Induction Of Nucleation Research Articles

Cr+6 Controlled Nucleation in SiO2-MgO-Al2O3-K2O-B2O3-F Glass Sealant (SOFC)

This study highlights the strong effect of chromium (Cr6+) as nucleating agent in SiO2-MgO-Al2O3-B2O3-K2O-F glass sealant. Al2O3 of the glass was gradually substituted by K2Cr2O7 content that considerably tuned the crystallization, microstructure, thermal and mechanical properties. The distinctive feature of this study is the induction of nucleation and crystallization in glass matrix on addition of Cr6+ content without performing any heat-treatment. The melt-quenched SiO2-MgO-Al2O3-B2O3-K2O-F glass with zero Cr6+ content is amorphous, which in presence of Cr6+ content became crystalline with MgCr2O4, K3CrF6, MgF2 and mullite (3Al2O3.2SiO2) phases. Glassy features in DSC and dilatometric thermal properties (Tg, Td, thermal expansion) was attained in glass without Cr- content, but glass-ceramic like features obtained for Cr- containing glasses. For those glasses large thermal expansion (>11 ×10-6/K at 50-800°C) was ascribed, that is compatible with solid oxide fuel cell (SOFC) components (electrode, interconnect etc) during operating temperature ~800°C. From FESEM study, dense microstructure morphology sorted with 200-500 nm sized crystallites is obtained in 2 mol% K2Cr2O7 containing glass. In higher Cr- containing glasses, the microstructure becomes more compact with 10-50 µm sized plate like crystals. Higher crystallinity thus ascertained for higher Cr- containing glasses, and this directly corresponds to density and mechanical properties. From nanoindentation test, the hardness and elastic modulus were estimated as 0.6 (±0.5) and 25 (±10) GPa, respectively for base glass and that increased to 3.3-8.4 and 58-94 GPa, respectively for Cr- containing glasses. Microhardness of the base glass is estimated 3.63 (±0.18) GPa which increased to 3.94-6.08 GPa in Cr- containing glasses. The typical microstructure, compatible thermal and mechanical properties make 2 mol% K2Cr2O7 doped SiO2-MgO-Al2O3-B2O3-K2O-F glasses suitable for high temperature sealing application like SOFC.

Induction of crystal nucleation by orientation-controlled binding of His6-tagged proteins to functionalized gold nanoparticles

Functionalized gold nanoparticles can induce crystal nucleation by orientation-controlled NTA–Ni2+– His6-tagged protein binding.

Simple and reliable quartz crystal microbalance technique for determination of solubility by cooling and heating solution.

A quartz crystal microbalance (QCM) is presented as a promising technique for determining the solubility and induction of nucleation via the cooling and reverse heating of a solution. When cooling and heating a solution, the resonant frequency (F) and resonant resistance (R) of the QCM responses change significantly due to vibrational loss related to the viscous and elastic friction that depend on the solution viscosity and solid mass on the sensor, respectively. Thus, obvious refraction points appear in the QCM response profile at the induction point of primary nucleation during cooling crystallization and at the saturated point during heating dissolution. Using an F-R plot of the QCM responses, the phase changes between liquid and solid at the induction and saturated points are confirmed. When compared with focused beam reflectance measurement (FBRM) and gravimetric methods, the QCM method is confirmed to be highly accurate and reliable for determining the solubility, making it a highly promising method for determining solubility and crystal nucleation with minimal effort based on simple temperature cycling, thereby avoiding precalibration and sampling.

046 Society for Cryobiology: Science, application and relevance of cryobiology today

Cryobiology was established necessarily as an interdisciplinary endeavor bringing together the biological and physical sciences to solve problems seemingly impossible to many lay observers. As Peter Mazur has described, difficulties in cryopreservation stem from a “complex concatenation of conflicting variables”. No single discipline is adequately equipped on its own to resolve the problems encountered in the field. As a result, many advances have been made based on fundamental understanding and application of cryobiology. Through manipulating variables such as the type and concentration of cryoprotectant, addition and removal methods, the use of controlled rate cooling combined with induction of ice nucleation and predictions of intracellular ice formation, these advances have culminated in the widespread use of cryobiology to facilitate research, agriculture and medicine. Indeed, application of the basic science of cryobiology readily lends itself to translation. Any cell or tissue of relevance benefits from the flexibility of shelf life that cryobiology can offer. This requires cryobiologists to interact with practitioners in many technical areas. The recently emerging field of regenerative medicine demonstrates such an example. The large scale manufacturing and banking of cells has been the backbone of this evolving discipline. The current technology for laboratory scale manufacturing and cryopreserved storage of cells has been convincingly successful; yet many important technical and medical issues remain. Many cell types of interest to cellular therapy still exhibit exquisite sensitivity to the thermal stresses they experience during the cryopreservation process, and existing approaches for preserving cells are labor-intensive and operator-dependent; consequently, as allogeneic “off-the-shelf” clinical transplantation or transfusion applications continue to be developed, large-scale manufacturing methods with appropriate quality assurance and quality control has become paramount. Despite its promise, however, the development of efficient and commercially viable processes for industrial scale cell manufacturing and banking is still in its infancy. And while manufacturing or processing of patient-specific cells may not have the same scale-up requirements that large allogeneic production requires, the same quality issues with respect to traceability, documentation, and the ultimate functional viability are just as imperative. The traditional understanding of cryopreservation damage is often focused on immediate post-thaw structural preservation, whereas cryopreservation-induced stress may increase over time, often resulting in the delayed onset of cell death. Since apoptotic cell death takes at least 24 h post-thaw to manifest the “true” or “functional” viability, the development of methods to evaluate this, and subsequently mitigate it are also needed. This is of particular importance where the cells may not succumb until hours or days post-transplant, resulting in seemingly acceptable post thaw results but yielding poor clinical efficacy. Other technical considerations involve the sample container, which must be scalable and should be at least a functionally closed system to meet safety and regulatory requirements. New strategies involving injectable cryoprotectants are also highly desirable for successful application of therapeutic cells. For cell based regenerative medicine to reach its potential in mainstream clinical applications, solutions based in sound scientific understanding of the biology and physical systems will need to continue through translation to ultimately solve these technical issues. Source of funding: None declared. Conflict of interest: None declared. Erik.Woods@CookGBT.com

Crystallization by Controlled Evaporation Leading to High Resolution Crystals of the C1 Domain of Cardiac Myosin Binding Protein-C (cMyBP-C)

This paper describes an optimization method for obtaining high quality crystals that has led to the successful structure determination of the C1 domain of cardiac myosin binding protein C. This method involved the controlled evaporation of hanging drops by induction of nucleation and its subsequent arrest. The crystals diffracted to a resolution of 1.5 A in contrast to a maximum resolution of 3 A when applying existing standard techniques. The method provides an efficient tool with immediate practical relevance to structural biologists.

Enamel Formation-Biochemical Aspect-

This review shows the biochemical aspect of enamel formation focused on porcine amelogenesis.Volumetric changes in the chemical components of secretory stage enamel intimate that enamel crystals thicken as amelogenin, the major protein component, decreases. Solubility behaviors and hydrophobicity analyses of amelogenin derivatives suggest the hypothesis that cylindrical amelogenin forms micelles. This model explains how amelogenin constructs a large structure, which forms a matrix, and continuously yields space as the crystals thicken. In porcine secretory enamel, mineral volume increases with depth, gaining space for thickening the existing crystallites by shrinking amelogenin micelles through the removal of C-terminal and 13-kDa peptides from the prototype 25-kDa amelogenin, the most abundant porcine amelogenin gene product, by the action of enamelysin (MMP-20) and enamel matrix serine proteinase (EMSP1), respectively.During the secretory stage, the crystallites thicken in the deeper secretory enamel, although calcium ions are supplied by ameloblasts. Another morphological feature of the crystallites is that they are all nearly the same size within the same developmental stage. There are several enamel proteins and their cleavage products have calcium binding activity and binding affinity for crystallites. The 25-kDa amelogenin and 89-kDa enamelin, both neutral insoluble, are involved in slow crystallite growth by trapping calcium ions secreted by ameloblasts, and may control by inhibiting newly nucleated crystals between existing crystallites. The calcium binding proteins derived from the C-terminal side of sheathlin (ameloblastin/amelin) and 32-kDa enamelin, belonging to the neutral soluble fraction, act as a calcium carrier to transport calcium ions to deeper secretory stage enamel. Sheath protein derived from the N-terminal side of sheathlin is the main protein constituent of the enamel sheath.Enamelin may be involved in initial crystal formation as it is immuno-histochemically shown to be localized on or around the initial nucleated crystals in a presecretory stage matrix. This is confirmed by no crystal formation in the enamel of enamelin knock-out mice. This conflicts with the inhibition of new nucleation between the existing crystallites in advanced secretory stage enamel. Enamelin may have multi-functions which are involved in the induction of nucleation in a particular phase of the molecule and inhibition in other phases, or change its function with the products produced during each degradation step.

Biomimetic Apatite/Polycaprolactone (PCL) Nanofibres for Bone Tissue Engineering Scaffolds

Chemical treatment of polycaprolactone was carried out to bioactivite the biodegradable polymer for bone tissue engineering application. The results show that surface modifications are necessary to introduce functional groups such as carboxylic groups for the effective induction of apatite nucleation, prior to SBF treatment. The functional groups, acting as anchors between the polymer and the apatite nuclei, dictate the duration of the induction period need for apatite nucleation. After the surface treatment with sodium hydroxide solution, the apatite nuclei will form and grow spontaneously into a dense and uniform layer of apatite, by taking up Ca2+ and PO4 2- ions that are present in the SBF, as SBF is supersaturated with respect to apatite. Similar surface treatment was applied to electrospun PCL nanofibres. Biomimetic apatite/PCL nanofibres were formed which can potentially be used as bone tissue engineering scaffolds.

Sonocrystallization: The Use of Ultrasound for Improved Industrial Crystallization

An overview of the application of power ultrasound to crystallization of organic molecules, and the equipment developed in recent years in which sonocrystallization and sonochemistry may be carried out at industrial scale, is presented. It includes both results from the research and development programs carried out by us and a survey of developments in the field more generally. The most important effect of ultrasound on crystallization is the induction of nucleation and the principal benefits derived from an ability to manipulate this effect. The reported effects of ultrasound on crystal nucleation and growth have been briefly reviewed, and examples are given of physical properties of the products having been manipulated by varying and controlling the insonation regime. New applications, directions, and developments have been identified. Developments in scale-up methods and available equipment have also been reviewed. It is the availability of robust large-scale equipment that has been critical to establi...

Novel Poly(butylene succinate)‐Based Ionomers with Sulfonated Succinate Units: Synthesis, Morphology, and the Unique Nucleation Effect on Crystallization

AbstractSummary: Poly(butylene succinate) (PBS) and PBS‐based ionomers (PBSi's) with 0.3 and 1.2 mol‐% of sodium sulfonated succinate unit were synthesized. The existence of ionic aggregates in the ionomer matrices was indicated by melt viscosity and glass transition data. It seems that the ionic aggregates have two opposing roles in crystallization: one is the induction of nucleation and the other is the interference with lamellar growth. Because of these two contrary effects, the crystallization behavior of the ionomers exhibited measurably different cooling rate‐dependencies than that of the parent PBS. The rate varied distinctly with ionic content.Spherulitic morphologies of PBS and PBSi's measured with polarizing optical microscopy.magnified imageSpherulitic morphologies of PBS and PBSi's measured with polarizing optical microscopy.