Nickel electrode plate thickening study

The rate of thickening of the nickel electrode with cycling, under geochronous conditions, was investigated. The experimental procedures used to study the effects of various operational parameters on the rate of the thickness growth are outlined. The parameters included temperature, electrolyte composition, manufacturing lot, cycle parameters, and reconditioning methods

On Condensations.

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Macroinvertebrate community responses to a dewatering disturbance gradient in a restored stream

Dewatering disturbances are common in aquatic systems and represent a relatively untapped field of disturbance ecology, yet studying dewatering events along gradients in non-dichotomous (i.e. wet/dry) terms is often difficult. Because many stream restorations can essentially be perceived as planned hydrologic manipulations, such systems can make ideal test-cases for understanding processes of hydrological disturbance. In this study we used an experimental drawdown in a 440 ha stream/wetland restoration site to assess aquatic macroinvertebrate community responses to dewatering and subsequent rewetting. The geomorphic nature of the site and the design of the restoration allowed dewatering to occur predictably along a gradient and decoupled the hydrologic response from any geomorphic (i.e. habitat heterogeneity) effects. In the absence of such heterogeneous habitat refugia, reach-scale wetted perimeter and depth conditions exerted a strong control on community structure. The community exhibited an incremental response to dewatering severity over the course of this disturbance, which was made manifest not as a change in community means but as an increase in community variability, or dispersion, at each site. The dewatering also affected inter-species abundance and distributional patterns, as dewatering and rewetting promoted alternate species groups with divergent habitat tolerances. Finally, our results indicate that rapid rewetting – analogous to a hurricane breaking a summer drought – may represent a recovery process rather than an additional disturbance and that such processes, even in newly restored systems, may be rapid

Storage-ring measurement of the hyperfine induced 47Ti18+(2s 2p 3P0 -> 2s2 1S0) transition rate

The hyperfine induced 2s 2p 3P0 > 2s2 1S0 transition rate AHFI in berylliumlike 47Ti18+ was measured. Resonant electron-ion recombination in a heavy-ion storage ring was employed to monitor the time dependent population of the 3P0 state. The experimental value AHFI=0.56(3)/s is almost 60% larger than theoretically predicted.Comment: 4 pages. 3 figures, 1 table, accepted for publication in Physical Review Letter

Impacts of Land Abandonment on Vegetation: Successional Pathways in European Habitats

Changes in traditional agricultural systems in Europe in recent decades have led to widespread abandonment and colonization of various habitats by shrubs and trees. We combined several vegetation databases to test whether patterns of changes in plant diversity after land abandonment in different habitats followed similar pathways. The impacts of land abandonment and subsequent woody colonization on vegetation composition and plant traits were studied in five semi-natural open habitats and two arable habitats in six regions of Europe. For each habitat, vegetation surveys were carried out in different stages of succession using either permanent or non-permanent plots. Consecutive stages of succession were defined on a physiognomic basis from initial open stages to late woody stages. Changes in vegetation composition, species richness, numbers of species on Red Lists, plant strategy types, Ellenberg indicator values of the vegetation, Grime CSR strategy types and seven ecological traits were assessed for each stage of the successional pathway. Abandonment of agro-pastoral land-use and subsequent woody colonization were associated with changes in floristic composition. Plant richness varied according to the different habitats and stages of succession, but semi-natural habitats differed from arable fields in several ecological traits and vegetation responses. Nevertheless, succession occurred along broadly predictable pathways. Vegetation in abandoned arable fields was characterized by a decreasing importance of R-strategists, annuals, seed plants with overwintering green leaves, insect-pollinated plants with hemi-rosette morphology and plants thriving in nutrient-rich conditions, but an increase in species considered as endangered according to the Red Lists. Conversely, changes in plant traits with succession within the initially-open semi-natural habitats showed an increase in plants thriving in nutrient-rich conditions, stress-tolerant plants and plants with sexual and vegetative reproduction, but a sharp decrease in protected species. In conclusion, our study showed a set of similarities in responses of the vegetation in plant traits after land abandonment, but we also highlighted differences between arable fields and semi-natural habitats, emphasizing the importance of land-use legacy

Precision spectroscopy of the 3s-3p fine structure doublet in Mg+

We apply a recently demonstrated method for precision spectroscopy on strong transitions in trapped ions to measure both fine structure components of the 3s-3p transition in 24-Mg+ and 26-Mg+. We deduce absolute frequency reference data for transition frequencies, isotope shifts and fine structure splittings that are in particular useful for comparison with quasar absorption spectra, which test possible space-time variations of the fine structure constant. The measurement accuracy improves previous literature values, when existing, by more than two orders of magnitude

Absolute rate coefficients for photorecombination and electron-impact ionization of magnesium-like iron ions from measurements at a heavy-ion storage ring

Rate coefficients for photorecombination (PR) and cross sections for electron-impact ionization (EII) of Fe$^{14+}$ forming Fe$^{13+}$ and Fe$^{15+}$, respectively, have been measured by employing the electron-ion merged-beams technique at a heavy-ion storage ring. Rate coefficients for PR and EII of Fe$^{14+}$ ions in a plasma are derived from the experimental measurements. Simple parametrizations of the experimentally derived plasma rate coefficients are provided for use in the modeling of photoionized and collisionally ionized plasmas. In the temperature ranges where Fe$^{14+}$ is expected to form in such plasmas the latest theoretical rate coefficients of Altun et al. [Astron. Astrophys. 474, 1051 (2007)] for PR and of Dere [Astron. Astrophys. 466, 771 (2007)] for EII agree with the experimental results to within the experimental uncertainties. Common features in the PR and EII resonance structures are identified and discussed.Comment: 12 pages, 6 figures, 3 tables, submitted for publication to Physical Review

Absolute rate coefficients for photorecombination of berylliumlike and boronlike silicon ions

We report measured rate coefficients for electron-ion recombination for Si10+ forming Si9+ and for Si9+ forming Si8+, respectively. The measurements were performed using the electron-ion merged-beams technique at a heavy-ion storage ring. Electron-ion collision energies ranged from 0 to 50 eV for Si9+ and from 0 to 2000 eV for Si10+, thus, extending previous measurements for Si10+ [Orban et al. 2010, Astrophys. J. 721, 1603] to much higher energies. Experimentally derived rate coefficients for the recombination of Si9+ and Si10+ ions in a plasma are presented along with simple parameterizations. These rate coefficients are useful for the modeling of the charge balance of silicon in photoionized plasmas (Si9+ and Si10+) and in collisionally ionized plasmas (Si10+ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties.Comment: 17 pages, 7 figures, 3 tables, 66 references, submitted to the J. Phys. B special issue on atomic and molecular data for astrophysicist

Evolutionary Rearrangement of the Amylase Genomic Regions Between Drosophila melanogaster and Drosophila pseudoobscura

Abstract Two Drosophila pseudoobscura genomic clones have sequence similarity to the Drosophila melanogaster amylase region that maps to the 53CD region on the D. melanogaster cytogenetic map. The two clones with similarity to amylase map to sections 73A and 78C of the D. pseudoobscura third chromosome cytogenetic map. The complete sequences of both the 73A and 78C regions were compared to the D. melanogaster genome to determine if the coding region for amylase is present in both regions and to determine the evolutionary mechanism responsible for the observed distribution of the amylase gene or genes. The D. pseudoobscura 73A and 78C linkage groups are conserved with the D. melanogaster 41E and 53CD regions, respectively. The amylase gene, however, has not maintained its conserved linkage between the two species. These data indicate that amylase has moved via a transposition event in the D. melanogaster or D. pseudoobscura lineage. The predicted genes within the 73A and 78C regions show patterns of molecular evolution in synonymous and nonsynonymous sites that are consistent with previous studies of these two species. Conserved synteny occurs when two or more homologous genes are located on the same chromosome in two or more species. Conserved linkage occurs when two or more homologous genes are syntenic and are in the same order on the chromosome in two or more species The third chromosome of Drosophila pseudoobscura is polymorphic for more than 30 gene arrangements that were generated through a series of overlapping paracentric inversions. The a-amylase gene maps to the third chromosome of D. pseudoobscura The 73A region encodes one to three amylase genes There are two broad explanations for why two regions of the third chromosome in D. pseudoobscura are similar to a-amylase. First, one of several a-amylase copies was moved to a new location through a paracentric inversion. The a-amylase gene appears to be capable of repeated duplication events and diversification to new functions This article presents a nucleotide sequence comparison of the 73A and 78C sections of the D. pseudoobscura third chromosome with the conserved linkage groups from the D. melanogaster genome. We will show here that the D. pseudoobscura 73A and 78C linkage groups are conserved with the D. melanogaster 41E and 53CD regions, respectively. The a-amylase gene, however, has not maintained its conserved linkage between the two species. These data suggest that the a-amylase locus has shifted its location via a nonreplicative transposition event in either the D. pseudoobscura or D. melanogaster lineage. Materials and Methods Nucleotide Sequences of the D. pseudoobscura 73A and 78C Regions A 12.6 kb clone that maps to section 78C on the D. pseudoobscura cytogenetic map was digested with the EcoRI restriction endonuclease into four fragments 2.9 kb, 3.8 kb, 1.5 kb, and 4.6 kb in length. These EcoRI fragments were subcloned into the plasmid sequencing vector pWSK29 (Wang and Kushner 1991) using the methods described in Nucleotide Sequence Analysis The 12 kb sequence of the 78C clone was submitted to the GenBank The alignment of sequences was achieved with the MEGALIGN program within the LASERGENE package of DNA sequence analysis software (Madison, WI). Molecular evolutionary sequence analysis was completed with Results Sequence of the 78C Region of D. pseudoobscura The complete sequence of the clone from the D. pseudoobscura 78C region is 12,592 bp in length. There is a slight A/T bias in the sequence, but the difference is not statistically significant from a 50:50 ratio of A/T (50.6%) to G/C (49.6%) with a chi-square goodness-of-fit test (v 2 ¼ 1.64, df ¼ 1, P ¼ .19). GenBank Searches The 12.6 kb sequence from 78C of D. pseudoobscura matched eight D. melanogaster accessions with an E value less than 5 3 10 ÿ9 . All of these accessions map to section 53CD on the D. melanogaster cytogenetic map. Two accessions, AC099032 and AC007520, were genomic sequences from D. melanogaster BAC clones of 163 and 171 kb, respectively. One accession, AE003804, was a 260 kb genomic scaffold assembled in the Drosophila genome project The 12.6 kb sequence from 78C may not provide a complete picture of the degree of conserved linkage between D. melanogaster and D. pseudoobscura because this cloned sequence is relatively small. We used this 12.6 kb sequence to identify a 73.7 kb contig from the D. pseudoobscura whole genome shotgun assembly (Contig1060; Human Genome Sequencing Center 2003). Contig1060 matched 40 D. melanogaster accessions with an E value less than 5 3 10 ÿ9 , including the two BAC clones (AC099032 and AC007520) and the genomic scaffold (AE003804) found with the shorter 78C sequence. This BLAST search also found a match to an additional 158 kb BAC clone (AC005713). Thirteen of the matched accessions were between the cytosolic leucine tRNA genes CR30234 and CR30235 in the 78C region and similar tRNA genes of D. melanogaster at four locations in the genome. The last 23 matched accessions were to short cDNA or genomic clones in the 78C region. The 260 kb genomic scaffold AE003804 was used in all comparisons of the D. pseudoobscura 78C region with the 53CD conserved linkage group of D. melanogaster. The 185 kb sequence (Contig6731_Contig3011) from D. pseudoobscura 73A matched 123 GenBank The D. melanogaster sequence has two a-amylase genes, Amy-p and Amy-d, which are divergently transcribed on the chromosome The CG15605 gene appears to have duplicated in D. pseudoobscura lineage based on dot plot analysis and on translated BLAST searches with the 78C region sequence. This second copy of CG15605 is on the opposite strand from the D. melanogaster homologue of the CG15605 gene, is located near the central microinversion, and appears to be a pseudogene (see below). One might argue that the 12.6 kb sequence from D. pseudoobscura 78C is too small to infer the degree of conserved linkage between the two species. Comparison of Contig1060 from the D. pseudoobscura genome project with the D. melanogaster 53CD region shows that the conserved linkage extends over at least 73.7 kb The conservation of genes between 41E in D. melanogaster and 73A in D. pseudoobscura is shown in Molecular Evolutionary Comparisons of Genes in D. melanogaster and D. pseudoobscura We estimated the frequency of synonymous and nonsynonymous changes between the two species for the genes in the two chromosomal regions A second CG15605 gene segment was identified in a dot plot analysis and appears to be a pseudogene that we designate CG15605w Discussion Rearrangement of the Amylase Region Between D. melanogaster and D. pseudoobscura The 78C region of D. pseudoobscura and the 53CD section of the D. melanogaster genome are conserved linkage groups. The amylase genes, however, are no longer part of this conserved linkage group because the D. pseudoobscura amylase genes are now located within section 73A on the D. pseudoobscura cytogenetic map The comparison of the D. pseudoobscura 73A and the 78C regions with the conserved linkage groups of D. melanogaster suggest that a transposition event rather than a paracentric inversion was responsible for the relocation of the amylase gene. If an inversion event had moved the amylase gene in D. pseudoobscura, then we might expect parts of both the 73A and We were unable to directly infer if the transposition occurred in the D. melanogaster or D. pseudoobscura lineage from the comparison of these two genome regions

Nitrogen fixation and release of fixed nitrogen by Trichodesmium spp. in the Gulf of Mexico

During a 3‐yr study in the Gulf of Mexico, we measured dinitrogen (N2) fixation and nitrogen (N) release by Trichodesmium and compared these rates with water column N demand and the estimated N necessary to support blooms of Karenia brevis, a toxic dinoflagellate that severely affects the West Florida shelf. Net and gross N2 fixation rates were compared in simultaneous incubations using δ15N2 uptake and acetylene reduction, respectively. The difference between net and gross N2 fixation is assumed to be an approximation of the rate of N release. Results demonstrate that Trichodesmium in the Gulf of Mexico are fixing N2 at high rates and that an average of 52% of this recently fixed N2 is rapidly released. Calculations suggest that observed densities of Trichodesmium can provide enough N to support moderately sized K. brevis blooms. Based on other studies where δ15N2 and acetylene reduction were compared directly, it appears that N release from Trichodesmium is common but varies in magnitude among environments. In addition, carbon (C) and N‐based doubling times for Trichodesmium vary among studies and environments. Comparing gross N2 fixation and C fixation directly, C‐based doubling times exceeded N‐based doubling times, which suggests an imbalance in elemental turnover or a failure to fully quantify Trichodesmium N use