The presence of a diffuse biodeterioration phenomena can be observed across large areas of the outer surface of the limestone walls of the Church of the Virgin in Martvili. A differential erosion phenomenon was detected, suggesting a possible association with biological colonization. The erosion phenomenon is characterized by a circular discoloration leading progressively to the detachment of flakes of limestone at its center. Since the aforementioned process has not been described in the literature until now, the present study was focused on the interpretation of its origin and evolution. Three sides of the Church are affected by a variety of occurrences of circular differential erosion which display different stages of the process, whereas the western side is affected by epilithic growths across its entire surface. Surveys of the petrographic, mineralogical and physical features of the stone were made, and parameters such as density and porosity were recorded. Samples were analyzed by optical microscopy and SEM analysis in order to detected the presence of microorganisms whose species were then identified by means of morphological and molecular examinations. The study of cross-sections stained using the PAS method has confirmed the causal connection between microorganisms and the deterioration phenomena, providing information about their spread of penetration into the substrate and their substantial potential for causing damage. Dryness appears to be the main ecological condition favoring endolithic rather than epilithic growth. The most common isolated microorganisms were cyanobacteria (Chroococcales) and, to a lesser extent, meristematic fungi. The characteristics of the stone, and especially some endogenous discontinuities related to the accumulation of sedimentary layers and to the action of stone carving tools, might explain why the same differential erosion phenomenon occurs in specific areas of the block stones. The development of the differential erosion phenomenon shows a variety of stages of biological colonization. The progressive evolution of the deterioration process has been observed in detail: (a) firstly, white circular discolorations appear on the stone, which darken over time eventually becoming almost black; (b) circular perforations appear around the perimeter; (c) and finally a flake detaches from the center, leaving a deep depression in the stone. 相似文献
A simple microwell-based microfluidic chip for microalgal cells trapping was
fabricated. An electrostaticcell trapping
mechanism, enabled by a positively charged glass surface, was used. The chip was capable of capturing multiple algal
cell types.
In the case of filamentous Spirulina platensis, we observed single filament
occupancy of up to ∼30% available wells, as high as some previously proposed methods. Captured
filaments were not of any preferential size, suggesting well randomized cell trapping. It was found
that the electrostatic
attraction did not affect the cell
growth. Total replacement of liquid inside the wells could be achieved by pumping
new solutions via the inlet, making single cell experiments in controlled chemical conditions
possible. After the top layer of the chip was removed, cells in the wells could be simply transferred using a
micropipette, turning the chip into a platform for strain selection. 相似文献
Background: Microorganisms are very important in day-to-day life, but they are inadequately addressed in the Spanish educational system. It is essential that students are well informed about their characteristics and functions.
Purpose: The study aims to find out primary school students’ perceptions of microorganisms and to analyze whether theoretical or practical teaching interventions produce different levels in student’s learning about this topic.
Sample: The sample consisted of 199 primary students in 2nd (aged 7–8) and 6th (11–12) grades from two public schools in Albacete (Spain).
Design and method: This study uses a pre- and post-intervention questionnaire to evaluate the knowledge of students on the issue of microorganisms. We compare differences by age and two teaching–learning intervention methodologies: theoretical and practical.
Results: Results from the pre-test showed a poor understanding and several misconceptions. Children have a limited and negative view of microorganisms, mainly derived from non-formal learning. Both types of intervention provided an improvement in knowledge, but closed questions did not reveal clear statistically significant differences between methods. Open questions showed how the scientific use of the language and quality of verbalization is much better in the groups that received a practical intervention.
Conclusion: The findings can be a starting point for curriculum planners and for teachers interested in engaging students in science learning. 相似文献
