from the World of science

Earthly meltdown formed the Moon: study

2010-02-01T09:57:00.000-08:00

A new study claims our Moon could have been born from a blob of the Earth's mantle, blasted outwards by the explosion of a runaway nuclear georeactor.

If correct, it would replace the scientifically accepted model for the origins of the Moon, known as the 'giant impact theory'.

That theory suggests a Mars-sized planet called Theia, slammed into the early proto-Earth about 62 million years after the solar system's birth - 4.6 billion years ago.

The iron and nickel core of both planets coalesced to form the Earth, while the lighter silicate mantle and crust, ejected into space, to forming the Moon - explaining why the Moon isn't as dense as Earth.

Computer simulations suggest about 80% of the Moon came from the impactor and 20% from the proto-Earth.

But Professor Rob de Meijer at the University of the Western Cape in South Affrica and Dr Wim van Westrenen of VU University in Amsterdam believe the theory has a problem.

"Both Moon and Earth rocks have almost the same isotopic content, which is put down to debris mixing in orbit as the Moon formed," they write in a paper published on the electronic preprint website arXiv.

"While that works for lighter elements, it can't easily account for the identical ratio of heavier elements such as chromium, neodymium and tungsten."

Blasted out
According to the paper, the Earth was once a rapidly spinning mass of molten rock; the force of gravity only just preventing it from spinning apart.

"Just a slight kick would have would have been enough to eject a blob into orbit, eventually forming the Moon," they write.

The idea's been around for ages, but rejected because nobody could work out where the energy to kick a lunar-sized blob into orbit, could have come from.

de Meijer and van Westrenen believe the energy could have come from a nuclear explosion deep in the Earth's mantle.

"High concentrations of radioactive elements like uranium and thorium near the Earth's surface could have caused a runaway nuclear chain reaction going supercritical," they write. "The explosion blasted material into orbit eventually forming the Moon".

But planetary scientist Dr Simon O'Toole of the Anglo Australian Observatory says "while it's an interesting idea, the science isn't strong."

"It's based around the disputed hypothesis of a naturally occurring georeactor going super critical."

O'Toole says, "the assumptions required for their idea to work are so large compared to the generally accepted theory, that if you apply Ockham's Razor and ask what's most likely, well, this isn't it!"

"The idea of the Earth spewing out the Moon is great for science fiction, but a bit hairy for science fact."

Reference: ABC Science

the Large Hadron Collider ( LHC )

2008-09-17T11:05:00.001-07:00

The LHC (Large Hadron Collider) is an international project, in which the UK has a leading role. This site includes the latest news from the project, accessible explanations of how the LHC works, how it is funded, who works there and what benefits it brings us. You can access a wide range of resources for the public, journalists and teachers and students, there are also many links to other sources of information.

Phoenix Mars Lander Delivers Soil Sample To Microscope

2008-06-23T10:43:00.000-07:00

This photograph shows the Robotic Arm on NASA's Phoenix Mars Lander carrying a scoop of Martian soil bound for the spacecraft's microscope. (Credit: NASA/JPL-Caltech/University of Arizona)

Mars Lander Saturday beamed back images showing that Phoenix’s Robotic Arm successfully sprinkled soil onto the delivery port of the lander's Optical Microscope.

Mission scientists said enough of the fine-grained soil sample remains in the scoop of the lander's Robotic Arm for delivery to either the Wet Chemistry Lab or Thermal and Evolved-Gas Analyzer. Both the Wet Chemistry Lab and the Optical Microscope are part of the Microscopy, Electrochemistry and Conductivity Analyzer, or MECA, instrument.

"We want to deliver similar soil samples to all three instruments," said Ray Arvidson, the mission's lead scientist for digging activities, from Washington University in St. Louis.

The lander's Robotic Arm has been commanded to remain in an "up" position to hold the collected soil in the scoop until it can be delivered to the other instruments.

The Phoenix mission is led by Peter Smith of the University of Arizona with project management at JPL and development partnership at Lockheed Martin, located in Denver. International contributions come from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological Institute.

NASA Probe Lands on Mars to Search for Signs of Life

2008-05-26T20:00:00.000-07:00

An artist's concept illustration depicts NASA's Phoenix Mars Lander, released to the media May 25, 2008. Source: NASA/JPL-Calech/University of Arizona News

May 26 -- NASA's Mars Phoenix Lander touched down safely today on the Red Planet, where the probe will sift through the icy soil for any signs that it once harbored life.

`We've passed the hardest part and we're breathing again,'' Mars Phoenix Project Manager Barry Goldstein said, according to NASA. The Red Planet's rocky terrain and equipment problems have led to the failure of more than half of all Mars missions, including a Phoenix predecessor destroyed in 1999.

Phoenix sent a signal confirming it landed safely in the northern polar region of Mars, the National Aeronautics and Space Administration said on its Web site. The message took 15 minutes to travel to Earth from Mars at the speed of light.

The probe is part of NASA's current theme in Mars exploration: follow the water. Ice is plentiful beneath the red soil and the space agency wants to know whether liquids also exist underground. ``Where there tends to be water on Earth, there tends to be life,'' Lynn Craig of NASA's Jet Propulsion Laboratory said in an interview. ``So it's potentially a place where life could have existed.'

After its landing, Phoenix relayed pictures from the planet showing the plain and horizon, a foot of the craft on the soil and its solar panels extended so that it will be able to generate power, according to NASA.

Landing Risk

The riskiest segment of the Phoenix's 420-million-mile (676-million-kilometer), 9-month journey was the end. The Phoenix had only seven minutes to slow in the thin Martian atmosphere from almost twice the speed of sound to the pace of an escalator. Parachutes and braking rockets accomplished the task, each step initiated by onboard computers.

`Landing is easy; doing it softly is the hard part,'' said Mark Lemmon, an atmospheric scientist at Texas A&M University and co-investigator on the NASA project.

The previous ``soft landing'' on a planet was three decades ago, with NASA's Viking probes. Recent crafts sent to Mars, such as NASA's wheeled rovers, weighed less and relied on air bags to cushion the final impact.

Now on the surface, the Phoenix must work quickly. Martian winter begins in three months. The sun will drop below the horizon, and a thick ice of water and carbon dioxide will coat the lander's solar panels, ending its life.

Digging Process

The golf cart-size probe will use an 8-foot robotic arm, as well as a drill, to penetrate several feet of soil at the landing spot, near Mars's northern polar ice cap.

The flexible arm will scoop dirt and ice into ovens about the size of a matchbox. They will heat samples to 1,800 degrees Fahrenheit (980 degrees Celsius).

The probe will then test the burned soil for organic chemicals and minerals crucial to life. Much of the information can be analyzed on the spot and radioed back to Earth.

NASA's Viking probes also examined Martian soil in the 1970s, when the primary concern was locating safe landing spots. Dirt samples at those sites lacked much water.

The Phoenix, built by Lockheed Martin Corp., will be NASA's third probe active on the planet, along with the wheeled rovers Spirit and Opportunity.

Like Phoenix, they were given three months to live after touchdown. To NASA's surprise, the vehicles are still working four years later.

Self-assembling Method Could Lead To Inexpensive Diamond-like Crystals For Technology

2008-04-23T09:49:00.000-07:00

Researchers at Purdue have developed a "self-assembling" technique to create a "nearly perfect two-dimensional colloidal crystal," or a precisely ordered layer of particles, a critical step toward growing three-dimensional crystals for use in optical communications and other technologies. The method works by positioning tiny particles onto a silicon template containing precisely spaced holes that are about one-hundredth the width of a human hair. This photograph, taken with a scanning electron microscopy, shows a side-by-side comparison between Purdue's structure (right) and a structure that results when a template is not used. (Credit: You-Yeon Won and Jaehyun Hur, Purdue University School of Chemical Engineering)

Chemical engineers have developed a "self-assembling" method that could lead to an inexpensive way of making diamondlike crystals to improve optical communications and other technologies.

The method, developed at Purdue University, works by positioning tiny particles onto a silicon template containing precisely spaced holes that are about one-hundredth the width of a human hair. The template is immersed in water on top of which particles are floating, and the particles automatically fill in the holes as the template is lifted.

The researchers have used the technique to create a "nearly perfect two-dimensional colloidal crystal," or a precisely ordered layer of particles. This is a critical step toward growing three-dimensional crystals for use in optical technologies, said You-Yeon Won, an assistant professor of chemical engineering.

More >>>

Gigantic Antarctic Ice Chunk Collapses

2008-03-30T20:05:00.000-07:00

March 25, 2008 -- A chunk of Antarctic ice about seven times the size of Manhattan suddenly collapsed, putting an even greater portion of glacial ice at risk, scientists said Tuesday.

Satellite images show the runaway disintegration of a 160-square-mile chunk in western Antarctica, which started Feb. 28. It was the edge of the Wilkins ice shelf and has been there for hundreds, maybe 1,500 years.

This is the result of global warming, said British Antarctic Survey scientist David Vaughan.

Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the ongoing collapse for rare pictures and video.

"It's an event we don't get to see very often," said Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colo. "The cracks fill with water and slice off and topple... That gets to be a runaway situation."

While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades, Vaughan said. The collapse is similar to what happens to hardened glass when it is smashed with a hammer, he said.

The rest of the Wilkins ice shelf, which is about the size of Connecticut, is holding on by a narrow beam of thin ice. Scientists worry that it too may collapse. Larger, more dramatic ice collapses occurred in 2002 and 1995.

Vaughan had predicted the Wilkins shelf would collapse about 15 years from now.

Scientists said they are not concerned about a rise in sea level from the latest event, but say it's a sign of worsening global warming.

Such occurrences are "more indicative of a tipping point or trigger in the climate system," said Sarah Das, a scientist at the Woods Hole Oceanographic Institute.

Top 5 Science Images of 2007 Honored

2007-11-10T10:45:00.000-08:00

A striking image of seaweed shows the complexity of even the simplest organisms.

Seen here is Irish moss—Chondrus crispus—a common Atlantic red alga that is routinely harvested for its carrageenan. The chemical is used as a thickener in many processed foods.

Andrea Ottesen of the University of Maryland's Department of Plant Science and Landscape Architecture shared a first place prize in the photography category of the 2007 International Science and Engineering Visualization Challenge for the natural light photo.

The awards are given out each year by the National Science Foundation and the journal Science for the imagery that best conveys complex scientific information and concepts. This year the winners are announced in the September 28 issue of Science.

It may look like a strange insect , but this is actually a CT image revealing the delicate structures underlying the human nose.

The multicolored pockets, seen in a cutaway from below the nose looking up, are the paranasal sinuses—the air-filled spaces in the skull that are the bane of many an allergy sufferer.

Kai-hung Fung of Pamela Youde Nethersole Eastern Hospital in Hong Kong captured the image, a co-winner in the photography category of the 2007 International Science and Engineering Visualization Challenge, while examining a 33-year-old Chinese woman for thyroid disease.

This is the fifth year that the prizes have been awarded.

Metal with the consistency of ribbon garnered engineering graduate student Adam Siegel and chemist George M. Whitesides of Harvard University an honorable mention in the photography category of the 2007 International Science and Engineering Visualization Challenge.

The pair created this image by injecting molten solder into a tiny silicone channel.

When the solder cooled, it formed a delicate metallic structure that was flexible enough to be tied into a knot—but could still conduct electricity.

Not pictured here are the winners of the informational graphics category.

"Modeling the Flight of a Bat" by David J. Willis of Brown University and the Massachusetts Institute of Technology and Mykhaylo Kostandov of Brown University earned the first place accolade, while "How Does A Muscle Work?" by Mark McGowan and David Goodsell of the Exploratorium Institute took honorable mention.

A still image from a 3-D animation shows how nicotine stimulates nerve impulses to the pleasure center of the brain.

Donna DeSmet and Jason Guerrero of Hurd Studios won the first-place prize in the noninteractive media category of the 2007 International Science and Engineering Visualization Challenge for the video, titled "Nicotine: The Physiologic Mechanism of Tobacco Dependence."

Not seen here is "Towers in the Tempest," an animation of soaring hurricane clouds, which earned Gregory W. Shirah and Lori K. Perkins of NASA's Goddard Space Flight Center an honorable mention in the noninteractive media category.

Understanding even basic geometrical transformations can be difficult—unless you get a little perspective.

This still image comes from "Mobius Transformations Revealed," a short film by Douglas N. Arnold and Jonathan Rogness of the University of Minnesota that shows how some mathematics can become simpler in higher dimensions.

The movie was an honorable mention in the noninteractive media category of the 2007 International Science and Engineering Visualization Challenge.

Other winners not shown here included the following:

First Place, Interactive Multimedia: "Physics Education Technology Project" (PhET) by Carl Wieman of the University of Colorado and the PhET Team.

Honorable Mention, Interactive Multimedia: "Breast Cancer Virtual Anatomy" by Cathryn Tune and Samantha Belmont of CCG Metamedia.

Referance :http://www.nationalgeographic.com/

Ancient Egyptian cosmetics and chemistry

2007-10-25T23:09:00.000-07:00

An analysis of Egyptian cosmetic powders dating back to as early as 2000 BC revealed an unexpected level of sophistication in the 'wet' chemistry practised by the ancient Egyptians.

It was already well-known that they were using fire-based technology to produce their blue pigments prior to 2500 BC. Yet this is the first time that the analysis of the black, green and white cosmetic powders shed light on the level of their practices in chemistry.

Researchers identified a number of organic and mineral ingredients in the powders. Two of the mineral ingredients were naturally occurring ores which were crushed, ore of galena (PbS) and cerussite (PbCO3). However, the surprise came from laurionite (PbOHCl) and phosgenite (Pb2Cl2CO3), which were both compounds which occurred rarely in nature. They are found when lead artefacts are weathered by sea water. Or in the case of phosgenite, the compound could also be found when lead-containing minerals were exposed to carbonated and chlorinated waters.

The researchers ruled out the possibility that these compounds were extracted from scarce natural sources since they were too abundant in the preserved cosmetic samples. Also they ruled out the alteration of the other natural lead compounds in the make-up as a source. And in doing so, they arrived at the conclusion that the Egyptians were capable of artificially synthesising the compounds.

They reconstructed the process which the Egyptians probably used by following recipes documented by classical authors. According to the ancient recipe crushed purified silver foam (PbO) was mixed with rock salt and sometimes with natron (Na2Co3). This mixture was filtered and the procedure was repeated daily for several weeks.

The authors recreated the process using PbO and salt powders in carbonate free water. The resulting precipitate was successfully identified as laurionite. The same process in the presence of carbonate would produce phosgenite.

Given that the procedures required repetitive operations, the manufacturing of these compound revealed a previously unknown level of sophistication of ancient Egyptian chemistry.

Original article: Nature, 11 February 1999; Making make-up in Ancient Egypt, P. Walter et al., p. 483-484

Star with vast tail astonishes scientists

2007-08-18T23:49:00.000-07:00

A NASA craft has spotted a surprisingly long comet-like tail behind a star streaking through space at supersonic speeds.

“This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved,” said Mark Seibert of the Observatory of the Carnegie Institution of Washington in Pasadena, Calif..

“We hope to be able to read Mira’s tail like a ticker tape to learn about the star’s life,” added Seibert, co-author of a paper describing the findings. Mira would be in a sense the first real “shooting star” known—since the streaks of light traditionally called shooting stars are really meteors, or rocks falling through the atmosphere.

This image is a mosaic made up of individual images taken by the far-ultraviolet light detector on NASA's Galaxy Evolution Explorer in November and December, 2006. (Credit: NASA/JPL-Caltech)

The star, named Mira after the Latin word for “wonderful,” has been a favorite of astronomers for approximately 400 years. It is a fast-moving, older red giant that is shedding massive amounts of surface material.

It’s “amazing to discover such a startlingly large and important feature of an object that has been known and studied for more than 400 years,” said James D. Neill of the California Institute of Technology In Pasadena, Calif. The institute leads the mission for NASA’s Galaxy Evolution Explorer spacecraft.

The craft scanned the popular star during an ongoing sky survey. Astronomers then noticed what looked like a comet with a giant tail. Material blowing off Mira is forming a wake 13 light-years long, or about 20,000 times the average distance of Pluto from the sun. Nothing like this has been seen before around a star.

“I was shocked when I first saw this completely unexpected, humongous tail trailing behind a well-known star,” said Caltech’s Christopher Martin. “It was amazing how Mira’s tail echoed on vast, interstellar scales the familiar phenomena” such as the stream of gas behind a jet or a speedboat’s turbulent wake.

Martin is principal investigator for the spacecraft and lead author of the paper, in the Aug. 15 edition of the research journal Nature.

Astronomers say Mira’s tail offers a unique opportunity to study how stars like our sun die and ultimately seed new solar systems. As Mira hurtles along, its tail sheds carbon, oxygen and other important elements needed to form new stars, planets and possibly even life. This tail material, visible for the first time, has been released during the past 30,000 years.

Billions of years ago, Mira was similar to our sun. Over time, it began to swell into what is called a variable red giant—a pulsating, puffed-up star that periodically grows bright enough to see with the naked eye. Mira eventually will eject all its remaining gas into space, forming a colorful shell called a planetary nebula, astronomers say. The nebula will fade with time, leaving only the burnt-out core of the original star, which will then be called a white dwarf.

Compared to other red giants, Mira is traveling unusually fast, possibly due to boosts from the gravity of passing stars, investigators said. It plows along at an estimated 291,000 miles per hour. Racing along with it is a small, distant companion thought to be a white dwarf. The pair, also known as Mira A (the red giant) and Mira B, orbit slowly around each other as they travel together in the constellation Cetus, 350 light-years from Earth.

In addition to Mira’s tail, the spacecraft also found a bow shock, a type of buildup of hot gas, in front of the star, and two sinuous streams of material emanating from the star’s front and back. Astronomers think hot gas in the bow shock is heating the gas blowing off the star, causing it to fluoresce with ultraviolet light. This glowing material then swirls around behind the star, creating a turbulent, tail-like wake. The process is similar to a speeding boat leaving a choppy wake or a steam train producing a trail of smoke.

Mira’s tail only glows with ultraviolet light, a type of light more energetic than that visible to the eye, which might explain why other telescopes have missed it, researchers said. The Galaxy Evolution Explorer is very sensitive to such light and also has an extremely wide field of view, so it can scan the sky for unusual ultraviolet activity.

Star with vast tail astonishes scientists

2007-08-18T23:35:00.000-07:00

A NASA craft has spotted a surprisingly long comet-like tail behind a star streaking through space at supersonic speeds.

“This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved,” said Mark Seibert of the Observatory of the Carnegie Institution of Washington in Pasadena, Calif..

“We hope to be able to read Mira’s tail like a ticker tape to learn about the star’s life,” added Seibert, co-author of a paper describing the findings. Mira would be in a sense the first real “shooting star” known—since the streaks of light traditionally called shooting stars are really meteors, or rocks falling through the atmosphere.

The star, named Mira after the Latin word for “wonderful,” has been a favorite of astronomers for approximately 400 years. It is a fast-moving, older red giant that is shedding massive amounts of surface material.

This image is a mosaic made up of individual images taken by the far-ultraviolet light detector on NASA's Galaxy Evolution Explorer in November and December, 2006. (Credit: NASA/JPL-Caltech)

It’s “amazing to discover such a startlingly large and important feature of an object that has been known and studied for more than 400 years,” said James D. Neill of the California Institute of Technology In Pasadena, Calif. The institute leads the mission for NASA’s Galaxy Evolution Explorer spacecraft.

The craft scanned the popular star during an ongoing sky survey. Astronomers then noticed what looked like a comet with a giant tail. Material blowing off Mira is forming a wake 13 light-years long, or about 20,000 times the average distance of Pluto from the sun. Nothing like this has been seen before around a star.

“I was shocked when I first saw this completely unexpected, humongous tail trailing behind a well-known star,” said Caltech’s Christopher Martin. “It was amazing how Mira’s tail echoed on vast, interstellar scales the familiar phenomena” such as the stream of gas behind a jet or a speedboat’s turbulent wake.

Martin is principal investigator for the spacecraft and lead author of the paper, in the Aug. 15 edition of the research journal Nature.

Astronomers say Mira’s tail offers a unique opportunity to study how stars like our sun die and ultimately seed new solar systems. As Mira hurtles along, its tail sheds carbon, oxygen and other important elements needed to form new stars, planets and possibly even life. This tail material, visible for the first time, has been released during the past 30,000 years.

Billions of years ago, Mira was similar to our sun. Over time, it began to swell into what is called a variable red giant—a pulsating, puffed-up star that periodically grows bright enough to see with the naked eye. Mira eventually will eject all its remaining gas into space, forming a colorful shell called a planetary nebula, astronomers say. The nebula will fade with time, leaving only the burnt-out core of the original star, which will then be called a white dwarf.

Compared to other red giants, Mira is traveling unusually fast, possibly due to boosts from the gravity of passing stars, investigators said. It plows along at an estimated 291,000 miles per hour. Racing along with it is a small, distant companion thought to be a white dwarf. The pair, also known as Mira A (the red giant) and Mira B, orbit slowly around each other as they travel together in the constellation Cetus, 350 light-years from Earth.

In addition to Mira’s tail, the spacecraft also found a bow shock, a type of buildup of hot gas, in front of the star, and two sinuous streams of material emanating from the star’s front and back. Astronomers think hot gas in the bow shock is heating the gas blowing off the star, causing it to fluoresce with ultraviolet light. This glowing material then swirls around behind the star, creating a turbulent, tail-like wake. The process is similar to a speeding boat leaving a choppy wake or a steam train producing a trail of smoke.

Mira’s tail only glows with ultraviolet light, a type of light more energetic than that visible to the eye, which might explain why other telescopes have missed it, researchers said. The Galaxy Evolution Explorer is very sensitive to such light and also has an extremely wide field of view, so it can scan the sky for unusual ultraviolet activity.

Nanorobots (nanobots, nanoids or nanites)

2007-07-14T21:25:00.001-07:00

Nanobots are machines or robots at or close to the scale of a nanometres (10-9 metres)

Nanorobots

2007-07-14T21:11:00.001-07:00

Nanorobotics is the technology of creating machines or robots at or close to the scale of a nanometres (10-9 metres). More specifically, nanorobotics refers to the still largely hypothetical nanotechnology engineering discipline of designing and building nanorobots. Nanorobots (nanoids, nanobots or nanites) would be typically devices ranging in size from 0.1-10 micrometres and constructed of nanoscale or molecular components. As no artificial non-biological nanorobots have so far been created, they remain a hypothetical concept at this time.
Another definition sometimes used is a robot which allows precision interactions with nanoscale objects, or can manipulate with nanoscale resolution. Following this definition even a large apparatus such as an atomic force microscope can be considered a nanorobotic instrument when configured to perform nanomanipulation. Also, macroscale robots or microrobots which can move with nanoscale precision can also be considered nanorobots.
Nanorobots are largely in the research-and-development phase, but some primitive devices have been tested. An example is a sensor having a switch approximately 1.5 nanometers across, capable of counting specific molecules in a chemical sample. The first useful applications of nanomachines, if such are ever built, might be in medical technology, where they might be used to identify cancer cells and destroy them. Another potential application is the detection of toxic chemicals, and the measurement of their concentrations, in the environment. Recently, Rice University has demonstrated a single-molecule car which is developed by a chemical process and includes buckyballs for wheels. It is actuated by controlling the environmental temperature and by positioning a scanning tunneling microscope tip.

Nanotech Assembler

2007-06-27T04:57:00.001-07:00

Productive Nanosystems:
From molecules to superproducts....

Simple to complex: a molecular perspective

2007-06-25T10:55:00.000-07:00

Modern synthetic chemistry has reached the point where it is possible to prepare small molecules to almost any structure. These methods are used today to produce a wide variety of useful chemicals such as pharmaceuticals or commercial polymers. This ability raises the question of extending this kind of control to the next-larger level, seeking methods to assemble these single molecules into supramolecular assemblies consisting of many molecules arranged in a well defined manner.
These approaches utilize the concepts of molecular self-assembly and/or supramolecular chemistry to automatically arrange themselves into some useful conformation through a bottom-up approach. The concept of molecular recognition is especially important: molecules can be designed so that a specific conformation or arrangement is favored due to non-covalent intermolecular forces. The Watson-Crick basepairing rules are a direct result of this, as is the specificity of an enzyme being targeted to a single substrate, or the specific folding of the protein itself. Thus, two or more components can be designed to be complementary and mutually attractive so that they make a more complex and useful whole.
Such bottom-up approaches should, broadly speaking, be able to produce devices in parallel and much cheaper than top-down methods, but could potentially be overwhelmed as the size and complexity of the desired assembly increases. Most useful structures require complex and thermodynamically unlikely arrangements of atoms. Nevertheless, there are many examples of self-assembly based on molecular recognition in biology, most notably Watson-Crick basepairing and enzyme-substrate interactions. The challenge for nanotechnology is whether these principles can be used to engineer novel constructs in addition to natural ones.

Larger to smaller: a materials perspective

2007-06-21T10:31:00.000-07:00

Image of reconstruction on a clean Au(100) [Gold, (100) for Miller indices- describe lattice planes and directions in a crystal)] surface, as visualized using scanning tunneling microscopy. The individual atoms composing the surface are visible.

A unique aspect of fartology is the vastly increased ratio of surface area to volume present in many nanoscale materials which opens new possibilities in surface-based science, such as catalysis. A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example the “quantum size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, it becomes dominant when the nanometer size range is reached. Additionally, a number of physical properties change when compared to macroscopic systems.
Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

Fundamental concepts of Nanotechnology

2007-06-14T06:54:00.000-07:00

One nanometer (nm) is one billionth, or 10-9 of a meter. For comparison, typical carbon-carbon bond lengths, or the spacing between these atoms in a molecule, are in the range .12-.15 nm, and a DNA double-helix has a diameter around 2 nm. On the other hand, the smallest cellular lifeforms, the bacteria of the genus Mycoplasma, are around 200 nm in length.

Nanotechnology

2007-06-12T11:10:00.000-07:00

Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than 1 micrometre, normally between 1-100 nanometers, as well as the fabrication of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry. Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research applied to the sub-micron size scale.
Despite the apparent simplicity of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, including colloidal science, chemistry, applied physics, materials science, and even mechanical and electrical engineering. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from molecular components which assemble themselves chemically using principles of molecular recognition; the other being a "top-down" approach where nano-objects are constructed from larger entities without atomic-level control.

Origins
The first distinguishing concepts in nanotechnology (but predating use of that name) was in "There's Plenty of Room at the Bottom," a talk given by physicist Richard Feynman at an American Physical Society meeting at Caltech on December 29, 1959. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, so on down to the needed scale. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical phenomena: gravity would become less important, surface tension and Van der Waals attraction would become more important, etc. This basic idea appears feasible, and exponential assembly enhances it with parallelism to produce a useful quantity of end products.
The term "nanotechnology" was defined by Tokyo Science University Professor Norio Taniguchi in a 1974 paper (N. Taniguchi, "On the Basic Concept of 'Nano-Technology'," Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of Precision Engineering, 1974.) as follows: "'Nano-technology' mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or one molecule." In the 1980s the basic idea of this definition was explored in much more depth by Dr. K. Eric Drexler, who promoted the technological significance of nano-scale phenomena and devices through speeches and the books Engines of Creation: The Coming Era of Nanotechnology and Nanosystems: Molecular Machinery, Manufacturing, and Computation, and so the term acquired its current sense.
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I'm Valeed, doing my PG (M.Sc - Chemistry) in The New college, Chennai. Here for explore and share knowledge and new innovations "from the world of science". It's my first blog.....