Third on Science's list of 2004 breakthroughs was the cloning of human embryos by South Korean researcher Woo San Hwang and his colleagues. The work was not an attempt to genetically duplicate a human. Instead, the researchers hoped to make embryonic stem cells for research purposes. Although many other mammals have been cloned, the work was the first to demonstrate that cloning techniques would work with human cells. 

Following are the rest of Science's 2004 selections. 

4. U.S. and Austrian scientists created a new form of condensate（冷凝物）, an ultracold gas that slips into a quantum state where a group of atoms act as a single superatom. The achievement was notable because it used fermions（费米子）, a class of atoms with a nuclear structure that makes it difficult to create a condensate.

5. Scientists discovered that "junk DNA," the base pairs between known genes in the human genetic structure, play an important role. Several research teams have found that DNA between genes helps determine how vigorously and often the genes are activated and shapes the coding for protein production. 

6. Astronomers discovered a pair of neutron stars（中子星） locked in orbit of each other and spewing out beams of radiation. Both objects are pulsars（脉冲星）, rapidly flickering on and off with pulses of energy. One object is pulsing at the rate of 44 times a second. By studying the radiation, astronomers hope for the first time to learn about the density of matter within a neutron star. 

7. Naturalists tracking the fate of wild species worldwide reported bad news. A survey of amphibians（两栖动物） found that of 5,700 known species, about 30% were at risk of extinction. A survey in the United Kingdom found that butterflies, songbirds and native plant species are all losing ground in the battle for species survival. 

8. It is one of the most common and universally known substances, but researchers are still learning more about water. Several teams of researchers made new discoveries about how water molecules（分子） bind together and how electrons（电子） and protons（质子） dissolve in water. Some of the findings are questioned and Science noted: "Water still gives researchers much to scratch their heads about." 

9. A new form of research and aid is creating "a revolution in public health," said Science. The partnership of public and private organizations worldwide is changing the way drugs are developed, tested and distributed to the poorest nations on Earth, the journal said. Researchers tallied at least 92 public-private partnerships worldwide attacking such diseases as malaria, tuberculosis and HIV. 

10. Researchers have developed techniques to identify genes in ocean water or in specimens recovered from deep underground. Thousands of new genes have been found. By sequencing these genes, researchers hope to identify news species and, perhaps, learn how organisms survive in harsh and forbidding locations on Earth.

By Paul Recer / from the Associated Pressliuxuepaper.com