Week In Science

Katharine Sanderson's article This quantum stuff just doesn't add up (published online 27 September 2007 | Nature | doi:10.1038/news070924-10) reveals possible paths to quantum cryptography. It would be based on some unusual adjustments to rules of addition and subtraction applicable to photons.

Marco Bellini and colleagues provided experimental data indicating that on a quantum level mathematical operations relevant to position and momentum of photons yield different results than would be expected were the objects apples and oranges instead. Bellini is from the National Institute of Applied Optics in Florence, Italy. He and his fellow researchers measured the mean number of photons in a laser beam shone through a spinning glass plate.

They found the number differed depending on whether photons were added first and then subtracted or whether the subtraction preceeded the addition. Oddly enough under certain conditions subtracting a photon could change the quantum state of the beam and cause an increase in the mean number of photons.

Varying quantum states through the addition or subtraction of photons could be a technique useful for encrypting new protocols.

Iapetus

Mystery of Saturn's Two-Faced Moon Solved is the title of an article from Space.com revealing the solution to a question that has long puzzled astronomers. Why does Saturn's moon Iapetus have a black and white appearance?

Images obtained from the passage of the spacecraft Cassini-Huygens over Iapetus provided the data needed to explain Iapetus's unique look. During its orbit Iapetus is bombarded by dusty material coming from other moons of Saturn. This darkens a regional surface of the moon which leads to a melting of surface ice. Evaporated water vapor condenses on other moon regions contributing ice and a brighter appearance to those parts of Iapetus. This cycle darkens the dark regions and makes the lighter regions brighter through this continuous process.

HIV-1

Why are humans infected by the immunodeficiency virus HIV-1 while other organisms are able to remain healthy even if the virus finds its way into their tissues? The answer to this is found in a paper published in Virology (Volume 367, Issue 1, 10 October 2007, Pages 19-29). The paper titled The ability of multimerized cyclophilin A to restrict retrovirus infection, focused on biomolecules of owl monkeys which have a differing retroviral restriction factor known as TRIMCyp. Retroviral restriction factors are proteins with anti-viral properties. They can bind to capsids and inhibit replication.

TRIMCyp, whose specific domains allow fusion with cyclophilin A, a member of the cyclophilin family of proteins which have distinct immunological functions, enable the inhibition of HIV-1 retroviral infection. Uncoating the viral HIV-1 capsid is possible through increased binding of cyclophilin A to the capsid. Restricted infection results from that.