Melt inclusions in veins: linking magmas and porphyry Cu deposits

At a porphyry copper-gold deposit in Bajo de la Alumbrera, Argentina, silicate-melt inclusions coexist with hypersaline liquid- and vapor-rich inclusions in the earliest magmatic-hydrothermal quartz veins. Copper concentrations of the hypersaline liquid and vapor inclusions reached maxima of 10.0 weight % (wt %) and 4.5 wt %, respectively. These unusually copper-rich inclusions are considered to be the most primitive ore fluid found thus far. Their preservation with coexisting melt allows for the direct quantification of important oreforming processes, including determination of bulk partition coefficients of metals from magma into ore-forming magmatic volatile phases.     

Stimulated Raman scattering in hydrogen-filled hollow-core photonic crystal fiber

We report on stimulated Raman scattering in an approximately 1-meter-long hollow-core photonic crystal fiber filled with hydrogen gas under pressure. Light was guided and confined in the 15-micrometer-diameter hollow core by a two-dimensional photonic bandgap. Using a pulsed laser source (pulse duration, 6 nanoseconds; wavelength, 532 nanometers), the threshold for Stokes (longer wavelength) generation was observed at pulse energies as low as 800 +/- 200 nanojoules, followed by a coherent anti-Stokes (shorter wavelength) generation threshold at 3.4 +/- 0.7 microjoules. The pump-to-Stokes conversion efficiency was 30 +/- 3% at a pulse energy of only 4.5 microjoules. These energies are almost two orders of magnitude lower than any other reported energy, moving gas-based nonlinear optics to previously inaccessible parameter regimes of high intensity and long interaction length.     

Soliton self-frequency shift cancellation in photonic crystal fibers

We report the cancellation of the soliton self-frequency shift in a silica-core photonic crystal fiber with a negative dispersion slope. Numerical and experimental results show that stabilization of the soliton wavelength is accompanied by exponential amplification of the red-shifted Cherenkov radiation emitted by the soliton. The spectral recoil from the radiation acts on the soliton to compensate for the Raman frequency shift. This phenomenon may find applications in the development of a family of optical parametric amplifiers.     

Structure of Nup58/45 suggests flexible nuclear pore diameter by intermolecular sliding

The nucleoporins Nup58 and Nup45 are part of the central transport channel of the nuclear pore complex, which is thought to have a flexible diameter. In the crystal structure of an alpha-helical region of mammalian Nup58/45, we identified distinct tetramers, each consisting of two antiparallel hairpin dimers. The intradimeric interface is hydrophobic, whereas dimer-dimer association occurs through large hydrophilic residues. These residues are laterally displaced in various tetramer conformations, which suggests an intermolecular sliding by 11 angstroms. We propose that circumferential sliding plays a role in adjusting the diameter of the central transport channel.     

Chemical transformations in individual ultrasmall biomimetic containers

Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes.     

Chromosomal localization of muscle nicotinic acetylcholine receptor genes in the mouse

The chromosomal localization of the genes encoding the four subunits of muscle nicotinic receptor was determined by analyzing restriction fragment length polymorphisms between two mouse species Mus musculus domesticus (DBA/2) and Mus spretus (SPE). Analysis of the progeny of the interspecies mouse backcross (DBA/2 X SPE) X DBA/2 showed that the alpha-subunit gene cosegregates with the alpha-cardiac actin gene on chromosome 17, that the beta-subunit gene is located on chromosome 11, and that the gamma- and delta-subunit genes cosegregate and are located on chromosome 1.     

Comment on "Preserved feedforward but impaired top-down processes in the vegetative state"

Boly et al. (Reports, 13 May 2011, p. 858) investigated cortical connectivity patterns in patients suffering from a disorder of consciousness, using electroencephalography in an auditory oddball paradigm. We point to several inconsistencies in their data, including a failure to replicate the classical mismatch negativity. Data quality, source reconstruction, and statistics would need to be improved to support their conclusions.     

Forests of the past: a window to future changes

The study of past forest change provides a necessary historical context for evaluating the outcome of human-induced climate change and biological invasions. Retrospective analyses based on fossil and genetic data greatly advance our understanding of tree colonization, adaptation, and extinction in response to past climatic change. For instance, these analyses reveal cryptic refugia near or north of continental ice sheets, leading to reevaluation of postglacial tree migration rates. Species extinctions appear to have occurred primarily during periods of high climatic variability. Transoceanic dispersal and colonization in the tropics were widespread at geological time scales, inconsistent with the idea that tropical forests are particularly resistant to biological invasions.