Microclimatic differences between young longleaf-pine silvopasture and open-pasture

Information is needed relative to changes that occur in microclimatic conditions in the early stages of open-pasture to pine silvopasture conversion in the Southeastern USA. This research tested the hypothesis that microclimatic conditions would vary between young-pine silvopasture and open-pasture. The research was conducted in a longleaf-pine (Pinus palustris Mill.)-bahiagrass (Paspalum notatum Flugge) silvopasture and adjacent open bahiagrass pasture at Americus, Georgia. Longleaf-pine was planted in the bahiagrass pasture in December 2000; the trees were not pruned or thinned until the study was completed. Microclimatic parameters (air temperature, soil temperature at 5 and 10 cm, wind speed, gust speed, wind direction, humidity, dew point, rainfall, soil-moisture content, total solar radiation, and photosynthetically active radiation) were collected from November 2005 to October 2008 using HOBO^© weather stations located in each pasture type. Data were analyzed to determine overall, as well as seasonal, monthly, and diurnal differences between pasture types. Evapotranspiration was calculated from air temperature, wind speed, relative humidity, and total solar radiation. With the exception of rainfall, overall average values for all microclimatic parameters were different between pasture types. Silvopasture had higher overall average values for air temperature, soil temperature at both depths, and soil water content, but lower values for all remaining microclimatic parameters. Seasonal, monthly, and diurnal differences between pasture types were also detected for several parameters. The results suggested that water loss can be significantly reduced in the early stages of open-pasture to longleaf-pine silvopasture conversion in the Southeastern USA.     

Guidance of peripheral pioneer neurons in the grasshopper: adhesive hierarchy of epithelial and neuronal surfaces

An important question in developmental neurobiology is how a neuron finds its way over long distances to its correct target during embryogenesis. Peripheral pioneer neurons in insect embryos have been used for study because of the relative simplicity of the early embryonic appendages, and the accessibility of the identified neurons whose growth cones traverse this terrain. The data presented suggest an adhesive hierarchy of both epithelial and neuronal surfaces that guides the first growth cones from the appendages of the grasshopper embryo.     

Adenosine receptors: autoradiographic evidence for their location on axon terminals of excitatory neurons

Adenosine receptors were made visible on light microscopy by autoradiography with tritiated cyclohexyladenosine. In the cerebellum, adenosine receptors were absent in Weaver mice, which lack granule cells, and were displaced in Reeler mice, which have displacements of granule cells. Thus, adenosine receptors appear to be located on the axon terminals of excitatory granule cells in the cerebellum. Removal of one eye of a rat depleted adenosine receptors in the contralateral superior colliculus, suggesting that the receptors occur on axon terminals of excitatory projections from retinal ganglion cells. The presence of adenosine receptors on excitatory axon terminals may explain synaptic inhibition by adenosine and the behavioral effects of xanthines.     

Switching repulsion to attraction: changing responses to slit during transition in mesoderm migration

Slit is secreted by cells at the midline of the central nervous system, where it binds to Roundabout (Robo) receptors and functions as a potent repellent. We found that migrating mesodermal cells in vivo respond to Slit as both an attractant and a repellent and that Robo receptors are required for both functions. Mesoderm cells expressing Robo receptors initially migrate away from Slit at the midline. A few hours after migration, these same cells change their behavior and require Robo to extend toward Slit-expressing muscle attachment sites. Thus, Slit functions as a chemoattractant to provide specificity for muscle patterning.     

A phylogenetic microarray targeting 16S rRNA genes from the bacterial division Acidobacteria reveals a lineage-specific distribution in a soil clay fraction

We designed an oligonucleotide microarray using probe sequences based upon a phylogenetic analysis of 16S rRNA genes recovered from members of the bacterial division Acidobacteria. A total of 42,194 oligonucleotide probes targeting members of the Acidobacteria division at multiple phylogenetic levels were included on a high-density microarray. Positive control hybridizations revealed a linear relationship between hybridization signal and template concentration, and a substantial decrease in non-specific hybridization was achieved through the addition of 2.5 M betaine to the hybridization buffer. A mean hybridization signal value was calculated for each Acidobacteria lineage, with the resultant lineage-specific hybridization data revealing strong predictive value for the positive control hybridizations. The Acidobacteria phylochip was then used to evaluate Acidobacteria rRNA genes from a Wisconsin soil and within a soil clay fraction. The Acidobacteria hybridization profile revealed the predominance of Acidobacteria subdivisions four and six, and also suggested a decrease in the abundance of subdivision six relative to subdivision four in the soil clay fraction. The change in relative abundance of these subdivisions in a soil clay fraction was supported by data from quantitative PCR. These results support the utility of a phylogenetic microarray in revealing changes in microbial population-level distributions in a complex soil microbial assemblage.     

Rapid chiral assembly of rigid DNA building blocks for molecular nanofabrication

Practical components for three-dimensional molecular nanofabrication must be simple to produce, stereopure, rigid, and adaptable. We report a family of DNA tetrahedra, less than 10 nanometers on a side, that can self-assemble in seconds with near-quantitative yield of one diastereomer. They can be connected by programmable DNA linkers. Their triangulated architecture confers structural stability; by compressing a DNA tetrahedron with an atomic force microscope, we have measured the axial compressibility of DNA and observed the buckling of the double helix under high loads.     

Solar neutrinos: proposal for a new test

The predicted flux on the earth of solar neutrinos has eluded detection, confounding current ideas of solar energy production by nuclear fusion. The dominant low-energy component of that flux can be detected by mass-spectrometric assay of the induced tiny concentration of 1.6 x 10(7) year lead-205 in old thallium minerals. Comments are solicited from those in all relevant disciplines.