| 1. |
- Madsen, L. M., et al.
(författare)
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Comparison of tTEM-IP and ERT-IP : cases from mine tailing sites in Sweden
- 2023
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Ingår i: 29th European Meeting of Environmental and Engineering Geophysics, Held at Near Surface Geoscience Conference and Exhibition 2023, NSG 2023. - 9789462824607
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Konferensbidrag (refereegranskat)abstract
- The induced polarization (IP) effect can be studied using both galvanic and inductive methods. Here we study IP and its manifestation in transient electromagnetic (TEM) data from a tTEM system and in time-domain electric resistivity tomography (ERT) data. Since the two methods are sensitive to two different frequency ranges, a direct IP spectrum comparison is not possible. Instead, we assess the IP resolution and compare both resistivity and chargeability inversion results. We show that tTEM data recorded in highly resistive environments with high IP, suffer from fast-decaying transients and sign-changes, which makes it difficult to resolve the true resistivity and IP model due equivalences. A comparison of the maximum phase shifts from two mine tailing sites shows that the chargeability structures gained from the inversion of tTEM data to some degree follow the structures of the chargeability resolved from the ERT data. However, the magnitudes of the resolved phases are generally below 50 mRad for ERT, but up to 500 mRad for tTEM. This indicates that different polarization mechanisms are dominating within the different frequency ranges of the tTEM and ERT methods.
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| 2. |
- Martin, T., et al.
(författare)
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Inversion of hydraulic conductivity from Induced Polarisation, Part B: field examples from five countries
- 2021
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Ingår i: Conference Proceedings, NSG2021 1st Conference on Hydrogeophysics. - : European Association of Geoscientists & Engineers. ; 2021
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Konferensbidrag (refereegranskat)abstract
- The knowledge about the hydraulic conductivity of the subsurface is crucial to know as it is a main parameter for groundwater flow characterization within an aquifer. The geophysical method time-domain Induced Polarisation has been shown to be useful for estimating the hydraulic conductivity. By using a new inversion approach, where we directly invert for hydraulic properties as inversion parameters, the estimation of the hydraulic conductivity can be improved. We have measured at several test sites across five European countries, all characterized by unconsolidated sediments, but with differences in terms of the water electrical conductivity. In particular, at the Zeeland site in the Netherlands, a strong gradient in the water electrical conductivity is present since a freshwater lens is overlaying the sea water. A very good agreement between the hydraulic conductivity values from the inversion with the present hydraulic model can be observed, despite of the high water electrical conductivity, which makes it challenging to identify the clay layers at the site. Similar results were achieved for the other tests sites. Therewith, this new methodology might open the way for reliable, cost-effective geophysical estimation of hydraulic conductivity in the field.
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| 3. |
- Umrao, S., et al.
(författare)
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Anticarcinogenic activity of blue fluorescent hexagonal boron nitride quantum dots : as an effective enhancer for DNA cleavage activity of anticancer drug doxorubicin
- 2019
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Ingår i: MATERIALS TODAY BIO. - : ELSEVIER. - 2590-0064. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Blue fluorescent hexagonal boron nitride quantum dots (h-BNQDs) of similar to 10 nm size as an effective enhancer for DNA cleavage activity of anticancer drug doxorubicin (DOX) were synthesized using simple one-step hydrothermal disintegration of exfoliated hexagonal boron nitride at very low temperature similar to 120 degrees C. Boron nitride quantum dots ( BNQDs) at a concentration of 25 mu g/ml enhanced DNA cleavage activity of DOX up to 70% as checked by converting supercoiled fragment into nicked circular PBR322 DNA. The interaction of BNQDs with DOX is proportional to the concentration of BNQDs, with binding constant K-b similar to 0.07338 mu g/ml. In addition, ab initio theoretical results indicate that DOX is absorbed on BNQDs at the N-terminated edge with binding energy -1.075 eV and prevented the normal replication mechanisms in DNA. BNQDs have been shown to kill the breast cancer cell MCF-7 extensively as compared with the normal human keratinocyte cell HaCaT. The cytotoxicity of BNQDs may be correlated with reduced reactive oxygen species level and increased apoptosis in MCF-7 cells, which may be liable to enhance the anticancerous activity of DOX. The results provide a base to develop BNQD-DOX as a more effective anticancer drug.
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