274 research outputs found
Data for: New insights into fluid-rock interaction mechanisms at mud volcanoes: Implications for fluid origin and mud provenance at Bahar and Zenbil (Azerbaijan)
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The role of bacterial sulfate reduction during dolomite precipitation: Implications from Upper Jurassic platform carbonates
No full textThe early diagenetic formation of dolomite in modern aquatic environments is limited mostly to evaporitic and marine-anoxic, organic-rich sediments dominated by bacterial sulfate reduction (BSR). In such environments, bacterial activity lowers the energy barriers for the nucleation and growth of dolomite and thus promotes the formation of non-stoichiometric, highly disordered and metastable (proto)dolomite. Although the boundary conditions for the formation of modern (proto)dolomites are considered to be generally understood, the role of BSR during limestone dolomitization in ancient marine environments remains questionable. Herein, we present a study about the physicochemical conditions and processes, which led to the formation of partly dolomitized limestone and dolostone in the presence of BSR on a stable carbonate platform during the Upper Jurassic at Oker (Northern German Basin). The dolomite textures, the spatial trace elemental patterns of the dolomite and of the surrounding limestone and the results of δ18O and δ13C isotope analyses reveal that the Oker dolomite has been formed by the early diagenetic replacement of magnesian calcite precursors at temperatures between 26°C and 37°C. We interpret the mineralizing fluids responsible for dolomitization as pristine-marine to slightly evaporitic and reducing seawater being modified during shallow seepage reflux and/or evaporitic tidal pumping. The elevated δ34SCAS values (+17.9 to +19.7‰, V-CDT) of the Oker dolomite, compared to ambient Upper Jurassic seawater, indicate that BSR facilitated dolomite formation. For the first time, we show that a linear anti-correlation exists between decreasing carbonate-associated sulfate (CAS) contents in dolomite and increasing ordering ratio of the dolomite lattice structure, with the degree of cation order in dolomite to be given by: degree of cation order(Dol): =-0.018·CAS(Dol)+68.3 (R2=0.98).This correlation implies that the CAS content of sedimentary dolomite can be used as a measure for dolomite maturity. The relationships between the ambient (paleo)environmental controls, the resultant dolomitization pathways and subsequently the structure and the composition of the precipitating dolomite are presented and discussed in relation to the stability of modern and ancient (proto)dolomites throughout burial diagenesis
The role of Fe on the formation and diagenesis of interstratified glauconite-smectite and illite-smectite: A case study of Upper Cretaceous shallow-water carbonates
No full textThe widespread formation of interstratified glauconite-smectite (Gl-S) and illite-smectite (I-S) in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral authigenesis. To date, however, significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry, temperature and reaction kinetics on the evolution of composition, mineralogy and microstructure of Gl-S and I-S. Herein, we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic Gl-S and late diagenetic I-S on a stable carbonate platform during the Cenomanian at Langenstein in the Northern German Basin. The texture and the K-Ar age (95.0 +/- 1.8 Ma) of the green glauconitized grains revealed that green-clay authigenesis progressed in initially organic-rich, semi-confined micromilieus, ie., in fecal pellets and in foraminifera, close to the sediment-seawater interface. The composition of Gl-S varied in the range (K0.20-0.74+Na0-0.10+Ca0-0.052+)(0.28-0.75) (Fe0.63- 1.203+Fe0.08-0.242+Al0.19-0.973+ Mg-0.29-0.52(2+))(2.01-2.12) [Al0.09-0.353+Si3.65-3.914+O10](OH2), and depended on the rate of aqueous Fe2+ and K+ ion diffusion, the micromilieu of glauconitization and on the bulk sedimentation rate. The mineralogical, microstructural and chemical changes of the ongoing Gl-S products revealed the following reaction for green-clay authigenesis at Langenstein: Fe(III)-smectite reacted with monosilicic acid, goethite and aqueous K+, Mg2+ and Fe2+ to form glauconite and aqueous Na+, Ca2+ and H+ ions. This process considers complex mineral transformations commonly associated with glauconitization, such as early diagenetic oxidation of organic matter and microbial-catalyzed dissolution of Fe-(oxy) hydroxides, carbonates and detrital silicates. In contrast, the K-Ar age of I-S (68.0 +/- 1.6Ma) and its compositional variability, (K0.29-0.45+Na0-0.10+Ca0-0.062+)(0.30-0.55) (Fe0.16-0.293+Fe0-0.102+Al1.37-1.683+Mg0.18-0.432+)(2.00-2.12) [Al0.17-0.393+Si3.61-3.834+O10](OH2), indicate a burial diagenetic origin for this mineral phase, rather than transformation of illitic clays into I-S during weathering under warm and humid climatic conditions. The results from kinetic modelling support a diagenetic origin of I-S (50-60% I layers and 50-40%S layers) and imply its formation by the replacement of pre-existing K-feldspar at high pore-fluid activity K/Na ratios and at low Fe2+ concentrations. We propose that the substitution of Al3+ for Fe3+, Fe2+ and Mg2+ in the octahedral sheet shifts the stability field of the kaolinite-Fe-Al-Mg-smectite-Fe-Al-Mg-illite (or glauconite) triple point to much lower monosilicic acid activities, and stabilizes the I-S (or Gl-S) structure. This reaction supports the idea that the (bio) availability of Fe is the rate-limiting factor for glauconitization, which is not the case for the diagenetic growth of I-S, whereby the porewater Fe2+ concentration may be limited by the competing formation of Fe-(oxy) hydroxides and/or Fesulfides. (C) 2017 Elsevier B.V. All rights reserved.NAWI Graz [F-AF7-221-01
What can we learn from 10 superintendents who identify as instructional leaders: a qualitative study
No full textThe purpose of this qualitative descriptive study was to explore the instructional leadership of experienced and effective superintendents, focusing on how they define it, the standard strategies they employ, and how they perceive different contexts influencing their work. The ten superintendents interviewed for this research are among the most successful and influential superintendents in the country. One was named the National School Superintendent of the Year, two were state superintendents of the year, and among the ten superintendents, they have collectively authored 24 books, all while serving as full-time practitioners. Nine of the ten have extensive consulting and presenting experience, including serving as keynote speakers at multiple national conferences on educational leadership. Braun and Clarke's (2006) reflexive thematic analysis and used to identify themes related to instructional leadership. Data sources included semi-structured interviews and demographic surveys. The final themes were (a) effective instructional leadership entails transformational and adaptive leadership style for long-run success, (b) leader-member exchanges (LMX) leadership styles for short run success, (c) instructional leadership begets boundary-spanning collaboration, (d) effective instructional leadership requires educators to feel responsibility, effective instructional leadership that requires universal (re) focus of all goals and roles on student learning, (f) effective instructional leadership requires direct participation in all levels by superintendents (g), the outcome of effective instructional leadership is student learning equity, and (h) a culture of instructional leadership that is requisite for minimizing student learning inequity. The findings demonstrate the value of collaborative and shared practices to support instructional leadership and student equity.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2026-02-19 without embargo termsThe student, Jack Baldermann, accepted the attached license on 2025-12-05 at 10:20.The student, Jack Baldermann, submitted this Dissertation for approval on 2025-12-05 at 10:31.This Dissertation was approved for publication on 2025-12-05 at 10:56.DSpace SAF Submission Ingestion Package generated from Vireo submission #23079 on 2026-02-19 at 18:29:4
Boiling and steaming induced changes in secondary metabolites in three different cultivars of pak choi (Brassica rapa subsp. chinensis)
No full textPak choi (Brassica rapa subsp. chinensis) is a leafy vegetable that is widely available in Asia and consumed in rising quantities in Europe. Pak choi contains high levels of secondary plant metabolites, such as carotenoids, chlorophylls, glucosinolates, phenolic compounds, and vitamin K, which are beneficial for humans if consumed on a regular basis. The evaluation of the genotype-induced variation of secondary plant metabolites revealed that the cultivar ‘Amur’ contained the highest concentration of secondary plant metabolites. Furthermore, steaming retained more chlorophylls, glucosinolates, phenolic acids and flavonoid compounds than boiling. In contrast, both domestic cooking methods – boiling, and steaming – reduced the formation of glucosinolate breakdown products, especially the undesired epithionitriles and nitriles but less of the health-beneficial isothiocyanates
Robust Small Area Estimation Under Spatial Non-stationarity
No full textThe effective use of spatial information in a regression-based approach to small area estimation is an important practical issue. One approach to account for geographic information is by extending the linear mixed model to allow for spatially correlated random area effects. An alternative is to
include the spatial information by a non-parametric mixed models. Another option is geographic weighted regression where the model coefficients vary spatially across the geography of interest. Although these approaches are useful for estimating small area means efficiently under strict parametric assumptions, they can be sensitive to outliers. In this paper, we propose robust extensions of the geographically weighted empirical best linear unbiased predictor. In particular, we introduce robust projective and predictive estimators under spatial non-stationarity. Mean squared error estimation is performed by two analytic approaches that account for the spatial structure in the data. Model-based simulations show that the methodology proposed often leads to more efficient estimators. Furthermore, the analytic mean squared error estimators introduced have appealing
properties in terms of stability and bias. Finally, we demonstrate in the application that the new methodology is a good choice for producing estimates for average rent prices of apartments in urban planning areas in Berlin
Indigenous leafy vegetables of Eastern Africa — A source of extraordinary secondary plant metabolites
No full textIndigenous African leafy vegetables vary enormously in their secondary plant metabolites whereat genus and the species have a great impact. In African nightshade (Solanum scabrum), spiderplant (Cleome gynandra), amaranth (Amaranthus cruentus), cowpea (Vigna unguiculata), Ethiopian kale (Brassica carinata) and common kale (Brassica oleracea) the specific secondary metabolite profile was elucidated and gained detailed data about carotenoids, chlorophylls, glucosinolates and phenolic compounds all having an appropriate contribution to health beneficial properties of indigenous African leafy vegetables. Exemplarily, various quercetin glycosides such as quercetin-3-rutinoside occur in high concentrations in African nightshade, spiderplant, and amaranth between similar to 1400-3300 mu g/g DW. Additionally the extraordinary hydroxydnnamic acid derivatives such as glucaric isomers and isocitric acid isomers are found especially in amaranth (up to similar to 1250 mu g/g DW) and spiderplant (up to 120 mu g/g DW). Carotenoids concentrations are high in amaranth (up to 101.7 mu g/g DW) and spiderplants (up to 64.7 mu g/g DW) showing high concentrations of beta-carotene, the pro-vitamin A. In contrast to the ubiquitous occurring phenolics and carotenoids, glucosinolates are only present in the Brassicales species Ethiopian kale, common kale and spiderplant characterized by diverse glucosinolate profiles. Generally, the consumption of a variety of these indigenous African leafy vegetables can be recommended to contribute to different benefits such as antioxidant activity, increase pro-vitamin A and anticancerogenic compounds in a healthy diet. (C) 2017 Elsevier Ltd. All rights reserved
Intercropping Induces Changes in Specific Secondary Metabolite Concentration in Ethiopian Kale (Brassica carinata) and African Nightshade (Solanum scabrum) under Controlled Conditions
No full textIntercropping is widespread in small-holder farming systems in tropical regions and is also practiced in the cultivation of indigenous vegetables, to alleviate the multiple burdens of malnutrition. Due to interspecific competition and/or complementation between intercrops, intercropping may lead to changes in plants accumulation of minerals and secondary metabolites and hence, alter nutritional quality for consumers. Intercropping aims to intensify land productivity, while ensuring that nutritional quality is not compromised. This study aimed to investigate changes in minerals and secondary plant metabolites in intercropped Brassica carinata and Solanum scabrum, two important African indigenous vegetables, and evaluated the suitability of this combination for dryer areas. B. carinata and S. scabrum were grown for 6 weeks under controlled conditions in a greenhouse trial. Large rootboxes (8000 cm3 volume) were specifically designed for this experiment. Each rootbox was planted with two plants, either of the same plant species (mono) or one of each plant species (mixed). A quartz sand/soil substrate was used and fertilized adequately for optimal plant growth. During the last 4 weeks of the experiment, the plants were either supplied with optimal (65% WHC) or low (30% WHC) irrigation, to test the effect of a late-season drought. Intercropping increased total glucosinolate content in B. carinata, while maintaining biomass production and the contents of other health related minerals in both B. carinata and S. scabrum. Moreover, low irrigation led to an increase in carotene accumulation in both mono and intercropped S. scabrum, but not in B. carinata, while the majority of kaempferol glycosides and hydroxycinnamic acid derivatives of both species were decreased by intercropping and drought treatment. This study indicates that some health-related phytochemicals can be modified by intercropping or late-season drought, but field validation of these results is necessary before definite recommendation can be made to stakeholders.Peer Reviewe
Effects of Amaranthus cruentus L. on aflatoxin B1- and oxidative stress-induced DNA damage in human liver (HepG2) cells
No full textAmaranth is presently an underutilized crop despite its high content of micronutrients/bioactive phytochemicals and its capacity to thrive in harsh environmental condition. The present study aimed at determining the health benefits of Amaranthus cruentus L. in terms of protection against DNA damage induced by the mycotoxin aflatoxin B1 (AFB1) and oxidative stress using comet assay. The antioxidant potential was further investigated using electron paramagnetic resonance spectroscopy (EPR) and an ARE/Nrf2 reporter gene assay in vitro in a human liver model using the HepG2 cell line. Ethanolic extracts from fresh leaves grown under controlled conditions were used and additionally analyzed for their phytochemical content using liquid chromatography-mass spectrometry (LC-MS). The extracts inhibited both AFB1- and oxidative stress-induced DNA damage in a concentration dependent way with a maximum effect of 57% and 81%, respectively. Oxidative stress triggered using ferrous sulfate was blocked by up to 38% (EPR); the potential to induce antioxidant enzymes using ARE/Nrf2-mediated gene expression was also confirmed. Based on these in vitro findings, further studies on the health-protecting effects of A. cruentus are encouraged to fully explore its health promoting potential and provide the scientific basis for encouraging its cultivation and consumption
Selenium Enhances Growth, Phenolic Compounds, Antioxidant Capacity in Brassica Oleracea Var. Italica
No full textSelenium is a micronutrient element that is beneficial for the growth and development of plants. It has antioxidant, anticancer, and antiviral properties that are essential for human and animal health. Low-consumption mineral elements such as selenium can be included in the diet from various sources. To investigate the growth and phytochemical attributes of a broccoli cultivar "Heracklion", an experiment with five levels of selenium concentration (0, 5, 10, 15, 20 mg/L sodium selenate) was carried out in a randomized complete block design with 3 replications in the field condition. With increasing the concentration of sodium selenate in the foliar application, the accumulation of sodium selenate in broccoli increased and the highest amount (1.47 mg/kg dry weight) was measured at 20 mg/L of sodium selenate. The highest amount of photosynthetic pigments in leaves was recorded at 15 mg/L of sodium selenate. In the case of glucosinolates, with increasing selenium concentration up to 20 mg/L concentration, glucoraphanin, 4-methoxy glucobrassicin, and aliphatic glucosinolates increased in leaves. It could be demonstrated that foliar application of selenium at 10 mg/L led to an improvement of secondary metabolites, especially glucoraphanin, both in leaves and florets, and could also have a positive effect on human nutrition
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