Release of dissolved free amino acids during a bloom of Thalassiosira rotula

Three large plastic enclosures (3-4 m3) were anchored in the outer harbour of Helgoland (German Bight) and filled with natural seawater which was filtered free of algae. The enclosed water bodies were enriched with inorganic nutrients and inoculated with the diatom Thalassiosira rotula. During the growth of the algae diurnal changes in concentration of dissolved free amino acids (DFAA) occurred. The periodic concentration changes of individual amino acids with a low carbon to nitrogen ratio showed significant interrelationships with the partly synchronous devisions of the diatoms. From the exponential to the stationary phase the carbon to nitrogen ratio of DFAA shifted to higher values pointing at an adaptation of the organisms to the decreasing inorganic nitrogen source. During the bloom amino acids relatively rich in nitrogen were mainly excreted but by the end of the growth amino acids with a higher carbon content predominated. At phases of high photosynthetic activity the organisms probably reduced the high osmotic pressure by exudation of DFAA

Interpreting the near-infrared spectra of the 'golden standard' Type Ia supernova 2005cf

We present nine near-infrared (NIR) spectra of supernova (SN) 2005cf at epochs from -10 d to +42 d with respect to B-band maximum, complementing the existing excellent data sets available for this prototypical Type Ia SN at other wavelengths. The spectra show a time evolution and spectral features characteristic of normal Type Ia SNe, as illustrated by a comparison with SNe 1999ee, 2002bo and 2003du. The broad-band spectral energy distribution (SED) of SN 2005cf is studied in combined ultraviolet (UV), optical and NIR spectra at five epochs between ~ 8 d before and ~ 10 d after maximum light. We also present synthetic spectra of the hydrodynamic explosion model W7, which reproduce the key properties of SN 2005cf not only at UV-optical as previously reported, but also at NIR wavelengths. From the radiative-transfer calculations we infer that fluorescence is the driving mechanism that shapes the SED of SNe Ia. In particular, the NIR part of the spectrum is almost devoid of absorption features, and instead dominated by fluorescent emission of both iron-group material and intermediate-mass elements at pre-maximum epochs, and pure iron-group material after maximum light. A single P-Cygni feature of Mg II at early epochs and a series of relatively unblended Co II lines at late phases allow us to constrain the regions of the ejecta in which the respective elements are abundant.Comment: 11 pages, 6 figures, accepted for publication in MNRA

Time-Resolved Photometry of the Optical Counterpart of Swift J2319.4+2619

Time-resolved CCD photometry is presented of the V~17 optical counterpart of the newly-discovered, hard-X-ray-emitting polar Swift J2619.4+2619. A total of ~20 hr of data obtained over five nights in various bandpasses (B, V, R, and I) reveals a strong quasi-sinusoidal modulation in the light curve at a best-fitting period of 0.1254 d (3.01 hr), which we associate with the orbital period of the system (one-day aliases of this period at 0.1114 d and 0.1435 d are considered, but appear to be ruled out by our analysis). The amplitude of the modulation increases with wavelength from ~0.8 mag in B to ~1.1 mag in R and I. The increase in amplitude with wavelength is typical of polar systems where the modulated radiation comes from cyclotron emission. The combination of the relatively long orbital period and the emission of hard X-rays suggest that Swift J2619.4+2619 may be a good candidate for an asynchronous polar system.Comment: 15 pages, 5 figures, Accepted for publication in the April 2008 PAS

The luminosity of supernovae of type Ia from TRGB distances and the value of H_0

Distances from the tip of the red-giant branch (TRGB) in the halo Population of galaxies - calibrated through RR Lyr stars as well as tied to Hipparcos parallaxes and further supported by stellar models - are used to determine the luminosity of six nearby type Ia supernovae (SN 2011fe, 2007sr, 1998bu, 1989B, 1972E, and 1937C). The result is M_V^corr = -19.41 +/- 0.05. If this value is applied to 62 SNe Ia with 3000< v < 20,000 km/s a large-scale value of the Hubble constant follows of H_0 = 64.0 +/- 1.6 +/- 2.0. The SN HST Project gave H_0 = 62.3 +/- 1.3 +/- 5.0 from ten Cepheid-calibrated SNe Ia (Sandage et al. 2006). The agreement of young Population I (Cepheids) and old, metal-poor Population II (TRGB) distance indicators is satisfactory. The combined weighted result is H_0 = 63.7 +/- 2.3 (i.e. +/-3.6%). The result can also be reconciled with WMAP5 data (Reid et al. 2010).Comment: 9 pages, 3 figures, 3 tables, accepted for publication in Astronomy and Astrophysic

Carbon flow through the pelagic food web in southern Chilean Patagonia: relevance of Euphausia vallentini as a key species

* Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an ‘indirect defence’. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been rarely tested. * We investigated whether there are fitness consequences for the charlock mustard Sinapis arvensis, a short-lived outcrossing annual weedy plant, when exposed to groups of large cabbage white (Pieris brassicae) caterpillars parasitized by either one of two wasp species, Hyposoter ebeninus and Cotesia glomerata, that allow the host to grow during parasitism. Hyposoter ebeninus is solitary and greatly reduces host growth compared with healthy caterpillars, whereas C. glomerata is gregarious and allows the host to grow approximately as large as unparasitized caterpillars. Both healthy and parasitized P. brassicae caterpillars initially feed on the foliage, but later stages preferentially consume the flowers. * In a garden experiment, plants damaged by parasitized caterpillars produced more seeds than conspecific plants damaged by unparasitized caterpillars. Reproductive potential (germination success multiplied by total seed number) was similar for plants that were not exposed to herbivory and those that were damaged by parasitized caterpillars and lower for plants that were damaged by healthy unparasitized caterpillars. However, these quantitative seed traits negatively correlated with the qualitative seed traits, individual seed size and germination success, suggesting a trade-off between these two types of traits. * We show that parasitism of insect herbivores that feed on reproductive plant tissues may have positive fitness consequences for S. arvensis. The extent to which plant fitness may benefit depends on parasitoid lifestyle (solitary or gregarious), which is correlated with the amount of damage inflicted on these tissues by the parasitized host

Some Like It Fat: Comparative Ultrastructure of the Embryo in Two Demosponges of the Genus Mycale (Order Poecilosclerida) from Antarctica and the Caribbean

0000-0002-7993-1523© 2015 Riesgo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License [4.0], which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article

Microscopic View on Short-Range Wetting at the Free Surface of the Binary Metallic Liquid Gallium-Bismuth: An X-ray Reflectivity and Square Gradient Theory Study

We present an x-ray reflectivity study of wetting at the free surface of the binary liquid metal gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the evolution of the microscopic structure of wetting films of the Bi-rich, low-surface-tension phase along different paths in the bulk phase diagram. A balance between the surface potential preferring the Bi-rich phase and the gravitational potential which favors the Ga-rich phase at the surface pins the interface of the two demixed liquid metallic phases close to the free surface. This enables us to resolve it on an Angstrom level and to apply a mean-field, square gradient model extended by thermally activated capillary waves as dominant thermal fluctuations. The sole free parameter of the gradient model, i.e. the so-called influence parameter, $\kappa$, is determined from our measurements. Relying on a calculation of the liquid/liquid interfacial tension that makes it possible to distinguish between intrinsic and capillary wave contributions to the interfacial structure we estimate that fluctuations affect the observed short-range, complete wetting phenomena only marginally. A critical wetting transition that should be sensitive to thermal fluctuations seems to be absent in this binary metallic alloy.Comment: RevTex4, twocolumn, 15 pages, 10 figure