Week of October 17, 2005

Bracelet navigates Net

The proliferation of cell phones that have Internet access is making it possible for people to find information about the everyday objects around them, and the likely proliferation of Radio Frequency Identification (RFID) tags in consumer products would make it easy to link physical objects with digital information.

Researchers from the Massachusetts Institute of Technology have developed a hands-free and eyes-free system that allows people to find information about objects without having to actively scan them, use a keypad, or use a speech interface in noisy or socially awkward settings.

The system, dubbed ReachMedia, consists of a bracelet that reads radio frequency identification tags to detect objects the user is holding, an accelerometer to detect hand gestures and a cell phone that connects to the Internet, plays sounds when objects and gestures are recognized, and provides audio information about the object in hand.

A person could, for example, pick up a book to search for reviews of the book online. She would hear a sound from her phone indicating information was available about the book, and would use gestures -- a downward flick and right and left rotation -- to select or go to the previous or next menu item of available information.

(ReachMedia: On-the-Move Interaction with Everyday Objects, International Symposium on Wearable Computers (ISWC'05), Osaka Japan, October 18 - 21, 2005)

Nanotube bombs kill cancer

Scientists and medical professionals often use violent imagery to depict techniques of destroying cancer cells. A type of cancer-killing carbon nanotubes more than lives up to the language.

Researchers from the University of Delaware have found a way to detonate nanotubes that have been absorbed by cancer cells to blow up the cells. The microscopic explosions kill cells containing the nanotubes but leave surrounding cells intact.

Carbon nanotubes are rolled-up sheets of carbon atoms and are extremely small. Single-walled carbon nanotubes are typically one nanometer in diameter, or about 5,000 times smaller than a red blood cell.

The detonation nanotubes are filled with water molecules. When the nanotubes are exposed to laser light, the water molecules vaporize, which produces enough pressure to blow up the tubes and any cancer cells in the immediate vicinity. Other researchers have developed ways of causing cancer cells to absorb nanotubes, which would be required to use the method for treating patients.

The explosion method has a distinct advantage over using carbon nanotubes to deliver anti-cancer drugs to cancer cells, according to the researchers. The explosions destroy the nanotubes along with the cancer cells, greatly reducing the risk that the tubes themselves could cause problems in the body.

Scientists have previously detonated carbon nanotubes, but only in air (see Light flashes fire up nanotubes, TRN May 1/8, 2002) by exposure to flashes of light.

(Single Wall Carbon Nanotube Nanobombs Kill Cancer Cells, Nanobiotechnology, scheduled for publication Fall 2005)

Mesh networks best

There are many kinds of networks, both natural and artificial. Here's just a sampling: connections among computers, social relationships among people, and interactions among chemicals used in the body.

With the advent of the easily-studied Internet, scientists have begun mapping the general properties of networks. Many networks are scale-free, meaning they have a few heavily-linked central hubs -- large Internet sites, people with many social contacts, or chemicals involved in many reactions -- and many more nodes that contain just a few links.

Physicists from the University of Granada in Spain and Boston University have found that more homogenous entangled networks, which have no central hubs, are more efficient than scale-free networks.

Entangled networks are more resistant to errors and attacks, more amenable to search algorithms and provide more efficient communication. They are, however, not common in the natural world, in part because this type of structure does not tend to grow naturally over time.

Entangled network structures could make computer networks more efficient and improve our understanding of how the brain works.

(Entangled Networks, Synchronization, and Optimal Network Topology, Physical Review Letters, accepted in October 2005)

DNA sensor shines brightly

One way to detect a type of DNA that indicates disease is to form strands of DNA that contain fluorescent molecules and can combine with the DNA to be detected. Combined, or hybridized, DNA boosts the energy of the fluorescent molecules, causing them to emit more light.

Researchers from Johns Hopkins University have dramatically improved this type of DNA detection with a sensor whose fluorescent molecules do not emit any light before the disease, or target, DNA has been captured, and emit a lot of concentrated light when it is captured. This increases the sensitivity of the sensor 100 fold.

The sensor sandwiches the target DNA with a pair of DNA molecules. One of the pair contains the fluorescent molecule and the other contains a molecule that links to a layer of molecules coating a nanoscale speck of semiconductor material. Many captured DNA molecules can link to a single nanoparticle, concentrating the fluorescent markers. In addition, when the quantum dot is lit by a laser, it transfers energy to the fluorescent markers, making them still brighter.

The researchers tested the sensor by detecting DNA from ovarian tumors. The method could also be used to detect other molecules like proteins and peptides, and to detect the presence of several types of biological molecules at once, which could make for more accurate medical diagnosis.

(Single-Quantum-Dot-Based DNA NanoSensor, Nature Materials, November 2005)

Bits and pieces

A protein from insect joints yields a super elastic rubber that could make for better medical implants; grids of radio frequency identification (RFID) tags promise to help blind people navigate unfamiliar places; bent copper nanowires recover their original shape when heated, making them potentially useful ingredients of nanodevices like biosensors.