The Role Of Mergers In Galaxy Formation And Transformations

Large scale structure and cosmolog

The release of wastewater contaminants in the Arctic : a case study from Cambridge Bay, Nunavut, Canada

The treatment of municipal wastewater in the Arctic is challenging due to a variety of financial, operational, climatic and technical issues. To better understand the efficacy of current wastewater treatment in this region and the hazard posed to receiving waters, we assessed the occurrence of contaminants (i.e., pharmaceuticals, antibiotic resistance genes and nutrients) as they moved through a lagoon-based treatment system in Cambridge Bay in Nunavut, Canada. Wastewater treatment in this community is performed by the use of a lagoon-tundra wetland system that is discharged into the marine environment and is representative of current common practices throughout the region. In 2014, samples were collected before and during lagoon discharge from two locations in the main lagoon, one location downstream from the lagoon effluent and three locations offshore. Grab samples were collected to measure nutrients (e.g. total nitrogen and phosphorus) and the presence of antibiotic resistance gene-bearing microbes, and Polar Organic Chemical Integrative Samplers (POCIS) were deployed to collect passively organic contaminants in all locations. A total of six pharmaceuticals were detected from a screen of twenty-eight analytes during the study: atenolol, carbamazepine, clarithromycin, metoprolol, sulfamethoxazole and trimethoprim. The greatest concentrations of nutrients, antibiotic resistance genes (ARGs) and pharmaceuticals were found in sampling locations within the treatment lagoon. Offshore of the release point, we observed limited to no detection of pharmaceuticals and ARGs and no change in total nitrogen and phosphorus from pre-release. We conclude that the current concentrations of monitored pharmaceuticals do not pose a significant hazard at this time to aquatic organisms in Cambridge Bay

FTIR autecological analysis of bottom-ice diatom taxa across a tidal strait in the Canadian Arctic

A recent study demonstrated that an Arctic tidal strait, where a shoaled and constricted waterway increases tidally driven sub-ice currents and turbulence, represents a “hotspot” for ice algal production due to a hypothesized enhanced ocean-ice nutrient supply. Based on these findings, we sampled the bottom-ice algal community across the same tidal strait between the Finlayson Islands within Dease Strait, Nunavut, Canada, in spring 2017. Our objective was to examine cellular responses of sea-ice diatoms to two expected nutrient supply gradients in their natural environment: (1) a horizontal gradient across the tidal strait and (2) a vertical gradient in the bottom-ice matrix. Two diatom taxa, Nitzschia frigida and Attheya spp. in bottomice sections (0–2, 2–5, and 5–10 cm) under thin snow cover (<5 cm), were selected for Fourier Transform Infrared (FTIR) spectrochemical analysis for lipid and protein content. Results from the FTIR technique strongly supported the existence of a horizontal nutrient gradient across the tidal strait of the Finlayson Islands, while estimates of particulate organic carbon and chlorophyll a concentrations were difficult to interpret. The larger N. frigida cells appeared to be more sensitive to the suspected horizontal nutrient gradient, significantly increasing in lipid content relative to protein beyond the tidal strait. In contrast, the epiphytic diatoms, Attheya spp., were more sensitive to the vertical gradient: above 2 cm in the bottom-ice matrix, the non-motile cells appeared to be trapped with a depleted nutrient inventory and evidence of a post-bloom state. Application of the FTIR technique to estimate biomolecular composition of algal cells provided new insights on the response of the bottom-ice algal community to the examined spatial gradients that could not be obtained from conventional bulk measurements alone. Future studies of sea ice and associated environments are thus encouraged to employ this technique

Melt Procedure Affects the Photosynthetic Response of Sea Ice Algae

The accuracy of sea ice algal production estimates is influenced by the range of melting procedures used in studies to obtain a liquid sample for incubation, particularly in relation to the duration of melt and the approach to buffering for osmotic shock. In this research, ice algal photophysiology from 14C incubations was compared in field samples prepared by three melt procedures: (i) a rapid 4 h melt of the bottommost ( < 1 cm) ice algal layer scraped into a large volume of filtered seawater (salinity 27–30), (ii) melt of a bottom 5 cm section diluted into a moderate volume of filtered seawater over 24 h (salinity 20–24), and (iii) melt of a bottom 5 cm section without any filtered seawater dilution over about 48 h (salinity 10–12). Maximum photosynthetic rate, photosynthetic efficiency and production at zero irradiance were significantly affected by the melt treatment employed in experiments. All variables were greatest in the highly diluted scrape sample and lowest in the bulk-ice samples melted in the absence of filtered seawater. Laboratory experiments exposing cultures of the common sea ice diatom Nitzschia frigida to different salinities and light conditions suggested that the field-based responses can be attributed to the rapid ( < 4 h) adverse effects of exposing cells to low salinities during melt without dilution. The observed differences in primary production between melt treatments were estimated to account for over 60% of the variability in production estimates reported for the Arctic. Future studies are strongly encouraged to replicate salinity conditions representative of in situ values during the melting process to minimize hypoosmotic stress, thereby most accurately estimating primary production

Late Winter Biogeochemical Conditions Under Sea Ice in the Canadian High Arctic

With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W) in the Canadian High Arctic. Results show relatively low surface water (1–10 m) nitrate (<1.3 µM) and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg−1), total alkalinity (mean±SD=2134±11.09 µmol kg−1) and under-ice pCO2sw (mean±SD=286±17 µatm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season

Massive Star Formation

This chapter reviews progress in the field of massive star formation. It focuses on evidence for accretion and current models that invoke high accretion rates. In particular it is noted that high accretion rates will cause the massive young stellar object to have a radius much larger than its eventual main sequence radius throughout much of the accretion phase. This results in low effective temperatures which may provide the explanation as to why luminous young stellar objects do not ionized their surroundings to form ultra-compact H II regions. The transition to the ultra-compact H II region phase would then be associated with the termination of the high accretion rate phase. Objects thought to be in a transition phase are discussed and diagnostic diagrams to distinguish between massive young stellar objects and ultra-compact H II regions in terms of line widths and radio luminosity are presented.Comment: 21 pages, 6 figures, chapter in Diffuse Matter from Star Forming Regions to Active Galaxies - A Volume Honouring John Dyson, Edited by T.W. Hartquist, J. M. Pittard, and S. A. E. G. Falle. Series: Astrophysics and Space Science Proceedings. Springer Dordrecht, 2007, p.6

Some aspects of the Liouville equation in mathematical physics and statistical mechanics

This paper presents some mathematical aspects of Classical Liouville theorem and we have noted some mathematical theorems about its initial value problem. Furthermore, we have implied on the formal frame work of Stochastic Liouville equation (SLE)

Remote estimates of ice algae biomass and their response to environmental conditions during spring melt

In this study, we support previous work showing that a normalized difference index (NDI) using two spectral bands of transmitted irradiance (478 and 490 nm) can be used as a non-invasive method to estimate sea ice chlorophyll a (chl a) following a simple calibration to the local region. Application of this method during the spring bloom period (9 May to 26 June) provided the first non-invasive time series dataset used to monitor changes in bottom ice chl a concentration, an index of algal biomass, at a single point location. The transmitted irradiance dataset was collected on landfast first-year sea ice of Allen Bay, Nunavut, in 2011, along with the physical variables thought to affect chl a accumulation and loss at the ice bottom. Time series biomass calculated using the NDI technique adhered well to core based biomass estimates although, chl a values remained low throughout the bloom, reaching a maximum of 27.6 mg m-2 at the end of May. It is likely that warming of the bottom ice contributed to loss of chl a through its positive influence on brine drainage and ice melt. Chl a content in the bottom ice was also significantly affected by a storm event on 10 June, which caused extensive surface melt and a rapid increase in the magnitude of transmitted irradiance. Furthermore, the velocity of current, measured below the ice at the end of a spring neap-tidal cycle, was negatively associated with ice algae chl a biomass (the stronger the current, the less biomass). The NDI method to remotely estimate ice algal biomass proved useful for application in our time series process study, providing a way to assess the effects of changes to the sea ice environment on the biomass of a single population of ice algae.La présente étude vient appuyer d’anciennes études selon lesquelles un indice par différence normalisée (IDN) recourant à deux bandes spectrales d’éclairement énergétique transmis (478 et 490 nm) peut servir de méthode non invasive d’estimation de la chlorophylle a (chl a) de glace de mer suivant un simple étalonnage dans une aire locale. Le recours à cette méthode pendant la saison de l’efflorescence printanière (du 9 mai au 26 juin) a permis d’obtenir le premier ensemble de données non invasives en séries chronologiques dans le but de surveiller les changements se manifestant dans la concentration de chl a de la glace de fond, un indice de biomasse algale, en un seul point. Les données relatives à l’éclairement énergétique transmis ont été recueillies à partir de la glace de mer de rive de l’année à la baie Allen, au Nunavut, en 2011, en même temps que les variables physiques censées avoir des effets sur l’accumulation de chl a et sur la perte de glace de fond. Les données chronologiques relatives à la biomasse calculées à l’aide de la technique de l’IDN cadraient bien avec les estimations de la biomasse obtenues à l’aide d’échantillons, bien que les valeurs de la chl a restaient à la baisse pendant l’efflorescence, pour atteindre un maximum de 27,6 mg m-2 à la fin du mois de mai. Il est vraisemblable que le réchauffement de la glace de fond a entraîné la perte de chl a en raison de son influence positive sur l’égouttage de la saumure et la fonte des glaces. La teneur en chl a de la glace de fond a également été fortement touchée par un événement pluvio-hydrologique qui a eu lieu le 10 juin, événement qui a entraîné une importante fonte en surface et l’augmentation rapide de la magnitude de l’éclairement énergétique transmis. Par ailleurs, la vélocité du courant, mesurée sous la glace à la fin d’un cycle printanier de marée de mortes-eaux, a été négativement liée à la biomasse en chl a de l’algue glaciaire (plus le courant était fort, moins la biomasse était grande). La méthode de l’IDN en vue d’estimer la biomasse de l’algue glaciaire à distance s’est avérée utile dans le cadre de l’application de notre étude en séries chronologiques, car elle a présenté un moyen d’évaluer les effets des changements caractérisant l’environnement de la glace de mer sur la biomasse d’une seule population d’algues glaciaires