A New Insight into the Nature of the Leached Layers Formed on Basaltic Glasses in Relation to the Choice of Constraints for Long Term Modelling

1988 ◽  
Vol 127 ◽  
Author(s):  
J. L. Crovisier ◽  
H. Atassi ◽  
V. Daux ◽  
J. Honnorez ◽  
J. C. Petit ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Basaltic Glass ◽  
Chemical Gradient ◽  
Glass Dissolution ◽  
Clayey Material ◽  
Congruent Dissolution ◽  
Ph Increase ◽  
Significant Chemical ◽  
Insight Into

ABSTRACTExperimental basaltic glass dissolution in fresh water is compared with analyses made on subglacial hyaloclastites from Iceland. The dissolution is initially selective and remains selective if the solution is renewed, whereas it becomes apparently congruent in non-renewed conditions. The congruent dissolution is ascribed to a pH increase (up to 7.0–7.5) which is hampered in the former conditions. The palagonite hydrated layer on the Icelandic basaltic glasses is made up of amorphous to crystallized clay-like materials. The chemical composition of palagonite is close to that of the intergranular clayey material, thus, it is inferred that in most cases no significant chemical gradient exists in the solution between the reaction zone, namely the glass/palagonite interface, and the intergranular solution. We conclude that the dissolution of basaltic glass under subglacial conditions is controlled by thermodynamics and that kinetic constraints, such as the diffusion of species through the altered layers, do not play a major role.

Alteration of Basaltic Glass in Iceland as a Natural Analogue for Nuclear Waste Glasses: Geochemical Modelling with DISSOL

1988 ◽  
Vol 127 ◽  
Author(s):  
J. L. Crovisier ◽  
T. Advocat ◽  
J. C. Petit ◽  
B. Fritz
Keyword(s):  
Computer Code ◽  
Solution Chemistry ◽  
Iron Hydroxides ◽  
Basaltic Glass ◽  
Secondary Products ◽  
Glass Dissolution ◽  
Mineral Phases ◽  
Kinetic Effects ◽  
Good Agreement

ABSTRACTThe long term geochemical consequences of basaltic glass dissolution in fresh water at 0°C have been calculated with the computer code DISSOL. The clay minerals were represented by an ideal solid solution model (CISSFIT) able to describe variations in chemical composition of a clay phase in response to variations of the solution chemistry. The predicted mineral phases were iron hydroxides followed by kaolinite, TOT clays, chabazite and cli-noptilolite. These results are in reasonably good agreement with experimental results and observations of altered subglacial hyaloclastites from Iceland. The formation of secondary products are mainly controlled by thermodynamic constraints. Kinetic effects, such as diffusion in the near glass surface are not important.

Fitting Element Profiles for Predicting Glass Dissolution Rates in Synthetic Interstitial Clay Water

2002 ◽  
Vol 757 ◽  
Author(s):  
Marc Aertsens ◽  
Karel Lemmens ◽  
Pierre Van Iseghem
Keyword(s):  
Diffusion Layer ◽  
Diffusion Coefficients ◽  
Water Flux ◽  
Dissolution Behavior ◽  
Matrix Elements ◽  
Hydrogen Water ◽  
Glass Dissolution ◽  
Gel Layer ◽  
Congruent Dissolution

ABSTRACTAn analytical model is developed to derive diffusion coefficients from the element profiles of the most mobile glass elements. Congruent dissolution is considered as a transient phenomenon and neglected. In the model, altered glass consists of two sublayers: a gel layer at the solution side, and a diffusion layer at the pristine glass side. In both layers, mobile glass elements diffuse towards the solution, while hydrogen/water diffuses towards the pristine glass.Fitting the element profiles of boron, sodium and lithium leads to diffusion coefficients in the diffusion layer, which at 90°C are typically of the order of 10-22m2/s to 10-21m2/s. At 40°C, these diffusion coefficients are typically a factor ten lower. The diffusion coefficients in the gel are by less than a factor two hundred larger than those in the diffusion layer.The diffusion coefficients derived from the profiles in this way are used to predict the dissolution behavior. These predictions, for which a constant value (representing congruent dissolution) is added to the predicted diffusive release, agree reasonably well with the measured dissolution data. Those results support the idea that diffusion determines the long term release of glass matrix elements in synthetic interstitial clay water. Flux conservation at the interface between the gel and the diffusion layer is not consistent with a constant (as a function of time) width of the diffusion layer. Some experimental evidence supports that this width increases with time.

Turkish Muslims in a German city: Entrepreneurial and residential self-determination

2015 ◽  
Vol 12 (1) ◽  
pp. 1-12
Author(s):  
Sarah Hackett
Keyword(s):  
Residential Patterns ◽  
Academic Literature ◽  
Self Employment ◽  
German City ◽  
Post War ◽  
Oral History Interviews ◽  
The City ◽  
Insight Into ◽  
Term Objective

Drawing upon a collection of oral history interviews, this paper offers an insight into entrepreneurial and residential patterns and behaviour amongst Turkish Muslims in the German city of Bremen. The academic literature has traditionally argued that Turkish migrants in Germany have been pushed into self-employment, low-quality housing and segregated neighbourhoods as a result of discrimination, and poor employment and housing opportunities. Yet the interviews reveal the extent to which Bremen’s Turkish Muslims’ performances and experiences have overwhelmingly been the consequences of personal choices and ambitions. For many of the city’s Turkish Muslim entrepreneurs, self-employment had been a long-term objective, and they have succeeded in establishing and running their businesses in the manner they choose with regards to location and clientele, for example. Similarly, interviewees stressed the way in which they were able to shape their housing experiences by opting which districts of the city to live in and by purchasing property. On the whole, they perceive their entrepreneurial and residential practices as both consequences and mediums of success, integration and a loyalty to the city of Bremen. The findings are contextualised within the wider debate regarding the long-term legacy of Germany’s post-war guest-worker system and its position as a “country of immigration”.

Moving Songs

2019 ◽  
pp. 590-606
Author(s):  
Sally Treloyn ◽  
Matthew Dembal Martin ◽  
Rona Goonginda Charles
Keyword(s):  
Cultural Heritage ◽  
Knowledge Transmission ◽  
Intercultural Relationships ◽  
Cultural Negotiation ◽  
Intercultural Collaboration ◽  
Present Collection ◽  
Intergenerational Knowledge ◽  
Early Phases ◽  
Insight Into

Repatriation has become almost ubiquitous in ethnomusicological research on Australian Indigenous song. This article provides insights into processes of a repatriation-centered song revitalization project in the Kimberley, northwest Australia. Authored by an ethnomusicologist and two members of the Ngarinyin cultural heritage community, the article provides firsthand accounts of the early phases of a long-term repatriation-centered project referred to locally as the Junba Project. The authors provide a sample of narratives and dialogues that deliver insight into experiences of the work of identifying recordings “in the archive” and cultural negotiation and use of recordings “on Country.” The entanglement of local epistemological frameworks with past and present collection, archival research, repatriation, and dissemination for intergenerational knowledge transmission between spirits, Country, and the living, is explored, showing how recordings move song knowledge from community to archive to community and from generation to generation, and move people in present-day communities. The chapter considers how these “moving songs” allow an interrogation of the fraught endeavor of intercultural collaboration in the pursuit of revitalizing Indigenous song traditions. It positions repatriation as a method that can support intergenerational knowledge transmission and as a method to consider past and present intercultural relationships within research projects and between cultural heritage communities and collecting institutions.

scholarly journals Hypocalcemic cardiomyopathy after parathyroidectomy in a patient with uremia: A case report and literature review

2020 ◽  
Vol 48 (7) ◽  
pp. 030006052094211
Author(s):  
Wei Zhang ◽  
Feng Xue ◽  
Quandong Bu ◽  
Xuemei Liu
Keyword(s):  
Heart Failure ◽  
Case Report ◽  
Secondary Hyperparathyroidism ◽  
Calcium Supplementation ◽  
Severe Heart Failure ◽  
Cardiac Complications ◽  
Refractory Heart Failure ◽  
First Case ◽  
Insight Into

Hypocalcemia is a rare, but reversible, cause of dilated cardiomyopathy. Although cardiomyopathy may cause severe heart failure, calcium supplementation can reverse heart failure. We report here a patient with uremia and secondary hyperparathyroidism, who was complicated by persistent hypocalcemia and refractory heart failure. The cardiac failure was refractory to treatment with digitalis and diuretics, but dramatically responded to calcium therapy and restoration of normocalcemia. As a result, the patient was eventually diagnosed with hypocalcemic cardiomyopathy. To the best of our knowledge, this is the first case of this disease to be reported in a patient with uremia. Findings from our case may help clinicians to better understand hypocalcemic cardiomyopathy. Our case might also provide new insight into long-term cardiac complications and prognoses of patients undergoing parathyroidectomy due to secondary hyperparathyroidism.

scholarly journals R Coronae Borealis Stars: Long-Term Photometric & Spectroscopic Studies

1998 ◽  
Vol 11 (1) ◽  
pp. 379-379
Author(s):  
P.L. Cottrell ◽  
L. Skuljan ◽  
P.M. Kilmartin ◽  
C. Gilmore ◽  
W.A. Lawson
Keyword(s):  
Radial Velocity ◽  
Spectroscopic Studies ◽  
Photometric Data ◽  
Decline Phase ◽  
Dust Clouds ◽  
Medium Resolution ◽  
Formation And Evolution ◽  
R Coronae Borealis Stars ◽  
Insight Into

For more than a decade we have been able to acquire and analyse a significant amount of photometric data of the highly variable R Coronae Borealis (RCB) stars. This has made been possible by a photometric service observing programme instigated at the Observatory. These photometric data have been combined with less extensive spectroscopic coverage, particularly of the decline phase of these stars. These have been supplemented by observations obtained at Mount Stromlo and Siding Spring Observatories for a radial velocity study. Significantly more spectroscopic observations are now being acquired with the development of a new medium resolution spectrograph at Mount John University Observatory. In this poster we will present recent photometric and spectroscopic results for a number of the RCB stars in our sample. This observational and analysis work can be used to provide further insight into the nature of these stars, their likely progeny and progenitors and the processes that are involved in the formation and evolution of the obscuring dust clouds which cause the decline phase.

scholarly journals Characteristics of Liparis loeselii (L.) Rich. populations in selected Natura 2000 areas in eastern Poland

2020 ◽  
Vol 55 (3) ◽  
pp. 151-162
Author(s):  
Danuta Urban ◽  
Joanna Sender ◽  
Ewelina Tokarz ◽  
Andrzej Różycki
Keyword(s):  
Natura 2000 ◽  
Total Carbon ◽  
Habitat Conditions ◽  
Total Carbon Content ◽  
Poor Fen ◽  
Calcareous Fen ◽  
Liparis Loeselii ◽  
The Individual ◽  
Insight Into

AbstractIn view of the sensitivity of Liparis loeselii to changes in habitat conditions, we carried out a study with the aim to monitor population numbers, identify the individual features of the Liparis loeselii population, analyse habitat conditions, identify threats and propose conservation measures to preserve the species. The investigations were conducted in seven unmanaged objects located in three Natura 2000 areas in eastern Poland. The results of this study provide a new insight into Liparis loeselii ecology. The analysed populations inhabited some habitat types: extremely poor fen, transitional mire, rich fen, calcareous fen, spring-fed fen. The content of nutrients was similar in all the habitats. A CCA analysis revealed that the total carbon content, pH, and redox potential of the substrate determine differences between the habitats analysed. Juvenile individuals represented a maximum of 12% of the analysed populations and were the least abundant group of these plants. The flowering was primarily influenced by hydrological conditions. Based on the long-term observations reported in this article, it can be assumed that the species stands a chance of surviving at the localities analysed, provided that the habitat conditions do not change dramatically.

scholarly journals Dark metabolism: a molecular insight into how the Antarctic sea‐ice diatom Fragilariopsis cylindrus survives long‐term darkness

2019 ◽  
Vol 223 (2) ◽  
pp. 675-691 ◽  
Author(s):  
Fraser Kennedy ◽  
Andrew Martin ◽  
John P. Bowman ◽  
Richard Wilson ◽  
Andrew McMinn
Keyword(s):  
Sea Ice ◽  
Antarctic Sea Ice ◽  
Fragilariopsis Cylindrus ◽  
Dark Metabolism ◽  
The Antarctic ◽  
Insight Into
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