Based on high-resolution spectra obtained during gravitational microlensing events we present a detailed elemental abundance analysis of 32 dwarf and subgiant stars in the Galactic bulge. Combined ...with the sample of 26 stars from the previous papers in this series, we now have 58 microlensed bulge dwarfs and subgiants that have been homogeneously analysed. The results from the microlensed bulge dwarf stars in combination with other findings in the literature, in particular the evidence that the bulge has cylindrical rotation, indicate that the Milky Way could be an almost pure disk galaxy. The bulge would then just be a conglomerate of the other Galactic stellar populations, residing together in the central parts of the Galaxy, influenced by the Galactic bar.
In the subtropical North Pacific, the east‐west gradient of iron deposition as atmospheric Asian dust strongly affects the zonal distribution of biological N2 fixation activity in numerical models, ...but the in‐situ relationship at a basin‐scale is not well examined. We examined the trans‐Pacific zonal variation in N2 fixation activity on 23°N in summer along with environmental parameters that potentially influence diazotrophy. Dissolved inorganic iron (DFe) was consistently low (<0.4 nM) throughout the transect. The atmospheric dust iron (dust‐Fe) flux increased westward, whereas phosphate and labile phosphoric monoesters in the surface decreased westward. N2 fixation varied between 34.6 and 298 μmol‐N m−2 d−1 and was high (>200 μmol‐N m−2 d−1) in the central area (150–180°W). N2 fixation rates significantly increased with dust‐Fe input only in the western area (137–180°E), whereas the contribution of DFe diffused from below the euphotic zone was often larger in the eastern area (120–170°W). N2 fixation was considerably low in the phosphate‐depleted western area despite the excess amount of iron relative to phosphate, and it increased with the labile phosphoric monoesters stock. These indicated that N2 fixation was primarily limited by phosphorus in the western area, though this activity also increased with iron supply from dust, likely due to phosphorus‐iron co‐limitation. In contrast, in the phosphorus‐repleted eastern area, iron supplied from dust and below the euphotic zone appeared to limit N2 fixation. Overall, N2 fixation in the subtropical North Pacific was likely limited by zonally different factors relating to iron and phosphorus availability.
Plain Language Summary
N2 fixation, a process that converts N2 gas into ammonia, substantially affects biological production in subtropical ecosystems, where nitrogenous nutrients are scarce. The availability of both iron and phosphorus are primary factors controlling the growth of N2‐fixing organisms. In North Pacific subtropical waters, iron input as atmospheric Asian dust is considered to control the east‐west variation in N2 fixation; however, their relationship is not well‐examined. Here, we investigated the trans‐Pacific distribution of N2 fixation activity with iron and phosphorus availability. Our results show that dust input correlates with N2 fixation in the western area (137–180°E), which is in contrast with the eastern area (120–170°W), where vertically diffused iron was also important. In the phosphate‐depleted western area, N2 fixation positively correlated with the proxies of phosphorus supply, suggesting phosphorus limitation. This indicates phosphorus availability substantially controls the zonal distribution of N2 fixation in the subtropical North Pacific through co‐limitation with iron. The limitations are relaxed in the central area (150–180°W), likely due to elevated nutrient supply caused by bottom topography, resulting in a peak in N2 fixation. Therefore, the dynamics of both iron and phosphorus must be considered simultaneously to predict the response of N2 fixation to environmental changes.
Key Points
Along the zonal transect in the subtropical North Pacific, N2 fixation activity was high in the central area (150–180°W)
The central North Pacific was characterized by intermediate iron and phosphorus supply in the euphotic zone
East‐west gradient of phosphorus availability controls the N2 fixation in the North Pacific through likely co‐limitation with iron
HI 1225 + 01 is an intergalactic gas cloud located on the outskirts of Virgo cluster. Its main components are two large clumps of comparable HI masses (M sub(HI) ~ 10 super(9) M sub(odot)) separated ...by about 100 kpc. One of the clumps hosts a blue low-surface-brightness galaxy J1227 + 0136, while the other has no identified stellar emission and is sometimes referred to as a promising candidate of a "dark galaxy," an optically invisible massive intergalactic system. We present a deep optical image covering the whole HI 1225 + 01 structure for the first time, as well as a collection of archival data from ultraviolet to far-infrared (IR) spectral region of the brightest knot "R1" in J1227 + 0136. We find that R1 has a young stellar population 10-100 Myr in age and mass ~10 super(6) M sub(odot), near-IR excess brightness which may point to the presence of hot dust with color temperature ~600 K, and relatively faint mid- to far-IR fluxes corresponding to the dust mass of up to ~100 M sub(odot). Overall, it seems to share the general properties with low-metallicity blue compact dwarf galaxies. On the other hand, no optical counterpart to the other clump is found in our deepest-ever image. Now the limiting surface brightness reaches down to R sub(AB) > 28 mag arcsec super(-2) for any emission extended over 10" (comparable to R1), which is more than one hundred times fainter than the brightest part of the companion galaxy J1227 + 0136.
This study aimed to determine the seasonality of reproduction throughout the year in Japanese wood mice (Apodemus speciosus). The effect of seasonal changes on testicular morphology and the periodic ...expression of circadian clock genes in the hypothalamus and testes of male individuals was evaluated. We also examined the morphology of the testes and caudae epididymides of male mice. In addition, RT-PCR analysis was carried out with mRNA extracted from the hypothalamus and testes to evaluate the expression of the circadian clock genes Clock, Bmal1, Per1, and Cry1. The complete induction of testicular activity was detected from February to April and from August to October, with testes weight increasing with the completion of spermatogenesis (reproductive season). From May to early June and from November to early January, testicular weight declined, the seminiferous tubules reduced in size, spermatogenesis was arrested, and sperm were not produced (non-reproductive season). From mid- June to July and mid-January, the re-induction of testicular activity for spermatogenesis was observed in the seminiferous tubules (transitional season). Out of the four examined genes, Cry1 had the highest expression level in both the hypothalamus and testes throughout the year, followed by Bmal1, Per1, and Clock. The expression of Bmal1 was significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive and non-reproductive seasons. Cry1 transcript levels were also significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive season. In conclusion, the results indicating changes in testicular morphology revealed annual reproductive, non-reproductive, and transmission periods in Japanese wood mice. When an increase in testicular activity was observed indicating the onset of the reproductive season, the mean day length was approximately 1113 h. The expression of the circadian clock genes Bmal1 and Cry1 in the hypothalamus and testes during the reproductive season was significantly higher than that of the same genes during the transitional season. Consequently, completion of spermatogenesis occurred in the seminiferous tubules of Japanese wood mice testes during the reproductive period.
Based on high-resolution spectra obtained during gravitational microlensing events we present a detailed elemental abundance analysis of 32 dwarf and subgiant stars in the Galactic bulge. Combined ...with the sample of 26 stars from the previous papers in this series, we now have 58 microlensed bulge dwarfs and subgiants that have been homogeneously analysed. The main characteristics of the sample and the findings that can be drawn are: (i) the metallicity distribution (MDF) is wide and spans all metallicities between Fe/H = −1.9 to +0.6; (ii) the dip in the MDF around solar metallicity that was apparent in our previous analysis of a smaller sample (26 microlensed stars) is no longer evident; instead it has a complex structure and indications of multiple components are starting to emerge. A tentative interpretation is that there could be different stellar populations at interplay, each with a different scale height: the thin disk, the thick disk, and a bar population; (iii) the stars with Fe/H ≲ −0.1 are old with ages between 10 and 12 Gyr; (iv) the metal-rich stars with Fe/H ≳ −0.1 show a wide variety of ages, ranging from 2 to 12 Gyr with a distribution that has a dominant peak around 4−5 Gyr and a tail towards higher ages; (v) there are indications in the α/Fe−Fe/H abundance trends that the “knee” occurs around Fe/H = −0.3to −0.2, which is a slightly higher metallicity as compared to the “knee” for the local thick disk. This suggests that the chemical enrichment of the metal-poor bulge has been somewhat faster than what is observed for the local thick disk. The results from the microlensed bulge dwarf stars in combination with other findings in the literature, in particular the evidence that the bulge has cylindrical rotation, indicate that the Milky Way could be an almost pure disk galaxy. The bulge would then just be a conglomerate of the other Galactic stellar populations (thin disk, thick disk, halo, and ...?), residing together in the central parts of the Galaxy, influenced by the Galactic bar.
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This study aimed to develop a polymerase chain reaction (PCR)‐based sexing and effective semen collection methods for black‐headed and straw‐necked ibis species. However, most birds are not ...sexually dimorphic, that is, the sexes appear similar. Therefore, the gender should be determined before semen collection. DNA was extracted from the blood samples of 11 black‐headed and 4 straw‐necked ibis. The sex was determined after PCR amplification of the EE0.6 region of W‐chromosome. The PCR products were separated using gel electrophoresis. A single band indicated the presence of the EE0.6 region and that the individual was a female, while no band indicated that the individual was a male. Further, the single bands from seven specimens were amplified. Semen collection was performed by massage or a combination of massage with electro‐ejaculation and was attempted during all four seasons. The semen was successfully collected in March from male straw‐necked ibis using the massage method. Limited motility, viability and concentration of straw‐necked ibis sperm were observed. The sperm length was 180 μm and that of the nucleus was 30 μm with acrosome located at the tip of the nucleus. Thus, the PCR‐based sexing proved to be an accurate molecular sexing method for black‐headed and straw‐necked ibis. Furthermore, we successfully collected semen and observed the stained sperm nucleus and acrosome of the straw‐necked ibis sperm. We propose that the use of this PCR methodology can be applied as a routine method for sex determination and semen collection in ibis species for future ecological research. However, considering our limited success, further studies on semen collection method are required.
Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will ...span the full range of significance levels including planetary signals too small to be distinguished from the noise. At present, we do not understand where the threshold is for detecting planets. MOA-2011-BLG-293Lb is the first planet to be published from the new surveys, and it also has substantial follow-up observations. This planet is robustly detected in survey+follow-up data ( Delta chi super(2) ~ 5400). The planet/host mass ratio is q = (5.3 + or - 0.2) x 10 super(-3). The best-fit projected separation is s = 0.548 + or - 0.005 Einstein radii. However, due to the s left right arrow s super(-1) degeneracy, projected separations of s super(-1) are only marginally disfavored at Delta chi super(2) = 3. A Bayesian estimate of the host mass gives ML = 0.43 super(+0.27) sub(-0.17) M sub(middot in circle), with a sharp upper limit of ML < 1.2 M sub(middot in circle) from upper limits on the lens flux. Hence, the planet mass is mp = 2.4 super(+1.5) sub(-0.9) M sub(Jup), and the physical projected separation is either r sub(perpendicular) Asymptotically = to 1.0 AU or r sub(perpendicular) Asymptotically = to 3.4 AU. We show that survey data alone predict this solution and are able to characterize the planet, but the Delta chi super(2) is much smaller ( Delta chi super(2) ~ 500) than with the follow-up data. The Delta chi super(2) for the survey data alone is smaller than for any other securely detected planet. This event suggests a means to probe the detection threshold, by analyzing a large sample of events like MOA-2011-BLG-293, which have both follow-up data and high-cadence survey data, to provide a guide for the interpretation of pure survey microlensing data.
H I 1225+01 is an intergalactic gas cloud located on the outskirts of Virgo cluster. Its main components are two large clumps of comparable H I masses (M{sub Hi}{approx}10{sup 9} M{sub Sun }) ...separated by about 100 kpc. One of the clumps hosts a blue low-surface-brightness galaxy J1227+0136, while the other has no identified stellar emission and is sometimes referred to as a promising candidate of a 'dark galaxy', an optically invisible massive intergalactic system. We present a deep optical image covering the whole H I 1225+01 structure for the first time, as well as a collection of archival data from ultraviolet to far-infrared (IR) spectral region of the brightest knot 'R1' in J1227+0136. We find that R1 has a young stellar population 10-100 Myr in age and mass {approx}10{sup 6} M{sub Sun }, near-IR excess brightness which may point to the presence of hot dust with color temperature {approx}600 K, and relatively faint mid- to far-IR fluxes corresponding to the dust mass of up to {approx}100 M{sub Sun }. Overall, it seems to share the general properties with low-metallicity blue compact dwarf galaxies. On the other hand, no optical counterpart to the other clump is found in our deepest-ever image. Now the limiting surface brightness reaches down to R{sub AB} > 28 mag arcsec{sup -2} for any emission extended over 10'' (comparable to R1), which is more than one hundred times fainter than the brightest part of the companion galaxy J1227+0136.
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