Concentrations of major ions in the stream water of the upper basin of the River Duddon, England, 1972-1974 [Dataset]

This dataset provides raw data of chemical analyses made during studies on seasonal variations of some major ions in the stream water of the upper basin of the River Duddon in Cumbria. Measurements of sodium, calcium, potassium, magnesium and chloride ions and pH were taken at 26 stations in the River Duddon basin between 1972 and 1974.

Population differentiation of Procypris rabaudi (Tchang) in the upper reaches of the Yangtze River revealed by mitochondrial DNA and RAPD markers

Procypris rabaudi (Tchang) is a cyprinid fish endermic to middle and upper reaches of the Yangtze River. Besides in main stream and large tributaries, there exists an early matured, small-sized ecological type in a small tributary, Tang River. In this study, mitochondrial DNA cytochrome h (cyt b) gene sequence analysis and randomly amplified polymorphic DNA (RAPD) analysis were performed to investigate the differentiation of the Tang River population from the Mudong reach population of the Yangtze River, with the purpose of conservation and exploitation of this fish. In the 1140 bps of cyt b gene sequence surveyed, 20 sites were found polymorphic, which defined 23 haplotypes. Among them, four haplotypes accounted for 54.4% of all individuals, while population-specific haplotypes occurred in low frequencies. Analysis of molecular variation on cyt b data revealed no significant partition existing between Tang River population and Mudong reach population. Analyses of 132 RAPD loci suggested that genetic variation between populations was significant, though values of different F-ST were not very high. The results revealed low genetic diversity and the beginning of population differentiation, suggesting that Tang River population should be designated as a separate Management Unit.

Population genetic structure of an endemic cyprinid fish, Ancherythroculter nigrocauda, in the upper reaches of the Yangtze River and its implication for conservation

Ancherythroculter nigrocauda is a cyprinid fish endemic to the upper reaches of the Yangtze River, which has been reported to have 2 or 3 chambers to its air bladder. Morphological studies showed no differences between individuals with different types of air bladder, but did demonstrate geographical differences from different sources. After the completion of the Three Gorges Dam, it was expected that the population of this species would decrease, but artificial breeding and stocking is under consideration to protect this species from extinction. In the present study, mtDNA cytochrome b gene sequences were determined and analyzed for A. nigrocauda samples of different morphotypes and sources to identify their genetic differentiations, and thereby guide plans for the artificial propagation and conservation of this species. Haplotype diversity index values (h) and nucleotide diversity values (pi) for all the populations were found to be high indicating their high level genetic diversity. An analysis of molecular variance identified no differentiation among the studied populations. Therefore, we suggested that the individuals of different morphological types and geographical sources belong to the same species. To maintain its high level genetic diversity, it mill he necessary to use large and diverse sources of parental fish for artificial reproduction.

Opacity in the upper atmosphere of AU Mic

In this paper we investigate the validity of the optically thin assumption in the transition region of the late-type star AU Mic. We use Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C III multiplet and O VI resonance lines, hence yielding information at two different levels within the atmosphere. Significant deviations from the optically thin fluxes are found for C III in both quiescent and flare spectra, where only 60% of the flux is actually observed. This could explain the apparent deviation of C III observed in emission measure distributions. We utilize escape probabilities for both homogeneous and inhomogeneous geometries and calculate optical depths as high as 10 for the C III 1175.71 Angstrom component of the multiplet. Using a lower limit to the electron density (10(11) cm(-3))we derive an effective thickness of

A detailed study of opacity in the upper atmosphere of Proxima Centauri

We present far-UV and UV spectroscopic observations of Proxima Centauri obtained as part of our continued investigation into the optically thin approximation assumed for the transition regions of late-type stars. Significant opacity is found in the C III lines during both the quiescent and flaring states of Proxima Cen, with up to 70% of the expected flux being lost in the latter. Our findings cast some doubt on the suitability of the C III lambda977 line for estimating the electron density in stellar atmospheres. However, the opacity has no significant effect on the observed line widths. We calculate optical depths for homogeneous and inhomogeneous geometries and estimate an electron density of 6 x 10(10) cm(-3) for the transition region using the O IV line ratios at 1400 Angstrom. The combination of electron density and optical depth indicates path lengths as low as approximate to 10 km, which are in excellent agreement with estimates of the small-scale structure seen in the solar transition region.

Opacity in the upper atmospheres of active stars - II. AD Leonis

We present FUV and UV spectroscopic observations of AD Leonis, with the aim of investigating opacity effects in the transition regions of late-type stars. The C III lines in FUSE spectra show significant opacity during both the quiescent and flaring states of AD Leonis, with up to 30% of the expected flux being lost during the latter. Other FUSE emission lines tested for opacity include those of O VI, while C IV, Si IV and N V transitions observed with STIS are also investigated. These lines only reveal modest amounts of opacity with losses during flaring of up to 20%. Optical depths have been calculated for homogeneous and inhomogeneous geometries, giving path lengths of approximate to 20 - 60 km and approximate to 10 - 30 km, respectively, under quiescent conditions. However path lengths derived during flaring are approximate to 2 - 3 times larger. These values are in excellent agreement with both estimates of the small-scale structure observed in the solar transition region, and path lengths derived previously for several other active late-type stars.

The Dissociative Recombination of Protonated Acrylonitrile, CH2CHCNH+, with Implications for Nitrile Chemistry in Dark Molecular Clouds and the Upper Atmosphere of Titan

Measurements on the dissociative recombination (DR) of protonated acrylonitrile, CH2CHCNH+, have been performed at the heavy ion storage ring CRYRING located in the Manne Siegbahn Laboratory in Stockholm, Sweden. It has been found that at~2meV relative kinetic energy about 50% of the DR events involve only ruptures of X–H bonds (where X=C or N)while the rest leads to the production of a pair of fragments each containing two heavy atoms (alongside H and/or H2). The absolute DR cross section has been investigated for relative kinetic energies ranging from ~1 meV to 1 eV. The thermal rate coefficient has been determined to follow the expression k(T) = 1.78 × 10-6 (T/300)-0.80 cm3 s-1 for electron temperatures ranging from ~10 to 1000 K. Gas-phase models of the nitrile chemistry in the dark molecular cloud TMC-1 have been run and results are compared with observations. Also, implications of the present results for the nitrile chemistry of Titan’s upper atmosphere are discussed.

Crinoids for lunch? An unexpected biotic interaction from the Upper Ordovician of Scotland

Specimens of the polyplacophoran mollusk 'Helminthochiton' thraivensis Reed from the Upper Ordovician of southwest Scotland provide rare examples of complete valve series preserved in near life position, albeit as external molds. Application of high-resolution X-ray microtomography to one such specimen has revealed the exceptional preservation of its last meal, which included elements of a crinoid column, in its intestine. The interaction was either predatory or scavenging; extant chitons are not known to be crinoidivorous. This is the earliest direct record of predation or scavenging on crinoids in the fossil record. It is also the first indication that the broad axial canal of primitive crinoids may have contained nutritious tissues. The predatory or scavenging habit of H. thraivensis is consistent with its inferred phylogenetic position as a stem-group aplacophoran and provides new data suggesting an origin of carnivory early in the evolution of this clade.

On the filling factor of emitting material in the upper atmosphere of ε Eri (K2 V)

The emission measure distribution in the upper transition region and corona of e Eri is derived from observed emission-line fluxes. Theoretical emission measure distributions are calculated assuming that the radiation losses are balanced by the net conductive flux. We discuss how the area factor of the emitting regions as a function of temperature can be derived from a comparison between these emission measure distributions. It is found that the filling factor varies from ~0.2 in the mid-transition region to ~1.0 in the inner corona. The sensitivity of these results to the adopted ion fractions, the iron abundance and other parameters is discussed. The area factors found are qualitatively similar to the observed structure of the solar atmosphere, and can be used to constrain two-component models of the chromosphere. Given further observations, the method could be applied to investigate the trends in filling factors with indicators of stellar activity.