Modeling dissolved oxygen dynamics and hypoxia

Abstract. Hypoxia conditions are increasing throughout the world, influencing biogeochemical cycles of elements and marine life. Hypoxia results from complex interactions between physical and biogeochemical processes, which can not be understood by observations alone. Models are invaluable tools at studying system dynamics, generalizing discrete observations and predicting future states. They are also useful as management tools for evaluating site-specific responses to management scenarios. Here we review oxygen dynamics models that have significantly contributed to a better understanding of the effects of natural processes and human perturbations on the development of hypoxia, factors controlling the extent and temporal variability of coastal hypoxia, and the effects of oxygen depletion on biogeochemical cycles. Because hypoxia occurs in a variety of environments and can be persistent, periodic or episodic, models differ significantly in their complexity and temporal and spatial resolution. We discuss the progress in developing hypoxia models for benthic and pelagic systems that range from simple box models to three dimensional circulation models. Applications of these models in five major hypoxia regions are presented. In the last decades, substantial progress has been made towards the parameterization of biogeochemical processes in both hypoxic water columns and sediments. In coastal regions, semi-empirical models have been used more frequently than mechanistic models to study nutrient enrichment and hypoxia relationships. Recent advances in three-dimensional coupled physical-ecological-biogeochemical models have allowed a better representation of physical-biological interactions in these systems. We discuss the remaining gaps in process descriptions and suggest directions for improvement. Better process representations in models will help us answer several important questions, such as those about the causes of the observed worldwide increase in hypoxic conditions, and future changes in the intensity and spread of coastal hypoxia. At the same time, quantitative model intercomparison studies suggest that the predictive ability of our models may be adversely affected by their increasing complexity, unless the models are properly constrained by observations. Natural and Human-Induced Hypoxia and Consequences for Coastal AreasPublisher's Versio

Синтез та антивірусна активність похідних [(9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]-триазино[2,3-с]хіназолін-6-іл)тіо]ацетамідів з фрагментами каркасних амінів

Alkylation of potassium 9-R1-10-R2-3-R-2-oxo-2Н-[1,2,4]triazino[2,3 с]quinazolin-6-thiolates by N-cycloalkyl-(cycloalkylaryl-)-2-chloracetamides and interaction of [(9-R1-10-R2-3-R-2-оxo-2H-[1,2,4]triazino[2,3-с]quinazolin-6-yl) thio]acetiс acids imidazolides and chloranhydrides with carcass amines yielded the corresponding amides. The structures of the compounds synthesized have been confirmed by 1H, 13C NMR, LC–MS and EI-MS analysis.The features of 1H, 13C NMR, LC–MS and EI-MS spectra have been described, and characteristic signals have been identified. The compounds synthesized have been studied for their antiviral activity. The results of the antiviral assay have shown that some compounds exhibit a moderate and high activity against the strains studied.The correlation between the structure and the antiviral action has been also discussed. According to the data obtained the conclusion can be made that the combination of carcass amine moieties with the fragment of little known [(9-R1-10-R2-3-R-2-оxo-2H-[1,2,4]-triazino[2,3-с]quinazolin-6-yl)thio]асetic acid results in compounds with a high antiviral activity. High indicators of the antiviral activity of compounds 3.2 and 3.14 against Influenza Type A H3N2 allow to suppose the expediency of further chemical modification of [1,2,4]triazino[2,3-с]quinazoline directed to obtaining new antiviral agents.Алкилирование калий 9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]триазино[2,3-c]хиназолин-6-тиолатов N-циклоалкил-(циклоалкиларил-)-2-хлорацетамидами и взаимодействие имидазолидов и хлорангидридов [(9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]триазино[2,3-c]хиназолин-6-ил)тио]уксусных кислот с каркасными аминами ведет к образованию амидов. Структуру и чистоту синтезированных соединений установлено комплексом физико-химических методов, в частности, 1H-, 13C-NMR, LC–MS и EI-MS анализом. Также были описаны особенности 1H-, 13C-NMR, LC–MS и EI-MS спектров и идентифицированы характеристические сигналы. Синтезированные соединения были исследованы на наличие противовирусной активности. Установлено, что отдельные представители класса синтезированных соединений проявляют умеренную или высокую противовирусную активность по отношению к изучаемым штаммам. Обсуждена корреляция «структура-действие». Согласно полученным данным можно сделать вывод, что комбинация структуры каркасных аминов с фрагментом малоизвестных [(9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]-триазино[2,3-с]хиназолин-6-ил)тио]уксусных кислот позволяет получить вещества с высокой противовирусной активностью. Высокие индикаторы противовирусной активности по отношению к штамму Influenza Type A H3N2 соединений 3.2 и 3.14 дают возможность прогнозировать перспективность дальнейшей химической модификации [1,2,4]триазино[2,3-c]хиназолина, направленной на получение новых противовирусных агентов.Алкілування калій 9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]триазино[2,3-c]хіназолін-6-тіолатів N-циклоалкіл-(циклоалкіларил-)-2-хлорацетамідами та взаємодія імідазолідів та хлорангідридів [(9-R1-10-R2-3-R-2-оксо-2H- [1,2,4]триазино[2,3-c]хіназолін-6-іл)тіо]оцтових кислот з каркасними амінами призвели до утворення відповідних амідів. Структуру та чистоту синтезованих сполук встановлено за допомогою комплексу фізико-хімічних методів, зокрема 1H, 13C-NMR, LC–MS та EI-MS аналізом. Особливості 1H, 13C NMR, LC–MS та EI-MS спектрів були обговорені, також були ідентифіковані характеристичні сигнали. Синтезовані сполуки були досліджені на наявність антивірусної активності. Встановлено, що окремі представники синтезованих сполук виявляють помірну та високу антивірусну активність по відношенню до штамів, що досліджувались. Кореляція взаємозв’язків «будова-дія» була обговорена. Відповідно до одержаних даних ми зробили висновок, що комбінація залишку каркасних амінів з фрагментами маловідомих [(9-R1-10-R2-3-R-2-оксо-2H-[1,2,4]-триазино[2,3-c]хіназолін-6-іл)тіо]оцтових кислот дозволяє одержати сполуки зі значною антивірусною активністю. Високі індикатори антивірусної активності по відношенню до штаму Influenza Type A H3N2 сполук 3.2 та 3.14 дозволяють передбачити перспективність подальшої хімічної модифікації [1,2,4]триазино[2,3-c]хіназоліну з метою пошуку нових антивірусних агентів

Scaling in long term data sets of geomagnetic indices and solar wind ϵ as seen by WIND spacecraft

We study scaling in fluctuations of the geomagnetic indices (AE, AU, and AL) that provide a measure of magnetospheric activity and of the ε parameter which is a measure of the solar wind driver. Generalized structure function (GSF) analysis shows that fluctuations exhibit self-similar scaling up to about 1 hour for the AU index and about 2 hours for AL, AE and ε when the most extreme fluctuations over 10 standard deviations are excluded. The scaling exponents of the GSF are found to be similar for the three AE indices, and to differ significantly from that of ε. This is corroborated by direct comparison of their rescaled probability density functions

Biogeochemistry of manganese in ferruginous Lake Matano, Indonesia

This study explores Mn biogeochemistry in a stratified, ferruginous lake, a modern analogue to ferruginous oceans. Intense Mn cycling occurs in the chemocline where Mn is recycled at least 15 times before sedimentation. The product of biologically catalyzed Mn oxidation in Lake Matano is birnessite. Although there is evidence for abiotic Mn reduction with Fe(II), Mn reduction likely occurs through a variety of pathways. The flux of Fe(II) is insufficient to balance the reduction of Mn at 125 m depth in the water column, and Mn reduction could be a significant contributor to CH<sub>4</sub> oxidation. By combining results from synchrotron-based X-ray fluorescence and X-ray spectroscopy, extractions of sinking particles, and reaction transport modeling, we find the kinetics of Mn reduction in the lake's reducing waters are sufficiently rapid to preclude the deposition of Mn oxides from the water column to the sediments underlying ferruginous water. This has strong implications for the interpretation of the sedimentary Mn record

Synthesis of New 6-{[ω-(Dialkylamino(heterocyclyl)alkyl]thio}-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones and Evaluation of their Anticancer and Antimicrobial Activities

Several novel 6-thio-3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-based compounds containing an ω-(dialkylamino(heterocyclyl)]alkyl fragment were synthesized to examine their anticancer activity. Some of the 6-{[ω-(hetero-cyclyl)alkyl]thio}-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones (3.1–3.10) were obtained by the nucleophilic substitution of 6-[ω-halogenalkyl]thio-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones (2.1–2.8) with azaheterocycles. Alternatively, compounds 3.1–3.22 were synthesized by alkylation of 3-R-6-thio-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones potassium salts (1.1–1.4) with (2-chloroethyl)-N,N-dialkylamine hydrochlorides or 1-(2-chloroethyl)heterocycle hydrochlorides. The structures of compounds were elucidated by 1H, 13C NMR, LC–MS and EI-MS analysis. Then anticancer and antibacterial, bioluminescence inhibition of Photobacterium leiognathi Sh1 activities of the substances were tested in vitro. It was found that compound 3.18 possessed a wide range of anticancer activity against 27 cell lines of cancer: non-small cell lung, colon, CNS, ovarian, renal, prostate, breast, melanoma and leukemia (log GI50 < −5.65). The “structure-activity” relationship was discussed. COMPARE analysis for synthesized anticancer active compounds was performed

Nonlinear time-series analysis of Hyperion's lightcurves

Hyperion is a satellite of Saturn that was predicted to remain in a chaotic rotational state. This was confirmed to some extent by Voyager 2 and Cassini series of images and some ground-based photometric observations. The aim of this aticle is to explore conditions for potential observations to meet in order to estimate a maximal Lyapunov Exponent (mLE), which being positive is an indicator of chaos and allows to characterise it quantitatively. Lightcurves existing in literature as well as numerical simulations are examined using standard tools of theory of chaos. It is found that existing datasets are too short and undersampled to detect a positive mLE, although its presence is not rejected. Analysis of simulated lightcurves leads to an assertion that observations from one site should be performed over a year-long period to detect a positive mLE, if present, in a reliable way. Another approach would be to use 2---3 telescopes spread over the world to have observations distributed more uniformly. This may be achieved without disrupting other observational projects being conducted. The necessity of time-series to be stationary is highly stressed.Comment: 34 pages, 12 figures, 4 tables; v2 after referee report; matches the version accepted in Astrophysics and Space Scienc

Organism-sediment interactions govern post-hypoxia recovery of ecosystem functioning

Hypoxia represents one of the major causes of biodiversity and ecosystem functioning loss for coastal waters. Since eutrophication-induced hypoxic events are becoming increasingly frequent and intense, understanding the response of ecosystems to hypoxia is of primary importance to understand and predict the stability of ecosystem functioning. Such ecological stability may greatly depend on the recovery patterns of communities and the return time of the system properties associated to these patterns. Here, we have examined how the reassembly of a benthic community contributed to the recovery of ecosystem functioning following experimentally-induced hypoxia in a tidal flat. We demonstrate that organism-sediment interactions that depend on organism size and relate to mobility traits and sediment reworking capacities are generally more important than recovering species richness to set the return time of the measured sediment processes and properties. Specifically, increasing macrofauna bioturbation potential during community reassembly significantly contributed to the recovery of sediment processes and properties such as denitrification, bedload sediment transport, primary production and deep pore water ammonium concentration. Such bioturbation potential was due to the replacement of the small-sized organisms that recolonised at early stages by large-sized bioturbating organisms, which had a disproportionately stronger influence on sediment. This study suggests that the complete recovery of organism-sediment interactions is a necessary condition for ecosystem functioning recovery, and that such process requires long periods after disturbance due to the slow growth of juveniles into adult stages involved in these interactions. Consequently, repeated episodes of disturbance at intervals smaller than the time needed for the system to fully recover organism-sediment interactions may greatly impair the resilience of ecosystem functioning.