643 research outputs found
Effect of L-alanyl-glycine dipeptide on calcium oxalate crystallization in artificial urine
No full textPathological crystallization of calcium oxalate (CaOx), the most common constituent of kidney stones, has attracted much attention due to recent surge in reported natural and synthetic additives effectively inhibiting its nucleation and growth. The aim of this study is to investigate the effect of L-alanyl–glycine (Ala–Gly), a dipeptide commonly found in human urine, on CaOx crystallization and its phase transformation in the presence of an artificial urine media. The nucleated CaOx crystals are characterized by XRD, FTIR, SEM, and dynamic light scattering in terms of changes in their crystalline form, morphology, and size. XRD and FTIR results revealed that Ala–Gly inhibited the formation of the thermodynamically most stable phase of CaOx, calcium oxalate monohydrate (COM) crystals. SEM images revealed that hexagonal plate-shaped COM crystals are transformed into the smaller tetragonal bipyramidal calcium oxalate dihydrate (COD) crystals with increasing additive concentrations. At 125 ppm Ala–Gly concentration more pronounced aggregation of CaOx crystals is observed accompanied with higher negative zeta potential value of −27.1 ± 2.9 mV. Moreover, the phase transformation from COM to COD is also confirmed through thermogravimetric analysis. Consequently, these results suggest that Ala–Gly has a profound effect on preventing the formation of COM crystals and helping to stabilize the COD crystals, a CaOx phase that is reported to have a lower tendency to stick to kidney cells thus decreasing the risk of stone formation. The reported suppression of COM in the presence of Ala–Gly might be significant to clinicians in their attempt to develop a long-term effective treatment for kidney stones.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Complex Fluid Processin
Non-photochemical Laser-Induced Nucleation of KCl from Aqueous solutions in a Droplet-Based Microfluidic System
No full textCrystallization is one of the most widely used purification and separation processes. Nevertheless, the initial step of the crystallization process, nucleation, is still poorly understood and highly stochastic. As a result, most crystallization processes lack fine control over the produced crystal properties. Non photochemical Laser Induced Nucleation is seen as a promising technique to optimize crystallization processes, by decreasing the induction time and potentially offering more control over crystal size, amount and morphology. However, as its underlying mechanism has not yet been unveiled its appli cation is still limited. Further study of the phenomenon is thus essential, yet limited by the stochastic nature of the process. Past research has been laborious and timeconsuming, due to the substantial number of samples needed to attain statistical significance of the results. Microfluidics could offer a solution to this issue, since it allows for the study of copious amounts of independent samples in short time frames, whilst using less resources. In this study, a microfluidic system previously designed and validated within Eral Lab was further improved. Once improved, the system was used to study the effects of common NPLIN parameters such as supersaturation, laser intensity and laser wavelength on the nucleation probability in thousands of independent micro droplets. The experiments were performed using KCl solutions of both 1.05 and 1.10 supersaturation index and irradiated with light of three different wavelengths and four different laser intensities. Control cooling experiments were conducted to serve as a reference and measure the effectiveness of irradiation. Results indicated that, increasing the supersaturation increases the nucleation probability. However, small differences between both supersaturations were observed, potentially indicating a supersatura tion dependent laser intensity threshold. A threshold possibly explained by the Nanoparticle Heating model used to describe Nonphotochemical Laser Induced Nucleation. Laser irradiation of 1.05 su persaturated solutions was seen to be effective with light of all colours at higher laser intensities (≥ 50 MW/cm2). In contrast, for 1.10 supersaturated solutions irradiation was, in most cases, already effective at lower laser intensities (≥ 25 MW/cm2). No significant wavelength effect was observed, besides irradiation with 355 nm light at higher laser intensities (≥ 50 MW/cm2) to be more effective on 1.10 supersaturated solutions. Further analysis of the data was done by investigating the ability of common nucleation models, such as the Classical Nucleation Theory and the Dielectric Polarization model, to describe the behaviour. Results of the Classical Nucleation Theory were highly uncertain due to a limited amount of data points at varying supersaturations. Yet, indicated a heterogeneous influence on the nucleation probability in both the control cooling and laser irradiation experiments. The Dielectric Polarization model was not able to properly describe the nucleation events observed in the experiments, as lability parameters calculated for the experiments were inconsistent with literature and suffered from significant errors.LightX: Light induced seed generation for industrial crystallizationChemical Engineerin
Effect of hyaluronic acid on the struvite crystallization: A structural, morphological, and thermal analysis study
No full textThe struvite crystals constitute one of the common types of urinary stones. Such stones are also referred as “infection stones” due to their tendency to cause infections in urinary tract. A considerable effort has been placed to identify natural or synthetic crystal-growth modifiers for this kind of urinary stone in literature, yet macromolecules commonly found in urine have been underexplored. In the present study, we experimentally focus on how hyaluronic acid, a protein commonly found in urine, alters the struvite crystallization in aqueous solution and in an artificial urine media. By gradually adding ammonium dihydrogen phosphate to a solution containing magnesium chloride hexahydrate, reactive crystallization is carried out in a well-mixed and thermostated vessel at 37 °C. The resulting struvite crystals are characterized structurally by XRD and FTIR as well as morphologically and in terms of their surface charge. In addition, the thermal decomposition behavior of the struvite with and without hyaluronic acid and released volatile products were simultaneously investigated using a TGA/FTIR system. The average activation energy calculated using the Friedman method was 49.2 ± 5.1 kJ/mol. The results of the kinetic and thermodynamic analyses showed that decomposition of the struvite crystals was endothermic and followed the multiple stage reaction mechanism.Complex Fluid Processin
Elucidating the role of hyaluronic acid in the structure and morphology of calcium oxalate crystals
No full textRecent surge in reports describing new additives that inhibiting the growth and nucleation of calcium oxalate (CaOx), the most common component of renal calculi or kidney stones, have rekindled interest in CaOx crystallization. In this in vitro study, the effect of hyaluronic acid (HA), a protein commonly found in urine, on the morphology and phase of the CaOx crystals is investigated. CaOx crystals were crystallized at pH 5.8 and 37 °C with a [Ca2+]:[C2O42-] ratio of 20:1, which is close to physiological conditions, in aqueous solution and artificial urine media. The obtained crystals were characterized structurally, morphologically and in terms of their surface charge. The crystals precipitated in aqueous solution without the HA additive were pure phase calcium oxalate monohydrate (COM) crystals with typical hexagonal morphology. The addition of HA partially promotes the transformation of COM into calcium oxalate dihydrate (COD) in aqueous solution. However, the only solid phase to form in artificial urine media with and without HA was identified as COD with tetragonal bipyramidal morphology. The results of this investigation will contribute to the understanding of the role HA plays on the morphology, structure, and thermal characteristics of CaOx and ultimately facilitate the development of effective treatments for kidney stones.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Complex Fluid Processin
The Mechanisms of Non-Photochemical Laser-Induced Nucleation: Theory and Experiment
No full textNon-photochemical laser-induced nucleation (NPLIN) is a crystallisation method in which a highly structured phase is formed out of solution by exposure to a laser beam. NPLIN offers unprecedented spatiotemporal control and characterisation of nucleation. NPLIN is energy efficient compared to conventional crystallisation methods and can be implemented in continuous microfluidic reactors, enabling sustainable operation. However, its working principles are not yet fully understood. This study contains an evaluation of four proposed mechanisms and a description of an experimental setup involving an ultrahigh speed camera. Two mechanisms describe interaction of molecular polarisation with the electric field, either isotropically known as dielectric polarisation (DP), or anisotropically via the optical Kerr effect (OKE). The other two mechanisms involve cavitation bubble formation by nanoparticle heating through light absorption. This work contains a refined description of this so-called cavity-induced nucleation where its consequences are distinguished into two mechanisms, either based on concentration enhancement (CICEN) or due to pressure enhancement (CIPEN). Novel theoretical calculations in conjunction with experimental data suggest that NPLIN phenomena are based on DP or CICEN, potentially operating in concert. It is conjectured that the influence of DP andCICEN can be quantified further by development of a topological description of DP, simulations of CICEN and relating nucleation probabilities to the metastable zone width of various solutes. The calculations suggest that OKE and CIPEN have little significance because involved energies are several orders of magnitudebelow kBT . The proposed setup allows for observing the NPLIN phenomena and establishing dependence on cavitation bubbles, providing empirical validation. Solutions to experimental problems are provided, including reduction of sample fluid evaporation, aligning the nucleation site with the region of interest of the camera and removing image noise.LightXMolecular Science & Technolog
Colloidal Allostery: Exploring the pathway to innovative separation technologies
No full textColloidal allostery is a regulatory mechanism where specific metabolites regulate the protein activity by binding to them and changing their energy landscape. The first steps to model this system on a colloidal scale were made by studying the depletion interaction between the hydrogel posts and the rigid polystyrene particles. Using soft lithography, hydrogel posts of different rigiditywere synthesized inside the microfluidic channel. Polystyrene particles and depletant (dextran) were added and the interaction between the posts and the particles was studied using optical microscopy and particle tracking.However, major issues such as poor statistics, incomplete cross-linking of the hydrogel posts and irreversible sticking of polystyrene particles to the hydrogel hindered with the experimental results. Therefore, in this project, efforts are made to improve the experimental implementation of the model.At the end of the project, it was observed that while optical tweezers offer a more controlled and refined way of measuring the interactive forces than the particle tracking using video microscopy, the limitations of the equipment in providing the location of the particle normal to the base of the channel hinder the estimation of the desired parameter. Furthermore, despite curing the hydrogel posts for a long period of time under the UV light, the rigid polystyrene particles still stick irreversibly to the post.It is therefore recommended that the optical tweezer apparatus must be upgraded to provide the researcher with the position of particle normal to channel bottom. This can allow better estimation of the effect of the wall on the motion of the particle. The photo-crosslinking characteristics of thehydrogel must be studied to determine the effect of the UV light on the gelation process.The ultimate vision of the project is to develop innovative separation technologies based on the fundamental understanding of the interplay of the depletion forces and elastic energy of deformation.of the hydrogel posts.Chemical Engineerin
Nanoemulsions: formation, properties and applications
No full textNanoemulsions are kinetically stable liquid-in-liquid dispersions with droplet sizes on the order of 100 nm. Their small size leads to useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology. Nanoemulsions are finding application in diverse areas such as drug delivery, food, cosmetics, pharmaceuticals, and material synthesis. Additionally, they serve as model systems to understand nanoscale colloidal dispersions. High and low energy methods are used to prepare nanoemulsions, including high pressure homogenization, ultrasonication, phase inversion temperature and emulsion inversion point, as well as recently developed approaches such as bubble bursting method. In this review article, we summarize the major methods to prepare nanoemulsions, theories to predict droplet size, physical conditions and chemical additives which affect droplet stability, and recent applications.Eni S.p.A
A review on suppression and utilization of the coffee-ring effect
No full textEvaporation of sessile droplets containing non-volatile solutes dispersed in a volatile solvent leaves behind ring-like solid stains. As the volatile species evaporates, pinning of the contact line gives rise to capillary flows that transport non-volatile solutes to the contact line. This phenomenon, called the coffee-ring effect, compromises the overall performance of industrially relevant manufacturing processes involving evaporation such as printing, biochemical analysis, manufacturing of nano-structured materials through colloidal and macromolecular patterning. Various approaches have been developed to suppress this phenomenon, which is otherwise difficult to avoid. The coffee-ring effect has also been leveraged to prepare new materials through convection induced assembly. This review underlines not only the strategies developed to suppress the coffee-ring effect but also sheds light on approaches to arrive at novel processes and materials. Working principles and applicability of these strategies are discussed together with a critical comparison.</p
Elongated particles in fluidized beds: From lab-scale experiments to constitutive models
No full textGas-solid fluidized beds are widely used in various industries due to their favourable mixing, and mass and heat transfer characteristics. Fluid catalytic cracking, polymerization, drying, and granulation are a few examples of their applications. In recent years, there has been increased application of fluidized beds in biomass gasification and clean energy production. Fluidization has been extensively studied, experimentally, theoretically and numerically, in the past. However, most of these studies focused on spherical particles while in practice granules are rarely spherical. Particle shape can have a significant effect on fluidization characteristics. It is therefore important to study the effect of particle shape on fluidization behavior in detail. One of the main reasons we still do not completely understand the fluidization phenomenon is because of complex hydrodynamic interactions and its large separation of scales. Industrial fluidized bed reactors of tens of meters in diameter can have hydrodynamic scales varying from micrometers to meters. Experimental setups of such large size are extremely expensive and therefore not practical. On the other hand, theoretical and empirical correlations are not accurate for scale-up and are rarely available for non-spherical particle shapes. Because of this, we need a different approach. One that takes advantage of experimental measurements and numerical simulations. The tasks are divided into three parts based on scales, each focusing on a particular aspect : DNS (direct numerical simulation), CFD-DEM (computational fluid dynamics - discrete element model) and TFM (two fluid model) or MP-PIC (multi-phase - particle in cell). In this thesis, the focus is on CFD-DEM modelling, a ’bridge’ that connects the DNS and TFM/MP-PIC models.Intensified Reaction and Separation System
Kidney stone in a chip: Understanding calcium oxalate kidney stone formation
No full textKidney stone formation is a global health problem with increasing prevalence. Stone formation is a physiochemical process involving crystallization of inorganic salts in the presence of biological constituents in the urinary system. To inhibit kidney stone formation, a better understanding of the underlying physicochemical mechanism of stone formation in the kidney is required. In this thesis, the solubility, nucleation and growth of calcium oxalate (CaOx), the most common inorganic constituent of kidney stones, were studied under different conditions such as ion concentration, pH value, and also the role of inhibitors in water or artificial urine was investigated. The first step towards this work was obtaining the solubility curve of calcium oxalate monohydrate (COM) in the solvent, such as ultrapure water and different buffers, to elucidate the physicochemical conditions which can cause the kidney stone formation (Chapter 2). Beside the solubility study, advanced technology to observe crystal formation in small scale and a very short time was needed. The volume, structure and flow properties inside the kidney inspired us to use microfluidic technology with comparable volume and flow rate. The developed microfluidic devices that mimic pathways in the human kidney were used to study the nucleation and growth of calcium oxalate crystals. The developed devices rendered an alternate perspective to the study of kidney stone formation and showed that microfluidics can provide precise, simple and fast detection of stone formation under various experimental conditions. Initially, the designed microfluidic device allowed us to build a testing platform for the study of nucleation kinetics of CaOx inside isolated environments provided by droplets. Preliminary experiments were performed by dissolving calcium chloride and sodium oxalate in ultrapure water. The aqueous solution, containing the ions, forms the droplet phase and oil were used as the continuous phase. Altering the pH values, as well as increasing the concentration of additives such as magnesium and osteopontin (OPN), were shown to slow down the nucleation kinetics, or even inhibit nucleation (Chapter 3). Complex Fluid Processin
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