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- Aludden, H., et al.
(author)
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Histomorphometric analyses of area fraction of different ratios of Bio-Oss((R)) and bone prior to grafting procedures - An in vitro study to demonstrate a baseline
- 2018
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In: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 29:2, s. 185-191
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Journal article (peer-reviewed)abstract
- ObjectiveThe objective of this study was to estimate the area fraction of different ratios of Bio-Oss((R)) and bone, prior to grafting in an in vitro model to demonstrate a histomorphometric baseline. MethodsBio-Oss((R)) particles were mixed with autogenous bone from pig jaw in three different ratios (50:50, 80:20 and 100:0) and packed in rice paper in a standardized procedure. Histomorphometric analyses were performed in 25 specimens and 74 regions of interest. The area percentage of Bio-Oss((R)), bone, and non-mineralized tissue (NMT) were calculated. Results were reported as mean values and 95% confidence interval (CI). ResultsThe mean area fraction of Bio-Oss((R)) was 20.6% (CI: 18.2-23) in the 50:50 mixture, 33.6% (CI: 29.7-37.6) in the 80:20 mixture, and 43.4% (CI: 40.5-46.3) in the 100:0 mixture. The mean area fraction of NMT was 60.5% (CI: 57.9-63.1) in the 50:50 mixture, 59.6% (CI: 56.4-62.7) in the 80:20 mixture, and 56.6% (CI: 53.7-59.5) in the 100:0 mixture. The mean area fraction of bone was 18.9% (CI: 16.9-20.9) in the 50:50 mixture and 6.8% (CI: 5-8.6) in the 80:20 mixture. ConclusionThere is a great difference in the clinically estimated percentage and the histomorphometrically evaluated percentage of Bio-Oss((R)) at baseline, prior to grafting. The area fraction of different tissues presented in this study may be beneficial as guidance for histomorphometrical baseline calculations when different mixtures of Bio-Oss((R)) and autogenous bone are used as grafting materials.
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- Bender, A. N., et al.
(author)
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Galaxy cluster scaling relations measured with APEX-SZ
- 2016
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 460:4, s. 3432-3446
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Journal article (peer-reviewed)abstract
- We present thermal Sunyaev-Zel'dovich effect (SZE) measurements for 42 galaxy clusters observed at 150 GHz with the APEX-SZ experiment. For each cluster, we model the pressure profile and calculate the integrated Comptonization Y to estimate the total thermal energy of the intraclustermedium (ICM). We compare the measured Y values to X-ray observables of the ICM from the literature (cluster gas mass M-gas, temperature T-X, and Y-X = MgasTX) that relate to total cluster mass. We measure power-law scaling relations, including an intrinsic scatter, between the SZE and X-ray observables for three subsamples within the set of 42 clusters that have uniform X-ray analysis in the literature. We observe that differences between these X-ray analyses introduce significant variance into the measured scaling relations, particularly affecting the normalization. For all three subsamples, we find results consistent with a selfsimilarmodel of cluster evolution dominated by gravitational effects. Comparing to predictions from numerical simulations, these scaling relations prefer models that include cooling and feedback in the ICM. Lastly, we measure an intrinsic scatter of similar to 28 per cent in the Y - Y-X scaling relation for all three subsamples.
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- Loke, M. H., et al.
(author)
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The use of positivity constraints in 4-D ERT inversion
- 2018
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Conference paper (peer-reviewed)abstract
- Time-lapse resistivity surveys are used to monitor changes in the subsurface. In some situations, it is expected the resistivity will only decrease (or vice versa) with time. The 4-D ERT inversion technique includes a temporal smoothness constraint to ensure that the resistivity changes in a smooth manner with time. However, it does not directly constrain the direction of the temporal changes in the resistivity. In some cases, the time-lapse models might show an increase in the resistivity with time in parts of the inverse model where it is expected to only decrease based on other information. We modify the 4-D ERT inversion method to remove this artefact. We first use the standard 4-D ERT inversion algorithm to generate an initial model. If the resistivity is expected to decrease with time, for the model cells that show a resistivity increase a truncation procedure is used where the resistivities of the different time models are reset to the mean value. The method of transformations is then used to ensure that the resistivities of the later time models are always less than the first model. The constraints can be applied to selected regions in the model in cases where additional information is available.
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| 6. |
- Loke, M. H., et al.
(author)
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Time-lapse 4-D resistivity imaging inversion with positivity constraints
- 2018
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In: 24th European Meeting of Environmental and Engineering Geophysics. - : European Association of Geoscientists & Engineers. - 9789462822634
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Conference paper (peer-reviewed)abstract
- Time-lapse resistivity surveys are used to monitor changes in the subsurface. In some situations, it is known that the resistivity will only decrease (or increase) with time. The 4-D ERT smoothness-constrained inversion method, that includes temporal smoothness constraint, has proved to be a robust method that reduces artefacts due to noise. However, in some cases, the time-lapse inverse models might show an increase in the resistivity with time where it is only expected to decrease. We modify the 4-D ERT inverse method to include a constraint that removes this artefact. The standard 4-D ERT inversion algorithm is first used to generate an initial model. If the resistivity is expected to decrease with time, for the model cells that show a resistivity increase with time, a truncation procedure is used where the resistivities of the different time models are reset to the mean value (corresponding to zero change with time). We then use the method of transformations in the inversion method that ensures the resistivities of the later time models are always less than the first model. The constraints can be modified so that they are only applied to selected regions in the model in cases where additional information is available.
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| 7. |
- Aludden, H. C., et al.
(author)
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Lateral ridge augmentation with Bio-Oss alone or Bio-Oss mixed with particulate autogenous bone graft: a systematic review
- 2017
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In: International Journal of Oral and Maxillofacial Surgery. - : Elsevier BV. - 0901-5027. ; 46:8, s. 1030-1038
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Journal article (peer-reviewed)abstract
- The objective of this systematic review was to test the hypothesis of no difference in implant treatment outcomes when using Bio-Oss alone or Bio-Oss mixed with particulate autogenous bone grafts for lateral ridge augmentation. A search of the MEDLINE, Cochrane Library, and Embase databases in combination with a hand-search of relevant journals was conducted. Human studies published in English from 1 January 1990 to 1 May 2016 were included. The search provided 337 titles and six studies fulfilled the inclusion criteria. Considerable variation prevented a meta-analysis from being performed. The two treatment modalities have never been compared within the same study. Non-comparative studies demonstrated a 3-year implant survival of 96% with 50% Bio-Oss mixed with 50% autogenous bone graft. Moreover, Bio-Oss alone or Bio-Oss mixed with autogenous bone graft seems to increase the amount of newly formed bone as well as the width of the alveolar process. Within the limitations of this systematic review, lateral ridge augmentation with Bio-Oss alone or in combination with autogenous bone graft seems to induce newly formed bone and increase the width of the alveolar process, with high short-term implant survival. However, long-term studies comparing the two treatment modalities are needed before final conclusions can be drawn.
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| 8. |
- Arrowsmith, CH, et al.
(author)
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The promise and peril of chemical probes
- 2015
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In: Nature chemical biology. - : Springer Science and Business Media LLC. - 1552-4469 .- 1552-4450. ; 11:8, s. 536-541
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Journal article (peer-reviewed)
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- Chirindja, F. J., et al.
(author)
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Improving the groundwater-well siting approach in consolidated rock in Nampula Province, Mozambique
- 2017
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In: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 25:5, s. 1423-1435
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Journal article (peer-reviewed)abstract
- Vertical electrical sounding was used for assessing the suitability of the drill sites in crystalline areas within a water supply project in Nampula Province in Mozambique. Many boreholes have insufficient yield (<600 L/h). Electrical resistivity tomography (ERT) was carried out over seven boreholes with sufficient yield, and five boreholes with insufficient yield, in Rapale District, in an attempt to understand the reason for the failed boreholes. Two significant hydrogeological units were identified: the altered zone (19–220 ohm-m) with disintegrated rock fragments characterized by intermediate porosity and permeability, and the fractured zone (>420 ohm-m) with low porosity and high permeability. In addition to this, there is unfractured nonpermeable intact rock with resistivity of thousands of ohm-m. The unsuccessful boreholes were drilled over a highly resistive zone corresponding to fresh crystalline rock and a narrow altered layer with lower resistivity. Successful boreholes were drilled in places where the upper layers with lower resistivity correspond to a well-developed altered layer or a well-fractured basement. There are a few exceptions with boreholes drilled in seemingly favourable locations but they were nevertheless unsuccessful boreholes for unknown reasons. Furthermore, there were boreholes drilled into very resistive zones that produced successful water wells, which may be due to narrow permeable fracture zones that are not resolved by ERT. Community involvement is proposed, in choosing between alternative borehole locations based on information acquired with a scientifically based approach, including conceptual geological models and ERT. This approach could probably lower the borehole failure rate.
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| 10. |
- Chirindja, F. J., et al.
(author)
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Reconstructing the formation of a costal aquifer in Nampula province, Mozambique, from ERT and IP methods for water prospection
- 2017
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In: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 76:1
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Journal article (peer-reviewed)abstract
- In continental margin basins, the hydrogeological setting is complex due to transgression/regression events that removed old sediments in the basin and formed new geologic units. Due to the geological complexity, the use of vertical electrical sounding has proven to be insufficient for groundwater explorations. The lack of understanding the geological underground has resulted in many boreholes with low yield or poor water quality. By performing electrical resistivity tomography (ERT) and induced polarization (IP) measurements in 11 villages in Mongicual district, three different layers covering the basement were identified: a weathered autochthon layer, a weathered allochthon layer (paleo-coastal dune) and eolian white sand layer. The drilling at successful boreholes penetrates formations where the resistivity value is between 220 and 770 Ωm, whereas at unsuccessful boreholes the lower parts of the drilled range have resistivity values higher than 770 Ωm. Also, the thickness ratio of the weathered and semi-weathered layer in the unsuccessful boreholes is less than 1/3, whereas in all successful boreholes the ration is higher than 1/2. The difference between autochthon and allochthon layers was detected by heavy minerals content in the red eolian sand layer (Tupuito formation) that increased the chargeability value. The groundwater with a conductivity higher than 2000 µS/cm is linked to the white eolian sand. The surface extension of white eolian sand layer is small to be mapped; therefore, by mapping the eolian white sand formation and the use of ERT and enhanced with IP method would lower the failure rate.
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