A light-conducting silica nanowire wraps a beam of light around a strand of human hair. The nanowires are flexible and can be as slender as 50 nanometers in width, about one-thousandth the width of a hair. Credit: Limin Tong/Harvard University

Researchers Develop Nanoscale Fibers that are Thinner than the Wavelengths of Light they Carry

Researchers have developed a process to create wires only 50 nanometers (billionths of a meter) thick. Made from silica, the same mineral found in quartz, the wires carry light in an unusual way. Because the wires are thinner than the wavelengths of light they transport, the material serves as a guide around which light waves flow. In addition, because the researchers can fabricate the wires with a uniform diameter and smooth surfaces down to the atomic level, the light waves remain coherent as they travel. The smaller fibers will allow devices to transmit more information while using less space. The new material may have applications in ever-shrinking medical products and tiny photonics equipment such as nanoscale laser systems, tools for communications and sensors. Size is of critical importance to sensing—with more, smaller-diameter fibers packed into the same area, sensors could detect many toxins, for example, at once and with greater precision and accuracy.
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The cap carbonate contains disrupted and cemented textures similar to modern methane seeps underneath the seafloor. Photo by Ganqing Jiang at the University of California at Riverside.

Stable Isotope Data Provide Evidence for Huge Global Methane Release about 600 Million Years Ago

The Earth's most severe ice coverings are thought to have occurred about 600 million years ago, with frozen ice sheets covering much of the globe. Some scientists have suggested the oceans froze over during that time, resulting in a white planet or "snowball Earth" that would have reflected much of the Sun's heat and resulted in a condition of persistent extreme cold. Now, in a study published in the December 18 issue of the journal Nature, scientists describe new evidence from south China that explains how the planet might have thawed from its icy past. According to geologist Ganqing Jiang of the University of California at Riverside and lead author of the paper, the results point to the release of the powerful "greenhouse gas" methane, than to the release of carbon dioxide, which has been believed to be the mechanism by which the Earth re-warmed.
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The flow chart depicts the process that George Daley, Niels Geijsen and their colleagues followed to derive sperm-like cells, and eventually culture embryoid bodies, from embryonic mouse stem cells. Credit: Niels Geijsen, Massachusetts General Hospital / National Science Foundation

Researchers Engineer Mouse Embryonic Stem Cells to Form Sperm Cell Precursors

For the first time, researchers using laboratory techniques alone and no animal hosts have isolated sex-cell precursors from mouse embryos, coaxed the cells into a sperm-like form, used them to fertilize mouse eggs, and ultimately formed early-stage embryos. The research may offer a breakthrough tool for studies of embryonic cells and gene delivery, potentially helping scientists develop treatments for infertility and providing insight into the growth of certain tumors. The researchers, led by George Daley of Children's Hospital and the Dana Farber Cancer Institute in Boston and Niels Geijsen of Massachusetts General Hospital, also in Boston, report their findings in the December 10, 2003 Nature (online). Researchers are excited about stem cells because they can be coaxed into forming a number of tissues, from bone to lung, while mature cells are limited to their given role.
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Detecting Terrorists and Other Hidden Groups on the Internet

In the free-form clamor of the Internet's discussion groups and other public forums, Mark Goldberg, Malik Magdon-Ismail and their colleagues at Rensselaer Polytechnic Institute want to listen for the whispers of groups trying to stay hidden. Since September 11, 2001, some have feared that general-interest Internet forums could be co-opted by terrorist groups to camouflage coded messages. To detect those groups amidst unrelated Internet traffic, the RPI team has combined statistical learning algorithms, graph theory, social network theories and other methods to trace the patterns of message exchange and study how they evolve. From the evolving patterns alone—and without the need to read or understand the messages themselves—they can reverse-engineer the social networks that form naturally among discussants, as well as the messages exchanged among the members of groups that had been concealing their communications.
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