Showing Spotlights 1921 - 1928 of 2140 in category (newest first):
Current medical and biological fluorescent imaging is limited by the use of dye markers, which are not photostable. The dyes can break down under photoexcitation, room light or higher temperatures. The observation of strong visible emission in porous silicon therefore has triggered substantial interest in exploring the synthesis and characterization of silicon nanoparticles. Due to their biocompatibility, high photoluminescence quantum efficiency and stability against photobleaching, silicon nanoparticles are expected to be an ideal candidate for replacing fluorescent dyes in many biological assays and fluorescence imaging techniques. For instance, they have been proposed as better quantum dots for in vivo applications, potentially replacing quantum dots of highly toxic cadmium. Different synthetic and physical methods have been used to prepare silicon nanoparticles. However, the yields of nanoparticles from these methods are very low and an HF (hydrofluoric acid) etching process is often necessary to obtain photoluminescent, hydrogen-terminated silicon nanoparticles. Now, researchers have developed a new solution route for the production of macroscopic amounts of hydrogen terminated silicon nanoparticles without hazardous material handling. This synthesis route is simple and thus offers great opportunity for scaled-up preparation of semiconductor materials.
Feb 19th, 2007
It's not quite like in Isaac Asimov's science fiction classic Fantastic Voyage, where five people travel in a submarine inside a person's blood stream, but scientists have talked for quite some time about micro and nanorobotic devices that can travel inside the human body and carry out a host of complex medical procedures such as monitoring, drug delivery and cell repair. Recent developments in micro- and nanoscale engineering have led to realization of various miniature mobile robots. It turns out that the most significant bottleneck for further miniaturization of mobile robots down to micrometer scale is the miniaturization of the on-board actuators and power sources required for mobility. Nature has already provided remarkable solutions to this problem by evolving chemically powered molecular motors. Such biomotors seem to be one of the most promising choices for on-board actuation. They are advantageous over man-made actuators because they are much smaller in size and are capable of producing more complicated motions. More importantly, they convert chemical energy to mechanical energy very efficiently. However, the major drawback of biomotors is that isolating and reconstituting them are complicated tasks with low yield and it is difficult to interface them with electronic circuitry. This has led scientists to successfully experiment with a new approach by using flagellar motors (the propulsion system of bacteria), still inside the intact cells, as actuators.
Feb 16th, 2007
The nanoworld cannot be portrayed with a camera, nor can it be seen even with the most powerful optical microscope. Only special instruments have access to images of the nanoworld. A fascinating new exhibition "Blow-up: images from the nanoworld" in Modena/Italy shows the work of scientists associated with the National Center on Nanostructures and Biosystems at Surfaces in Modena, Italy, headed by Elisa Molinari. The images have been manipulated in a variety of ways by photographer, Lucia Covi. Covi is particularly sensible to the aesthetic paradigms of scientists: her gaze thus grasps essential aspects of the portrayed objects and allows her to shine them with a new light, as they are revealed now. This exhibition brings to the public images that are usually accessible to few, because they remain confined in the research laboratories, on the scientists' desks. The images are stills that, over time, have been put together from different framings, and that we can look at thanks to the mediation of machines. Some of them represent exceptional events, outstanding results that ended on the cover of scientific journals. Others were born from everyday research. All of them show a landscape that is being unraveled by scientists, scenery that is very different from the one we can see in the media, largely obtained through computer graphics and "artistic" interpretations, when not directly borrowed from science fiction.
Dec 29th, 2006
Non-volatile random access memory (NVRAM) is the general name used to describe any type of random access memory which does not lose its information when power is turned off. This is in contrast to the most common forms of random access memory today, DRAM and SRAM, which both require continual power in order to maintain their data. NVRAM is a subgroup of the more general class of non-volatile memory types, the difference being that NVRAM devices offer random access, as opposed to sequential access like hard disks. The best-known form of NVRAM memory today is flash memory, which is found in a wide variety of consumer electronics, including memory cards, digital music players, digital cameras and cell phones. One problem with flash memory is its relatively low speed. Also, as chip designers and engineers reach size barriers in downscaling the size of such chips, the research focus shifts towards new types of nanomemory. Molecular-scale memory promises to be low-power and high frequency: imagine a computer that boots up immediately on powering up and that writes data directly onto its hard drive making saving a thing of the past. Researchers are designing the building blocks for this type of memory device using telescoping carbon nanotubes as high-speed, low power microswitches. The design would allow the use of these binary or three-stage switches to become part of molecular-scale computers.
Feb 14th, 2007
For several years now, researchers have documented the many intriguing mechanical and electrical properties of carbon nanotubes (CNTs). Some researchers have focused on the optical properties of CNTs. Studying the passive optical response of CNTs they have revealed the manner in which CNTs' optical properties are related to shape and structure of CNTs. It was found that periodic CNT arrays exhibit Bragg diffraction, photonic bandgap properties, and plasmonic resonance; nonperiodic CNT arrays interact with light waves similarly to the way in which radio antennae interact with radio waves. In conventional radio antenna theory an antenna acts as a resonator of the external electromagnetic radiation. Scientists now have demonstrated that a single multiwall carbon nanotube (MWCNT) acts as an optical antenna, whose response is fully consistent with conventional radio antenna theory.
Feb 13th, 2007
Gold nanoparticles have gained significant prominence in the design and development of nanoscale devices and nanosensors. The ubiquitous place of gold in nanoscience stems from its unique chemical property of serving in the unoxidized state at the nanoparticulate level. In sharp contrast, most of the surfaces of the less-noble metals are susceptible to oxidation to a depth of several nanometers or more, often obliterating the nanoscale properties. The high surface reactivity of gold nanoparticles, coupled with their biocompatible properties, has spawned major interest in the utility of gold nanoparticles for in vivo molecular imaging and therapeutic applications. The core of nanomedicine embodies high surface area and the size relationship of nanoparticles to cellular domains so that individual cells can be targeted for diagnostic imaging or therapy of cancer and other diseases. The development of biocompatible and non-toxic nanoparticles is of paramount importance for their utility in nanomedicine applications. Despite the huge potential for gold nanoparticle-based nanomedicinal products, nontoxic gold nanoparticle constructs and formulations that can be readily administered are still rare. Hypothesizing that the ability of plants to absorb and assimilate metals will provide opportunities to utilize plant extracts as nontoxic vehicles to stabilize and deliver nanoparticles for in vivo nanomedicinal applications, researchers now have used Gum Arabic as a plant-derived, nontoxic construct for stabilizing gold nanoparticles. The development of readily injectable, in vivo stable and non-toxic gold nanoparticulate vectors, especially built from currently accepted human food ingredients, would be pivotal in their many uses (e.g. in vivo sensors, photoactive agents for optical imaging, drug carriers, contrast enhancers in computer tomography, X-ray absorbers).
Feb 12th, 2007
There is currently no cure for Alzheimer's disease and its ultimate cause is still unknown. The disease affects an estimated 4.5 million people in the United States alone. That figure is expected to rise dramatically as the population ages, experts predict. Genetic factors are known to be important in causing the disease, and dominant mutations in different genes have been identified that account for both early onset and late onset Alzheimer's. For a number of years, researchers have been working to alleviate neurodegenerative disorders such as Alzheimer's or Parkinson's disease through gene therapy. In this type of treatment, a gene's DNA is delivered to the neurons in individual cells, allowing them to produce their own therapeutic proteins. Gene therapy typically aims to supplement a defective mutant allele (the location of DNA codings on a chromosome) with a functional one. Currently, the most common carrier vehicles to deliver the therapeutic genes to the patient's target cells are viruses that have been genetically altered to carry normal human DNA. These viruses infect cells, deposit their DNA payloads, and take over the cells' machinery to produce the desirable proteins. One problem with this method is that the human body has developed a very effective immune system that protects it from viral infections. Thanks to advances in nanotechnological fabrication techniques, the development of nonviral nanocarriers for gene delivery has become possible. This is attractive due to the potential for improved safety, reduced ability to provoke an immune response, ease of manufacturing and scale up, and the ability to accommodate larger DNA molecules compared to virus-based delivery tools.
Feb 9th, 2007
Without doubt, nanotechnology is having a major impact on medicine and the treatment of disease, notably in imaging and targeted drug delivery. Nanotechnology promises us a radically different medicine than the cut, poke and carpet bomb (think chemo therapy) medicine of today. The two major differences of nanomedicine will be a) the tools it uses - the main workhorse will be multifunctional nanoparticles and b) it will enable a perfectly targeted and individual treatment: organs and bones, really any body tissue, can be diagnosed and treated on a cell by cell basis with precise dosing and monitoring through the use of biomolecular sensors. Notwithstanding the huge amount of research going into this field, nanomedicine by and large is still in the basic research stage. Some fundamental problems like the targeting of nanoparticles in vivo, the transport of unstable drugs, and the dosage control of drug-carrying nanoparticles lead some scientists to think even one step further. Rather than delivering external drugs into the body, they conceptualize "pseudo-cell" nanofactories that work with raw ingredients already in the body to manufacture the proper amount of drug in-situ under the control of a molecular biosensor.
Feb 8th, 2007