Influence of Particle Morphology and Flow Conditions on the Dispersion Behavior of Fumed Silica in Silicone Polymers

The dispersion behavior of agglomerates of several grades of fumed silica in poly(dimethyl siloxane) liquids has been studied as a function of particle morphology and applied flow conditions. The effects of primary particle size and aggregate density and structure on cohesivity were probed through tensile and shear strength tests on particle compacts. These cohesivity tests indicated that the shear strength of particle compacts was two orders of magnitude higher than the tensile strength at the same overall packing density. Experiments carried out in both steady and time‐varying simple‐shear flows indicate that dispersion occurs through tensile failure. In the steady‐shear experiments,enhanced dispersion was obtained at higher levels of applied stress and, at comparable levels of applied stress, dispersion was found to proceed faster at higher shear rates. Experiments conducted in time‐varying flows further corroborated the results obtained in tensile cohesivity tests. Experiments in which the mean and maximum stresses in the time‐varying flows were matched to the stresses produced in steady shear flows highlight the influence of flow dynamics on dispersion behavior.     

Developments and applications of separation and microfluidics methods coupled to electrospray mass spectrometry in glycomics of nervous system gangliosides

Gangliosides are particularly abundant in the nervous system (NS) where their pattern and structure in a certain milieu or a defined region exhibit a pronounced specificity. Since gangliosides are useful biomarkers for diagnosis of NS ailments, a clear-cut mapping of individual components represents a prerequisite for designing ganglioside-based diagnostic procedures, treatments, or vaccines. These bioclinical aspects and the high diversity of ganglioside species claim for development of specific analytical strategies. This review summarizes the state-of-the-art in the implementation of separation techniques and microfluidics coupled to MS, which have contributed significantly to the advancement of the field. In the first part, the review discusses relevant approaches based on HPLC MS and CE coupled to ESI MS and their applications in the characterization of gangliosides expressed in healthy and diseased NS. A considerable section is dedicated to microfluidics MS and ion mobility separation MS, developed for the study of brain gangliosidome and its changes triggered by various factors, as well as for ganglioside biomarker discovery in neurodegenerative diseases and brain cancer. In the last part of the review, the benefits and perspectives in ganglioside research of these high-performance techniques are presented.     

Analysis of mixing efficiency in polymer processing equipment

Flow patterns In various processing equipment were obtained based on 3D isothermal flow simulations. These flow patterns were further processed for mixing efficiency analysis. The dynamics of the mixing process was studied numerically by means of tracers and their trajectories In the processing equipment. Dispersive mixing efficiency was studied in terms of shear stresses and elongational flow components distributions. Distributive mixing efficiency was characterized using length stretch distributions and average values. Features of chaotic flow were also analyzed. The framework developed to analyze mixing efficiency opens the way for an unambiguous evaluation of equipment performance and for process optimization.     

Danckwerts Revisited – The Use of Entropy to Define Scale and Intensity of Segregation

Rényi statistical entropy as a means to quantify mixing in two‐dimensional binary systems is presented. The use of Rényi entropies in defining the scale and intensity of segregation for mixing quality determination is analyzed. Finally, the relationship between the mixing process and the structures generated in the system is explored by using the Rényi entropy as an easy and computationally efficient method to calculate the system spectrum of fractal dimensions.

     

Quantifying Fluid Mixing with the Shannon Entropy

Summary: We introduce a methodology to quantify the quality of mixing in various systems, including polymeric ones, by adapting the Shannon information entropy. For illustrative purposes we use particle advection of two species in a two‐dimensional cavity flow. We compute the entropy by using the probability of finding a suitable chosen group/complex of particles of a given species, at a given location. By choosing the size of the group to be in direct proportion to the overall concentration of the components in the mixture we ensure that the entropic measure is maximized for the case of perfect mixing, that is, when at each location the component concentration is equal to the corresponding overall component concentrations. The scale of observation role in evaluating mixing is analyzed using the entropic methodology. We also illustrate the effect of initial conditions on mixing in a laminar system, typical in operations involving polymers.

     

High-Resolution Tandem Mass Spectrometry Identifies a Particular Ganglioside Pattern in Early Diabetic Kidney Disease of Type 2 Diabetes Mellitus Patients

Considering the valuable information provided by glycosphingolipids as molecular markers and the limited data available for their detection and characterization in patients suffering from Type 2 diabetic kidney disease (DKD), we developed and implemented a superior method based on high-resolution (HR) mass spectrometry (MS) and tandem MS (MS/MS) for the determination of gangliosides in the urine of DKD patients. This study was focused on: (i) testing of the HR MS and MS/MS feasibility and performances in mapping and sequencing of renal gangliosides in Type 2 DM patients; (ii) determination of the changes in the urine gangliosidome of DKD patients in different stages of the disease—normo-, micro-, and macroalbuminuria—in a comparative assay with healthy controls. Due to the high resolution and mass accuracy, the comparative MS screening revealed that the sialylation status of the ganglioside components; their modification by O-acetyl, CH₃COO⁻, O-fucosyl, and O-GalNAc; as well as the composition of the ceramide represent possible markers for early DKD detection, the assessment of disease progression, and follow-up treatment. Moreover, structural investigation by MS/MS demonstrated that GQ1d(d18:1/18:0), GT1α(d18:1/18:0) and GT1b(d18:1/18:0) isomers are associated with macroalbuminuria, meriting further investigation in relation to their role in DKD.     

Glycomics by ion mobility tandem mass spectrometry of chondroitin sulfate disaccharide domain in biglycan

Biglycan (BGN), a small leucine-rich repeat proteoglycan, is involved in a variety of pathological processes including malignant transformation, for which the upregulation of BGN was found related to cancer cell invasiveness. Because the functions of BGN are mediated by its chondroitin/dermatan sulfate (CS/DS) chains through the sulfates, the determination of CS/DS structure and sulfation pattern is of major importance. In this study, we have implemented an advanced glycomics method based on ion mobility separation (IMS) mass spectrometry (MS) and tandem MS (MS/MS) to characterize the CS disaccharide domains in BGN. The high separation efficiency and sensitivity of this technique allowed the discrimination of five distinct CS disaccharide motifs, of which four irregulated in their sulfation pattern. For the first time, trisulfated unsaturated and bisulfated saturated disaccharides were found in BGN, the latter species documenting the non-reducing end of the chains. The structural investigation by IMS MS/MS disclosed that in one or both of the CS/DS chains, the non-reducing end is 3-O-sulfated GlcA in a rather rare bisulfated motif having the structure 3-O-sulfated GlcA-4-O-sulfated GalNAc. Considering the role played by BGN in cancer cell spreading, the influence on this process of the newly identified sequences will be investigated in the future.     

Characterization of Sub‐Micron Perovskite Suspensions Formed Through Cavitation Processing

The size distribution within and electrokinetic properties of aqueous perovskite (LaCoO₃) suspensions, have been characterized as a function of processing conditions. Submicron–sized perovskite particles have been obtained using a cavitation technique in which the suspension is passed through a series of small orifices under extreme driving pressure drops. When no additives were used, the zeta potential of the particles was found to be positive over the entire pH range studied. Use of an acrylic copolymer surfactant with multiple negatively charged sites during the cavitation processing was found to improve dispersion stability. The observed variations in zeta potential and particle size for the suspensions are explained in terms of electrostatic interactions between particles, the tendency for the surfactant to adsorb onto the particles, and the degree of steric stabilization provided by the surfactant.     

Gangliosidome of a Human Hippocampus in Temporal Lobe Epilepsy Resolved by High-Resolution Tandem Mass Spectrometry

In this study, we developed a high-resolution tandem mass spectrometry (HR MS) approach to assess presumed changes in gangliosidome of a human hippocampus affected by temporal lobe epilepsy (TLE) in comparison with a normal hippocampus. Gangliosides, membrane glycolipids, are particularly diverse and abundant in the human brain, and participate in ion transport and modulation of neuronal excitability. Changes in structural ganglioside pattern potentially linked to TLE molecular pathogenesis have not been explored in detail. Aiming to characterize TLE-specific gangliosidome, we analyzed the native gangliosides purified from a human hippocampal tissue sample affected by TLE and a control hippocampus using HR MS. Marked differences of ganglioside expression were shown in TLE vs. control, particularly with respect to the sialylation degree of components, discovered as a characteristic feature of TLE. Another major finding is the occurrence of tetrasialofucogangliosides in TLE and species modified by either O-acetylation or CH₃COO⁻. Structural analysis by higher-energy collisional dissociation (HCD) MS/MS gave rise to fragmentation patterns implying that the GQ1b (d18:1/18:0) isomer is specifically associated with TLE. Further investigation in a larger sample is needed in order to confirm the discovery of ganglioside structures specifically expressed in human TLE and to provide information on the probable role of gangliosides in the molecular events underlying seizures.     

Revisiting thermoplastic polyurethane,from composition to morphology and properties

Thermoplastic polyurethanes (TPUs) are among the most versatile engineering polymers. The presence of hard and soft segments on their backbone and specific hydrogen bond interactions between the hard segments, provide TPUs with outstanding engineering properties while rendering them as very complex systems to study. Knowledge of morphology–property relationship is essential for TPUs since their thermal and mechanical behavior are directly dictated by their complicated morphology. In this research, TPU morphological features related to the hard segment content (HSC) were explored in tandem with system macroscopic properties. It was observed that TPUs display multiscale phase separated morphology with specific morphological features dependent on the HSC. At a certain critical HSC, an interconnected network of hard segments was formed which resulted in significant changes in TPU properties. This was explained in analogy with percolation phenomena in filler reinforced systems and considering the hard segments as reinforcing agent. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1553–1564