【光学技术】 Technology for thinner probes. Nature 2012 491: 641 doi:10.1038-491641d.
A single optical fibre could form the basis of thinner endoscopes — long imaging probes with medical military and industrial uses.
Current endoscopes are made up of millimetre-sized bundles of up to 100000 fibres. Each fibre transports a single mode of light wave coming from the object being imaged because the mixing of modes can cause light-wave distortion.
Wonshik Choi at Korea University in Seoul and his colleagues have used a single 200-micrometre-wide fibre to transport multiple modes by measuring and reverse engineering the distortion that each mode suffers. The authors used their technique to make a three-dimensional map of a sample of rat intestine.
Phys. Rev. Lett. 109 203901 (2012)
【植物学】Plant fertilization protein found. Nature 2012 491: 640 doi:10.1038-491640b.
Fertilization in flowering plants is dependent on a protein that is secreted by the egg cell and activates incoming sperm.
Stefanie Sprunck at the University of Regensburg in Germany and her colleagues show that in the model plant Arabidopsis thaliana the arrival of sperm cells near the egg causes the release of a protein they call EGG CELL 1 (EC1). This triggers the redistribution of a second protein — one linked to fusion of the sex cells or gametes — from inside the sperm to the sperm cell surface.
Sperm cells interacting with mutant Arabidopsis eggs that have faulty ec1 genes failed to fuse and the plant’s pollen tubes continued to deliver sperm into the embryo sac. These results suggest that EC1 controls gamete fusion.
【The Kyoto Protocol专题】
Even though countries are burning unprecedented amounts of oil and gas the estimates of how much is left continue to grow thanks to high prices and new technologies that have enabled companies to find and extract new resources. A decade ago it was the tar sands of Canada and Venezuela. More recently hydraulic-fracturing technologies have opened up oil and gas resources in the United States. Across the globe proven oil and gas reserves are 60% higher today than they were in 1991. At current consumption rates those reserves would last for about 60 years — and that could be extended by new discoveries and unconventional deposits. Coal reserves have not increased in size but the supply will last for at least a century at current rates of consumption.
Renewables such as solar and wind power are growing faster than any other source of energy but are bare
