Ecology of Blue‐Green Algae in Aquaculture Ponds

Cyanobacteria (blue‐green algae) in the genera Anabaena, Aphanizomenon, Microcystis, and Oscillatoria often form extensive and persistent blooms in freshwater aquaculture ponds. Bloom‐forming cyanobacteria are undesirable in aquaculture ponds because: 1) they are a relatively poor base for aquatic food chains; 2) they are poor oxygenators of the water and have undesirable growth habits; 3) some species produce odorous metabolites that impart undesirable flavors to the cultured animal; and 4) some species may produce compounds that are toxic to aquatic animals. Development of cyanobacterial blooms is favored under conditions of high nutrient loading rates (particularly if the availability of nitrogen is limited relative to phosphorus), low rates of vertical mixing, and warm water temperatures. Under those conditions, dominance of phytoplankton communities by cyanobacteria is the result of certain unique physiological attributes (in particular, N2 fixation and buoyancy regulation) that allow cyanobacteria to compete effectively with other phytoplankton. The ability to fix N2 provides a competitive advantage under severe nitrogen limitation because it allows certain cyanobacterial species to make use of a source of nitrogen unavailable to other phytoplankton. The ability to regulate cell buoyancy through environmentally‐controlled collapse ad reformation of intracellular gas vacuoles is perhaps the primary reason for the frequent dominance of aquaculture pond phytoplankton communities by cyanobacteria. Cyanobacteria that can regulate their position in the water column gain a distinct advantage over other phototrophs in poorly mixed bodies of water. In addition to the physicochemical interactions that influence phytoplankton community dynamics, cyanobacterial‐microbial associations may play an important regulatory role in determining community structure. Cyanobacteria are always found in close association with a diverse array of microorganisms, including eubacteria, fungi, and protozoans. These associations, which in the past have often been viewed as antagonistic, are increasingly seen as mutualistic and may function in a positive manner during bloom development

Overexpression of HvCslF6 in barley grain alters carbohydrate partitioning plus transfer tissue and endosperm development

In cereal grain sucrose is converted into storage carbohydrates; mainly starch, fructan and (1,3;1,4)-β-glucan (MLG). Previously, endosperm-specific overexpression of the HvCslF6 gene in hull-less barley resulted in high MLG and low starch content in mature grains. Morphological changes included inwardly elongated aleurone cells, irregular cell shapes of peripheral endosperm and smaller starch granules of starchy endosperm. Here we explored the physiological basis for these defects by investigating how changes in carbohydrate composition of developing grain impact mature grain morphology. Augmented MLG coincided with increased levels of soluble carbohydrates in the cavity and endosperm at the storage phase. Transcript levels of genes relating to cell wall, starch, sucrose and fructan metabolism were perturbed in all tissues. The cell walls of endosperm transfer cells (ETC) in transgenic grain were thinner and showed reduced mannan labelling relative to wild type. At the early storage phase rupture of the non-uniformly developed ETC and disorganization of adjacent endosperm cells was observed. Soluble sugars accumulated in the developing grain cavity, suggesting a disturbance of carbohydrate flow from the cavity towards the endosperm, resulting in a shrunken mature grain phenotype. Our findings demonstrate the importance of regulating carbohydrate partitioning in maintenance of grain cellularization and filling processes.Wai Li Lim, Helen M. Collins, Caitlin S. Byrt, Jelle Lahnstein, Neil J. Shirley, Matthew K. Aubert, Matthew R. Tucker, Manuela Peukert, Andrea Matros, and Rachel A. Burto

Quasar Accretion Disk Sizes from Continuum Reverberation Mapping in the DES Standard-star Fields

Measurements of the physical properties of accretion disks in active galactic nuclei are important for better understanding the growth and evolution of supermassive black holes. We present the accretion disk sizes of 22 quasars from continuum reverberation mapping with data from the Dark Energy Survey (DES) standard-star fields and the supernova C fields. We construct continuum light curves with the griz photometry that span five seasons of DES observations. These data sample the time variability of the quasars with a cadence as short as 1 day, which corresponds to a rest-frame cadence that is a factor of a few higher than most previous work. We derive time lags between bands with both JAVELIN and the interpolated cross-correlation function method and fit for accretion disk sizes using the JAVELIN thin-disk model. These new measurements include disks around black holes with masses as small as ~107 M ⊙, which have equivalent sizes at 2500 A as small as ~0.1 lt-day in the rest frame. We find that most objects have accretion disk sizes consistent with the prediction of the standard thin-disk model when we take disk variability into account. We have also simulated the expected yield of accretion disk measurements under various observational scenarios for the Large Synoptic Survey Telescope Deep Drilling Fields. We find that the number of disk measurements would increase significantly if the default cadence is changed from 3 days to 2 days or 1 day

Quasar Accretion Disk Sizes from Continuum Reverberation Mapping from the Dark Energy Survey

We present accretion disk size measurements for 15 luminous quasars at 0.7 ≤ z ≤ 1.9 derived from griz light curves from the Dark Energy Survey. We measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well described by a single blackbody. In the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. From this, we are only able to constrain upper limits on disk sizes, as many are consistent with no lag the 2σ level. The second method fits the model parameters for the canonical thin disk directly rather than solving for the individual time lags between the light curves. Our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3 and 1 times the Eddington rate. Given our large uncertainties, our measurements are also consistent with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results, that find disk sizes that are a factor of a few (∼3) larger than predictions

New fossil remains of Homo naledi from the Lesedi Chamber, South Africa

The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.SP201

An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types

A virtual graphic log for clastic sediments

Drawing a graphic log is a standard method to describe sedimentary rocks at outcrops or from borehole cores. Graphic logs give a visual impression of the rocks, their lithology, particle size, bedding contacts, sedimentary structures, palaeocurrents and fossil content as well as trends such as coarsening or fining upwards. The format of graphic logs and their styles vary. This paper includes outcrop photographs that were collected as part of a distance learning module in Sedimentology and provides an opportunity for students to practice drawing a graphic log without having to venture into the field, effectively bringing the field into the classroom. Instructions for drawing a graphic log are included. There is potential for virtual logs to provide a more open science approach to outcrop interpretation, enabling researchers to visit outcrops virtually and make their own descriptions and interpretations

Photometric and Spectroscopic Properties of Type Ia Supernova 2018oh with Early Excess Emission from the Kepler 2 Observations

Supernova (SN) 2018oh (ASASSN-18bt) is the first spectroscopically confirmed Type Ia supernova (SN Ia) observed in the Kepler field. The Kepler data revealed an excess emission in its early light curve, allowing us to place interesting constraints on its progenitor system. Here we present extensive optical, ultraviolet, and near-infrared photometry, as well as dense sampling of optical spectra, for this object. SN 2018oh is relatively normal in its photometric evolution, with a rise time of 18.3 ± 0.3 days and Δm 15(B) = 0.96 ± 0.03 mag, but it seems to have bluer B − V colors. We construct the "UVOIR" bolometric light curve having a peak luminosity of 1.49 × 1043 erg s−1, from which we derive a nickel mass as 0.55 ± 0.04 M ⊙ by fitting radiation diffusion models powered by centrally located 56Ni. Note that the moment when nickel-powered luminosity starts to emerge is +3.85 days after the first light in the Kepler data, suggesting other origins of the early-time emission, e.g., mixing of 56Ni to outer layers of the ejecta or interaction between the ejecta and nearby circumstellar material or a nondegenerate companion star. The spectral evolution of SN 2018oh is similar to that of a normal SN Ia but is characterized by prominent and persistent carbon absorption features. The C ii features can be detected from the early phases to about 3 weeks after the maximum light, representing the latest detection of carbon ever recorded in an SN Ia. This indicates that a considerable amount of unburned carbon exists in the ejecta of SN 2018oh and may mix into deeper layers.Funding for the LJT has been provided by Chinese Academy of Sciences and the People’s Government of Yunnan Province. ZsB acknowledges the support provided by the National Research, Development and Innovation Fund of Hungary, financed under the PD_17 funding scheme, project No. PD123910. Support for JJH was provided by NASA through Hubble Fellowship grant #HST-HF2-51357.001-A, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555, as well as NASA K2 Cycle 4 grant NNX17AE92G. Based on observations obtained at the South. Funding for the K2 mission is provided by the NASA Science Mission directorate. KEGS is supported in part by NASA K2 cycle 4 and 5 grants NNX17AI64G and 80NSSC18K0302, respectively. AR and his groups are supported in part by HST grants GO-12577 and HST AR-1285