomogne astrofizi�arima da razumeju nove planetarne sisteme.
Ostatak na
[Link mogu videti samo ulogovani korisnici]

[Link mogu videti samo ulogovani korisnici]

Rodjendan Nikole Tesle

nobody@mycity.rs (guest76439) — Tue, 10 Jul 2012 02:20:33 +0100

Danas (10.07.2012) je tacno 156 godina od rodjenja velikog srpskog izumitelja Nikole Tesle, coveka koji je zaduzio citav svet i koji je "izumeo" XX i XXI vek.
Vest sa sajta dnevnih novina "Pravda"

Povodom ovog dogadjaja bice odrzane dve izlozbe (u Beogradu i Leskovcu), a vise o tome mozete saznati na sledecim stranicama:
1.RTS: Teslina vizija interneta

2.Juzne vesti: "Teslin dan" u Leskovcu

Takodje je i direktor Muzeja Nikole Tesle Vladimir Jelenkovi� izneo svoje misljenje povodom godisljice od rodjenja Nikole Tesle:
Blic: Jelenkovic"Svet tek sad prepoznaje Teslino vizionarsko delo"
Akter: Svet prepoznaje teslino vizionarsko delo

I za kraj jos lepih vesti. Reditelj "Harija Potera" re�ira film o Tesli.
Blic: Reditelj "Harija Potera" re�ira film o Tesli

Molim moderatore u slucaju da sam temu otvorio na pogresnom mestu da je ne brisu vec da je samo prebace u prikladni deo foruma.

Fizi�ari i Higsov bozon

nobody@mycity.rs (Nomak_) — Tue, 26 Jun 2012 22:05:20 +0100

O rezultatima poslednjih istra�ivanja na konferenciji u Australiji

Me�u fizi�arima raste napetost u i��ekivanju najnovijih rezultata u potrazi za Higsovim bozonom, koji bi trebalo da budu objavljeni u julu na Me�unarodnoj konferenciji Fizike visoke energije u Melburnu, Australija.

Glasine o predstoje�em veoma va�nom obave�tenju u vezi Higsove �estice na susretu fizi�ara ve� su izazvale pomamu za novostima na Internetu, podstaknutu blogovima u kojima se naveliko �pekuli�e nekompletnim informacijama o mogu�em otkri�u Higsa.

Dva tima koja rade na otkrivanju do sada neuhvatljive �estice, pri Cernovom Velikom hadronskom sudara�u (LHC) u blizini �eneve, �vajcarska, ne ogla�avaju se.

"Molimo vas da budete strpljivi jo� nekoliko nedelja", izjavljuje fizi�ar Guido Tonelli, �lan i biv�i potparol Compact Muon Solenoid tima. "Upravo smo zavr�ili sa prikupljanjem podataka, i ljudi rade dan i no�, uklju�uju�i i vikendom, da bi do�li do nau�no validnog rezultata". Tonelli o�ekuje da �e u CMS dobiti rezultate koje �e mo�i da prezentuje u javnost, ali ka�e da je "pritisak ogroman".

Tonelli upozorava da se rezultati u analizi podataka 'pomeraju' gotovo neprestano, i ka�e "Veoma sam iznena�en da se �ire glasine o ne�emu �to je tek u razvoju, druga�ije iz dana u dan".

Higsov bozon izmi�e potrazi decenijama, uprkos ponavljanim naporima da se �estica istera na �istac iz svog kvantnog okru�enja. Fizi�ari su krenuli za potragom �ezdesetih godina kada se �estica pojavila kao nusproizvod mehanizma kojim se obja�njava kako druge osnovne �estice sti�u masu. U standardnom modelu fizike �estica, Higsova �estica je za sada jedina koja izmi�e, koju ne uspevaju da detektuju u eksperimentima u sudaranju i razbijanju �estica.

U CERN, nau�nici tragaju za bozonom tako �to navode snopove protona jedne na druge i posle sudara pretra�uju ima li tragova Higsovog bozona. Higsova �estica nastala iz energije protona koji su se sudarili ostaje nedirnuta za tako kratko vreme da ju je nemogu�e direktno uo�iti. Zato se analiziraju i izvode zaklju�ci o postojanju iste na osnovu tragova nastalih nakon njenog raspada. Ako se u ovim tragovima na�e dovoljno toga �to bi sabrano odgovaralo �estici iste mase, nau�nici bi mogli da ustvrde da su na�li dokaz postojanja Higsova bozona.

Mada su raniji rezultati LHC tima, prezentovani u decembru, nagovestili Higsov bozon mase oko 125 milijardi elektrovolti, nije bilo dovoljno materijala nakon sudara da bi se uspostavio statisti�ki validan rezultat. Fizi�ari bi sa sigurno��u ustvrdili otkri�e samo kada bi se na�lo mase do ne�ega nastalog slu�ajno osim jednom u 3.5 miliona puta (ako sam dobro razumela, only when the piles amass to something produced by chance less than once out of 3.5 million times, prim. prev.)

Glasine o mogu�em otkri�u toliko su uzele maha da su za kratko preplavile i Tviter. Na ovoj dru�tvenoj mre�i nalazimo poruke poput "Visoki Savet Troje sankcioni�e Templare u nameri da se sa�uva tajna Higsova bozona" ili "Higsov bozon otkriva svoju masu, osim u Severnoj Karolini, gde je to zabranjeno".

izvor: [Link mogu videti samo ulogovani korisnici]

Otkrivene �estice br�e od svetlosti

nobody@mycity.rs (Rogi) — Fri, 23 Sep 2011 08:17:10 +0100

�eneva -- Nau�nici najve�e svetske laboratorije za nuklearnu fiziku saop�tili su da su zabele�ili kretanje subatomskih �estica br�ih od brzine svetlosti.

Ukoliko se to ispostavi kao ta�no, to otkri�e bi uni�tilo, u najmanju ruku ozbiljno preokrenulo osnovni temelj fizike. Prema dosada�njim nau�nim saznanjima, ni�ta se ne kre�e br�e od svetlosti.

Fizi�ari ka�u, me�utim, da su neutrino �estice - koje spadaju u najneobi�nije poznate �estice u fizici - potukle rekord najve�e kosmi�ke brzine od 299.792 kilometara u sekundi.

Evropska organizacija za nuklearna istra�ivanja (CERN) saop�tila je da je brzina zabele�ena u snopu neutrina ispaljenom iz �eneve ka jednoj laboratoriji udaljenoj 730 kilometara, u Italiji.

Izvor i nastavak: [Link mogu videti samo ulogovani korisnici]

Stiven Hoking dobio opkladu veka?

nobody@mycity.rs (Rogi) — Wed, 31 Aug 2011 08:44:37 +0100

Pre nekoliko godina svetski mediji objavili su provokativnu vest da se slavni britanski fizi�ar Stiven Hoking (Stephen Hawking) javno kladio u 100 dolara da Veliki hadronski sudara� (LHC), ali i drugi akseleratori nikad ne�e uspeti da prona�u Higsov bozon, koji se smatra nosiocem mase ve�ine elementarnih �estica

Njegova je tvrdnja izazvala pravu uzbunu u nau�noj zajednici, a �kotski fizi�ar Piter Higs (Peter Higgs), po kojem je bozon dobio ime (istra�ivanja Higsa i njegovih kolega 1960-ih udarila su temelje ideji o postojanju misteriozne �estice) provokaciju je do�ivio kao li�nu uvredu. Higs se tada po�alio da bi odgovor na Hokingov izazov bio poput 'kritikovanja princeze Dajane', me�utim kona�no je ipak uspeo da mu uzvrati 2008. godine, nakon �to se Hoking u jednom intervjuu na�alio rekav�i da bi zapravo bilo zanimljivije kada LHC ne bi prona�ao bozon.

Tom prigodom Higs je izjavio da Hokingovi prora�uni na kojima je utemeljio svoje tvrdnje nisu ta�ni, kao ni da ideja kojom je vo�en nije dobra jer je 'poku�ao da objedini teorije fizike �estica i gravitacije... na na�in na koji to nijedan teorijski fizi�ar ne bi smatrao ispravnim'.

Izvor i nastavak: [Link mogu videti samo ulogovani korisnici]

"Ne treba se plasiti razbijaca atoma"

nobody@mycity.rs (ljubicasta) — Sun, 29 Jun 2008 16:17:53 +0100

MEYRIN, Switzerland
Najjaci 'razbijac atoma' ikada izgradjen bi mogao da dovede do nekih bizarnih otkrica, kao sto je nevidiljiva materija ili jos dimenzija u svemiru, posto bude ukljucen u avgustu.

[Link mogu videti samo ulogovani korisnici]

Ali neki kriticari se boje da Large Hadron Collider moze da prevazidje najludju mastu fizicara: da li ce stvoriti crnu rupu koja moze progutati zemlju. Ili stvoriti cestice koje bi Zemlju pretvorile u vrelu mrtvu planetu.

Naucnici iz Evropske organiziacije za nuklearna istrazivanja (CERN) kazu da je to smesno. Neki od ovih naucnika su radili celu generaciju na LHC razbijacu atoma vrednom 5.8 milijardi dolara.

"Naravno, svet nece propasti kada se LHC ukljuci", rekao je vodja projekta Lyn Evans.

(ostatak teksta na [Link mogu videti samo ulogovani korisnici])

----------- Dopuna: 29 Jun 2008 16:21 ---------

link ka clanku na wikipediji:
[Link mogu videti samo ulogovani korisnici]

----------- Dopuna: 09 Avg 2008 10:59 ---------

[Link mogu videti samo ulogovani korisnici]

jo� vesti na temu

Neverovatne lekcije iz fizike - video

nobody@mycity.rs (Stane) — Fri, 21 Dec 2007 17:52:54 +0100

Video snimci lekcija iz fizike Profesora H. G. Lewin sa MITa

[Link mogu videti samo ulogovani korisnici]

[Link mogu videti samo ulogovani korisnici]

[Link mogu videti samo ulogovani korisnici]

E da mi je ovakav profa bio na studijama.

Warp Drive?

nobody@mycity.rs (Stane) — Sat, 15 Dec 2007 00:33:00 +0100

Na respektabilnom sajtu arXiv.org, pre par dana osvanuo je �lanak koji razra�uje teorijski metod putovanja nadsvetlosnom brzinom.

Koliko sam uspeo da shvatim ovo rad nije objavljen ni u jednom od klasi�nih �asopisa, barem za sada.

Autori rada su Richard Obousy i Gerald Cleaver, sa Bajlor univerziteta. arXiv.org je prili�no cenjen sajt tako da ovo verovatno nije potpuno �arlatanstvo.

Prenosimo apstrakt rada:

"Certain classes of higher dimensional models suggest that the Casimir Effect is a candidate for the cosmological constant. In this paper we demonstrate that a sufficiently advanced civilization could, in principal, manipulate the radius of the extra dimension to locally adjust the value of the cosmological constant. This adjustment could be tuned to generate an expansion/contraction of spacetime around a spacecraft creating an exotic form of field-propulsion. Due to the fact that spacetime expansion itself is not restricted by relativity, a faster-than-light 'warp drive' could be created. Calculations of the energy requirements of such a drive are performed and an 'ultimate' speed limit, based on the Planckian limits on the size of the extra dimensions is found."

Celo rad mo�ete prona�i ovde:
[Link mogu videti samo ulogovani korisnici]

Teslin Kalem i za�tita od lopova

nobody@mycity.rs (Stane) — Mon, 19 Feb 2007 17:45:19 +0100

�ta ti mo�e �iv �ovek! Aj da vidim nekog da se usudi da obije ovaj auto. Ljudi izvinte za sliku na prvoj strani ali ovo vredi videti.

Ina�e ovo �udo nije proizvod photoshopa ve� teslinog kalema, detaljnije ovde:

[Link mogu videti samo ulogovani korisnici]

Pritisak u flasi

nobody@mycity.rs (Leopardvegetarian) — Tue, 30 Jan 2007 14:38:53 +0100

Kao sto znamo na nivou mora pritisak iznosi jednu atmosferu.

Kaze se da je taj pritisak izazvan tezinom stuba molekula atmosfere koji "pristiscu odozgo". Bas lepo od njih.

Pitanje glasi:

Koliki pritisak ce pokazati instrument ako ga na nivou mora zatvorimo hermeticki u nestisljiv kontejner kao sto je npr flasa?

Zasto?

Prvi Srpski Akcelerator - nastavak izgradnje

nobody@mycity.rs (Stane) — Wed, 17 Jan 2007 22:27:22 +0100

Ne znam da li ste znali, ali zemlja Srbija poseduje i akcelerator, ili barem par�e od akceleratora. Naime krajem osamdesetih Institut za nuklearna istra�ivanja Vin�a otpo�eo je svoj najambiciozniji projekat izgradnju ovog postrojenja. Po�to po�etak devedesetih nije ba� bio najsretnije vreme na ovim prostorima, finansije su ubrzo presu�ile. I pored utucanih 14 miliona evra izgradnja je jo� uvek daleko od zavr�etka. Ipak vremena se menjaju. Izgleda da su finansije, bar donekle, obezbe�ene.

Citat:
Sredinom decembra ministri Srbije i Ruske Federacije parafirali su sporazum o klirin�kom dugu u iznosu od 288 miliona dolara, kojim je predvi�eno da se do januara 2009. godine pet miliona ulo�i u dovr�avanje Akceleratorske instalacije TESLA, koju gradi Laboratorija za fiziku broj 10 na Institutu za nuklearne nauke "Vin�a". Uz to, planirano je da u aprilu ove godine zapo�ne i realizacija ugovora sa Objedinjenim institutom za nuklearna istra�ivanja u Dubni u Rusiji, gde �e biti izra�eni nedostaju�i delovi ciklotrona, a od Ministarstva nauke i za�tite �ivotne sredine je zatra�eno jo� 2,5 miliona evra.

�ta �e nama uop�te akcelerator:
Citat:"Polaznim konceptom TESLA je definisan kao nau�no-medicinsko vi�enamensko akceleratorsko postrojenje", ka�e Ne�kovi�, obja�njavaju�i da �e pored fundamentalnih istra�ivanja u fizici, hemiji i biologiji, TESLA slu�iti za razvoj tehnologije materijala, ali i za proizvodnju radionuklida i radiofarmaceutika.

U Vin�i �e se proizvoditi radionuklid jod-124, koji je potreban za rad PET centra, kao i jod-123 koji �e se koristiti za gama kamere kakve ve� postoje u mnogim klinikama u Srbiji. Tako se vrlo redak i skup radionuklid jod-123 mo�e dobiti pri bombardovanju ksenona-124 ubrzanim protonima.

Vi�e o ovome u odli�nom tekstu u novom broju �asopisa Vreme:
[Link mogu videti samo ulogovani korisnici]

Nevidljivost, ponovo

nobody@mycity.rs (Stane) — Thu, 19 Oct 2006 22:23:03 +0100

Tim Ameri�kih nau�nika napravio je ure�aj koji posti�e da se talasi u mikrotalasnom ospegu savijaju oko objekta i iza njega ponovo rekombinuju, kao da su kroz njega pro�li bez zastoja. Najpribli�nije obja�njenje bi bilo da je ovo nalik na kretanje vode oko nekog objekta u nju potopljenog. Ovaj ure�aj �ini ibjekat nevidljivim u mikrotalasnom podru�ju. Prava opti�ka nevidljivost u vidljivom delu spektra je jo� uvek daleko, ali se nau�nici nadaju da �e mo�i da iskoriste isti princip.

[Link mogu videti samo ulogovani korisnici]

Nano-tehnologija

nobody@mycity.rs (Vladimir) — Wed, 17 Aug 2005 08:23:06 +0100

When it comes to taking the next "giant leap" in space exploration, NASA is thinking small -- really small.
n laboratories around the country, NASA is supporting the burgeoning science of nanotechnology. The basic idea is to learn to deal with matter at the atomic scale -- to be able to control individual atoms and molecules well enough to design molecule-size machines, advanced electronics and "smart" materials.

If visionaries are right, nanotechnology could lead to robots you can hold on your fingertip, self-healing spacesuits, space elevators and other fantastic devices. Some of these things may take 20+ years to fully develop; others are taking shape in the laboratory today.

Thinking Small

Simply making things smaller has its advantages. Imagine, for example, if the Mars rovers Spirit and Opportunity could have been made as small as a beetle, and could scurry over rocks and gravel as a beetle can, sampling minerals and searching for clues to the history of water on Mars. Hundreds or thousands of these diminutive robots could have been sent in the same capsules that carried the two desk-size rovers, enabling scientists to explore much more of the planet's surface -- and increasing the odds of stumbling across a fossilized Martian bacterium!

But nanotech is about more than just shrinking things. When scientists can deliberately order and structure matter at the molecular level, amazing new properties sometimes emerge.

An excellent example is that darling of the nanotech world, the carbon nanotube. Carbon occurs naturally as graphite -- the soft, black material often used in pencil leads -- and as diamond. The only difference between the two is the arrangement of the carbon atoms. When scientists arrange the same carbon atoms into a "chicken wire" pattern and roll them up into miniscule tubes only 10 atoms across, the resulting "nanotubes" acquire some rather extraordinary traits. Nanotubes:

* have 100 times the tensile strength of steel, but only 1/6 the weight;

* are 40 times stronger than graphite fibers;

* conduct electricity better than copper;

* can be either conductors or semiconductors (like computer chips), depending on the arrangement of atoms;

* and are excellent conductors of heat.

Much of current nanotechnology research worldwide focuses on these nanotubes. Scientists have proposed using them for a wide range of applications: in the high-strength, low-weight cable needed for a space elevator; as molecular wires for nano-scale electronics; embedded in microprocessors to help siphon off heat; and as tiny rods and gears in nano-scale machines, just to name a few.

Nanotubes figure prominently in research being done at the NASA Ames Center for Nanotechnology (CNT). The center was established in 1997 and now employs about 50 full-time researchers.

"[We] try to focus on technologies that could yield useable products within a few years to a decade," says CNT director Meyya Meyyappan. "For example, we're looking at how nano-materials could be used for advanced life support, DNA sequencers, ultra-powerful computers, and tiny sensors for chemicals or even sensors for cancer."

A chemical sensor they developed using nanotubes is scheduled to fly a demonstration mission into space aboard a Navy rocket next year. This tiny sensor can detect as little as a few parts per billion of specific chemicals--like toxic gases--making it useful for both space exploration and homeland defense. CNT has also developed a way to use nanotubes to cool the microprocessors in personal computers, a major challenge as CPUs get more and more powerful. This cooling technology has been licensed to a Santa Clara, California, start-up called Nanoconduction, and Intel has even expressed interest, Meyyappan says.

Designing the future

If these near-term uses of nanotechnology seem impressive, the long-term possibilities are truly mind-boggling.

The NASA Institute for Advanced Concepts (NIAC), an independent, NASA-funded organization located in Atlanta, Georgia, was created to promote forward-looking research on radical space technologies that will take 10 to 40 years to come to fruition.

For example, one recent NIAC grant funded a feasibility study of nanoscale manufacturing--in other words, using vast numbers of microscopic molecular machines to produce any desired object by assembling it atom by atom!

That NIAC grant was awarded to Chris Phoenix of the Center for Responsible Nanotechnology.

In his 112 page report, Phoenix explains that such a "nanofactory" could produce, say, spacecraft parts with atomic precision, meaning that every atom within the object is placed exactly where it belongs. The resulting part would be extremely strong, and its shape could be within a single atom's width of the ideal design. Ultra-smooth surfaces would need no polishing or lubrication, and would suffer virtually no "wear and tear" over time. Such high precision and reliability of spacecraft parts are paramount when the lives of astronauts are at stake.

Although Phoenix sketched out some design ideas for a desktop nanofactory in his report, he acknowledges that -- short of a big-budget "Nanhatten Project," as he calls it -- a working nanofactory is at least a decade away, and possibly much longer.

Taking a cue from biology, Constantinos Mavroidis, director of the Computational Bionanorobotics Laboratory at Northeastern University in Boston, is exploring an alternative approach to nanotech: Rather than starting from scratch, the concepts in Mavroidis's NIAC-funded study employ pre-existing, functional molecular "machines" that can be found in all living cells: DNA molecules, proteins, enzymes, etc.

Shaped by evolution over millions of years, these biological molecules are already very adept at manipulating matter at the molecular scale -- which is why a plant can combine air, water, and dirt and produce a juicy red strawberry, and a person's body can convert last night's potato dinner into today's new red blood cells. The rearranging of atoms that makes these feats possible is performed by hundreds of specialized enzymes and proteins, and DNA stores the code for making them.

Making use of these "pre-made" molecular machines -- or using them as starting points for new designs -- is a popular approach to nanotechnology called "bio-nanotech."

"Why reinvent the wheel?" Mavroidis says. "Nature has given us all this great, highly refined nanotechnology inside of living things, so why not use it -- and try to learn something from it?"

The specific uses of bio-nanotech that Mavroidis proposes in his study are very futuristic. One idea involves draping a kind of "spider's web" of hair-thin tubes packed with bio-nanotech sensors across dozens of miles of terrain, as a way to map the environment of some alien planet in great detail. Another concept he proposes is a "second skin" for astronauts to wear under their spacesuits that would use bio-nanotech to sense and respond to radiation penetrating the suit, and to quickly seal over any cuts or punctures.

Futuristic? Certainly. Possible? Maybe. Mavroidis admits that such technologies are probably decades away, and that technology so far in the future will probably be very different from what we imagine now. Still, he says he believes it's important to start thinking now about what nanotechnology might make possible many years down the road.

Considering that life itself is, in a sense, the ultimate example of nanotech, the possibilities are exciting indeed.
Ovde

Prvi nanofluidni tranzistor

nobody@mycity.rs (Vladimir) — Sat, 13 Aug 2005 21:28:28 +0100

University of California, Berkeley, researchers have invented a variation on the standard electronic transistor, creating the first "nanofluidic" transistor that allows them to control the movement of ions through sub-microscopic, water-filled channels.
The researchers - a chemist and a mechanical engineer - predict that, just as the electronic transistor became the main component of microprocessors and integrated circuits, so will nanofluidic transistors anchor molecular processors, allowing microscopic chemical plants on a chip that operate without moving parts. No valves to get stuck, no pumps to blow, no mixers to get clogged.
"A transistor is like a valve, but you use electricity to open or close it," explained Arun Majumdar, professor of mechanical engineering at UC Berkeley. "Here, we use a voltage to open or close an ion channel. Now that we've shown you can make this building block, we can hook it up to an electronic chip to control the fluidics."

One application Majumdar and colleague Peidong Yang, UC Berkeley professor of chemistry, are exploring is cancer diagnosis. A nanoscale chemical analysis chip could, theoretically, take the contents of as few as 10 cancer cells and pull out protein markers that can tip doctors to the best means of attacking the cancer.

"This is an ideal way to open up cells and identify the proteins or enzymes inside," he said. "An enzyme profile would tell doctors a lot about the kind of cancer, especially in its early stages when there are only a few cells around."

Yang, who built a variation of the transistor using nanotubes, is equally intrigued by the computational possibilities of the device.

"It may sound a little bit far fetched, but we're thinking about whether we can do the same thing with nanofluidic transistors as we can currently with MOSFETs," he said, referring to the Metal-Oxide Semiconductor Field Effect Transistors used in most of today's microprocessor chips. "Using molecules to process information gives you a fundamentally different information processing device."

Majumdar, Yang and colleagues Rohit Karnik, a mechanical engineering graduate student; Rong Fan, a chemistry graduate student; and mechanical engineering students Min Yue and Deyu Li reported their success - the product of three years of effort - in the May issue of the journal Nanoletters. Yang and Majumdar are also faculty scientists at Lawrence Berkeley National Laboratory.

One big advantage of nanofluidic transistors, Majumdar said, is that they could be made using the same manufacturing technology that today produces integrated circuits. Nanofluidic channels could be integrated with electronics on a single silicon chip, with the electronics controlling the operation of the nanofluidics. The only microscale parts of the device are the microchannels for injecting liquid.

Majumdar and Yang's team constructed a 35-nanometer-high channel between two silicon dioxide plates, then filled the channel with water and potassium chloride salt. They showed that by applying a voltage across the channel by means of electrodes attached to the plates, they could shut off the flow of potassium ions through the water. This is analogous to the control of electron flow through a transistor by means of a gate voltage.

Such ion manipulations are not possible through microscopic channels because ions in the liquid quickly move to the plates and cancel out the voltage, basically shielding the interior of the liquid from the electric field. Channels less than 100 nanometers across, however, are so small that this shielding doesn't occur, so ions in the bulk liquid can be pushed or pulled by electric voltages.

If the ions are proteins, they can be shuttled through channels lined with fluorescent antibodies for detecting or sensing. If the ions are pieces of DNA, they can be sorted and sequenced. In fact, the authors say, any highly sensitive biomolecular sensing down to the level of a single molecule could be performed with nanofluidic transistors. They demonstrated that labeled, charged DNA fragments could be manipulated in their transistor.

Yang, who is adept at making nanoscale lasers, tubes, wires and other devices, created a version of the transistor using nanotubes with internal diameters of 20 nanometers, proving that the same sort of molecular processing can be done with these innovative structures. While Majumdar foresees putting electronic and nanofluidic transistors on the same chip to provide computer control of chemical processing, Yang foresees the computing and chemical processing being done by the same nanofluidic channels.

"With nanotubes, you have access to much smaller dimensions compared to conventional nanofabrication, but in terms of integration, it's more difficult," Yang said. "For the future, both processes are fundamentally interesting, and eventually devices will combine both."

Majumdar and Yang acknowledge that a lot more work needs to be done, including understanding the surface effects inside nanochannels. In addition, the voltage required to shut off ion flow is now 75 volts, far too high for any of today's integrated circuits. But their team has a few other papers waiting to appear in Nanoletters and in the Physical Review Letters that push the technology farther than this initial paper. They hope to beat the time lag between invention of the transistor in 1947 and creation of the first integrated circuit in 1960.

"We want to be the first to build integrated circuits with just three transistors able to do sorting and eluting, just as a two- or three-bit processor can do multiplexing and addressing," Majumdar said.

The work was supported by the National Cancer Institute's Innovative Molecular Analysis Technologies program and by the Department of Energy. Current work is being funded by the National Science Foundation.
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