Synthesis, structure, and high-temperature thermoelectric properties of boron-doped Ba_8Al_(14)Si_(31) clathrate I phases

Single crystals of boron-doped Ba_8Al_(14)Si_(31) clathrate I phase were prepared using Al flux growth. The structure and elemental composition of the samples were characterized by single-crystal and powder X-ray diffraction; elemental analysis; and multinuclear ^(27)Al, ^(11)B, and ^(29)Si solid-state NMR. The samples' compositions of Ba_8B_(0.17)Al_(14)Si_(31), Ba_8B_(0.19)Al_(15)Si_(31), and Ba_8B_(0.32)Al_(14)Si_(310) were consistent with the framework-deficient clathrate I structure Ba_8Al_xSi_(42-3/4x)□_(4-1/4x) (X = 14, □ = lattice defect). Solid-state NMR provides further evidence for boron doped into the framework structure. Temperature-dependent resistivity indicates metallic behavior, and the negative Seebeck coefficient indicates that transport processes are dominated by electrons. Thermal conductivity is low, but not significantly lower than that observed in the undoped Ba_8Al_(14)Si_(31) prepared in the same manner

The MANTA: An RPV design to investigate forces and moments on a lifting surface

The overall goal was to investigate and exploit the advantages of using remotely powered vehicles (RPV's) for in-flight data collection at low Reynold's numbers. The data to be collected is on actual flight loads for any type of rectangular or tapered airfoil section, including vertical and horizontal stabilizers. The data will be on a test specimen using a force-balance system which is located forward of the aircraft to insure an undisturbed air flow over the test section. The collected data of the lift, drag and moment of the test specimen is to be radioed to a grand receiver, thus providing real-time data acquisition. The design of the mission profile and the selection of the instrumentation to satisfy aerodynamic requirements are studied and tested. A half-size demonstrator was constructed and flown to test the flight worthiness of the system

An automated high-content screening image analysis pipeline for the identification of selective autophagic inducers in human cancer cell lines.

Automated image processing is a critical and often rate-limiting step in high-content screening (HCS) workflows. The authors describe an open-source imaging-statistical framework with emphasis on segmentation to identify novel selective pharmacological inducers of autophagy. They screened a human alveolar cancer cell line and evaluated images by both local adaptive and global segmentation. At an individual cell level, region-growing segmentation was compared with histogram-derived segmentation. The histogram approach allowed segmentation of a sporadic-pattern foreground and hence the attainment of pixel-level precision. Single-cell phenotypic features were measured and reduced after assessing assay quality control. Hit compounds selected by machine learning corresponded well to the subjective threshold-based hits determined by expert analysis. Histogram-derived segmentation displayed robustness against image noise, a factor adversely affecting region growing segmentation

Does soil erosion rejuvenate the soil phosphorus inventory?

Phosphorus (P) is an essential nutrient for life. Deficits in soil P reduce primary production and alter biodiversity. A soil P paradigm based on studies of soils that form on flat topography, where erosion rates are minimal, indicates P is supplied to soil mainly as apatite from the underlying parent material and over time is lost via weathering or transformed into labile and less-bioavailable secondary forms. However, little is systematically known about P transformation and bioavailability on eroding hillslopes, which make up the majority of Earth's surface. By linking soil residence time to P fractions in soils and parent material, we show that the traditional concept of P transformation as a function of time has limited applicability to hillslope soils of the western Southern Alps (New Zealand) and Northern Sierra Nevada (USA). Instead, the P inventory of eroding soils at these sites is dominated by secondary P forms across a range of soil residence times, an observation consistent with previously published soil P data. The findings for hillslope soils contrast with those from minimally eroding soils used in chronosequence studies, where the soil P paradigm originated, because chronosequences are often located on landforms where parent materials are less chemically altered and therefore richer in apatite P compared to soils on hillslopes, which are generally underlain by pre-weathered parent material (e.g., saprolite). The geomorphic history of the soil parent material is the likely cause of soil P inventory differences for eroding hillslope soils versus geomorphically stable chronosequence soils. Additionally, plants and dust seem to play an important role in vertically redistributing P in hillslope soils. Given the dominance of secondary soil P in hillslope soils, limits to ecosystem development caused by an undersupply of bio-available P may be more relevant to hillslopes than previously thought

Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use.

Genetic decoding is not 'frozen' as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational 'correction' of problem or 'savior' indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5' or 3' of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3' from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.This work was supported by grants from Science Foundation Ireland [12/IP/1492 and 13/1A/1853 to J.F.A; 12/IA/1335 to P.V.B.], US. National Institutes of Health [RO3 MH098688 to J.F.A.], the Wellcome Trust [106207 to A.E.F and 094423 to P.V.B.] and the European Research Council (ERC) grant No. 646891 to A.E.F.]This is the final version of the article. It first appeared from Oxford University Press via https://doi.org/10.1093/nar/gkw53

Pools, transformations, and sources of P in high-elevation soils: Implications for nutrient transfer to Sierra Nevada lakes

In high-elevation lakes of the Sierra Nevada (California), increases in P supply have been inferred from shifts in P to N limitation. To examine factors possibly leading to changes in P supply, we measured pools and transformations in soil P, and developed a long-term mass balance to estimate the contribution of parent material weathering to soil P stocks. Common Sierra Nevada soils were found to not be P-deficient and to be retentive of P due to the influence of Fe- and Al-oxides. Total P averaged 867μgPg-1 in the top 10cm of soil (O and A horizons) and 597μgPg-1 in the 10-60cm depth (B horizons), of which 70% in A horizons and 60% in B horizons was freely exchangeable or associated with Fe and Al. Weathering of parent material explained 69% of the P found in soils and lost from the catchment since deglaciation, implying that long-term atmospheric P deposition (0.02kgha-1yr-1) represented the balance of P inputs (31%) during the past 10,000years of soil development. During spring snowmelt ~27% of the total soil P was transferred between organic and inorganic pools; average inorganic P pools decreased by 232μgPg-1, while organic P pools increased by 242μgPg-1. Microbial biomass P was highest during winter and decreased six-fold to a minimum in the fall. Interactions between hydrology and biological processes strongly influence the rate of P transfer from catchment soils to lakes. © 2013 Elsevier B.V

Phosphorus fertilization by active dust deposition in a super-humid, temperate environment – Soil phosphorus fractionation and accession processes

The inventory of soil phosphorus (P) is subject to significant changes over time. The main primary form, bedrock-derived apatite P, becomes progressively lost through leaching, or transformed into more immobile and less plant-accessible, secondary organic and mineral forms. Here we studied the rejuvenating effect of dust deposition on soil P along an active dust flux gradient downwind of a braided river. Along the gradient, we measured soil P fractions to 50 cm depth of six Spodosols and one Inceptisol, supplemented by tree foliage P concentrations. While an increasing dust flux correlates with a twofold increase of foliar P and soil organic P along the gradient, apatite P declines from ~50 to 3 g m⁻² and total P shows no response. Compared to dust-unaffected Spodosols, depth distribution of total P becomes increasingly uniform and organic P propagates deeper into the soil under dust flux. Further, the effect of topsoil P eluviation attenuates due to higher organic P content and the zone of high apatite P concentrations associated with un-weathered subsoil becomes progressively removed from the upper 50 cm. We interpret these patterns as being consistent with upbuilding pedogenesi and conclude that dust-derived mineral P is assimilated in the organic surface horizon and does not reach the mineral soil. Dust-derived mineral P is temporarily stored in the living biomass and returns to the soil with plant and microbial detritus as organic P, which is subsequently buried by further dust increments. We further conclude that (1) the efficiency of P fertilization of the ecosystem by dust accession is higher than through P advection in dust-unaffected Spodosols and (2) organic P may serve as an important source of labile P in a high-leaching environment. ©2013. American Geophysical Union. All Rights Reserved