Advanced rechargeable sodium batteries with novel cathodes

Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 Wh/kg theoretical). Energy densities in excess of 180 Wh/kg have been realized in practical batteries. More recently, cathodes other than sulfur are being evaluated. Researchers at JPL are evaluating various new cathode materials for use in high energy density sodium batteries for advanced space applications. The approach is to carry out basic electrochemical studies of these materials in a sodium cell configuration in order to understand their fundamental behaviors. Thus far studies have focused on alternate metal chlorides such as CuCl2 and organic cathode materials such as tetracyanoethylene (TCNE)

Copper chloride cathode for a secondary battery

Higher energy and power densities are achieved in a secondary battery based on molten sodium and a solid, ceramic separator such as a beta alumina and a molten catholyte such as sodium tetrachloroaluminate and a copper chloride cathode. The higher cell voltage of copper chloride provides higher energy densities and the higher power density results from increased conductivity resulting from formation of copper as discharge proceeds

Organic cathode for a secondary battery

A liquid catholyte for a battery based on liquid metal such as sodium anode and a solid, ceramic separator such as beta alumina (BASE) comprises a mixture of a Group I-III metal salt such as sodium tetrachloroaluminate and a minor amount of an organic carbonitrile depolarizer having at least one adjacent ethylenic band such as 1 to 40 percent by weight of tetracyanoethylene. The tetracyanoethylene forms an adduct with the molten metal salt

Quality control of the sheep bacterial artificial chromosome library, CHORI-243

<p>Abstract</p> <p>Background</p> <p>The sheep CHORI-243 bacterial artificial chromosome (BAC) library is being used in the construction of the virtual sheep genome, the sequencing and construction of the actual sheep genome assembly and as a source of DNA for regions of the genome of biological interest. The objective of our study is to assess the integrity of the clones and plates which make up the CHORI-243 library using the virtual sheep genome.</p> <p>Findings</p> <p>A series of analyses were undertaken based on the mapping the sheep BAC-end sequences (BESs) to the virtual sheep genome. Overall, very few plate specific biases were identified, with only three of the 528 plates in the library significantly affected. The analysis of the number of tail-to-tail (concordant) BACs on the plates identified a number of plates with lower than average numbers of such BACs. For plates 198 and 213 a partial swap of the BESs determined with one of the two primers appear to have occurred. A third plate, 341, also with a significant deficit in tail-to-tail BACs, appeared to contain a substantial number of sequences determined from contaminating eubacterial 16 S rRNA DNA. Additionally a small number of eubacterial 16 S rRNA DNA sequences were present on two other plates, 111 and 338, in the library.</p> <p>Conclusions</p> <p>The comparative genomic approach can be used to assess BAC library integrity in the absence of fingerprinting. The sequences of the sheep CHORI-243 library BACs have high integrity, especially with the corrections detailed above. The library represents a high quality resource for use by the sheep genomics community.</p

Using paired-end sequences to optimise parameters for alignment of sequence reads against related genomes

<p>Abstract</p> <p>Background</p> <p>The advent of cheap high through-put sequencing methods has facilitated low coverage skims of a large number of organisms. To maximise the utility of the sequences, assembly into contigs and then ordering of those contigs is required. Whilst sequences can be assembled into contigs <it>de novo</it>, using assembled genomes of closely related organisms as a framework can considerably aid the process. However, the preferred search programs and parameters that will optimise the sensitivity and specificity of the alignments between the sequence reads and the framework genome(s) are not necessarily obvious. Here we demonstrate a process that uses paired-end sequence reads to choose an optimal program and alignment parameters.</p> <p>Results</p> <p>Unlike two single fragment reads, in paired-end sequence reads, such as BAC-end sequences, the two sequences in the pair have a known positional relationship in the original genome. This provides an additional level of confidence over match scores and e-values in the accuracy of the positional assignment of the reads in the comparative genome. Three commonly used sequence alignment programs: MegaBLAST, Blastz and PatternHunter were used to align a set of ovine BAC-end sequences against the equine genome assembly. A range of different search parameters, with a particular focus on contiguous and discontiguous seeds, were used for each program. The number of reads with a hit and the number of read pairs with hits for the two end sequences in the tail-to-tail paired-end configuration were plotted relative to the theoretical maximum expected curve. Of the programs tested, MegaBLAST with short contiguous seed lengths (word size 8-11) performed best in this particular task. In addition the data also provides estimates of the false positive and false negative rates, which can be used to determine the appropriate values of additional parameters, such as score cut-off, to balance sensitivity and specificity. To determine whether the approach also worked for the alignment of shorter reads, the first 240 bases of each BAC end sequence were also aligned to the equine genome. Again, contiguous MegaBLAST performed the best in optimising the sensitivity and specificity with which sheep BAC end reads map to the equine and bovine genomes.</p> <p>Conclusions</p> <p>Paired-end reads, such as BAC-end sequences, provide an efficient mechanism to optimise sequence alignment parameters, for example for comparative genome assemblies, by providing an objective standard to evaluate performance.</p

Groundnut (Arachis hypogaea) genotypes tolerant to intermittent drought maintain a high harvest index and have small leaf canopy under stress

Intermittent drought, which varies in intensity, severely limits groundnut (Arachis hypogaea L.) yields. Experiments were conducted to assess root development, water uptake, transpiration efficiency, yield components and their relationships, in 20 groundnut genotypes under well watered (WW), and mild (DS-1), medium (DS-2) and severe (DS-3) intermittent stress. Pod yield decreased 70%, 55% and 35% under severe, medium and mild stress, respectively. Pod yield varied among genotypes, and showed significant genotype-by-treatment effects. Root length density (RLD) varied among genotypes before and after stress, although RLD did not discriminate tolerant from sensitive lines. Total water uptake and RLD under water stress had a weakly significant relationship. Water extraction from the soil profile was highest under severe stress. Water uptake varied among genotypes in all water regimes, but correlated with pod yield under WW conditions. The relative harvest index (HI) (i.e. the ratio of the HI under stress to HI under WW conditions) was closely related to the pod yield in all three intermittent stresses (R2 = 0.68 in DS-1; R2 = 0.65 in DS-2; R2 = 0.86 in DS-3) and was used as an index of stress tolerance. Under medium and severe stresses, the relative HI was negatively related to plant leaf weight (R2 = 0.79 in DS-2; R2 = 0.53 in DS-3), but less so under mild stress (R2 = 0.31). The results suggest that under intermittent stress, genotypes with a lower leaf area may use water more sparingly during the drying cycle with less damaging consequences for reproduction and pod