Rotation and activity in the solar-type stars of NGC 2547

We present high resolution spectroscopy of a sample of 24 solar-type stars in the young (15-40 Myr), open cluster, NGC 2547. We use our spectra to confirm cluster membership in 23 of these stars, determine projected equatorial velocities and chromospheric activity, and to search for the presence of accretion discs. We have found examples of both fast (vsini>50kms) and slow (vsini<10kms) rotators, but find no evidence for active accretion in any of the sample. The distribution of projected rotation velocities is indistinguishable from the slightly older IC 2391 and IC 2602 clusters, implying similar initial angular momentum distributions and circumstellar disc lifetimes. The presence of very slow rotators indicates that either long (10-40 Myr) disc lifetimes or internal differential rotation are needed, or that NGC 2547 (and IC 2391/2602) were born with more slowly rotating stars than are presently seen in even younger clusters and associations. The solar-type stars in NGC 2547 follow a similar rotation-activity relationship to that seen in older clusters. X-ray activity increases until a saturation level is reached for vsini>15-20kms. We are unable to explain why this saturation level, of log (L_x/L_bol)~-3.3, is a factor of two lower than in other clusters, but rule out anomalously slow rotation rates or uncertainties in X-ray flux calculations.Comment: Accepted by MNRA

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Assessment of key reproductive markers after hormonal induction of spawning, using gonadotrophin-releasing hormone in female yellow belly flounder (Rhombosolea leporine):.

Yellow belly flounder (YBF) (Rhombosolea leporina) are of interest to the New Zealand aquaculture industry as a novel culture species. This is due to their high commercial value and low trophic feeding level. However, when held in captive settings, YBF are observed to undergo reproductive failure. GnRHa has been used as a spawning inducing agent within many cultured fish species. Flounder gonadotrophin levels were traced after induction and oocyte development was histologically assessed. At pituitary level it was seen that the GnRHa induction resulted in increased follicle stimulating hormone (FSH) levels. Luteinising hormone (LH) was seen to be unaffected. However, neither of these changes were significant P>0.05. These weak results were most likely caused by seasonality. Oocyte development was seen to follow a similar trend to other flounder and flatfish species, when oocyte size, development stages and features were tracked using histological analysis. Relationships between Gonadosomatic index (GSI) and gonadotrophins FSH and LH displayed weak correlations (P>0.05). This again could be linked to seasonal variability in temperature and photoperiod. The presence of large amounts of atretic oocytes observed in the gonads indicated that the ovary had already spawned for the season before initial capture, or that oocytes had been aborted. A likely cause of this would be captivity -induced stress, or fish having previously spawned before capture. All fish that ovulated were part of the GnRHa treated group. Fish were strip-spawned, fertilised and embryonic development was tracked. Incubation temperatures were 17 and 19°C. It was established that of the two temperatures, 17°C was optimum. A larger percentage of these embryos survived from fertilisation to hatch, which took approximately 68 hours. Bacterial infection was seen to be a problem in eggs incubated at the higher 19°C temperature. Egg quality was assessed by looking at the 8 cell blastomere stage, and grading charts were made for reference. these assessed blastomere size, shape, symmetry and cohesion. It is suggested that future research efforts focus on seasonal variations of gonadotrophin levels and gonadal development, in order to gain clearer understanding of these seasonal effects. Effects of cortisol on the reproductive axis would also be a beneficial research area. This would provide insight into how stress affects sex steroid production and the maturation of the gonad and oocytes in YBF

Facilitated diffusion. The case of carbon monoxide.

Abstract An application of a singular perturbation method to the case of carbon monoxide similar to that used previously for the case of oxygen (Murray, J. D., Proc. Roy. Soc. London B Biol. Sci., 178, 95 (1971)) shows that the absence of any observed facilitation of diffusion of this ligand by either hemoglobin or myoglobin in all of the experiments so far performed results from the very high affinity of both proteins for the gas. At every point in the solution both proteins were essentially at equilibrium with the gas but it was evidently impossible to reduce the pressure of carbon monoxide on the low pressure face of the solution sufficiently to remove a significant amount of the carbon monoxide from combination with the macromolecular carrier. The principle that a macromolecule can only function as a carrier under conditions in which its saturation with the ligand is incomplete in some region of the solution is quite general

A Political History of the Establishment Clause

Now pending before the Supreme Court is the most important church-state issue of our time: whether publicly funded vouchers may be used at private, religious schools without violating the Establishment Clause. The last time the Court considered school aid, it overruled precedent and upheld a government program providing computers and other instructional materials to parochial schools. In a plurality opinion defending that result, Justice Thomas dismissed as irrelevant the fact that some aid recipients were pervasively sectarian. That label, said Thomas, had a shameful pedigree. He traced it to the Blaine Amendment, proposed in 1875, which would have altered the Constitution to ban aid to sectarian institutions. At the time, it was an open secret that \u27sectarian\u27 was code for \u27Catholic.\u27 Of course, said Thomas, the word could describe schools of other religions, but the Court eliminated this possibility of confusion by coining the phrase pervasively sectarian - a term applicable almost exelusively to Catholic parochial schools. The exclusion of pervasively sectarian schools from otherwise permissible aid to education was, Thomas concluded, not a neutral interpretation of constitutional command but a doctrine born of bigotry. Justice Thomas did not attack the ban against aid to pervasively sectarian schools merely as a misunderstanding of text or original intent. He charged, rather, that the hostility to pervasively sectarian institutions reflected political conflict and popular prejudice. This is not the usual stuff of Supreme Court debate. Perhaps for that reason, Justice Souter\u27s dissent did not so much answer the accusation as make fun of it, noting only that some pervasively sectarian schools are not Catholic and that some Catholics oppose school aid. Nevertheless, Thomas\u27s account is at least partly true. The constitutional disfavor of pervasively sectarian institutions is indeed a doctrine born, if not of bigotry, at least of a highly partisan understanding of laws respecting an establishment of religion. The first and narrowest ambition of this Article is to document that assertion

X-ray Emission From Nearby M-dwarfs: the Super-saturation Phenomenon

A rotation rate and X-ray luminosity analysis is presented for rapidly rotating single and binary M-dwarf systems. X-ray luminosities for the majority of both single & binary M-dwarf systems with periods below $\simeq 5-6$ days (equatorial velocities, V$_{eq}>$ 6 km~s$^{-1}$) are consistent with the current rotation-activity paradigm, and appear to saturate at about $10^{-3}$ of the stellar bolometric luminosity. The single M-dwarf data show tentative evidence for the super-saturation phenomenon observed in some ultra-fast rotating ($>$ 100 km~s$^{-1}$) G & K-dwarfs in the IC 2391, IC 2602 and Alpha Persei clusters. The IC 2391 M star VXR60b is the least X-ray active and most rapidly rotating of the short period (P$_{rot}<$ 2 days) stars considered herein, with a period of 0.212 days and an X-ray activity level about 1.5 sigma below the mean X-ray emission level for most of the single M-dwarf sample. For this star, and possibly one other, we cautiously believe that we have identified the first evidence of super-saturation in M-dwarfs. If we are wrong, we demonstrate that only M-dwarfs rotating close to their break up velocities are likely to exhibit the super-saturation effect at X-ray wavelengths.Comment: 12 pages, 4 figures, accepted by MNRA