The outcome of Ebola infections often depends on a patient's access to sophisticated medical care. But there's the possibility that it could be influenced by genetics as well. That suggestion comes from the authors of a new paper that looked at what happens when genetically diverse groups of mice were exposed to the virus. As it turns out, the results ranged from losing a bit of weight to complete mortality.
The work doesn't seem to have been inspired by looking for insight into the progression of hemorrhagic fever in humans. Instead, the researchers involved appear to have been frustrated by the fact that the most convenient research mammal, the mouse, doesn't experience the symptoms typical of Ebola infections in humans: no problems with blood coagulation, no hemorrhages, and no shock. So they decided to see if they could find a mouse strain that did show these symptoms (and would thus enable convenient studies).
To do so, they started with something called the Collaborative Cross collection. Most of the mouse strains used in research have been inbred until all members of the strain are genetically identical. There are, however, differences between strains; C57 mice are genetically distinct from 129 mice. So it's possible to see very different things happen if you do the same experiment in different strains.
Inflation—in the cosmic sense, at least—has been in the news lately. Early this year, researchers announced that they found conclusive evidence that our Universe experienced a period of rapid expansion fractions of a second after the Big Bang, an event that left its mark on the present-day Universe. Unfortunately, that result hasn't held up well under more intense scrutiny.
But it's worth understanding what all the fuss is about. Inflation is the only way we have of explaining how the Big Bang could possibly produce the Universe that we find ourselves in today. And the theory has consequences, including the implication that our Universe is not alone; other universes would pop into existence as inflation sped faster than the boundaries of our Universe expanded.
If this sounds like your cup of tea, then you'll have a great opportunity tomorrow afternoon. Alan Guth, the theoretical physicist who was instrumental in developing inflationary theory, is doing a live session in which he'll explain inflation and field questions about it.
Even the simplest forms of life, like bacteria, have a handedness, one that's built into the chemicals they're composed of. The complex, three-dimensional molecules that are essential to life can have the same exact set of atoms, yet be physically distinct—one the mirror image of the other. All the amino acids that life uses have a single orientation; same with all the sugars.
While life is very good at operating with this handedness, called chirality, nature isn't. Most chemical reactions produce a mixture of left and right forms of molecules. This seemingly creates a problem for the origin of life—if both chiral forms were available, how did life pick just one? The problem is even more severe than that. If both forms are present, then the reactions that duplicate DNA and RNA molecules don't work. And without those reactions, life won't work.
Now, researchers have found this doesn't pose much of a barrier at all. Through a little test-tube based evolution, they were able to make an RNA molecule that could copy other RNA molecules with the opposite chirality. In other words, they made a right hand that could only copy the left. But the duplicate, the left-handed form, could then readily copy the right-handed version. And as an added bonus, the new RNA molecule may be one of the most useful copying enzymes yet evolved.
Early in my training, I learned one rule: loss is not your friend. In laser physics, loss means that every photon that goes missing is a photon that no longer stimulates emission. And, with every lost photon, it becomes just that little bit harder to keep a laser going. So, when Science published a paper showing that this rule doesn't always hold, I was intrigued.
Also it gives me the chance to talk about lasers, which I never tire of.Gain, loss, and lasers
Before we get to the experiment, let's talk about lasers in general. Lasers emit light through a process called stimulated emission. Stimulated emission only dominates under two conditions: there have to be more emitters ready to emit light instead of to absorb light. This is referred to as population inversion and provides the gain (or the source of light amplification). The other requirement is that there is light present to stimulate emission. To put it slightly incorrectly, the amplifier needs something to amplify.
How did Earth develop its current atmosphere? A study published in the journal Nature Geoscience links the composition of Earth’s nitrogen-rich atmosphere to the same tectonic forces that drive mountain-building and volcanism on our planet. It goes some way to explaining why, when compared to our nearest neighbors Venus and Mars, Earth’s air is richer in nitrogen.
The chemistry of the air we breathe is partially the result of billions of years of photosynthesis. Plant life has transformed our world from one cloaked in a carbon dioxide-rich atmosphere, as seen on Mars or Venus, to one with significant oxygen. About a fifth of the air is made up of oxygen, but almost all the rest is nitrogen—completely unlike Mars and Venus. The origins of the relatively high nitrogen content of Earth’s air have been something of a mystery.
Geoscientists Sami Mikhail and Dimitri Sverjensky of the Carnegie Institution of Washington have calculated what nitrogen is expected to do when the churning cycle of plate tectonics cycles it through the rocks of the deep Earth. Active volcanoes not only shower volcanic rock and superheated ash as they erupt molten rock into the air; they also vent huge amounts of gas from Earth’s depths. The latest eruptions in Iceland, for example, have been noted for the amount of sulfurous fumes they have emitted.