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Nucleation in atomic crystallization remains poorly understood, despite advances in classical nucleation theory. The nucleation process has been described to involve a nonclassical mechanism that includes a spontaneous transition from disordered to crystalline states, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporal resolution shows that the early stage of atomic crystallization proceeds through dynamic structural fluctuations between disordered and crystalline states, rather than through a single irreversible transition. Our experimental and theoretical analyses support the idea that structural fluctuations originate from size-dependent thermodynamic stability of the two states in atomic clusters. These findings, based on dynamics in a real atomic system, reshape and improve our understanding of nucleation mechanisms in atomic crystallization. [ABSTRACT FROM AUTHOR]

This article reports that South Korean cloning researcher Woo Suk Hwang has asked the journal "Science" to retract his celebrated paper reporting the creation of embryonic stem (ES) cells from 11 patients suffering from diabetes, an immune system disease, and spinal cord injury. But as "Science" went to press, Hwang was insisting that, contrary to the claims of a collaborator, his team succeeded in creating these patient-specific stem cells and that they intend to replicate their results. Pressure on Hwang and his group has been growing as scientists and the press have raised questions about the evidence presented in the paper, first published online in May this year. In the 2005 paper, another group led by Hwang reported that they had established 11 ES cell lines from embryos cloned from patients, a step toward someday making genetically matched replacement tissue. But in early December 2005 on a Korean Web site, an anonymous writer, who claims to be a life scientist, pointed out duplications in some of the photographs of ES cells published in the 2005 paper. According to a "Science" statement, a few hours later Hwang notified "Science"'s editorial offices of what he called an unintentional error that led to about 4 pictures being used redundantly.

The article informs that embattled Korean stem cell scientist Woo Suk Hwang and his university have bowed to pressure for an investigation into a growing list of questions about a landmark paper he and colleagues published in Science in June 2005. Meanwhile, stem cell researchers elsewhere are worried about the possible fallout. The lab's as-yet-unreplicated feat of creating human embryonic stem (ES) cell lines that match the DNA of patients inspired a global ramp-up in stem cell efforts. Such ES cell lines might one day provide replacement cells genetically matched to a patient suffering from Parkinson's disease or diabetes. The latest revelations center on the DNA fingerprinting in the paper's supplementary online material first posted on 19 May 2005; the fingerprinting data purportedly show that the ES cells are genetically identical to the patients. There are also new allegations about another set of images in the online material that Woo Suk Hwang last week told editors at Science had been erroneously duplicated.