Physicists at the Technical University of Munich, the Los Alamos National Laboratory and Stanford University (USA) have tracked down semiconductor nanostructure mechanisms that can result in the loss of stored information - and halted the amnesia using an external magnetic field. The new nanostructures comprise common semiconductor materials compatible with standard manufacturing processes.
Quantum bits, qubits for short, are the basic logical elements of quantum information processing (QIP) that may represent the future of computer technology. Since they process problems in a quantum-mechanical manner, such quantum computers might one day solve complex problems much more quickly than currently possible, so the hope of researchers.
Silicates on Iapetus from Cassini's Composite Infrared Spectrometer
Authors:
Young et al
Abstract:
We present the first spectral features obtained from Cassini's Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal to noise ratios (S/Rs) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/R and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts. We attribute the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm-1. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm-1 and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.
Precipitation of iron silicate nanoparticles in early Precambrian oceans marks Earth's first iron age
Authors:
Rasmussen et al
Abstract:
The early ocean was characterized by anoxic, iron-rich (ferruginous) conditions before the rise of atmospheric oxygen ∼2.45 b.y. ago. A proxy for ferruginous conditions in the ancient ocean is the deposition of banded iron formations (BIFs), which are iron- and silica-rich chemical sediments whose constituents were largely derived from seawater. Although experiments simulating ancient ocean chemistry support the rapid growth of iron-silicate phases, the main iron precipitates are hypothesized to have been ferric oxyhydroxides. The paradox between the prevailing reducing conditions and the deposition of oxidized iron phases is explained by biologically mediated oxidation in the water column. New high-resolution microscopy of BIFs and shales throughout the 2.63–2.45 b.y. old Hamersley Group, Australia, reveals the presence of vast quantities of nanometer-sized iron-silicate particles in laminated chert. The nanoparticles are finely disseminated in early diagenetic chert and locally define sedimentary lamination, indicating that they represent relicts of the original sediments. By inference from experimental studies simulating the composition of the early Precambrian ocean, we suggest that the nanoparticles precipitated from anoxic seawater enriched in silica and dissolved iron, and were silicified upon deposition. The prevalence of iron-silicate nanoparticles implies that they were pervasive background precipitates in ferruginous, silica-enriched oceans, forming the primary sediments of BIFs during periods of enhanced submarine mafic volcanism. Our results imply that silicate precipitation was a major sink of seawater iron and silica before the Great Oxidation Event and, because of the reactivity of nanoparticle surfaces, may also have influenced the transport and geochemical cycling of trace metals and nutrients. Our hypothesis that the basic building blocks of BIFs were predominantly iron-silicate muds rather than iron oxides and/or hydroxides may lead to new insights into seawater chemistry on the early Earth and the role of biology in the deposition of BIFs.
