84 research outputs found
The characteristics of aluminum–scandium alloys processed by ECAP
No full textAluminum–scandium alloys were prepared having different scandium additions of 0.2, 1.0 and 2.0 wt.% and these alloys were processed by equal-channel angular pressing (ECAP) at 473 K. The results show the grain refinement of the aluminum matrix and the morphology of the Al3Sc precipitates depends strongly on the scandium concentration. The tensile properties were evaluated after ECAP by pulling to failure at initial strain rates from 1.0 × 10?3 to 1.0 × 10?1 s?1. The Al–1% Sc alloy exhibited the highest tensile strength of 250 MPa at a strain rate of 1.0 × 10?1 s?1. This alloy also exhibited a superior grain refinement of 0.4 ?m after ECAP where this is attributed to a smaller initial grain size and an optimum volume fraction of dispersed Al3Sc precipitates having both micrometer and nanometer sizes.<br/
Slow Dynamics In Complex Fluids : Confined Polymers And Soft Colloids
No full textThe thesis describes the study of slow dynamics of confined polymers and
soft colloids. We study the finite size effect on the dynamics of glassy polymers
using newly developed interfacial microrheology technique. Systematic
measurement have been performed to address the issue of reduction of glass
transition under confinements. Slow and heterogeneous dynamics are the underlined observed behavior for dynamics in confined glassy polymers. The slow relaxation dynamics and dynamical heterogeneity in polymer grafted nanoparticles (PGNPs) systems were studied using advanced X - ray photon correlation spectroscopy (XPCS) techniques. Our studies presented in this thesis on dynamics of polymer grafted nanoparticle systems in melts and solution are the first attempt to study them experimentally. Thus our work shed the light about new technique to study confined system more accurately and explore new soft colloidal system to study fascinating dynamics and interesting phase behavior.
In Chapter 1, we provide the theoretical background along with brief review of the literature for understanding the results presented in this thesis. The details of the experimental set up and their operating principle along with the details of the experimental conditions are provided in Chapter 2. In Chapter 3 we present our newly developed technique (interfacial microrhelogy) and its consequences to study the complex fluids at interface. Chapter 4 discusses the concentration and temperature dependent glassy dynamics in confined glassy
polymers. In Chapter 5 we provide the structural and dynamical study of polymer
grafted nanoparticles in melts and solutions. We provide the summary of
our result and the future prospective of the work in Chapter 6.
Chapter-1 provides the ground work and theoretical aspects for understanding
the results presented in this thesis. It starts with the discussion about
the slow dynamics of complex fluids and transit to dynamic behavior of polymer
in confinement, glassy dynamics in confinements . This also discusses
the basic aspects of studying viscoelastic properties using rheology, interface
rheology, microrheology, interface microrheology techinques. In continuation it
discusses structure and dynamics of different soft colloids investigated for last decade and then theoretical aspects of XPCS is discussed. Towards the end
of this Chapter, we discuss the procedure to explain and understand systems
dynamical heterogeneity near glass like phase transition.
Chapter-2 contains the details of the experimental techniques which has been used for the study of confined polymers and soft colloids. Brief introduction to basic principles of the measurements followed by details of the material and
methods have been provided.
Chapter-3 we discuss the interafacial microrheology of different complex fluids and advantages of the techniques is discussed in Chapter 3. This includes
discussion about the technique sensitivity at the surface using quantum dots
(QDs) as a probe and about the configuration of the QDs at/on monolayer. Later
on establishment of the technique has been demonstrated through easurements on arachidic acid, poly(methylmethacrylate) (PMMA), poly(vinylacetate) (PVAc), poly(methylacrylate) (PMA) monolayers. The extracted subdiffusive nature of QDs in on monolayers through mean square displacement has been explained using fractional Brownian motion model. Towards the end of the chapter we discuss about the extraction of real and imaginary elastic modulus from mean square displacement data using generalized Stokes-Einstein relation for the quasi two dimensional systems and explains about the possible viscoelastic transition in the different monolayers.
The concentration and temperature dependent glassy dynamics of confined polymers (PMMA) are discussed in Chapter-4. We demonstrate the microscopic nature of spatio-temporal variation of dynamics of glassy polymers confined to a monolayer of 2 3 nm thickness as a function of surface density and temperature. It illustrates the systems dynamical heterogeneity and explain the observed large reduction of glass transition temperature in confined system through finite size effect.
In Chapter 5 we discuss the result based on systematic studies of dynamics of PGNPs in melts and solutions. In addition it also illustrates the structural anisotropy and anomalous dynamical transitions in binary mixture of PGNPs and homopolymers in good solvent condition. It provides temperature
and wave vector dependent XPCS measurements on polymer grafted nanoparticles with the variation of functionality. The functionality ( f ) dependent nonmonotonic relaxation in melts of PGNPs and solvent quality dependent non monotonic relaxation of PGNPs system have been elaborated in the continuation.
We present possible phase behavior of PGNPs system in good solvent with addition of homopolymer of two different molecular weight.
Chapter 6 contains the summary and the future perspective of the work presented
Ceramic-Metal Joining Using Active Filler Alloy-An In-Depth Electron Microscopic Study
No full textNon
Dansyl cadaverine regulates ligand induced endocytosis of interleukin-8 receptor in human polymorphonuclear neutrophils
No full textAbstractInterleukin-8 (IL-8), a neutrophil chemotactic agent, acts as a key mediator in a large number of acute and chronic inflammatory diseases. At 37°C, the receptor for IL-8 is rapidly internalized with its ligand. But no specific inhibitor of this ligand induced internalization of the receptor has been reported so far. We have found that monodansyl cadaverine (MDC) inhibited about 70% of IL-8 induced endocytosis and caused 70% and 66% inhibition of IL-8 mediated chemotaxis and respiratory burst response, respectively, in neutrophils. The uninternalized receptor was detected by anti IL-8R antibody in MDC treated cells. The endocytosis of IL-8R was strongly inhibited under Ca2+ depleted conditions which was restored on addition of 1 mM CaCl2 indicating the critical involvement of a Ca2+ ion in the process. Absence of receptor internalisation makes the MDC treated neutrophils suitable for studying the interaction of IL-8R with potential therapeutic agents e.g. for in vitro screening of anti-inflammatory agents
Cost Optimization of a Hybrid Off-Grid Power System for Remote Localities: A Statistical Model
No full textEffect of catalysts and temperature on silicon carbide whiskers formation from rice husk
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