5,818 research outputs found
Exploring the role of nanocellulose as potential sustainable material for enhanced oil recovery:New paradigm for a circular economy
Presently, due to growing global energy demand and depletion of existing oil reservoirs, oil industry is focussing on development of novel and effective ways to enhance crude oil recovery and exploration of new oil reserves, which are typically found in challenging environment and require deep drilling in high temperature and high-pressure regime. The nanocelluloses with numerous advantages such as high temperature and pressure stability, ecofriendly nature, excellent rheology modifying ability, interfacial tension reduction capability, etc., have shown a huge potential in oil recovery over conventional chemicals and macro/micro sized biopolymers-based approach. In present review, an attempt has been made to thoroughly investigate the potential of nanocellulose (cellulose nanocrystals/nanofibers) in development of drilling fluid and in enhancement of oil recovery. The impact of various factors such as nanocellulose shape, charge density, inter-particle or inter-fibers interactions after surface functionalization, rheometer geometries, additives, post processing techniques, etc., which provides insight into the attributes of nanocellulose suspension and exemplify their behaviour during oil recovery have also been reviewed and discussed. Finally, the conclusion and challenges in utility of nanocellulose for oilfield applications are addressed. Knowing how to adjust/quantify nanocrystals/nanofibers shape and size; and monitor their interactions might promote their utility in oilfield industry.</p
Planetary Hinterlands:Extraction, Abandonment and Care
This open access book considers the concept of the hinterland as a crucial tool for understanding the global and planetary present as a time defined by the lasting legacies of colonialism, increasing labor precarity under late capitalist regimes, and looming climate disasters. Traditionally seen to serve a (colonial) port or market town, the hinterland here becomes a lens to attend to the times and spaces shaped and experienced across the received categories of the urban, rural, wilderness or nature. In straddling these categories, the concept of the hinterland foregrounds the human and more-than-human lively processes and forms of care that go on even in sites defined by capitalist extraction and political abandonment. Bringing together scholars from the humanities and social sciences, the book rethinks hinterland materialities, affectivities, and ecologies across places and cultural imaginations, Global North and South, urban and rural, and land and water
Synthesis of multifunctional glyco-pseudodendrimers and glyco-dendrimers and their investigation as anti-Alzheimer agents
As the world population is aging, the cases of Alzheimer’s Disease (AD) are increasing. AD is a disorder of the brain which is characterized by the aggregation of amyloid beta (Aβ) plaques. This leads to the death of numerous brain cells thus affecting the cognitive and motor functions of the individual. Till date, no cure for the disease is available. Aβ are peptides with 40/42 amino acid residues but, their exact mechanism(s) of action in AD is under debate. Having different amino acid residues makes them susceptible to form hydrogen bonds. Dendrimers with sugar units are often referred to as glycopolymers and have been shown to have potential anti-amyloidogenic activity. However, they also have drawbacks, the synthesis involves multiple tedious steps, and dendrimers themselves offer only a limited number of functional units. Pseudodendrimers are another class of branched polymers based on hyperbranched polymers. Unlike the dendrimers, they are easy to synthesize with a dense shell of functional units on the surface. One of the main goals in this dissertation is the synthesis and characterization of pseudodendrimers and dendrimers based on 2,2-bis(hydroxymethyl)-propionic acid (bis-MPA), an aliphatic polyester scaffold, as it offers biocompatibility and easy degradability. Furthermore, they are decorated with mannose units on the surface using a ‘click’ reaction forming glyco-pseudodendrimers and glyco-dendrimers. A detailed characterization of their structures and physical properties was undertaken using techniques such as size exclusion chromatography, asymmetric flow field flow fractionation (AF4), and dynamic light scattering.
The second main focus of this work has been to investigate the interaction of synthesized glyco-pseudodendrimers and glyco-dendrimers with Aβ 40 peptides. For this task, five different concentrations of the synthesized glycopolymers were tested with Aβ 40 using the Thioflavin T assay. The results of the synthesized polymers which produced the best results of showing maximum anti-aggregation behavior against Aβ 40 were confirmed with circular dichroism spectroscopy. AF4 was also used to investigate Aβ 40-glycopolymer aggregates, which has never been done before and constitutes the highlight of this dissertation. Atomic force microscopy was used to image Aβ 40-glycopseudodenrimer aggregates.
A basic but important step in the development of drug delivery platforms is to evaluate the toxicity of the drugs synthesized. In this work, preliminary studies of the cytotoxicity of glyco-pseudodendrimers were performed in two different cell lines. Thus, this study comprises a preliminary investigation of the anti-amyloidogenic activity of glyco-pseudodendrimers synthesized on an aliphatic polyester backbone.:Abstract
List of Tables
List of Figures
Abbreviations
1 Introduction
1.1 Objectives of the work
1.2 Thesis overview
2 Fundamentals and Literature
2.1 Alzheimer’s Disease and its impact
2.1.1 Neurological diagnosis of AD
2.1.2 Histopathology of AD
2.1.3 Amyloid precursor protein (APP) and its role in AD
2.2. Amyloid Beta (Aβ) peptide
2.2.1 Aβ peptide
2.2.2. Location and function
2.2.3 Amyloid hypothesis
2.2.4 The mechanism of Aβ aggregation
2.2.5 Amyloid fibrils
2.2.6 Toxicity of Aβ
2.3 Research methods to study Aβ aggregates
2.3.1 Models to study the mode of action of aggregates
2.3.2 Endogenous Aβ aggregates and synthetic aggregates
2.3.3 Strategies to alter aggregation of amyloids
2.4 Treatment and therapeutics
2.4.1 Current therapeutics
2.4.2 Current therapeutic research
2.4.2.1 Reduction of Aβ production
2.4.2.2 Reduction of Aβ plaque accumulation
2.4.2.2.1 Anti-amyloid aggregation agents
2.4.2.2.2 Metals
2.4.2.2.3 Immunotherapy
2.4.2.2.4 Dendrimers as potential anti-amyloidogenic agent
2.6 Dendrimers
2.6.1 Definition
2.6.2 Structure
Table of Contents
2.6.3 Synthesis
2.6.4 Properties
2.7 Pseudodendrimers - a sub-class of hyperbranched polymer
2.7.1 Definition
2.7.2 Structure
2.7.3 Synthesis
3 Analytical Techniques
3.1 Size Exclusion Chromatography Coupled to Light Scattering (SEC-MALS)
3.2 Asymmetric Flow Field Flow Fractionation (AF4)
3.3 Dynamic Light Scattering
3.4 Molecular Dynamics Simulation
3.5 Nuclear Magnetic Resonance Spectroscopy
3.6 Thioflavin T fluorescence
3.6.1 Kinetic analysis
3.7 Circular Dichroism Spectroscopy
3.8 Atomic Force Microscopy
3.9 Cytotoxic assay
3.9.1 MTT assay
3.9.2 Determining the level of reactive oxygen species
3.9.3 Changes in mitochondrial transmembrane potential
3.9.4 Flow cytometric detection of phosphatidyl serine exposure
4 Experimental Details and Methodology
4.1 Details of chemicals/components used
4.1.1 Other materials
4.1.2 Peptide preparation
4.1.3 Buffer preparation
4.1.4 Fibril growth conditions
4.2 Synthesis and characterization of polymers
4.2.1 Synthesis and characterization of pseudodendrimers and dendrimers
4.2.1.1 Synthesis of hyperbranched polymer (1)
4.2.1.2 Synthesis of protected monomer
4.2.1.2.1 bis-MPA acetonide (2)
4.2.1.2.2 bis-MPA-acetonide anhydride (3)
4.2.1.3 Synthesis of protected pseudodendrimers (4, 6 and 8) and
protected dendrimers (10, 12, and 14)
4.2.1.4 Deprotection of pseudodendrimers (5,7, and 9) and dendrimers
(11,13 and 15)
4.2.2 Synthesis of glyco-pseudodendrimers and glyco-dendrimers
4.2.2.1 Pentynoic anhydride (16)
4.2.2.2 Synthesis of pentinate modified pseudodendrimers (17, 18
and 19) and dendrimers (20, 21 and 22)
4.2.2.3 3-Azido-1-propanol (23)
4.2.2.4 Mannose propyl azide tetraacetate (24)
Table of Contents
4.2.2.5 Mannosepropylazide (25)
4.2.2.6 Glyco-pseudodendrimers (Gl-P) (26, 27 and 28) and glyco-
dendrimers (Gl-D) (29, 30 and 31)
4.3 Analytical techniques and their general details
4.3.1 SEC-MALS - Instrumentation, software and analysis
4.3.2 AF4 - Instrumentation, software and analysis
4.3.2.1 Sample preparation
4.3.2.2 Method development for analysis of Gl-P and Gl-D
4.3.2.3 Method development for analysis of Aβ 40 and its interaction
with Gl-P and Gl-D
4.3.3 Batch DLS - Instrumentation, software and analysis
4.3.3.1 Sample preparation
4.3.4 Theoretical calculations and molecular dynamics simulations
4.3.4.1 Ab-initio calculations
4.3.4.2 Modelling of the polymer structures
4.3.4.2.1 Pseudodendrimers
4.3.4.2.2 Dendrimers
4.3.4.2.3 Modification of the polymers with special end groups
4.3.4.2.4 Preparing of the THF solvent box
4.3.4.2.5 Solvation of the polymer structures
4.3.4.3 Molecular dynamics simulations
4.3.4.3.1 Evaluation of the simulation trajectories
4.4 Investigation of interaction of Gl-P and Gl-D with amyloid beta (Aβ 40)
4.4.1 ThT Assay - Instrumentation and software
4.4.1.1 Sample preparation
4.4.1.2 Kinetics based on ThT assay- software and data analysis
4.4.2 CD spectroscopy - Instrumentation and software
4.4.2.1 Sample preparation
4.4.3 AFM - Instrumentation and software
4.4.3.1 Substrate and sample preparation
4.4.3.2 Height determination and counting procedures
4.4.3.3 Topography and diameter
4.5 Cytotoxicity
4.5.1 Zeta potential
4.5.2 Cell culturing
4.5.3 Sample preparation
4.5.4 MTT assay
4.5.5 Changes in mitochondrial transmembrane potential (JC-1 method)
4.5.6 Flow cytometric detection of phosphatidyl serine exposure
(Annexin V and PI method)
5 Results and Discussion
5.1 Synthesis and characterization of glyco-pseudodendrimers and glyco-
dendrimers
5.1.1 Synthesis and characterization of hyperbranched polyester
Table of Contents
5.1.2 Synthesis and characterization of pseudodendrimers P-G1-OH,
P-G2-OH and P-G3-OH
5.1.3 Synthesis and characterization of dendrimers D-G4-OH, D-G5-OH
and D-G6-OH
5.1.4 Synthesis and characterization of Gl-P and Gl-D
5.1.4.1 Molecular size determination of Gl-P and Gl-D using SEC
5.1.4.2 Particle size determination using batch DLS
5.1.4.3 Apparent densities
5.1.4.4 Molecular size determination of Gl-P and Gl-D using AF4 .....
5.1.5 Molecular dynamics simulation
5.2 Investigation of interaction of Gl-P and Gl-D with amyloid beta (Aβ 40) ......
5.2.1 ThT Assay
5.2.1.1 Kinetics based on ThT assay
5.2.2 CD spectroscopy
5.2.3 Time dependent AF4
5.3.2.1 Separation of Aβ 40 by AF4
5.3.2.2 Aβ 40 amyloid aggregation in the presence of Gl-P and Gl-D
5.2.4 AFM
5.2.4.1 Height
5.2.4.2 Topography and diameter
5.2.4.3 Length
5.2.4.4 Morphology
5.2.5 Cytotoxicity
5.2.5.1 MTT assay
5.2.5.2 Changes in mitochondrial transmembrane potential
5.2.5.3 Flow cytometric detection of phosphatidyl serine exposure
6 Conclusions and Outlook
7 Bibliography
Appendix
Acknowledgement
Amphiphilic block copolymers as dual flocculation-flotation agents for rapid solid–liquid separation of radioactive wastes
The potential of poly(acrylic acid)-b-poly(n-butyl acrylate) as a dual flocculant-collector in combined flotation-sedimentation dewatering operations was investigated. The amphiphilic block copolymers were synthesised with consistent hydrophilic chain lengths and varying hydrophobic chain lengths. Various techniques were employed to analyse polymer behaviour at the air–water interface, being interfacial surface tension and dilational viscoelasticity. Polymer adsorption onto Mg(OH)2 was determined differentially using UV–Vis spectroscopy. Floc structures were determined using static light scattering, and flocculation-flotation performance was analysed using settling tests and flotation cell material balances. Results showed that longer hydrophobic chains were less surface-active, reducing foamability and water entrainment. The unimer-micellar adsorption transition points were identified through viscoelastic properties and particle adsorption studies. A distinct change in floc density and structure was observed for the largest molecular weight copolymer when the dosed concentration increased into the micellar adsorption region, suggesting a pseudo-bridging flocculation mechanism. Settling rates were significantly higher for particles flocculated with the larger molecular weight polymer, correlating to their larger aggregate sizes, especially over the micellar transition point. The largest molecular weight block copolymer demonstrated superior collection efficiency compared to the traditional surfactant, sodium dodecylsulfate (SDS), below its micellar adsorption transition point. However, beyond this point, the lack of exposed hydrophobic blocks hindered the hydrophobisation of Mg(OH)2 particles, reducing collection efficiency. Comparing flotation cell particle size distributions, it was suggested that recovery may be hydrodynamically hindered by the largest floc sizes, though recovery was observed for particles in the order of < 600 μm
Practical Inherently Safer Design Approaches During Early Process Design Stages Aiming for Sustainability
In traditional industrial process design approaches, techno-economic criteria have been the primary objectives in the early process design stages. Safety is often considered only in the later design stage (e.g., detailed engineering stage). Such a traditional approach is that most of the design degrees of freedom, including technology and configuration issues, have already been determined when considering safety. Modifying a process is costly or unreliable at later stages. To solve this issue, there have been numerous attempts to consider process safety during the early design stages in safety engineers and researchers. In particular, special attention to adopting inherently safer design (ISD) has been made because ISD is deemed the most cost-effective risk reduction strategy at early design stages. However, it is still challenging to adopt ISD for process engineers at the early design stages because of the lack of guidance and insufficient information on upcoming process facilities.
To address this challenge, this dissertation consists of three peer-reviewed journal papers [Articles #1 - #3]. With respect to the progress of inherently safer design (in particular, during the early design stage) over the last three decades, Article #1 selects 73 inherent safety assessment tools, which can be utilized during the early design stages, and categorized into three groups: hazard-based inherent safety assessment tools (H-ISATs) for 22 tools, risk-based inherent safety assessment tools (R-ISATs) for 33 tools, and cost-optimal inherent safety assessment tools (CO-ISATs) for 18 tools. The goal of this article is to enable process engineers to use all the available design degrees of freedom to mitigate risk early enough in the design process.
Article #2 analyzes 94 chemical process incidents investigated by the U.S. Chemical Safety and Hazard Investigation Board (CSB) reports. To analyze in a systematic approach, this article proposes 17 incident cause factors, 6 scenario factors, and 6 consequence factors to find out whether ISD would have helped to prevent these incidents.
Article #3 proposes hands-on predictive models of the flash point, the heat of combustion, lower flammability limit (LFL), and upper flammability limit (UFL). By incorporating the nonlinearity and transformation along with linearity of variables, this article constructed practical, reliable regression models thoroughly with readily available variables—the number of all atoms, molecular weights, and boiling points. The purpose is to enable a process engineer to quickly obtain hazardous properties of intended process materials
Utilizing Fluorescent Nanoscale Particles to Create a Map of the Electric Double Layer
The interactions between charged particles in solution and an applied electric field follow several models, most notably the Gouy-Chapman-Stern model, for the establishment of an electric double layer along the electrode, but these models make several assumptions of ionic concentrations and an infinite bulk solution. As more scientific progress is made for the finite and single molecule reactions inside microfluidic cells, the limitations of the models become more extreme. Thus, creating an accurate map of the precise response of charged nanoparticles in an electric field becomes increasingly vital. Another compounding factor is Brownian motion’s inverse relationship with size: large easily observable particles have relatively small Brownian movements, while nanoscale particles are simultaneously more difficult to be observed directly and have much larger magnitude Brownian movements. The research presented here tackles both cases simultaneously using fluorescently tagged, negatively charged, 20 nm diameter polystyrene nanoparticles. By utilizing parallel plate electrodes within a specially constructed microfluidic device that limits the z-direction, the nanoparticle movements become restricted to two dimensions. By using one axis to measure purely Brownian motion, while the other axis has both Brownian motion and ballistic movement from the applied electric field, the ballistic component can be disentangled and isolated. Using this terminal velocity to calculate the direct effect of the field on a single nanoparticle, as opposed to the reaction of the bulk solution, several curious phenomena were observed: the trajectory of the nanoparticle suggests that the charge time of the electrode is several magnitudes larger than the theoretical value, lasting for over a minute instead of tens of milliseconds. Additionally, the effective electric field does not reduce to below the Brownian limit, but instead has a continued influence for far longer than the model suggests. Finally, when the electrode was toggled off, a repeatable response was observed where the nanoparticle would immediately alter course in the opposite direction of the previously established field, rebounding with a high degree of force for several seconds after the potential had been cut before settling to a neutral and stochastic Brownian motion. While some initial hypotheses are presented in this dissertation as possible explanations, these findings indicate the need for additional experiments to find the root cause of these unexpected results and observations
Nanofluids with optimised thermal properties based on metal chalcogenides with different morphology
Over the last decades, the interest around renewable energies has increased considerably because of the growing energy demand and the environmental problems derived from fossil fuels combustion. In this scenario, concentrating solar power (CSP) is a renewable energy with a high potential to cover the global energy demand. However, improving the efficiency and reducing the cost of technologies based on this type of energy to make it more competitive is still a work in progress.
One of the current lines of research is the replacement of the heat transfer fluid used in the absorber tube of parabolic trough collectors with nano-colloidal suspensions of nanomaterials in a base fluid, typically named nanofluids. Nanofluids are considered as a new generation of heat transfer fluids since they exhibit thermophysical properties improvements compared with conventional heat transfer fluids. But there are still some barriers to overcome for the implementation of nanofluids. For example, obtaining nanofluids with high stability is a priority challenge for this kind of system. Also ensuring that nanoparticles will not clog pipes or cause pressure drops.
In this Doctoral Thesis, the use of transition metal dichalcogenide-based nanofluids as a heat transfer fluid in solar power plants has been investigated for the first time. Specifically, nanofluids based on one-dimensional, two-dimensional and three-dimensional MoS2 , WS2 and WSe2 nanostructures have been researched. The base fluid used in the preparation of these nanofluids is the eutectic mixture of biphenyl and diphenyl oxide typically employed as heat transfer fluid in concentrating solar power plants. Mainly two preparation methods have been explored: the liquid phase exfoliation method, and the solvothermal synthesis of the nanomaterial and its subsequent dispersion in the thermal oil by ultrasound. Experimental parameters such as surfactant concentration, time and sonication frequency for preparation of nanofluids have also been analysed. The nanofluids have been subjected to an extensive characterisation which includes the study of colloidal stability over time, characterisation of thermal properties such as isobaric specific heat or thermal conductivity, rheological properties and optical properties. The results have revealed that nanofluids based on 1D and 2D nanostructures of transition metal dichalcogenides are colloidally stable over time and exhibit improved thermal properties compared to the typical thermal fluid used in solar power plants. The most promising nanofluids are those based on MoS 2 nanosheets and those based on WSe 2 nanosheets with heat transfer coefficient improvements of 36.2% and 34.1% respectively with respect to thermal oil. Furthermore, the dramatic role of WSe2 nanosheets in enhancing optical extinction of the thermal oil suggests the use of these nanofluids in direct absorption solar collectors. In conclusion, the present work demonstrates the feasibility of using nanofluids based on transition metal dichalcogenide nanostructures as heat transfer fluids in concentrating solar power plants based on parabolic trough collectors.En las últimas décadas, el interés en torno a las energías renovables ha
aumentado considerablemente debido a la creciente demanda energética y a
los problemas medioambientales derivados de la combustión de combustibles
fósiles. En este escenario, la energía solar de concentración (CSP) es una
energía renovable con un alto potencial para cubrir la demanda energética
mundial. Sin embargo, es necesario trabajar para mejorar la eficiencia y reducir
el coste de las tecnologías basadas en este tipo de energía con el objetivo de
hacerla más competitiva.
Una de las líneas de investigación actuales es la sustitución del fluido
caloportador utilizado en el tubo absorbedor de los colectores cilindroparabólicos por suspensiones nanocoloidales de nanomateriales en un fluido
base, típicamente denominados nanofluidos. Los nanofluidos se consideran
una nueva generación de fluidos de transferencia de calor, ya que presentan
mejoras en sus propiedades termofísicas en comparación con los fluidos de
transferencia de calor convencionales. Pero aún quedan algunos obstáculos por
superar para la aplicación de los nanofluidos. Por ejemplo, obtener nanofluidos
con alta estabilidad es un reto prioritario en este tipo de sistemas. También
garantizar que las nanopartículas no obstruyan las tuberías ni provoquen caídas
de presión.
En esta Tesis Doctoral se ha investigado por primera vez el uso de nanofluidos
basados en dicalcogenuros de metales de transición como fluido caloportador
en centrales solares. En concreto, se han investigado nanofluidos basados en
nanoestructuras unidimensionales, bidimensionales y tridimensionales de
MoS2, WS2 y WSe2. El fluido base utilizado en la preparación de estos
nanofluidos es la mezcla eutéctica de bifenilo y óxido de difenilo empleada
habitualmente como fluido de transferencia de calor en las centrales de
concentración de energía solar. Se han explorado principalmente dos métodos
de preparación: el método de exfoliación en fase líquida y la síntesis
solvotermal del nanomaterial y su posterior dispersión en el aceite térmico mediante ultrasonidos. También se han analizado parámetros experimentales
como la concentración de surfactante, el tiempo y la frecuencia de sonicación
para la preparación de los nanofluidos. Los nanofluidos han sido sometidos a
una extensa caracterización que incluye el estudio de la estabilidad coloidal a
lo largo del tiempo, la caracterización de propiedades térmicas como el calor
específico isobárico o la conductividad térmica, propiedades reológicas y
propiedades ópticas. Los resultados han revelado que los nanofluidos basados
en nanoestructuras 1D y 2D de dicalcogenuros de metales de transición son
coloidalmente estables en el tiempo y presentan propiedades térmicas
mejoradas en comparación con el fluido térmico típico utilizado en las
centrales solares. Los nanofluidos más prometedores son los basados en
nanoláminas de MoS2 y los basados en nanoláminas de WSe2, con mejoras del
coeficiente de transferencia térmica del 36,2% y el 34,1%, respectivamente,
con respecto al aceite térmico. Además, el espectacular papel de las
nanoláminas de WSe2 en la mejora de la extinción óptica del aceite térmico
sugiere el uso de estos nanofluidos en colectores solares de absorción directa.
En conclusión, el presente trabajo demuestra la viabilidad del uso de
nanofluidos basados en nanoestructuras de dicalcogenuros de metales de
transición como fluidos de transferencia de calor en centrales solares de
concentración basadas en colectores cilindro-parabólicos
Hybrid photocatalytic materials for contaminants of emerging concern degradation
228 p.Contaminants of emerging concern (CECs) such as pharmaceuticals represent a new global problem for water quality because these compounds are very resistant to conventional wastewater treatments and can get into environment, causing severe threats to aquatic organisms and human health. In the last decades, semiconductor photocatalysis has become a promising technology to degrade these contaminants. However, poor efficiency of photocatalysts under sunlight and time-consuming and expensive processes for photocatalyst recovery/reuse are two main limitations for photocatalysis application in water remediation. This doctoral thesis focuses on surpassing these obstacles. Firstly, the importance of the interaction between pollutants and photocatalysts, the generation of reactive oxygen species (ROS) for photocatalytic performance is considered. Then, the development of Au-functionalised plasmonic photocatalysts is carried out. Later, novel and more efficient photocatalysts using Au nanostar functionalising TiO2 are developed and tested for photocatalytic application. Finally, the novel photocatalysts are immobilised into polymer matrix through different techniques for their reusability and recovery in photocatalytic application. The results obtained show the prepared hybrid photocatalytic materials opening the door to cost-effectively degrade a high variety of CECs under sunlight for water remediation.BCMATERIALS: Basque Center for Materials, Applications & Nanostructure
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