Carbohydrates are central players in a number of important biological processes including cell signaling, cell adhesion, and the regulation of biochemical pathways. Unlike nucleic acids and proteins, the biosynthesis of carbohydrates is not template-driven. They occur in nature as heterogeneous mixtures, often of high complexity. There is no method for amplifying the amount of a carbohydrate analogous to overexpression for proteins or polymerase chain reaction for nucleic acids, and so carbohydrate analysis is typically limited to what can be obtained from natural sources, thus the researcher must cope with small quantities of heterogeneous material. Mass spectrometry has high sensitivity and is tolerant of mixtures, and is a natural choice for the analysis of this class of molecules.

Compared to advances in protein analysis, progress in the application of mass spectrometry to carbohydrates has evolved somewhat slowly, principally because carbohydrates are a more challenging set of targets for structural characterization. In contrast to proteins, there is no database containing an inclusive and closed set of sequences representing all possible carbohydrate structures. The characterization of carbohydrates relies upon obtaining the full details of structure from the mass spectrum. Subtle differences due to isomerism or chirality can produce molecules with very different biological activities, making complete structural analysis even more demanding.

Mass spectrometry methodologies and technologies for biomolecule analysis continue to rapidly evolve and improve, and these developments have benefited carbohydrate analysis. These developments include approaches for improved ionization, new and improved methods of ion activation, advances in chromatographic separations of carbohydrates, the hybridization of ion mobility and mass spectrometry, and better software for data collection and interpretation. It thus seems timely to examine how these developments affect carbohydrate analysis. This review covers developments in the application of mass spectrometry to the analysis of carbohydrates, with an emphasis on work that has occurred from January 2011 through October 2013. The coverage is not mean to be exhaustive, but rather focuses on significant developments that, in the opinion of the authors, have advanced the field.

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Oligosaccharide analysis by mass spectrometry: A review of recent developments

Production and emission of CO2 from different sources have caused significant changes in the climate, which is the major concern related to global warming. Among other CO2 removal approaches, microalgae can efficiently remove CO2 through the rapid production of algal biomass. In addition, microalgae have the potential to be used in wastewater treatment. Although, wastewater treatment and CO2 removal by microalgae have been studied separately for a long time, there is no detailed information available on combining both processes. In this review article, microalgae-based CO2 biofixation, various microalgae cultivation systems,¯ and microalgae-derived wastewater treatment are separately discussed, followed by the concept of integration of CO2 biofixation process and wastewater treatment. In each section, details of energy efficiency and differences across microalgae species are also given.

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The Use of Microalgae for Coupling Wastewater Treatment With CO2 Biofixation.

A comprehensive review of asphaltene deposition in petroleum reservoirs: Theory, challenges, and tips

Asphaltene is a component of crude oil that has been reported to cause severe problems during production and transportation of the oil from the reservoir. It is a solid component of the oil that has different structures and molecular makeup which makes it one of the most complex components of the oil. This research provides a detailed review of asphaltene properties, characteristics, and previous studies to construct a guideline to asphaltene and its impact on oil recovery. The research begins with an explanation of the main components of crude oil and their relation to asphaltene. The method by which asphaltene is quantified in the crude oil is then explained. Due to its different structures, asphaltene has been modeled using different models all of which are then discussed. All chemical analysis methods that have been used to characterize and study asphaltene are then mentioned and the most commonly used method is shown. Asphaltene will pass through several phases in the reservoir beginning from its stability phase up to its deposition in the pores, wellbore, and facilities. All these phases are explained, and the reason they may occur is mentioned. Following this, the methods by which asphaltene can damage oil recovery are presented. Asphaltene rheology and flow mechanism in the reservoir are then explained in detail including asphaltene onset pressure determination and significance and the use of micro- and nanofluidics to model asphaltene. Finally, the mathematical models, previous laboratory, and oilfield studies conducted to evaluate asphaltene are discussed. This research will help increase the understanding of asphaltene and provide a guideline to properly study and model asphaltene in future studies.

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Critical review of asphaltene properties and factors impacting its stability in crude oil

Stabilization mechanism and chemical demulsification of water-in-oil and oil-in-water emulsions in petroleum industry: A review

Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Peclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection–diffusion effects on deposition.

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Examining Asphaltene Solubility on Deposition in Model Porous Media.

Asphaltenes are components in crude oil known to deposit and interrupt flows in critical regions during oil production, such as the wellbore and transportation pipelines. Chemical dispersants are commonly used to disperse asphaltenes into smaller agglomerates or increase asphaltene stability in solution with the goal of preventing deposition. However, in many cases, these chemical dispersants fail in the field or even worsen the deposition problems in the wellbores. Further understanding of the mechanisms by which dispersants alter asphaltene deposition under dynamic flowing conditions is needed to better understand flow assurance problems. Here, we describe the use of porous media microfluidic devices to evaluate how chemical dispersants change asphaltene deposition. Four commercially used alkylphenol model chemical dispersants are tested with model oils flowing through porous media, and the resulting deposition kinetics are visualized at both the matrix scale and pore scale. Interestingly, initial asphaltene deposition worsens in the presence of the tested dispersants, but the mechanism by which plugging and permeability reduction in the porous media varies. The velocity profiles near the deposit are analyzed to further investigate how shear forces affect asphaltene deposition. The deposition tendency is also related to the intermolecular interactions governing the asphaltene–dispersant systems. Furthermore, the model system is extended to a real case. The use of porous media microfluidic devices offers a unique platform to develop and design effective chemical dispersants for flow assurance problems.

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Characterizing Asphaltene Deposition in the Presence of Chemical Dispersants in Porous Media Micromodels

This study presents in situ visualization of the emulsification/demulsification of asphaltene-stabilized water-in-oil emulsions using microfluidic devices. Monodisperse water-in-oil emulsions were generated using a T-junction, and droplet coalescence was analyzed further upstream of the collision chamber. The state of aggregation of asphaltenes contained in the model oil was found to strongly affect the stability of the emulsions. The aqueous phases used in this study contained either surfactant (C12–15E7) or microemulsion with and without demulsifiers. Different demulsifiers and their concentrations were observed to dramatically affect the coalescence rate. The dilatational surface viscoelasticity properties were also measured using a pendant drop tensiometer. Surprisingly, no correlation was found between the dilatational surface viscoelasticity response and the coalescence rate of the water-in-oil emulsions.

Microfluidic Investigation of Asphaltenes-Stabilized Water-in-Oil Emulsions

Asphaltenes are surface-active polyaromatic molecules in crude oil that are known to deposit in pipelines or stabilize water droplets by flocculating at interfaces resulting highly viscous emulsions, leading to significant flow assurance problems. Commercial dispersants have been developed to disturb asphaltene aggregation to mitigate deposition, but their role on the interfacial properties of asphaltene films is unclear. In this study, we elucidate asphaltene interfacial rheology at air-water and oil-water interfaces at high and low asphaltene surface coverage and in the presence of dispersants. A modified Langmuir trough with double-wall ring rheometer is used to simultaneously visualize the microstructure of asphaltene interface and measure the rheological responses. Two surface coverages, 0.5 and 4 μg cm−2, show widely different rheological responses at air-water interfaces. Strong yielding behavior was observed for higher coverage while a less yielding behavior and wider linear viscoelastic regime we...

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Yu-Jiun Lin

Papers

Examining Asphaltene Solubility on Deposition in Model Porous Media.

Characterizing Asphaltene Deposition in the Presence of Chemical Dispersants in Porous Media Micromodels

Microfluidic Investigation of Asphaltenes-Stabilized Water-in-Oil Emulsions

Combined interfacial shear rheology and microstructure visualization of asphaltenes at air-water and oil-water interfaces

Three dimensional measurements of asphaltene deposition in a transparent micro-channel