Effect of the Cross-Linking with Calcium Ions on the Structural and Thermo-Mechanical Properties of Alginate Films

2011 ◽  
Vol 1355 ◽  
Author(s):  
Turner K. Vidal Urquiza ◽  
O. Perales Pérez ◽  
M. Gálvez Saldaña
Keyword(s):  
Calcium Ions ◽  
Calcium Alginate ◽  
Immersion Time ◽  
Nitrogen Atmosphere ◽  
Cross Linking ◽  
Molecular Response ◽  
Vibration Modes ◽  
Ca Ions ◽  
Na Ions ◽  
Response To Temperature

ABSTRACTThe present research discusses the thermal and structural properties of calcium alginate films synthesized by cross linking precursor sodium alginate films with Ca2+ ions. Raman and FTIR spectroscopy analyses evinced the interchange of Na ions with Ca ions. Both techniques revealed a shift of the COO- vibration modes; the symmetrical COO- peak of calcium alginate exhibited a shift towards higher wavenumber (∼14 cm−1) from 1415 cm−1 to 1429 cm−1 in the Raman spectra. TGA and TMA analyses performed under a nitrogen atmosphere revealed that increasing the Ca-molarity and immersion time resulted in an increase in the glass transition temperature (Tg) and the strain deformation of the Ca-alginate film. The increase in Tg can be attributed to the Ca-cross-linking that could restrict the molecular response to temperature change whereas the increased strain could be due to the enhanced entrapment of water between the molecular chains of the polymer.

Research on Biological Performance of Partially Oxidized Calcium Alginate Gel

2011 ◽  
Vol 403-408 ◽  
pp. 2985-2988
Author(s):  
Ping Zhang ◽  
Ling Bin Lu ◽  
Hai Feng Yang ◽  
Yang Cao
Keyword(s):  
Mechanical Strength ◽  
Calcium Ions ◽  
Compression Strength ◽  
Calcium Alginate ◽  
Cross Linking ◽  
Swelling Ratio ◽  
Oxidation Degree ◽  
Calcium Alginate Gel ◽  
Biological Performance ◽  
Oxidized Sodium Alginate

The degradable and well-distributed calcium alginates were obtained successfully by ionically cross-linking reaction which was the oxidized Sodium Alginate reflected with calcium ions. Their biological performances were investigated by testing swelling ratio, compression strength and degradation. The effects of oxidation degree and cross-linking density on the properties of calcium alginate were assessed. The results show the swelling ratios of samples were almost no effect whether modified or unmodified, furthermore modified calcium alginate had better degradation performance than unmodified.Lastly, oxidation may reduced the compression strength of samples,but increasing of ionically cross-linking density can enhance the mechanical strength.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Nitrification and Autotrophic Denitrification in Calcium Alginate Beads

1987 ◽  
Vol 19 (1-2) ◽  
pp. 175-182 ◽  
Author(s):  
Z. Lewandowski ◽  
R. Bakke ◽  
W. G. Characklis
Keyword(s):  
Calcium Carbonate ◽  
Calcium Ions ◽  
Continuous Flow ◽  
Calcium Alginate ◽  
Microbial Respiration ◽  
Flow System ◽  
Alginate Beads ◽  
Alginate Gel ◽  
Gel Beads ◽  
Calcium Alginate Gel

Immobilization of nitrifiers and autotrophic denitrifiers (Thiobacillus denitrificans) within calcium alginate gel was demonstrated. Calcium carbonate reagent was immobilized along with bacteria as the stabilizing agent. Protons released as a result of microbial respiration reacted with calcium carbonate producing calcium ions which internally stabilized the calcium alginate gel. The microbially active gel beads were mechanically stable and active for three months in a continuous flow system without addition of calcium.

Movement of Calcium Ions and their Role in the Activation of Platelets

1978 ◽  
Vol 40 (02) ◽  
pp. 212-218 ◽  
Author(s):  
P Massini ◽  
R Käser-Glanzmann ◽  
E F Lüscher
Keyword(s):  
Plasma Membrane ◽  
Platelet Activation ◽  
Calcium Ions ◽  
Binding Sites ◽  
Shape Change ◽  
Release Reaction ◽  
Dense Bodies ◽  
Activated Platelets ◽  
Different Types ◽  
Ca Ions

SummaryThe increase of the cytoplasmic Ca-concentration plays a central role in the initiation of platelet activation. Four kinds of movements of Ca-ions are presumed to occur during this process: a) Ca-ions liberated from membranes induce the rapid shape change, b) Vesicular organelles release Ca-ions into the cytoplasm which initiate the release reaction, c) The storage organelles called dense bodies, secrete their contents including Ca-ions to the outside during the release reaction, d) At the same time a rearrangement of the plasma membrane occurs, resulting in an increase in its permeability for Ca-ions as well as in an increase in the number of Ca-binding sites.Since most processes occurring during platelet activation are reversible, the platelet must be equipped with a mechanism which removes Ca-ions from the cytoplasm. A vesicular fraction obtained from homogenized platelets indeed accumulates Ca actively. This Ca- pump is stimulated by cyclic AMP and protein kinase; it may be involved in the recovery of platelets after activation.It becomes increasingly clear that the various manifestations of platelet activation are triggered by a rise in the cytoplasmic Ca2+-concentration. The evidence for this and possible mechanisms involved are discussed in some detail in the contributions by Detwiler et al. and by Gerrard and White to this symposium. In this article we shall discuss four different types of mobilization of Ca-ions which occur in the course of the activation of platelets. In addition, at least one transport step involved in the removal of Ca2+ must occur during relaxation of activated platelets.

Swelling pressure and microstructure of an activated swelling clay with temperature

Clay Minerals ◽  
1998 ◽  
Vol 33 (2) ◽  
pp. 255-267 ◽  
Author(s):  
D. Tessier ◽  
M. Dardaine ◽  
A. Beaumont ◽  
A. M. Jaunet
Keyword(s):  
Room Temperature ◽  
Swelling Pressure ◽  
Radioactive Waste Disposal ◽  
Basic Medium ◽  
Hydraulic Pressure ◽  
Swelling Behaviour ◽  
Transmission Electron ◽  
Ca Ions ◽  
Na Ions ◽  
Marked Drop

AbstractClay from Fourges has been selected by the Commissariat à l'Energie Atomique as a support in radioactive waste disposal studies. This material was activated by adding Na2CO3, then compacted at 60 MPa. Subsequently, its swelling behaviour was monitored at 90°C and 145°C for 330 days and at the end of this period the samples were examined by transmission electron microscopy (TEM). For this, they were embedded in a resin then sectioned with an ultramicrotome for mineralogical and chemical analyses. The initial material is essentially composed of kaolinite and smectite. Addition of Na2CO3 at room temperature induces a replacement of Ca ions by Na ions and the precipitation of finely divided carbonates on the surface of the constituents. At the end of 330 days at 90°C under a hydraulic pressure of 1 MPa, the initial particles combine and the material exerts a swelling pressure of 20 MPa. A complete reorganisation of the clay crystallites is observed without significant dissolution of the solid phases. After the same time at 145°C under a hydraulic pressure of 10 MPa, in a basic medium, the combined conditions are such that a high proportion of the clay is dissolved with formation of amorphous aluminosilicates correlated with a marked drop in the swelling pressure to 5 MPa. This work establishes the advantages of following the macroscopic properties in parallel with the microstructure variations for understanding the changes in the properties of clays.

scholarly journals Adsorption Capacity of Ca2+ by Hydrochloric Acid Activated Kaolin

2021 ◽  
Vol 926 (1) ◽  
pp. 012082
Author(s):  
N Wahyuni
Keyword(s):  
Hydrochloric Acid ◽  
Adsorption Capacity ◽  
Calcium Ions ◽  
Contact Time ◽  
Maximum Adsorption Capacity ◽  
High Concentration ◽  
Straightforward Method ◽  
Diamine Tetraacetate ◽  
Ca Ions ◽  
Time Variations

Abstract A high concentration of calcium ions in water is a problem as it can cause blockages in engine pipes. Adsorption is a relatively cheap and straightforward method that can be used to reduce the calcium ion content in water. Kaolin is a mineral that has a potential as an adsorbent and whose adsorption capacity can be increased by activation. This research studied the adsorption capacity of activated kaolin by hydrochloric acid against Ca2+ ions. Kaolin was chemically activated using 6 M HCl solution for 24 hours. The adsorption contact time in batches was varied with time variations of 30, 90, 150, and 180 minutes. The maximum adsorption capacity of activated kaolin to the Ca2+ was determined by varying the initial concentrations of water samples, namely 4, 7, 10, and 13 mg/L. The concentration of Ca2+ was determined by a titration method using ethylene diamine tetraacetate (EDTA). The results showed that the activation of kaolin with 6 M HCl at the optimum contact time of adsorption, namely 150 minutes, increased the percentage of adsorbed Ca ions to 2 times of that of natural kaolin, from 33.3% to 68.3%. Based on the Langmuir equation, the maximum adsorption capacity of calcium ions by activated kaolin HCl 6 M increased 1.7 times from natural kaolin to 0.346 mg/g.

Synthesis of spherical porous cross-linked glutaraldehyde/poly(vinyl alcohol) hydrogels

2016 ◽  
Vol 36 (9) ◽  
pp. 891-898
Author(s):  
Sadao Araki ◽  
Yuko Shirakura ◽  
Harufumi Suzuki ◽  
Hideki Yamamoto
Keyword(s):  
Sodium Alginate ◽  
Vinyl Alcohol ◽  
Calcium Alginate ◽  
Chloride Solution ◽  
Calcium Chloride Solution ◽  
Inorganic Salts ◽  
Poly Vinyl Alcohol ◽  
Cross Linking ◽  
Alginate Content ◽  
Calcium Alginate Gels

Abstract Spherical glutaraldehyde cross-linked poly(vinyl alcohol) (PVA) hydrogels (G-PVA) were prepared in three steps: gelatification, cross-linking, and removal of alginate. Gelatification was carried out by dropping a solution of alginate, PVA, and glutaraldehyde into a calcium chloride solution to form calcium alginate. Calcium alginate gels were prepared at 20°C, 40°C, 60°C, and 80°C to study the effect of gelatification temperature on the formation of pores on the surface of G-PVA. The effect of the alginate content was studied. PVA and glutaraldehyde were cross-linked by immersion of the gels in a solution of H2SO4 and Na2SO4. The effect of sodium alginate and inorganic salts, such as MgSO4 and K2SO4, on the formation of pores on the surface of G-PVA was confirmed.

Ca and Na selectivity of the active membrane of rabbit AV nodal cells

1979 ◽  
Vol 236 (1) ◽  
pp. C1-C8 ◽  
Author(s):  
T. Akiyama ◽  
H. A. Fozzard
Keyword(s):  
Outward Current ◽  
Rabbit Heart ◽  
Ionic Channel ◽  
Slow Inward Current ◽  
Constant Field ◽  
Total Removal ◽  
Similar Dependence ◽  
Inward Currents ◽  
Ca Ions ◽  
Na Ions

The atrioventricular (AV) node is thought to have a slow ionic channel. These experiments were designed to measure the relative contributions of Na and Ca ions to inward currents in the AV nodal cells of rabbit heart superfused with Tyrode solution. The effects of tetrodoxin (TTX), Mn2+, and verapamil observed in this study were in agreement with reports by others. The overshoot of AV nodal (N) cells was related to external Ca, with a slope of 12 mV/decade, unchanged by addition of TTX. Similar dependence of overshoot on external Na was seen, with a slope of 20 mV/decade. The slope did not change on addition of TTX. Total removal of either Na or Ca from the solution abolished excitability. Using a constant field equation, we estimated relative permeability (P) of the membrane at the time of maximal overshoot to be PCa/PNa congruent to 60 similar to or approximately 100 and PK/PNa congruent to 1. Relative contributions of these ions to the currents were estimated as ICa congruent to 17%, INa congruent to 33% (inward currents), and IK congruent to 50% (outward current). In conclusion, AV nodal cells have "slow inward-current channels" that are selective for Ca over Na ions.

Sign in / Sign up

Export Citation Format

Share Document