Single Idealized Cracks: A Tool for Understanding Fractured Glass Block Leaching

2008 ◽  
Vol 1107 ◽  
Author(s):  
Laure Chomat ◽  
Frédéric Bouyer ◽  
Stéphane Gin ◽  
Stéphane Roux
Keyword(s):  
Molecular Diffusion ◽  
Convective Transport ◽  
Glass Block ◽  
Transport Mechanisms ◽  
Realistic Condition ◽  
Glass Model ◽  
Gravity Driven ◽  
Original Device ◽  
Glass Leaching

AbstractWithin the scope of the long term behaviour of the R7T7 glass, which is the French nuclear glass, leaching and its coupling with transport mechanisms is studied. Experiments carried out on a SON 68 glass (inactive R7T7 type glass) model cracks in static basic conditions show a strong coupling between solution transport and glass leaching, depending on crack aperture. Moreover, gravity driven convective transport was evidenced for vertical model cracks, whereas only molecular diffusion was detected for horizontal model cracks under the same alteration conditions. In addition, an original device was developed to study the influence of temperature gradients on alteration kinetics as a convective driving force. These experiments show conclusively that thermally- or gravity-induced convective flow must be taken into account, even if such convective effects have not been established experimentally in neutral condition, which is more realistic condition for geological storage. A modeling, based on a porous geochemical software (HYTEC) accounting for both chemistry and transport, has been successfully applied to describe alteration within simple silicate glass cracks. It will be extended to study SON 68 glass model cracks, and more complex fracture networks.

The Spread of Pollutants from Harbour Sludge Depots

1984 ◽  
Vol 16 (3-4) ◽  
pp. 623-633
Author(s):  
M Loxham ◽  
F Weststrate
Keyword(s):  
Time Scales ◽  
Molecular Diffusion ◽  
Near Field ◽  
Parameter Analysis ◽  
Migration Patterns ◽  
Long Time ◽  
Dilution Effects ◽  
Short Time ◽  
Harbour Sludge

It is generally agreed that both the landfill option, or the civil techniques option for the final disposal of contaminated harbour sludge involves the isolation of the sludge from the environment. For short time scales, engineered barriers such as a bentonite screen, plastic sheets, pumping strategies etc. can be used. However for long time scales the effectiveness of such measures cannot be counted upon. It is thus necessary to be able to predict the long term environmenttal spread of contaminants from a mature landfill. A model is presented that considers diffusion and adsorption in the landfill site and convection and adsorption in the underlaying aquifer. From a parameter analysis starting form practical values it is shown that the adsorption behaviour and the molecular diffusion coefficient of the sludge, are the key parameters involved in the near field. The dilution effects of the far field migration patterns are also illustrated.

An Insight into the Polymeric Nanoparticles Applications in Diabetes Diagnosis and Treatment

2021 ◽  
Vol 21 ◽  
Author(s):  
Parisa Dehghani ◽  
Monireh Esameili Rad ◽  
Atefeh Zarepour ◽  
Ponnurengam Malliappan Sivakumar ◽  
Ali Zarrabi
Keyword(s):  
Polymeric Nanoparticles ◽  
Synthetic Polymers ◽  
Diagnostic Methods ◽  
Diagnosis And Treatment ◽  
Diabetes Diagnosis ◽  
Transport Mechanisms ◽  
Different Types ◽  
Treatment And Diagnosis ◽  
Insight Into

: Diabetes mellitus (DM) is a type of chronic metabolic disease that has affected millions of people worldwide and is known with a defect in the amount of insulin secretion, insulin functions, or both. This deficiency leads to an increase in the amounts of glucose, which could be accompanied by long-term damages to other organs such as eyes, kidneys, heart, and nervous system. Thus, introducing an appropriate approach for diagnosis and treatment of different types of DM is the aim of several researches. By the emergence of nanotechnology and its application in medicine, new approaches were presented for these purposes. The object of this review article is to introduce different types of polymeric nanoparticles (PNPs), as one of the most important classes of nanoparticles, for diabetic management. To achieve this goal, at first, some of the conventional therapeutic and diagnostic methods of DM will be reviewed. Then, different types of PNPs, in two forms of natural and synthetic polymers with different properties, as a new method for DM treatment and diagnosis will be introduced. In the next section, the transport mechanisms of these types of nano-carriers across the epithelium, via paracellular and transcellular pathways will be explained. Finally, the clinical use of PNPs in the treatment and diagnosis of DM will be summarized. Based on the results of this literature review, PNPs could be considered one of the most promising methods for DM management.

scholarly journals Candida albicans exhibits distinct cytoprotective responses to anti-fungal drugs that facilitate the evolution of drug resistance

2020 ◽  
Author(s):  
V Bettauer ◽  
S Massahi ◽  
S Khurdia ◽  
ACBP Costa ◽  
RP Omran ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Drug Exposure ◽  
Fluorescent Imaging ◽  
Late Time ◽  
Transport Mechanisms ◽  
Short Term ◽  
Anti Fungal ◽  
Initial Drug

AbstractWe developed a modified protocol for nanolitre droplet-based single cell sequencing appropriate for fungal settings, and used it to transcriptionally profiled several thousands cells from a prototrophic Candida albicans population and several drug exposed colonies (incl. fluconazole, caspofungin and nystatin). Thousands of cells from each colony were profiled both at early and late time points post-treatment in order to infer survival trajectories from initial drug tolerance to drug resistance. We find that prototrophic C. albicans populations differentially and stochastically express cytoprotective epigenetic programs. For all drugs, there is evidence that tolerant individuals partition into distinct subpopulations, each with a unique survival strategy involving different regulatory programs. These responses are weakly related to changes in morphology (shift from white to opaque forms, or shift from yeast to filamentous forms). In turn, those subpopulations that successfully reach resistance each have a distinct multivariate epigenetic response that coordinates the expression of efflux pumps, chaperones, transport mechanisms, and cell wall maintenance. Live cell fluorescent imaging was used to validate predictions of which molecular responses most often led to survival after drug exposure. Together our findings provide evidence that C. albicans has a robust toolkit of short-term epigenetic cytoprotective responses designed to “buy time” and increase the chance of acquiring long-term resistance.

scholarly journals Change in turbopause altitude at 52 and 70° N

2016 ◽  
Vol 16 (4) ◽  
pp. 2299-2308 ◽  
Author(s):  
Chris M. Hall ◽  
Silje E. Holmen ◽  
Chris E. Meek ◽  
Alan H. Manson ◽  
Satonori Nozawa
Keyword(s):  
Time Series ◽  
Atomic Oxygen ◽  
Molecular Diffusion ◽  
Temporal Evolution ◽  
Molecular Mixing ◽  
Trace Species ◽  
Term Change ◽  
Meteor Trail ◽  
Altitude Estimation

Abstract. The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general region of transition between turbulent and molecular mixing coincides with the base of the ionosphere, the lower region in which molecular oxygen is dissociated, and, at high latitude in summer, the coldest part of the whole atmosphere. This study updates previous reports of turbopause altitude, extending the time series by half a decade, and thus shedding new light on the nature of change over solar-cycle timescales. Assuming there is no trend in temperature, at 70° N there is evidence for a summer trend of  ∼  1.6 km decade−1, but for winter and at 52° N there is no significant evidence for change at all. If the temperature at 90 km is estimated using meteor trail data, it is possible to estimate a cooling rate, which, if applied to the turbopause altitude estimation, fails to alter the trend significantly irrespective of season. The observed increase in turbopause height supports a hypothesis of corresponding negative trends in atomic oxygen density, [O]. This supports independent studies of atomic oxygen density, [O], using mid-latitude time series dating from 1975, which show negative trends since 2002.

Numerical Investigation of Multi-Scale Mixing in Microchannel T-Junction With Wavy Structure

2012 ◽  
Author(s):  
Nita Solehati ◽  
Joonsoo Bae ◽  
Agus Pulung Sasmito
Keyword(s):  
Schmidt Number ◽  
Molecular Diffusion ◽  
Chaotic Mixing ◽  
Small Scale ◽  
Transport Mechanisms ◽  
Huge Amount ◽  
Multi Scale ◽  
Wavy Structure ◽  
Mixing Quality

Mixing in chemical microreactors is a multi-scale processes as the transport mechanisms occur at different length scales. The small scale mixing depends mainly on molecular diffusion which causes conventional microchannel T-junction has poor mixing quality. To improve the quality, one can utilize secondary flow generated by wavy structure to enhance chaotic mixing. To gain better understanding of the interplay of transport mechanism, we develop numerical model for mixing in micro-channel T-junction with wavy structure. To ensure robust and accurate solutions, several discretization methods and mesh sizes were tested and compared. It is found that the solutions are sensitive to the Reynolds; huge amount of mesh (>107) is required to resolve small molecular diffusion and chaotic mixing especially at high Schmidt number, whilst relatively lesser mesh is found to be sufficient for conventional T-junction. Further, parallelization is found to be beneficial to expedite the computation, albeit the speed is not linear with the number of the processors. The mixing quality of T-junction with wavy structure is then compared with that of conventional T-junction counterpart. It is noted that up to 50% improvement of mixing quality is achieved with wavy structure which has potential for several applications.

Permeability of Cortical Bone to Large Molecular Weight Proteins Under Diffusive and Load-Induced Convective Transport Mechanisms

2004 ◽  
Author(s):  
R. B. Patel ◽  
A. E. Tami ◽  
M. L. Knothe Tate
Keyword(s):  
Molecular Weight ◽  
Fluid Flow ◽  
Cortical Bone ◽  
Molecular Size ◽  
Convective Transport ◽  
Transport Mechanisms ◽  
Quantitative Evidence ◽  
Macromolecular Transport ◽  
Large Molecular Weight ◽  
Poroelasticity Theory

The composition of bone is 75% mineral and organic components and 25% fluid; yet until the past 30 years, the fluid component of bone had been ignored [1]. The idea of load induced fluid flow via pressure gradients was hypothesized for the first time by Piekarski et al in his application of Biot’s poroelasticity theory [2]. Poroelasticity theory mathematically describes the sponge-like behavior of bone: when bone is squeezed(loaded) fluid will be induced to flow. However although the concept of load induced fluid flow is well accepted in the orhopedic field, our study is the first to provide quantitative evidence of the effect of load induced fluid on macromolecular transport. Hence the goals of this study include observing permeability of large molecular weight tracers in cortical bone, ii.) comparing molecular size dependence on tracer permeability in cortical bone, and iii.) comparing effects of convective and diffusive transport mechanisms on permeability.

Transient analysis of macromolecular transport across microvascular wall and into interstitium

1993 ◽  
Vol 265 (3) ◽  
pp. H993-H999 ◽  
Author(s):  
D. Kim ◽  
P. M. Armenante ◽  
W. N. Duran
Keyword(s):  
Molecular Diffusion ◽  
Fluid Velocity ◽  
Calcium Ionophore ◽  
Convective Transport ◽  
Cheek Pouch ◽  
Solute Flux ◽  
Ionophore A23187 ◽  
Transport Parameters ◽  
Macromolecular Transport ◽  
Dextran 70

We studied the dynamics of macromolecular transport across the microvascular wall in the hamster cheek pouch using intravital microscopy and digital video-image analysis. We used fluorescein isothiocyanate-dextrans of 70,000 and 150,000 Da (FITC-Dextran 70 and 150, respectively) as tracers. We applied our mathematical model and our in vivo calibration to determine the diffusion coefficient (D) and the average fluid velocity (V) in the microvascular wall and in the interstitium from the experimental data. The value of D for FITC-Dextran 70 was 0.90 +/- 0.04 x 10(-11) cm2/s in the wall and 1.29 +/- 0.05 x 10(-8) cm2/s in the interstitium. In both regions, V was 2.05 +/- 0.05 x 10(-8) cm/s. The transport parameters for FITC-Dextran 150 were 0.27 +/- 0.02 x 10(-11) cm2/s, 0.55 +/- 0.05 x 10(-8) cm2/s, and 1.71 +/- 0.48 x 10(-8) cm/s for D in the wall and interstitium and V, respectively. The topical application of either calcium ionophore A23187 (7 x 10(-7) M) or bradykinin (5 x 10(-7) M) increased D for FITC-Dextran 70 and 150 2-fold and V 10-fold relative to their control values. We used these values to quantify the relative importance of the diffusive and convective mechanisms in the total solute flux. Molecular diffusion dominates convective transport in both the microvascular wall and the interstitial space.

Effects of Rocks and Backfill Materials on Waste Glass Leaching

1985 ◽  
Vol 50 ◽  
Author(s):  
K. Ishiguro ◽  
N. Sasaki ◽  
H. Kashihara ◽  
M. Yamamoto
Keyword(s):  
Waste Glass ◽  
Distilled Water ◽  
Leach Rate ◽  
Glass Dissolution ◽  
Crushed Granite ◽  
Backfill Materials ◽  
Long Term Experiment ◽  
Static Conditions ◽  
Glass Leaching

AbstractExtensive studies have been made on the interactions between a waste glass and repository materials under static conditions. One of the PNC reference glasses was leached in the solution prepared from water in contact with crushed granite, tuff, diabase and backfill materials such as bentonite and zeolite. The leachant solutions except for some bentonite solutions reduced the glass leach rate compared with that measured in distilled water. The extent of the reduction was a function of silicon concentration in solution. The bentonite solutions enhanced the glass dissolution rate by a factor of 2 to 3 at low bentonite/water ratios but the effect was found to be less important at high bentonite/water ratios and in the long-term experiment. Addition of granite and zeolite to the bentonite solutions decreased the leach rate below the value measured in distilled water.

Long-Term Radioactivity Release from Solidified High-Level Waste - Part II Parametric Study of Waste form Properties, Temperature and Time

1982 ◽  
Vol 15 ◽  
Author(s):  
Friedrich K. Altenhein ◽  
Werner Lutze ◽  
Rodney C. Ewing
Keyword(s):  
Parametric Study ◽  
Computer Code ◽  
Salt Dome ◽  
Waste Form ◽  
Glass Block ◽  
High Level Waste ◽  
Surface Layers ◽  
History Of ◽  
High Level

The computer code QTERM has been used to calculate the total released activity from a single glass block when in contact with brine in a salt dome repository as a function of: (1) waste form properties, (2) leaching mechanisms, (3) retention or precipitation of specific radionuclides in surface layers, (4) thermal history of the repository and (5) decreasing activity as a function of time.

scholarly journals Method for predicting the dissemination of hazardous substances in the soil during long-term storage of galvanic waste

2022 ◽  
pp. 12-22
Author(s):  
Larisa Tretiakova ◽  
Liudmyla Mitiuk ◽  
Igor Panasiuk ◽  
Elina Rebuel
Keyword(s):  
Heavy Metals ◽  
Mathematical Model ◽  
Soil Salinity ◽  
Molecular Diffusion ◽  
Hazardous Substances ◽  
Depth Of Penetration ◽  
Long Term Storage ◽  
Harmful Substances ◽  
Term Storage

The problem of production waste storage in open areas of an enterprise with a galvanic shop for the production of chips and microchips has been investigated. The composition of the sludge obtained after sewage treatment of the production of the copper line was investigated. The aim of the article is to develop a mathematical model for predicting the distribution of compounds with heavy metals in the soil during long-term storage of galvanic sludge in open areas. Modeling the process of movement of salts from the earth's surface into the lower layers of the aeration zone occurs according to the laws of molecular diffusion. The method is developed on the basis of a mathematical model that makes it possible to estimate the spread over the depth of the ground and level of soil salinity over time using initial information about soil structure and its characteristics (molecular diffusion coefficient, volume humidity), annual volumes and conditions of sludge storage in the enterprise. Restrictions are set: the presence of harmful substances on the soil surface with a concentration that exceeds the permissible level; inadmissibility of harmful substances to aquifers. The practical use of the method made it possible to identify the main dangers during long-term storage of galvanic waste in open areas. The dynamics of soil salinity levels and the depth of penetration of heavy metals increase over twenty years of conservation has been determined, as well as the possibility of hazardous compounds entering groundwater has been assessed. Polyvinyl chloride packaging has a maximum life span of 15 years. Waste should not be stored in packages and in closed areas for more than 10 years. According to the prediction results, it can be stated that storage in landfills of galvanic waste for more than 15 years leads to significant salinization of the soil and creates conditions for an emergency situation, which is caused by harmful substances entering the water horizons. Recommendations for improving storage conditions are given and the need for recycling of industrial waste is substantiated

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