scholarly journals Identifying areas prone to coastal hypoxia – the role of topography

2019 ◽  
Author(s):  
Elina A. Virtanen ◽  
Alf Norkko ◽  
Antonia Nyström Sandman ◽  
Markku Viitasalo
Keyword(s):  
Oxygen Deficiency ◽  
Coastal Areas ◽  
Management Actions ◽  
In Situ Data ◽  
Efficient Management ◽  
Stockholm Archipelago ◽  
Oxygen Dynamics ◽  
Made In

Abstract. Hypoxia is an increasing problem in marine ecosystems around the world, and recent projections indicate that anoxic dead zones will be spreading in the forthcoming decades. While major advances have been made in our understanding of the drivers of hypoxia, it fundamentally hinges on patterns of water circulation that can be difficult to resolve in coastal regions. The complexity of many coastal areas and lack of detailed in situ data has hindered the development of models describing oxygen dynamics at a sufficient resolution for efficient management actions to take place. We hypothesized that the enclosed nature of seafloors facilitates hypoxia formation. We developed simple proxies of seafloor heterogeneity and modelled oxygen deficiency in complex coastal areas in the northern Baltic Sea. We discovered that topographically sheltered seafloors and sinkholes with stagnant water are prone to the development of hypoxia. Approximately half of the monitoring sites in Stockholm Archipelago and one third of sites in southern Finland experienced severe hypoxia (O2 

scholarly journals Identifying areas prone to coastal hypoxia – the role of topography

2019 ◽  
Vol 16 (16) ◽  
pp. 3183-3195 ◽  
Author(s):  
Elina A. Virtanen ◽  
Alf Norkko ◽  
Antonia Nyström Sandman ◽  
Markku Viitasalo
Keyword(s):  
Nutrient Loading ◽  
Oxygen Deficiency ◽  
Late Summer ◽  
Coastal Areas ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
Management Actions ◽  
In Situ Data ◽  
Biogeochemical Models ◽  
Oxygen Dynamics

Abstract. Hypoxia is an increasing problem in marine ecosystems around the world. While major advances have been made in our understanding of the drivers of hypoxia, challenges remain in describing oxygen dynamics in coastal regions. The complexity of many coastal areas and lack of detailed in situ data have hindered the development of models describing oxygen dynamics at a sufficient spatial resolution for efficient management actions to take place. It is well known that the enclosed nature of seafloors and reduced water mixing facilitates hypoxia formation, but the degree to which topography contributes to hypoxia formation and small-scale variability of coastal hypoxia has not been previously quantified. We developed simple proxies of seafloor heterogeneity and modeled oxygen deficiency in complex coastal areas in the northern Baltic Sea. According to our models, topographical parameters alone explained ∼80 % of hypoxia occurrences. The models also revealed that less than 25 % of the studied seascapes were prone to hypoxia during late summer (August–September). However, large variation existed in the spatial and temporal patterns of hypoxia, as certain areas were prone to occasional severe hypoxia (O2 < 2 mg L−1), while others were more susceptible to recurrent moderate hypoxia (O2 < 4.6 mg L−1). Areas identified as problematic in our study were characterized by low exposure to wave forcing, high topographic shelter from surrounding areas and isolation from the open sea, all contributing to longer water residence times in seabed depressions. Deviations from this topographical background are probably caused by strong currents or high nutrient loading, thus improving or worsening oxygen status, respectively. In some areas, connectivity with adjacent deeper basins may also influence coastal oxygen dynamics. Developed models could boost the performance of biogeochemical models, aid developing nutrient abatement measures and pinpoint areas where management actions are most urgently needed.

scholarly journals Capturing the dynamic and cyclical nature of regulation: Methodological Progress in understanding socially shared regulation in learning

2019 ◽  
Vol 14 (4) ◽  
pp. 425-441 ◽  
Author(s):  
Sanna Järvelä ◽  
Hanna Järvenoja ◽  
Jonna Malmberg
Keyword(s):  
Collaborative Learning ◽  
Self Regulation ◽  
Learning Context ◽  
Computer Supported Collaborative Learning ◽  
In Situ Data ◽  
Complex Process ◽  
The Social ◽  
Made In ◽  
Socially Shared Regulation

AbstractSelf-regulation is critical for successful learning, and socially shared regulation contributes to productive collaborative learning. The problem is that the psychological processes at the foundation of regulation are invisible and, thus, very challenging to understand, support, and influence. The aim of this paper is to review the progress in socially shared regulation research data collection methods for trying to understand the complex process of regulation in the social learning context, for example, collaborative learning and computer-supported collaborative learning. We highlight the importance of tracing the sequential and temporal characteristics of regulation in learning by focusing on data for individual- and group-level shared regulatory activities that use technological research tools and by gathering in-situ data about students’ challenges that provoke regulation of learning. We explain how we understand regulation in a social context, argue why methodological progress is needed, and review the progress made in researching regulation of learning.

scholarly journals Análisis multisensor para el estudio de los patrones de turbidez en el estuario del Guadalquivir

2016 ◽  
pp. 1 ◽  
Author(s):  
I. Caballero ◽  
G. Navarro
Keyword(s):  
Water Quality ◽  
Suspended Solids ◽  
Water Quality Management ◽  
Quality Parameters ◽  
In Situ Data ◽  
Nao Index ◽  
Del Rio ◽  
Different Characteristics

<p>A detailed study of the mechanisms generated through the turbidity plume and its variability at the Guadalquivir estuary has been carried out with remote sensing and in situ data. Several sensors with different characteristics have been required (spatial, temporal and spectral resolution), thereby providing information for a multi-sensor analysis. The main objective was to determine the water quality parameters (suspended solids and chlorophyll) and implement the methodology to define the empirical and semi-analytical algorithms from satellite data (MODIS, METIS, Deimos-1). The processes occurred in the estuary and adjacent region have been examined identifying those involved in the different variability scales. The forcings associated with rainfall and discharge from Alcalá del Río dam in addition to the climatic NAO index control seasonal and inter-annual fluctuations, while tide effects (semi-daily and fortnightly cycles) modulate the plume at the mouth throughout the year with significant variability. Special emphasis is focused on diagnosing the role of these mechanisms on the continental shelf ecosystems, constituting a powerful tool for the water quality management and coastal resources.</p>

scholarly journals An instrument for in-situ measurement of total ozone reactivity

2019 ◽  
Author(s):  
Roberto Sommariva ◽  
Louisa J. Kramer ◽  
Leigh R. Crilley ◽  
Mohammed S. Alam ◽  
William J. Bloss
Keyword(s):  
Total Ozone ◽  
Diurnal Pattern ◽  
Aromatic Plants ◽  
Ambient Conditions ◽  
Mixing Ratios ◽  
Ozone Reactivity ◽  
Ambient Levels ◽  
Made In

Abstract. We present an instrument for the measurement of total ozone reactivity (RO3), i.e. the reciprocal of the chemical lifetime of ozone (O3) in the troposphere. The Total Ozone Reactivity System (TORS) was developed with the objective to study the role of biogenic organic compounds (BVOCs) as chemical sinks of tropospheric ozone. The instrument was extensively characterized and tested in the laboratory using individual compounds and small plants (lemonthyme, Thymus citriodorus) in a Teflon bag and proved able to measure reactivities corresponding to > 4.5 × 10−5 s−1, corresponding to 20 ppb of α-pinene or 150 ppb of isoprene in isolation – larger than typical ambient levels but consistent with levels commonly found in environmental chamber and enclosure experiments. The functionality of TORS was demonstrated in quasi-ambient conditions with a deployment in a horticultural glasshouse containing a range of aromatic plants. The measurements of total ozone reactivity made in the glasshouse showed a clear diurnal pattern, following the emissions of BVOCs, and is consistent with mixing ratios of tens ppb of monoterpenes and several ppb of sesquiterpenes.

scholarly journals The role of oxygen in avascular tumor growth

2015 ◽  
Author(s):  
David Robert Grimes ◽  
Pavitra Kannan ◽  
Alan McIntyre ◽  
Anthony Kavanagh ◽  
Abul Siddiky ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Growth Curves ◽  
Mechanistic Explanation ◽  
Treatment Prognosis ◽  
Sigmoidal Growth ◽  
Oxygen Dynamics ◽  
Local Oxygen ◽  
Avascular Tumor

AbstractThe oxygen status of a tumor has significant clinical implications for treatment prognosis, with well-oxygenated subvolumes responding markedly better to radiotherapy than poorly supplied regions. Oxygen is essential for tumor growth, yet estimation of local oxygen distribution can be difficult to ascertain in situ, due to chaotic patterns of vasculature. It is possible to avoid this confounding influence by using avascular tumor models, such as tumor spheroids, a much better approximation of realistic tumor dynamics than monolayers, where oxygen supply can be described by diffusion alone. Similar to in situ tumours, spheroids exhibit an approximately sigmoidal growth curve, often approximated and fitted by logistic and Gompertzian sigmoid functions. These describe the basic rate of growth well, but do not offer an explicitly mechanistic explanation. This work examines the oxygen dynamics of spheroids and demonstrates that this growth can be derived mechanistically with cellular doubling time and oxygen consumption rate (OCR) being key parameters. The model is fitted to growth curves for a range of cell lines and derived values of OCR are validated using clinical measurement. Finally, we illustrate how changes in OCR due to gemcitabine treatment can be directly inferred using this model.

The potential of satellite derived surface state to empirically estimate pan-arctic ground temperature at specific depths and the essential role of in-situ data

2020 ◽  
Author(s):  
Christine Kroisleitner ◽  
Annett Bartsch ◽  
Birgitt Heim ◽  
Mareike Wiezorek
Keyword(s):  
Surface State ◽  
High Arctic ◽  
Ground Temperature ◽  
Data Availability ◽  
Ground Temperatures ◽  
In Situ Data ◽  
Arctic Regions ◽  
Northern Russia

&lt;p&gt;Surface state information, derived from ASCAT microwave sensors (C-band scatterometer), were empirically linked to in-situ arctic ground temperature measurements. The resulting FT2T-regressionmodel was established using the sum of days of year frozen and in-situ mean annual ground temperatures, both at specific depths and years. Regionally, the model showed the best results in Scandinavia and northern Russia with less than 1&amp;#176;C difference to the in-situ data. Overall, the results were valid for most depths and regions, with a slight tendency for underestimation of the ground temperatures on the Eurasian continent (about -1&amp;#176;C) and an overestimation on the American continent up to 2 &amp;#176;C.&amp;#160; The most northern parts of Greenland, the Canadian High Arctic Islands and Alaska, however, showed a high positive bias of more than 10&amp;#176;C. Reasons for this overshooting include the limited amount of measurements in those regions, the oceanic influence and possibly snow cover effects.&amp;#160; &lt;br&gt;Due to the inaccessibility of many arctic regions, in-situ data availability is still sparse and if available not harmonized. We used the currently revised annual ground temperature dataset from CCI+ Permafrost, which combines in-situ data from the GTNP-database, RosHydroMet and additional regional arctic ground temperature datasets (e.g. Nordicana). The resulting determination coefficients of the FT2T-model showed 55% explained variance at shallow borehole-depths below 80cm and decrease with depth to around 25% at 20 meters. This suggests that the sum of frozen days of year delivers better result at shallow depths in the active layer than at the actual permafrost table. The RMSE showed a dependency on the spread of measurement stations considered in the model calibration step. The more input regions we could use, the larger the RMSE got due to the increase of variability in the input data. Inevitably, it&amp;#8217;s the in-situ information which enables the translation between ground temperatures and microwave backscatter and thus it fundamentally affects the accuracy of the result.&lt;/p&gt;

scholarly journals An instrument for in situ measurement of total ozone reactivity

2020 ◽  
Vol 13 (3) ◽  
pp. 1655-1670
Author(s):  
Roberto Sommariva ◽  
Louisa J. Kramer ◽  
Leigh R. Crilley ◽  
Mohammed S. Alam ◽  
William J. Bloss
Keyword(s):  
Total Ozone ◽  
Ambient Conditions ◽  
Total Uncertainty ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Averaging Time ◽  
Ozone Reactivity ◽  
Made In

Abstract. We present an instrument for the measurement of total ozone reactivity – the reciprocal of the chemical lifetime of ozone (O3) – in the troposphere. The Total Ozone Reactivity System (TORS) was developed with the objective to study the role of biogenic volatile organic compounds (BVOCs) as chemical sinks of tropospheric ozone. The instrument was extensively characterized and tested in the laboratory using individual BVOCs and small plants (lemon thyme, Thymus citriodorus) in a Teflon bag and proved able to measure reactivities corresponding to >4.5×10-5 s−1 (at 5 min averaging time), with an estimated total uncertainty of ∼32%. Such reactivities correspond to >20 ppb of α-pinene or >150 ppb of isoprene in isolation – larger than typical ambient levels but observable in environmental chamber and enclosure experiments as well as in BVOC-rich environments. The functionality of TORS was demonstrated in quasi-ambient conditions with a deployment in a horticultural glasshouse containing a range of aromatic plants. The measurements of total ozone reactivity made in the glasshouse showed a clear diurnal pattern, following the emissions of BVOCs, and are consistent with mixing ratios of tens of parts per billion of monoterpenes and several parts per billion of sesquiterpenes.

scholarly journals Vertical profile of peroxyacetyl nitrate (PAN) from MIPAS-STR measurements over Brazil in February 2005 and the role of PAN in the UT tropical NO<sub>y</sub> partitioning

2008 ◽  
Vol 8 (2) ◽  
pp. 6983-7016
Author(s):  
C. Keim ◽  
G. Y. Liu ◽  
C. E. Blom ◽  
H. Fischer ◽  
T. Gulde ◽  
...  
Keyword(s):  
Vertical Profile ◽  
Trace Gases ◽  
Remote Sensor ◽  
Research Aircraft ◽  
Careful Handling ◽  
Tropical Troposphere ◽  
Selection Of ◽  
Made In

Abstract. We report on the retrieval of PAN (CH3C(O)OONO2) in the upper tropical troposphere from limb measurements by the remote-sensor MIPAS-STR on board the Russian high altitude research aircraft M55-Geophysica. The measurements were performed close to Araçatuba, Brazil, on 17 February 2005. The retrieval was made in the spectral range 775–820 cm−1 where PAN exhibits its strongest feature but also more than 10 species interfere. Especially trace gases such as CH3CCl3, CFC-113, CFC-11, and CFC-22, emitting also in spectrally broad not-resolved branches, make the processing of PAN prone to errors. Therefore, the selection of appropriate spectral windows, the separate retrieval of several interfering species and the careful handling of the water vapour profile are part of the study presented. The retrieved profile of PAN has a maximum of about 0.14 ppbv at 10 km altitude, slightly larger than the lowest reported values (<0.1 ppbv) and much lower than the highest (0.65 ppbv). Besides the NOy constituents measured by MIPAS-STR (HNO3, ClONO2, PAN), the situ instruments aboard the Geophysica provide simultaneous measurements of NO, NO2, and the sum NOy. Comparing the sum of in-situ and remotely derived NO+NO2+HNO3+ClONO2+PAN with total NOy a deficit of 30–40% (0.2–0.3 ppbv) in the troposphere remains unexplained whereas the values fit well in the stratosphere.

ASPECTS IN BUILDING A COMPANY WEB-SITE AND ITS ROLE FOR THE DEVELOPMENT OF BUSINESS

2018 ◽  
pp. 117-124
Author(s):  
Petar Halachev ◽  
Victoria Radeva ◽  
Albena Nikiforova ◽  
Miglena Veneva
Keyword(s):  
Life Cycle ◽  
Web Site ◽  
The Internet ◽  
A Company ◽  
The Web ◽  
Design Construction ◽  
Made In ◽  
Site Types

This report is dedicated to the role of the web site as an important tool for presenting business on the Internet. Classification of site types has been made in terms of their application in the business and the types of structures in their construction. The Models of the Life Cycle for designing business websites are analyzed and are outlined their strengths and weaknesses. The stages in the design, construction, commissioning, and maintenance of a business website are distinguished and the activities and requirements of each stage are specified.

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