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Monday, August 18, 2008

Carbon nanotubes and Applications

Climatic change on carbon nanotubes – Carbon nanotubes have many characteristics that promise to revolutionize the world of structural materials. There are different ways to grow carbon nanotubes, especially the CVD technique, which allows obtaining SWCNT’s on a silicon surface. These SWCNT can be carried from the silicon surface to another surface, as HOPG, without suffering changes on their properties. That means nanomanipulation of carbon nanotubes.
Carbon Nanotubes
The intent of this section is to convey a general understanding of what carbon Nanotubes are, how they are produced, their many unique and interesting properties, markets, and applications.

In 1980 we knew of only three forms of carbon, namely diamond, graphite, and amorphous carbon. Today we know there is a whole family of other forms of carbon. The first to be discovered was the hollow, cage-like buckminsterfullerene molecule - also known as the buckyball, or the C60 fullerene. There are now thirty or more forms of fullerenes, and also an extended family of linear molecules, carbon nanotubes. C60 is the first spherical carbon molecule, with carbon atoms arranged in a soccer ball shape. In the structure there are 60 carbon atoms and a number of five-membered rings isolated by six-membered rings. The second, slightly elongated, spherical carbon molecule in the same group resembles a rugby ball, has seventy carbon atoms and is known as C70. C70’s structure has extra six-membered carbon rings, but there are also a large number of other potential structures containing the same number of carbon atoms. Their particular shapes depend on whether five-membered rings are isolated or not, or whether seven-membered rings are present. Many other forms of fullerenes up to and beyond C120 have been characterized, and it is possible to make other fullerene structures with five-membered rings in different positions and sometimes adjoining one another. The important fact for nanotechnology is that useful dopant atoms can be placed inside the hollow fullerene ball. Atoms contained within the fullerene are said to be endohedral. Of course they can also be bonded to fullerenes outside the ball as salts, if the fullerene can gain electrons. Endohedral fullerenes can be produced in which metal atoms are captured within the fullerene cages. Theory shows that the maximum electrical conductivity is to be expected for endohedral metal atoms, which will transfer three electrons to the fullerene. Fullerenes can be dispersed on the surface as a monolayer. That is, there is only one layer of molecules, and they are said to be mono dispersed. Provided fullerenes can be placed in very specific locations, they may be aligned to form a fullerene wire. Systems with appropriate material inside the fullerene ball are conducting and are of particular interest because they can be deposited to produce bead-like conducting circuits. Combining endohedrally doped structures with non-doped structures changes the actual composition of a fullerene wire, so that it may be tailored in-situ during patterning. Hence within a single wire, insulating and conducting regions may be precisely defined. One-dimensional junction engineering becomes realistic with fullerenes. Possibly more important than fullerenes are Carbon nanotubes, which are related to graphite. The molecular structure of graphite resembles stacked, one-atom-thick sheets of chicken wire - a planar network of interconnected hexagonal rings of carbon atoms. In conventional graphite, the sheets of carbon are stacked on top of one another, allowing them to easily slide over each other. That is why graphite is not hard, but it feels greasy, and can be used as a lubricant. When graphene sheets are rolled into a cylinder and their edges joined, they form CNTs. Only the tangents of the graphitic planes come into contact with each other, and hence their properties are more like those of a molecule. CNTs come in a variety of diameters, lengths, and functional group content. CNTs today are available for industrial applications in bulk quantities up metric ton quantities from Cheap Tubes. Several CNT manufacturers have >100 ton per year production capacity for multi walled nanotubes. A nanotube may consist of one tube of graphite, a one-atom thick single-wall nanotube, or a number of concentric tubes called multiwalled nanotubes. When viewed with a transmission electron microscope these tubes appear as planes. Whereas single walled nanotubes appear as two planes, in multi walled nanotubes more than two planes are observed, and can be seen as a series of parallel lines. There are different types of CNTs, because the graphitic sheets can be rolled in different ways. The three types of CNTs are Zigzag, Armchair, and Chiral. It is possible to recognize zigzag, armchair, and chiral CNTs just by following the pattern across the diameter of the tubes, and analyzing their cross-sectional structure. Multi walled nanotubes can come in an even more complex array of forms, because each concentric single-walled nanotube can have different structures, and hence there are a variety of sequential arrangements. The simplest sequence is when concentric layers are identical but different in diameter. However, mixed variants are possible, consisting of two or more types of concentric CNTs arranged in different orders. These can have either regular layering or random layering. The structure of the nanotube influences its properties - including electrical and thermal conductivity, density, and lattice structure. Both type and diameter are important. The wider the diameter of the nanotube, the more it behaves like graphite. The narrower the diameter of the nanotube, the more its intrinsic properties depends upon its specific type.
The special nature of carbon combined with the molecular perfection of single-walled nanotubes to endow them with exceptional material properties, such as very high electrical and thermal conductivity, strength, stiffness, and toughness. No other element in the periodic table bonds to itself in an extended network with the strength of the carbon-carbon bond. The delocalized pi-electron donated by each atom is free to move about the entire structure, rather than remain with its donor atom, giving rise to the first known molecule with metallic-type electrical conductivity. Furthermore, the high-frequency carbon-carbon bonds vibrations provide an intrinsic thermal conductivity higher than even diamond. In most conventional materials, however, the actual observed material properties - strength, electrical conductivity, etc. - are degraded very substantially by the occurrence of defects in their structure. For example, high-strength steel typically fails at only about 1% of its theoretical breaking strength. CNTs, however, achieve values very close to their theoretical limits because of their molecular perfection of structure.
This aspect is part of the unique story of CNTs. CNTs are an example of true nanotechnology: they are under 100 nanometers in diameter, but are molecules that can be manipulated chemically and physically in very useful ways. They open an incredible range of applications in materials science, electronics, chemical processing, energy management, and many other fields. CNTs have extraordinary electrical conductivity, heat conductivity, and mechanical properties. They are probably the best electron field-emitter possible. They are polymers of pure carbon and can be reacted and manipulated using the well-known and the tremendously rich chemistry of carbon. This provides opportunity to modify their structure, and to optimize their solubility and dispersion. Very significantly, CNTs are molecularly perfect, which means that they are normally free of property-degrading flaws in the nanotube structure. Their material properties can therefore approach closely the very high levels intrinsic to them. These extraordinary characteristics give CNTs potential in numerous applications.
a) Field Emission
CNTs are the best known field emitters of any material. This is understandable, given their high electrical conductivity, and the incredible sharpness of their tip. The smaller the tip’s radius of curvature, the more concentrated the electric field will be, leading to increased field emission. The sharpness of the tip also means that they emit at especially low voltage, an important fact for building low-power electrical devices that utilize this feature. CNTs can carry an astonishingly high current density. Furthermore, the current is extremely stable. An immediate application of this behavior receiving considerable interest is in field-emission flat-panel displays. Instead of a single electron gun, as in a traditional cathode ray tube display, in CNT-based displays there is a separate nanotube electron gun for each individual pixel in the display. Their high current density, low turn-on and operating voltages, and steady, long-lived behavior make CNTs very attractive field emitters in this application. Other applications utilizing the field-emission characteristics of CNTs include general types of low-voltage cold-cathode lighting sources, lightning arrestors, and electron microscope sources.
b) Conductive or Reinforced Plastics
Much of the history of plastics over the last half-century has involved their use as a replacement for metals. For structural applications, plastics have made tremendous headway, but not where electrical conductivity is required, because plastics are very good electrical insulators. This deficiency is overcome by loading plastics up with conductive fillers, such as carbon black and larger graphite fibers. The loading required to provide the necessary conductivity using conventional fillers is typically high, however, resulting in heavy parts, and more importantly, plastic parts whose structural properties are highly degraded. It is well-established that the higher the aspect ratio of the filler particles, the lower the loading required to achieve a given level of conductivity.
CNTs are ideal in this sense, since they have the highest aspect ratio of any carbon fiber. In addition, their natural tendency to form ropes provides inherently very long conductive pathways even at ultra-low loadings. Applications that exploit this behavior of CNTs include EMI/RFI shielding composites; coatings for enclosures, gaskets, and other uses such as electrostatic dissipation; antistatic materials, transparent conductive coatings; and radar-absorbing materials for stealth applications.
A lot of automotive plastics companies are using CNTs as well. CNTs have been added into the side mirror plastics on automobiles in the US since the late 1990s. I have seen forecasts predicting that GM alone will consume over 500 pounds of CNT masterbatches in 2006 for using in all areas of automotive plastics. Masterbatches normally contain 20 wt% cnts which are already very well dispersed. Manufacturers then need to perform a “let down” or dilution procedure prior to using the masterbatch in production
c) Energy Storage
CNTs have the intrinsic characteristics desired in material used as electrodes in batteries and capacitors, two technologies of rapidly increasing importance. CNTs have a tremendously high surface area, good electrical conductivity, and very importantly, their linear geometry makes their surface highly accessible to the electrolyte.
Research has shown that CNTs have the highest reversible capacity of any carbon material for use in lithium ion batteries. In addition, CNTs are outstanding materials for super capacitor electrodes and are now being marketed for this application. CNTs also have applications in a variety of fuel cell components. They have a number of properties, including high surface area and thermal conductivity, which make them useful as electrode catalyst supports in PEM fuel cells. Because of their high electrical conductivity, they may also be used in gas diffusion layers, as well as current collectors. CNTs' high strength and toughness-to-weight characteristics may also prove valuable as part of composite components in fuel cells that are deployed in transport applications, where durability is extremely important
d) Conductive Adhesives and Connectors
The same properties that make CNTs attractive as conductive fillers for use in electromagnetic shielding, ESD materials, etc., make them attractive for electronics packaging and interconnection applications, such as adhesives, potting compounds, coaxial cables, and other types of connectors.
e) Molecular Electronics
The idea of building electronic circuits out of the essential building blocks of materials - molecules - has seen a revival the past few years, and is a key component of nanotechnology. In any electronic circuit, but particularly as dimensions shrink to the nanoscale, the interconnections between switches and other active devices become increasingly important. Their geometry, electrical conductivity, and ability to be precisely derived, make CNTs the ideal candidates for the connections in molecular electronics. In addition, they have been demonstrated as switches themselves.
There are already companies such as Nantero from Woburn, MA that are already making CNT based non-volitle random access memory for PC’s. A lot of research is being done to design CNT based transistors as well.
f) Thermal Materials
The record-setting anisotropic thermal conductivity of CNTs is enabling many applications where heat needs to move from one place to another. Such an application is found in electronics, particularly heat sinks for chips used in advanced computing, where uncooled chips now routinely reach over 100oC. The technology for creating aligned structures and ribbons of CNTs [D.Walters, et al., Chem. Phys. Lett. 338, 14 (2001)] is a step toward realizing incredibly efficient heat conduits. In addition, composites with CNTs have been shown to dramatically increase their bulk thermal conductivity, even at very small loadings.
g) Structural Composites
The superior properties of CNTs are not limited to electrical and thermal conductivities, but also include mechanical properties, such as stiffness, toughness, and strength. These properties lead to a wealth of applications exploiting them, including advanced composites requiring high values of one or more of these properties.
h) Fibers and Fabrics
Fibers spun of pure CNTs have recently been demonstrated and are undergoing rapid development, along with CNT composite fibers. Such super-strong fibers will have many applications including body and vehicle armor, transmission line cables, woven fabrics and textiles.
i) Catalyst Support
CNTs intrinsically have an enormously high surface area; in fact, for single walled nanotubes every atom is not just on one surface - each atom is on two surfaces, the inside and the outside of the nanotube! Combined with the ability to attach essentially any chemical species to their sidewalls this provides an opportunity for unique catalyst supports. Their electrical conductivity may also be exploited in the search for new catalysts and catalytic behavior.
j) CNT Ceramics
A ceramic material reinforced with carbon nanotubes has been made by materials scientists at UC Davis. The new material is far tougher than conventional ceramics, conducts electricity and can both conduct heat and act as a thermal barrier, depending on the orientation of the nanotubes. Ceramic materials are very hard and resistant to heat and chemical attack, making them useful for applications such as coating turbine blades, but they are also very brittle.
The researchers mixed powdered alumina (aluminum oxide) with 5 to 10 percent carbon nanotubes and a further 5 percent finely milled niobium. The researchers treated the mixture with an electrical pulse in a process called spark-plasma sintering. This process consolidates ceramic powders more quickly and at lower temperatures than conventional processes.
The new material has up to five times the fracture toughness -- resistance to cracking under stress -- of conventional alumina. The material shows electrical conductivity seven times that of previous ceramics made with nanotubes. It also has interesting thermal properties, conducting heat in one direction, along the alignment of the nanotubes, but reflecting heat at right angles to the nanotubes, making it an attractive material for thermal barrier coatings.
k) Biomedical Applications
The exploration of CNTs in biomedical applications is just underway, but has significant potential. Since a large part of the human body consists of carbon, it is generally thought of as a very biocompatible material. Cells have been shown to grow on CNTs, so they appear to have no toxic effect. The cells also do not adhere to the CNTs, potentially giving rise to applications such as coatings for prosthetics and surgical implants. The ability to functionalize the sidewalls of CNTs also leads to biomedical applications such as vascular stents, and neuron growth and regeneration. It has also been shown that a single strand of DNA can be bonded to a nanotube, which can then be successfully inserted into a cell; this has potential applications in gene therapy.
l) Air, Water and Gas Filtration
Many researchers and corporations have already developed CNT based air and water filtration devices. It has been reported that these filters can not only block the smallest particles but also kill most bacteria. This is another area where CNTs have already been commercialized and products are on the market now. Someday CNTs may be used to filter other liquids such as fuels and lubricants as well.
A lot of research is being done in the development of CNT based air and gas filtration. Filtration has been shown to be another area where it is cost effective to use CNTs already. The research I’ve seen suggests that 1 gram of MWNTs can be dispersed onto 1 sq ft of filter media. Manufacturers can get their cost down to 35 cents per gram of purified MWNTs when purchasing ton quantities.
m) Other Applications
Some commercial products on the market today utilizing CNTs include stain resistant textiles, CNT reinforced tennis rackets and baseball bats. Companies like Kraft foods are heavily funding cnt based plastic packaging. Food will stay fresh longer if the packaging is less permeable to atmosphere. Coors Brewing company has developed new plastic beer bottles that stay cold for longer periods of time. Samsung already has CNT based flat panel displays on the market. A lot of companies are looking forward to being able to produce transparent conductive coatings and phase out ITO coatings. Samsung uses align SWNTs in the transparent conductive layer of their display manufacturing process.

Showing the light of new era for mechanical engineers: get into nanotechnology

It's not much,if we say in all section of science ,Engineering and Technology - Nanotechnology is showing the light of new era,
The term 'mechanical engineering' generally describes the branch of engineering that deals with the design and construction and operation of machines and other mechanical systems. Students training to become engineering professionals have to delve into subjects such as instrumentation and measurement, thermodynamics, statics and dynamics, heat transfer, strengths of materials and solid mechanics with instruction in CAD and CAM, energy conversion, fluid dynamics and mechanics, kinematics, hydraulics and pneumatics, engineering design and so on. If you are currently doing coursework in mechanical engineering, better add nanotechnology courses to your core curriculum.
Back in April, the American Society of Mechanical Engineers (ASME) convened more than 120 engineering and science leaders from 19 countries representing industry, academia and government in Washington, DC to imagine what mechanical engineering will become between now and 2028. They identified the elements of a shared vision that mechanical engineering will collaborate as a global profession over the next 20 years to develop engineering solutions that foster a cleaner, healthier, safer and sustainable world.
One of the key conclusions from this Global Summit on the Future of Mechanical Engineering was that nanotechnology and biotechnology will dominate technological development in the next 20 years and will be incorporated into all aspects of technology that affect our lives on a daily basis. Bio- and nanotechnologies will provide the building blocks that future engineers will use to solve pressing problems in diverse fields including medicine, energy, water management, aeronautics, agriculture and environmental management.
"Mechanical engineers over the next two decades will be called upon to develop technologies that foster a cleaner, healthier, safer and sustainable global environment" reads one of the key statements from the summit's final report "2028 Vision for Mechanical Engineering" (pdf download, 1.5 MB).
As it is becoming more and more obvious that biotechnologies and nanotechnologies lie at the core of technological innovation, many of the greatest opportunities for mechanical engineers lie in the intersection of these two fields of technology. If you follow this argument, than mechanical engineering will become THE field to get into if you want to make the world a better place.
Among the many interesting trends and ideas captured by the ASME report are two particularly intriguing conclusions: the curriculum for mechanical engineers must be restructured to include addressing the needs of destitute people; and because globalization has made the world 'flat', a convergence of emerging technologies will drastically change how engineers work and create a renaissance for engineering entrepreneurs that actually strengthens local operations.
Developing sustainability
The report states that one of the most critical challenges facing mechanical engineers is developing engineering solutions that will foster a cleaner, healthier, safer and sustainable world.
One of the panelists, Maria Prieto-Laffargue, President-elect, World Federation of Engineering Organisations, emphasized that the necessary tools to combat problems like poverty and many environmental issues already exist. What are needed are more and better engineering solutions that are tailored to specific places and situations.
Globally there is a huge market for mechanical engineering that serves the poorest among us. The ASME report estimates that, currently, around four billion people live on less than $2 per day. By 2030, almost two billion additional people are expected to populate the earth, ninety-five percent of them in developing or underdeveloped countries. "This large and growing population will need access to food and clean water, effective sanitation, energy, education, healthcare and affordable transportation."
(Just to take the example of clean water, and how nanotechnologies can address some of the problems, we have addressed this issue extensively in two previous Spotlights "Nanotechnology and water treatment" and "Water, nanotechnology's promises, and economic reality".)
The ASME panel argues that serving this population requires a restructuring of how engineers are taught to approach their profession. "This market is not populated by poor victims of circumstance, but resilient and creative entrepreneurs and potential customers. There is tremendous value in helping these people achieve a better quality of life. At present, most engineering schools do not address the needs of destitute people, even though many of these people live in industrialized countries. Yet, the needs of the underserved for engineering solutions are likely to increase as population grows. Teaching engineers how to develop locally appropriate engineering solutions for the underserved is a key to developing sustainably. For example, Engineers Without Borders is fostering sustainable development and teaching engineers valuable skills for the future."
Mechanical engineering in your basement?
"By 2028, advances in computer aided design, materials, robotics, nanotechnology and biotechnology will democratize the process of designing and creating new devices. Engineers will be able to design solutions to local problems. Individual engineers will have more latitude to design and build their devices using indigenous materials and labor " creating a renaissance for engineering entrepreneurs. The engineering workforce will change as more engineers work at home as part of larger decentralized engineering companies or as independent entrepreneurs."
Echoing a trend that already has taken shape among globally operating industrial companies, the ASME panel argues that emerging technologies in computer aided design (CAD), materials, robotics, nanotechnology and biotechnology will likely come together to transform how engineers work. "Faster processing and network speeds will soon allow future engineers to design entire products as a system rather than separate pieces. This will expand the capacities of engineers and enable more complex designs to be completed anywhere.
"Within 20 years, it is likely that home based personal fabricators will be economically attractive and available to anyone who wants them. Engineers will be able to act as independent operators interacting with colleagues around the world. They can design at home with advanced CAD systems or in collaboration with their global colleagues in virtual worlds. They will be able to use home-based fabrication technology to test many of their designs. Engineers of the future will have better tools to build careers as individual inventors, independent entrepreneurs and employees in distributed businesses that draw on engineering talent from around the world."
One panel member, futurist Rohit Talwar highlighted virtual worlds, like Second Life, as one of the new technologies transforming how we perceive reality. "Virtual worlds could soon become truly interactive environments for interacting with colleagues. Combined with advances in CAD systems, it will be possible for mechanical engineers to collaborate in immersive interactive environments where they can design collaboratively, test hypothesis, run models and simulations and observe their creations in three dimensions much as an engineer can observe a car being built with their colleagues on the shop floor."
As every mechanical engineer knows, change is hard to predict in a dynamic system. And the rate of change we are experiencing due to technological advances can appear frightening at times. Society with its institutions, cultures and economies moves at a much slower rate. But, as the ASME panel emphasized, the grand challenges of energy, water and food are great at the global scale and they must now be addressed.
"Whenever society has needed great contribution from mechanical engineering in the past, the profession has stepped up to the challenge. All that will be different in 2028 is the increased scope of the challenges and the increased number of people who will be living in a cleaner, healthier, safer and sustainable world because mechanical engineers believed they should."
Encouraging words. So, to all you mechanical engineering student: Brush up on your bio and nano and go make it happen

Turkcell signed a deal with Apple to sell iPhone 3G in Turkey

Turkcell said Monday it will bring Apple Inc.'s new iPhone 3G to Turkey later this year.

The iPhone 3G, which promises faster Web browsing than the year-old original model, went on sale July 11 in the United States and 21 other countries.

Turkcell, the leading wireless provider in Turkey with 35.4 million customers, did not give a specific date or price for the Turkish launch. Turkcell said the iPhone will be available to customers of both its prepaid plans and recurring subscription services.

The iPhone 3G continues to sweep across the world, an unstoppable force that…er…cannot be stopped. Aple’s added yet another partner to its extensive list of iPhone 3G cohorts: Turkish cell phone provider Turkcell.

While Apple had already made a deal with Vodafone to distribute the iPhone 3G in Turkey, it has now reached an understanding with Turkcell, which, with over 35 million subscribers, is the largest mobile operator in the country (that’s about half the population of Turkey). Turkcell offers both pre- and postpaid cell phone plans, and in a statement it promised to bring the iPhone 3G to both kind of customers later this year.

That’s a pretty sizeable chunk of potential iPhone customers, to be sure, as well as one that gives the iPhone a good foothold in the Middle East. While Turkey may not be among the twenty countries to get rolled out this very week, we imagine that we’ll be seeing it in the not too distant future.

discovered a switching mechanism in the mammals eye

A white albino pet or lab mouse isolated on a white background.
Light Receptors In Eye Play Key Role In Setting Biological Clock, Study Shows
Biologists at the University of Virginia have discovered a switching mechanism in the eye that plays a key role in regulating the sleep/wake cycles in mammals.

The new finding demonstrates that light receptor cells in the eye are central to setting the rhythms of the brain's primary timekeeper, the suprachiasmatic nuclei, which regulates activity and rest cycles.

"The finding is significant because it changes our understanding of how light input from the eye can affect activity and sleep patterns," said Susan Doyle, a research scientist at U.Va. and the study's lead investigator.

The finding appears in the current issue of the Proceedings of the National Academy of Sciences.

The U.Va. researchers discovered that they could reverse the "temporal niche" of mice – meaning that the animals' activity phase could be switched from their normal nocturnality, or night activity, to being diurnal, or day active.

The investigators did this by both reducing the intensity of light given to normal mice, and also creating a mutated line of mice with reduced light sensitivity in their eyes, which rendered them fully active in the day but inactive at night, a complete reversal of the normal activity/rest cycles of mice.

"This suggests that we have discovered an additional mechanism for regulating nocturnity and diurnity that is located in the light input pathways of the eye," Doyle said. "The significance of this research for humans is that it could ultimately lead to new treatments for sleep disorders, perhaps even eye drops that would target neural pathways to the brain's central timekeeper."

Biological clocks are the body's complex network of internal oscillators that regulate daily activity/rest cycles and other important aspects of physiology, including body temperature, heart rate and food intake. Besides sleep disorders, research in this field may eventually help treat the negative effects of shift work, aging and jet lag.

About 20 to 25 percent of U.S. workers are shift workers, many of whom have difficulty sleeping during the day when they are not working, and likewise find it hard to stay alert at night while on the job.

An estimated one in six people in the United States suffer from sleep disorders, including insomnia and excessive sleepiness. And as the U.S. population ages, a growing number of people are developing visual impairments that can result in sleep disorders.

"Currently, one in 28 Americans age 40 and over suffer from blindness or low vision, and this number is estimated to double in the next 15 years," Doyle said. "Our discovery of the switching mechanism in the eye has direct relevance with respect to the eventual development of therapies to treat circadian and sleep disorders in the visually impaired."

Doyle conducted her research with colleagues Tomoko Yoshikawa, a visiting scholar from Japan, and Holly Hillson, a U.Va. undergraduate student, in the laboratory of Michael Menaker, a leading researcher in the study of circadian rhythms. The work is funded by the National Institute for Mental Health.

New Mode Of Gene Regulation Discovered In Mammals
Researchers at the University of California, Santa Cruz, have discovered a type of gene regulation never before observed in mammals -- a "ribozyme" that controls the activity of an important family of genes in several different species.
The findings, published July 9 in the journal Nature, describe a new and surprising role for the so-called hammerhead ribozyme, an unusual molecule previously associated with obscure virus-like plant pathogens called viroids. The UCSC researchers found the ribozyme embedded within certain genes in mice, rats, horses, platypuses, and several other mammals. The genes are involved in the immune response and bone metabolism.

"The unique thing about these ribozymes is that they control the expression of the genes they're embedded in," said Monika Martick, a UCSC postdoctoral researcher and first author of the Nature paper.

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