Wood is formed from secondary xylem tissue consisting of cells with a heavily thickened secondary cell wall that is enriched in lignin and cellulose. In contrast, primary cell walls are composed mainly of polysaccharides (including cellulose), but contain very little lignin. Wood formation occurs through a complex series of steps involving cell division and expansion and the biosynthesis of lignin and cellulose. In addition, heartwood (darker wood at the center of the trunk) forms in many tree species through a highly regulated process of programmed cell death. Although herbaceous plants by definition do not form wood as in trees and shrubs, they nonetheless form secondary xylem tissue that is in many respects similar to that of their woody relatives.

Data collected in 2005 from Hurricane Rita is providing the first documented evidence that rapid intensity changes can be caused by clouds outside the wall of a hurricane's eye coming together to form a new eyewall.

Hurricanes can gain or lose intensity with startling quickness, a phenomenon never more obvious than during the historic 2005 hurricane season that spawned the remarkably destructive Katrina and Rita.

Researchers flew through Rita, Katrina and other 2005 storms trying to unlock the key to intensity changes.

The criminal justice system, often the subject of political controversy, gains major insights from the unbiased analytical tools that operations researchers introduced beginning with the President's Crime Commission in the 1960s, according to a career retrospective by the winner of the Stockholm Prize in Criminology.

The paper, "An O.R.

A team of researchers from Rensselaer Polytechnic Institute has created the world’s first material that reflects virtually no light. Reporting in the March issue of Nature Photonics, they describe an optical coating made from the material that enables vastly improved control over the basic properties of light. The research could open the door to much brighter LEDs, more efficient solar cells, and a new class of "smart" light sources that adjust to specific environments, among many other potential applications.

Researchers have long said they won't be able to understand the brain until they can put together a "wiring diagram" – a map of how billions of neurons are interconnected. Now, researchers at the Salk Institute for Biological Studies have jumped what many believe to be a major hurdle to preparing that chart: identifying all of the connections to a single neuron.

In the March 1 issue of the journal Neuron, the researchers describe how they modified the deadly rabies virus, turning it into a tool that can cross the synaptic space of a targeted nerve cell just once to identify all the neurons to which it is directly connected.

"We've wanted to do this for a very long time and finally found a way to make it possible," says the study's senior author, Edward M.

Sweat may be another way to pass on hepatitis B infection during contact sports, suggests research published ahead of print in the British Journal of Sports Medicine.

Hepatitis B virus attacks the liver and can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.

The research team analysed blood and sweat samples from 70 male Olympic wrestlers for evidence of hepatitis B infection (HBV).

The wrestlers, who were all aged between 18 and 30, were all asked about injuries, as blood-borne infection is a common route of transmission.

Over a third said they had had bleeding or weeping wounds during training and competition.