Soil mapping for precision agriculture using support vector machines combined with inverse distance weighting

Precision Agriculture - Kriging has been shown to be the best interpolator to interpolate maps in precision agriculture. However, Kriging requires a high number of sampling points to generate...     

Massive CO₂ ice deposits sequestered in the south polar layered deposits of Mars

Shallow Radar soundings from the Mars Reconnaissance Orbiter reveal a buried deposit of carbon dioxide (CO(2)) ice within the south polar layered deposits of Mars with a volume of 9500 to 12,500 cubic kilometers, about 30 times that previously estimated for the south pole residual cap. The deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior CO(2) volatile release. If released into the atmosphere at times of high obliquity, the CO(2) reservoir would increase the atmospheric mass by up to 80%, leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling.     

Forces for morphogenesis investigated with laser microsurgery and quantitative modeling

We investigated the forces that connect the genetic program of development to morphogenesis in Drosophila. We focused on dorsal closure, a powerful model system for development and wound healing. We found that the bulk of progress toward closure is driven by contractility in supracellular "purse strings" and in the amnioserosa, whereas adhesion-mediated zipping coordinates the forces produced by the purse strings and is essential only for the end stages. We applied quantitative modeling to show that these forces, generated in distinct cells, are coordinated in space and synchronized in time. Modeling of wild-type and mutant phenotypes is predictive; although closure in myospheroid mutants ultimately fails when the cell sheets rip themselves apart, our analysis indicates that beta(PS) integrin has an earlier, important role in zipping.     

Spin crossover in ferropericlase at high pressure: a seismologically transparent transition?

Seismic discontinuities in Earth typically arise from structural, chemical, or temperature variations with increasing depth. The pressure-induced iron spin state transition in the lower mantle may influence seismic wave velocities by changing the elasticity of iron-bearing minerals, but no seismological evidence of an anomaly exists. Inelastic x-ray scattering measurements on (Mg(0.83)Fe(0.17))O-ferropericlase at pressures across the spin transition show effects limited to the only shear moduli of the elastic tensor. This explains the absence of deviation in the aggregate seismic velocities and, thus, the lack of a one-dimensional seismic signature of the spin crossover. The spin state transition does, however, influence shear anisotropy of ferropericlase and should contribute to the seismic shear wave anisotropy of the lower mantle.     

Strong association of de novo copy number mutations with autism

We tested the hypothesis that de novo copy number variation (CNV) is associated with autism spectrum disorders (ASDs). We performed comparative genomic hybridization (CGH) on the genomic DNA of patients and unaffected subjects to detect copy number variants not present in their respective parents. Candidate genomic regions were validated by higher-resolution CGH, paternity testing, cytogenetics, fluorescence in situ hybridization, and microsatellite genotyping. Confirmed de novo CNVs were significantly associated with autism (P = 0.0005). Such CNVs were identified in 12 out of 118 (10%) of patients with sporadic autism, in 2 out of 77 (3%) of patients with an affected first-degree relative, and in 2 out of 196 (1%) of controls. Most de novo CNVs were smaller than microscopic resolution. Affected genomic regions were highly heterogeneous and included mutations of single genes. These findings establish de novo germline mutation as a more significant risk factor for ASD than previously recognized.     

Control of nutrient-sensitive transcription programs by the unconventional prefoldin URI

Prefoldins (PFDs) are members of a recently identified, small-molecular weight protein family able to assemble into molecular chaperone complexes. Here we describe an unusually large member of this family, termed URI, that forms complexes with other small-molecular weight PFDs and with RPB5, a shared subunit of all three RNA polymerases. Functional analysis of the yeast and human orthologs of URI revealed that both are targets of nutrient signaling and participate in gene expression controlled by the TOR kinase. Thus, URI is a component of a signaling pathway that coordinates nutrient availability with gene expression.     

An age-induced switch to a hyper-recombinational state

There is a strong correlation between age and cancer, but the mechanism by which this phenomenon occurs is unclear. We chose Saccharomyces cerevisiae to examine one of the hallmarks of cancer--genomic instability--as a function of cellular age. As diploid yeast mother cells aged, an approximately 100-fold increase in loss of heterozygosity (LOH) occurred. Extending life-span altered neither the onset nor the frequency of age-induced LOH; the switch to hyper-LOH appears to be on its own clock. In young cells, LOH occurs by reciprocal recombination, whereas LOH in old cells was nonreciprocal, occurring predominantly in the old mother's progeny. Thus, nuclear genomes may be inherently unstable with age.     

Rapid evolution of egg size in captive salmon

Captive breeding and release programs, widely used to supplement populations of declining species, minimize juvenile mortality to achieve rapid population growth. However, raising animals in benign environments may promote traits that are adaptive in captivity but maladaptive in nature. In chinook salmon, hatchery rearing relaxes natural selection favoring large eggs, allowing fecundity selection to drive exceptionally rapid evolution of small eggs. Trends toward small eggs are also evident in natural populations heavily supplemented by hatcheries, but not in minimally supplemented populations. Unintentional selection in captivity can lead to rapid changes in critical life-history traits that may reduce the success of supplementation or reintroduction programs.     

A sulfur dioxide climate feedback on early Mars

Ancient Mars had liquid water on its surface and a CO2-rich atmosphere. Despite the implication that massive carbonate deposits should have formed, these have not been detected. On the basis of fundamental chemical and physical principles, we propose that climatic conditions enabling the existence of liquid water were maintained by appreciable atmospheric concentrations of volcanically degassed SO2 and H2S. The geochemistry resulting from equilibration of this atmosphere with the hydrological cycle is shown to inhibit the formation of carbonates. We propose an early martian climate feedback involving SO2, much like that maintained by CO2 on Earth.