scholarly journals Chemical and geochemical modeling. Thermodynamic models for binary fluoride systems from low to very high concentration (> 35 m) at 298.15 K

2021 ◽  
Vol 8 (2) ◽  
pp. 1-15
Author(s):  
Stanislav Donchev ◽  
Tsvetan V. Tsenov ◽  
Christomir Christov
Keyword(s):  
Activity Coefficients ◽  
Binary Systems ◽  
Geochemical Modeling ◽  
Osmotic Coefficients ◽  
Model Parameters ◽  
Thermodynamic Models ◽  
High Concentration ◽  
Activity Data ◽  
Solubility Products ◽  
Very High

Abstract In this study we developed well validated thermodynamic models for solution behavior and solid-liquid equilibrium for all fluoride binary systems, for which activity data are available. The subject of modeling study are 5 fluoride systems of the type 1-1 (HF-H2O, NaF-H2O, KF-H2O, RbF-H2O, and CsF-H2O) and one of 1-2 type (H2SiF6-H2O) from low to very high concentration at 298.15 K. Models are developed on the basis of Pitzer ion interactions approach. The recommendations on mean activity coefficients (γ±) have been used to construct the model for HF-H2O system. To parameterize models for all other 5 binary systems we used all available raw experimental osmotic coefficients data (φ) for whole concentration range of solutions, and up to saturation point. The predictions of new developed here models are in excellent agreement with experimental osmotic coefficients data, and with recommendations on activity coefficients in binary solutions from low to very high concentration: up to 20 mol. kg−1 in HF-H2O, and up to 35.6 mol.kg−1 in CsF-H2O. The Deliquescence Relative Humidity (DRH (%)) and thermodynamic solubility products (as ln Ko sp) of 4 solid phases [NaF(s), KF.2H2O(s), RbF(s), and CsF(s)] have been determined on the basis of evaluated model parameters and using experimental m(sat) solubility data.

Ground water quality of selected areas of Punjab and Sind Provinces, Pakistan: Chemical and microbiological aspects

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Ionic Concentration ◽  
Chloride Ions ◽  
Potassium Ions ◽  
Ammonium Ions ◽  
High Concentration ◽  
Phosphate Ions ◽  
Sodium Magnesium ◽  
Very High ◽  
Microbiological Aspects

The assessment of groundwater is essential for the estimation of suitability of water for safe use. An attempt has been made to study the groundwater of selected areas of Punjab (Sheikhupura & Sahiwal) and Sindh (Sindh, Jawar Dharki and Dharki), Pakistan. The results indicate that pH, color and odor were all within limits of WHO that is pH ranges 6.5–8.5, colorless and odorless, respectively. The high values of suspended solids were observed in the Sindh-1 and Dharki samples. Microbiologically only Sahiwal and Jawar Dharki were found fit for drinking purpose. Trace metals analysis of Sheikhupura-1 and Sindh-1 showed that values do not fall within limits of WHO for Iron. The ionic concentration analysis showed that high bicarbonate (HCO3-), ions are present in the samples of Sahiwal and Dharki; Sindh-1 and Jawar Dharki samples showed very high concentration for chloride ions, all samples were satisfactory level for sulphate (SO42-), sodium, magnesium and phosphate ions except samples of Sindh-1 and Jawar Dharki. High concentration of calcium and potassium ions was observed in samples of Sindh-1, while all other samples were found fit for drinking purposes in respect of nitrate, nitrite and ammonium ions. The high concentration of Fluoride was found only in Sheikhupura-2 samples.

scholarly journals Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yingfeng Yang ◽  
Hanze Ying ◽  
Zhixia Li ◽  
Jiang Wang ◽  
Yingying Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Molecular Structures ◽  
High Yield ◽  
Kinetic Control ◽  
High Concentration ◽  
Weak Association ◽  
Quantitative Synthesis ◽  
Thermodynamic Stabilization ◽  
Discrete Structures ◽  
Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

Small-volume vitrification and rapid warming yield high survivals of one-cell rat embryos in cryotubes

2021 ◽  
Author(s):  
Yasuyoshi Fukuda ◽  
Misako Higashiya ◽  
Takahiro Obata ◽  
Keita Basaki ◽  
Megumi Yano ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Small Volume ◽  
Sucrose Solution ◽  
High Concentration ◽  
Rat Embryos ◽  
Low Concentrations ◽  
Intracellular Ice Formation ◽  
Intracellular Ice ◽  
Warming Rate ◽  
Very High

Abstract To cryopreserve cells, it is essential to avoid intracellular ice formation during cooling and warming. One way to achieve this is to convert the water inside the cells into a non-crystalline glass. It is currently believed that to accomplish this vitrification, the cells must be suspended in a very high concentration (20–40%) of a glass-inducing solute, and subsequently cooled very rapidly. Herein, we report that this belief is erroneous with respect to the vitrification of one-cell rat embryos. In the present study, one-cell rat embryos were vitrified with 5 μL of EFS10 (a mixture of 10% ethylene glycol, 27% Ficoll, and 0.45 M sucrose) in cryotubes at a moderate cooling rate, and warmed at various rates. Survival was assessed according to the ability of the cells to develop into blastocysts and to develop to term. When embryos were vitrified at a 2,613 °C/min cooling rate and thawed by adding 1 mL of sucrose solution (0.3 M, 50 °C) at a warming rate of 18,467 °C/min, 58.1 ± 3.5% of the EFS10-vitrified embryos developed into blastocysts, and 50.0 ± 4.7% developed to term. These rates were similar to those of non-treated intact embryos. Using a conventional cryotube, we achieved developmental capabilities in one-cell rat embryos by rapid warming that were comparable to those of intact embryos, even using low concentrations (10%) of cell-permeating cryoprotectant and at low cooling rates.

Diffusion In Insect Wing Muscle, The Most Active Tissue Known

1964 ◽  
Vol 41 (2) ◽  
pp. 229-256 ◽  
Author(s):  
TORKEL WEIS-FOGH
Keyword(s):  
Liquid Phase ◽  
Safety Factor ◽  
Metabolic Rates ◽  
High Concentration ◽  
Tracheal System ◽  
Insect Wing ◽  
Main Site ◽  
Normal Diffusion ◽  
Large Fibre ◽  
Very High

1. The tracheal system of insect wing muscle is so dense that between 10-1 and 10-3 of any cut area is occupied by air tubes. In most cases, air tube diffusion of O2 and CO2 through the muscle is therefore several thousand times quicker than diffusion in the liquid phase. 2. In large insects the primary tracheal supply must be strongly ventilated while diffusion is sufficient in the remaining part of the air tubes, even at the highest metabolic rates encountered in any insect. 3. The tracheoles represent the main site of exchange between the gaseous and the liquid phase while the tracheae are of little significance in this respect. The fibres cannot exceed about 20 µ in diameter unless the tracheoles indent the surface and become ‘internal’. 4. Muscular pumping of air and blood due to shortening is of little importance for the exchange of gases but of major importance for the supply with fuel for combustion. However, the large fibre diameters and the tidal nature of the pumping necessitates a very high concentration of fuel in the haemolymph. The high concentration of trehalose in insect blood is considered to be an essential adaptation to flapping flight. 5. The transport by diffusion of O2 and CO2 was followed in detail in a number of concrete examples in the gaseous as well as in the liquid phase. Within a safety factor of 2-3, the rate of transport was always found to be adequate. There is no reason to suggest other mechanisms than a simple, normal diffusion.

Solid-Fluid Phase Equilibria Measurement for Mixtures of Methane, Carbon-Dioxide and N-Hexadecane

2021 ◽  
Author(s):  
Oluwakemi Victoria Eniolorunda ◽  
Antonin Chapoy ◽  
Rod Burgass
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Equation Of State ◽  
Phase Equilibria ◽  
Activity Coefficients ◽  
Fluid Phase ◽  
Ternary Mixtures ◽  
Binary Interaction ◽  
Thermodynamic Models ◽  
Methane Carbon

Abstract In this study, new experimental data using a reliable approach are reported for solid-fluid phase equilibrium of ternary mixtures of Methane-Carbon-dioxide- n-Hexadecane for 30-73 mol% CO2 and pressures up to 24 MPa. The effect of varying CO2 composition on the overall phase transition of the systems were investigated. Three thermodynamic models were used to predict the liquid phase fugacity, this includes the Peng Robison equation of state (PR-EoS), Soave Redlich-Kwong equation of state (SRK-EoS) and the Cubic plus Association (CPA) equation of state with the classical mixing rule and a group contribution approach for calculating binary interaction parameters in all cases. To describe the wax (solid) phase, three activity coefficient models based on the solid solution theory were investigated: the predictive universal quasichemical activity coefficients (UNIQUAC), Universal quasi-chemical Functional Group activity coefficients (UNIFAC) and the predictive Wilson approach. The solid-fluid equilibria experimental data gathered in this experimental work including those from saturated and under-saturated conditions were used to check the reliability of the various phase equilibria thermodynamic models.

Vaporization and Ultra-Fine Particle Generation during the Plasma Spraying Process

1997 ◽  
Author(s):  
K.A. Gross ◽  
P. Fauchais ◽  
M. Vardelle ◽  
J. Tikkanen ◽  
J. Keskinen
Keyword(s):  
Fine Particles ◽  
High Concentration ◽  
Thermal Spray Process ◽  
Particle Generation ◽  
Spray Process ◽  
Ultra Fine Particle ◽  
Fast Cooling ◽  
Ultra Fine Particles ◽  
Plasma Spraying Process ◽  
Very High

Abstract The thermal spray process melts powder at very high temperatures and propels the molten material to the substrate to produce a coherent deposit. This heating produces a certain amount of vaporization of the feedstock. Upon exiting the plasma plume the fast cooling conditions lead to condensation of the vapor. An electrical low pressure impactor was used to monitor the concentration of ultra-fine particles at various radial and axial distances. Metal, namely iron powder, showed very high concentration levels which increase with distance. Ultra-fine particles from ZrO2-8Y2O3 reached a peak concentration at 6 cm. Use of an air barrier during spraying decreases the population of ultra-fine particles facilitating the production of a stronger coating.

scholarly journals Synthesis of [1,2-3H2]cholecalciferol and metabolism of [4-14C,1,2-3H2]- and [4-14C,1-3H]-cholecalciferol in rachitic rats and chicks

1971 ◽  
Vol 121 (4) ◽  
pp. 673-682 ◽  
Author(s):  
D. E. M. Lawson ◽  
B. Pelc ◽  
P. A. Bell ◽  
P. W. Wilson ◽  
E. Kodicek
Keyword(s):  
Vitamin D ◽  
Substance P ◽  
Rat Kidney ◽  
Intracellular Localization ◽  
Specific Radioactivity ◽  
Experimental Period ◽  
Time Interval ◽  
High Concentration ◽  
Very High ◽  
25 Hydroxycholecalciferol

[1,2-3H2]Cholecalciferol has been synthesized with a specific radioactivity of 508mCi/mmol by using tristriphenylphosphinerhodium chloride, the homogeneous hydrogen catalyst. With doses of 125ng (5i.u.) of [4-14C,1-3H2]cholecalciferol the tissue distribution in rachitic rats of cholecalciferol and its metabolites (25-hydroxycholecalciferol and peak P material) was similar to that found in chicken with 500ng doses of the double-labelled vitamin. The only exceptions were rat kidney, with a very high concentration of vitamin D, and rat blood, with a higher proportion of peak P material, containing a substance formed from vitamin D with the loss of hydrogen from C-1. Substance P formed from [4-14C,1,2-3H2]cholecalciferol retained 36% of 3H, the amount expected from its distribution between C-1 and C-2, the 3H at C-1 being lost. 25-Hydroxycholecalciferol does not seem to have any specific intracellular localization within the intestine of rachitic chicks. The 3H-deficient substance P was present in the intestine and bone 1h after a dose of vitamin D and 30min after 25-hydroxycholecalciferol. There was very little 25-hydroxycholecalciferol in intestine at any time-interval, but bone and blood continued to take it up over the 8h experimental period. It is suggested that the intestinal 3H-deficient substance P originates from outside this tissue. The polar metabolite found in blood and which has retained its 3H at C-1 is not a precursor of the intestinal 3H-deficient substance P.

NaCl and CaCl2 activity coefficients in mixed aqueous solutions

1965 ◽  
Vol 20 (6) ◽  
pp. 1332-1336 ◽  
Author(s):  
Edward W. Moore ◽  
James W. Ross
Keyword(s):  
Ionic Strength ◽  
Activity Coefficients ◽  
Technical Assistance ◽  
Osmotic Coefficients ◽  
Electrode System ◽  
Glass Electrode ◽  
Concentration Data ◽  
Harned's Rule ◽  
Potentiometric Measurement

In the investigation of numerous physiological phenomena it is the activity of an ion species which is desired, rather than stoichiometric concentration. The calculation of mean ionic activity from known concentration data requires accurate activity coefficients (ggr). This report concerns the determination of ggrNaCl and ggrCaCl2 in mixed NaCl-CaCl2 solutions by potentiometric measurement with a sodium-selective glass electrode-Ag/AgCl electrode system over the ionic strength range 0.05–0.5 m. Log ggrNaCl varied linearly, at constant total ionic strength, with the ionic strength of CaCl2 in the mixture, in accordance with Harned's rule. From data thus obtained, ggrCaCl2 coefficients in such mixed solutions have been calculated and compared with values calculated from published osmotic data. Resulting activity coefficient curves for ggrCaCl2 are presented over the concentration range encountered in serum and other extracellular fluids. Note: (With the Technical Assistance of Leonard Kaye and Leonard L. Anderson) glass electrodes; ion interaction; electrolyte metabolism; Harned's rule; membrane transport; osmotic coefficients Submitted on March 11, 1965

scholarly journals Production And Use Of A Shelf-Stable Bovine Blood Powder For Food Fortification As A Food-Based Strategy To Combat Iron Deficiency Anaemia In Sub-Saharan Africa

2005 ◽  
Vol 05 (01) ◽  
pp. 01-18
Author(s):  
JK Kikafunda ◽  
◽  
P Sserumaga ◽  
Keyword(s):  
Developing Countries ◽  
Iron Deficiency ◽  
Iron Deficiency Anaemia ◽  
Sub Saharan Africa ◽  
Bovine Blood ◽  
High Concentration ◽  
Deficiency Anaemia ◽  
Sub Saharan ◽  
Shelf Stable ◽  
Very High

Iron deficiency anaemia (IDA) is the most widespread micro-nutrient deficiency disease world-wide, particularly in developing countries. Although there are several strategies to combat IDA, food-based strategies are the most sustainable and yet little research has been carried out in this area. The study aimed at developing a technology for processing and preserving bovine blood into a shelf-stable powder, which would easily be utilised in fortifying commonly consumed food items, as a food-based strategy in the fight against iron deficiency anaemia. A shelf-stable powder was processed from fresh bovine blood and the physical, chemical, microbiological and shelf-life characteristics assessed using conventional methods. The results of the chemical analysis showed that bovine blood powder has a very high concentration of haeme iron at 195.46 mg/100g of powder. This is more than ten times the level of iron in bovine liver, one of the most commonly used food source of haeme iron whose iron content is only 17 mg/100gm of liver. Although microbiological tests carried out on the freshly processed blood powder and on the same powder after one and three months of storage at room temperature found a significant rise in yeast, mould and total plate counts, these values were low and within safe limits. The blood powder was used to fortify a bean sauce. Sensory analysis panellists considered the fortified bean sauce moderately acceptable with a mean score of 4.667 (like slightly) compared to a mean score of 2.333 (like very much) for the non-fortified sauce, on a nine point Hedonic scale. These findings show that processed bovine blood powder has very high levels of haeme iron and thus has great potential as a food-based strategy to combat iron-deficiency anaemia in resource-poor developing countries, particularly those in sub-Saharan Africa. However, more research is needed to improve the microbiological and sensory characteristics of the blood powder.

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