No other stem cell is more thoroughly understood than the blood, or hematopoietic, stem cell. These occasional and rare cells, scattered sparingly throughout the marrow and capable of replenishing an entire blood system, have been the driving force behind successful bone marrow transplants for decades.

Scientists, for the most part, have seen this as the hematopoietic stem cell’s (HSC) singular role: to remain in the bone marrow indefinitely and to replenish blood and immune system cells only when called upon.

Fertilizing the ocean with iron or other nutrients to cause large algal blooms, has been proposed as a possible solution to global warming because the growing algae absorb carbon dioxide but research performed at Stanford and Oregon State Universities and published in the Journal of Geophysical Research suggests that ocean fertilization may not be an effective method of reducing carbon dioxide in the atmosphere.

Astronomers at the University of Illinois have found the first clear evidence for a cradle in space where planets and moons form. The cradle, revealed in photographs taken with NASA’s Spitzer Space Telescope, consists of a flattened envelope of gas and dust surrounding a young protostar.

“We are seeing this object in the early stages of stellar birth,” said U. of I. astronomy professor Leslie Looney, the lead author of a paper accepted for publication in Astrophysical Journal Letters. “Eventually, the protostar will form into a star much like our sun, and the disk will form into planets and moons.”

Located about 800 light-years away in the constellation Cepheus, the object is obscured by dust and therefore invisible to the eye.

Meiosis is a type of cell division that produces cells with only one copy of each chromosome—spores in yeast, and eggs and sperm in higher organisms.

During meiosis, chromosome pairs line up in the middle of the cell. The chromosome pairs are then pulled apart, with complete copies of all of the chromosomes ending up at opposite sides of the cell. To ensure that the chromosomes align properly in the middle of the cell, the chromosomes crossover—swap certain sections of genes. Without the crossovers, the chromosomes could misalign and both copies of a chromosome could end up in one cell. When this happens, the cells die or suffer from severe genetic problems, such as Down syndrome.

Scientists analysing data gathered by Cassini have confirmed the presence of heavy negative ions in the upper regions of Titan’s atmosphere. These particles may act as building blocks for more complicated organic molecules.

The discovery was completely unexpected because of the chemical composition of the atmosphere (which lacks oxygen - responsible for forming negative ions in the lower ionosphere of the Earth - and mainly consists of nitrogen and methane). The observation has now been verified on 16 different encounters.

Prof Andrew Coates, researcher at University College London’s Mullard Space Science Laboratory and lead author of the paper, says: “Cassini’s electron spectrometer has enabled us to detect negative ions which have 10 000 times the mass of hydrogen.

“When biologists talk about the ‘Battle of the Sexes,’ they often tacitly assume that the battle is between persistent males who always want to mate and females who don’t,” says Jakob Bro-Jørgensen of University of Jyväskylä in Finland. “However, in topi antelopes, where females are known to prefer to mate with males in the center of mating arenas, we’ve found a reversal of these stereotypic sex roles.”

The classical view of sexual conflict holds that males, for whom reproducing is cheap, will mate as much as possible. On the other hand, females, who must pay a heftier price, are choosier about their mating partners.