The basic theory of how chemical reactions happen--molecules approach each other, overcome potential energy, and then form new reactants--has held up in experiments almost every time. But the theory doesn't fully explain what happens when a molecule approaches a metal surface, such as the surface of an industrial catalyst. This is important because metal catalysts are widely used in catalytic converters, fuel cells, and even to make margarine.

What makes metals tricky is that they don't have discrete energy states like molecules--rather than jumping from one specific energy level to another, electrons move between energy states in a metal in a more continuous way.

Two papers published in the journal Science this week use new algorithms to better describe what happens at the surface of metals including catalysts.

One describes the interactions between a gold surface and nitric oxide molecules excited using a laser. Older models predict that when the gas hits the gold surface it will still be vibrating. The new model predicts what actually happens: the molecule electronically couples to the gold.

The second paper looks at the interaction that cause hydrogen atoms on a copper surface to bond with one another and form hydrogen gas. It remains to be seen whether these results can be generalized, but if they can it could lead to a better understanding of the metal catalysts widely used in industrial chemistry.

We are constantly inundated with new information, and to manage it effectively it's sometimes necessary to forget old, irrelevant memories.

Researchers at Vanderbilt University have now developed an algorithm that mimics this kind of forgetfulness in robots, as a way to filter out less useful information.

"Forgetting is a critical capability when operating in dynamic environments," says PhD student Sanford Freedman, who presented the group's data filtering-software, called ActSimple, in a paper published at the IASTED Robotics and Applications conference held this week in Cambridge, MA.

ActSimple draws on two facets of human memory: time-based decay, or the way that memories disappear over time, and interference, which is the failure to recall information due to other memories competing for attention. ActSimple assigns different pieces of data values depending on how often they are used, and how similar it is to other pieces of information.

To test the software, the researchers used it to control a simulated robot that measured the strength of WiFi signals in a virtual environment. The robot recorded WiFi readings on a scale of 1-100, as it moved through the virtual setting and these WiFi readings also had different levels of noise (errors) associated with them. At intervals, the robot relied on its memory to create an estimated WiFi signal map by recalling signal strength information it had gathered and stored. The researchers tested ActSimple against four other algorithms, including one that strictly disregarded the oldest information, and another that out filtered random information.

The Team found that on average, ActSimple created the most reliable estimated WiFi map. Interestingly, when the robot "remembered" everything--that is, used all of its gathered information (errors and all)--it generated the least accurate map overall.

The back of your knee probably has more microbes than your mouth or your gut--that's just one of the somewhat disturbing revelations from a study published today online in Science. Researchers from the University of Colorado, Boulder have developed the most complete map yet of the microbes that dwell on and in us. "The highest diversity skin sites were the forearms, palm, index finger, back of the knee and sole of the foot. The armpits and soles of the feet showed some similarities, perhaps because they are from dark and moist environments," said Noah Fierer, one of the study's authors, in a statement.

Scientists are mapping our microbial inhabitants in order to better understand their role in human health and disease. As I noted in a previous feature:

Each of us contains roughly 10 times as many microbial cells as human ones. And while some microbes make us sick, many play vital roles in our physiology. They give us the ability to digest foods whose nutrients would otherwise be lost to us, and they make essential vitamins and amino acids our bodies can't. And yet, because the vast majority of these microbes die when extracted from their native habitat, they have been impossible to study and have remained a mystery...

New ultrafast DNA-sequencing technologies allow scientists to study the genetic makeup of entire microbial communities, each of which may contain hundreds or thousands of different species. For the first time, microbiologists can compare genetic snapshots of all the microbes inhabiting people who differ by age, origin, and health status. By analyzing the functions of those microbes' genes, they can figure out the main roles the organisms play in our bodies.

The new study, which analyzed 27 sites on the body of nine different volunteers, found that microbial diversity varies highly, both between individuals and from place to place in the same person. According to a release from the University of Colorado, Boulder:

The study showed humans carry "personalized" communities of bacteria around that vary widely from our foreheads and feet to our noses and navels, said CU-Boulder's Rob Knight, senior author on the paper. "This is the most complete view we have yet of the microbial side of ourselves, one that our group and others will be adding to over the coming years," said Knight, an assistant professor in CU-Boulder's chemistry and biochemistry department. "The goal is to find out what is normal for a healthy person, which will provide a baseline for further studies to look at people with diseased states. One of the biggest surprises was how much variation there was from person to person in a healthy group of subjects."

"We have an immense number of questions to answer," said Fierer, an assistant professor in CU-Boulder's ecology and evolutionary biology department who was a co-author on the study. "Why do healthy people have such different microbial communities? Do we each have distinct microbial signatures at birth, or do they evolve as we age? And how much do they matter? We just don't know yet."