A Comparison of Microstructure and Uniaxial Compressive Response of Ice-Templated Porous Alumina Scaffolds Fabricated from Two Different Particle Sizes

Development of bio-inspired highly porous (\u3e50 vol.%) cellular ceramics is crucial to meet the demand of high-performance lightweight and damage-tolerant materials for a number of cutting-edge applications including impact energy absorption, biomedical implants, and energy storage. A key design feature that is observed in many natural materials (e.g., nacre, bamboo, wood, etc.) is the presence of hierarchical microstructure that results in an excellent synergy of various material properties, which are otherwise considered as mutually exclusive in current paradigm of materials design. To this end, development of multilayered, interconnected and anisotropic cellular ceramics could benefit the aforementioned applications. However, mimicking natural design principles to develop robust cellular materials is of paramount challenge because most of the available processing techniques are limited to the fabrication of simple materials microstructures. In contrast, freeze casting is one emerging technique that has shown great promise to develop nature-inspired hierarchical cellular ceramics. While a large number of recent studies focused on the development of process-structure correlations of freeze-cast ceramics, understanding of the structure-property relationships has been extremely limited. Therefore, this thesis develops a custom-made unidirectional freeze casting device to investigate the effects of the variation of the particle size (0.3 μm vs. 0.9 μm) on the microstructure and uniaxial compressive response of ice-templated sintered alumina scaffolds as a function of solids loading and freezing front velocity (FFV). For comparable solids loading and FFV, particle size effects on the microstructure of the scaffolds are observed to be significant. Moreover, transition of the pore morphology with the increasing solids loading and FFV is observed to be more drastic for the scaffolds processed from the 0.9 μm particles compared to the 0.3 μm particles. Similarly, particle size variations also significantly influenced the relative density and porosity of the scaffolds. However, in spite of the observed differences of the microstructure, relative density and porosity, uniaxial compressive stress-strain measurements revealed marginal particle size effects on the compressive strength. The apparent marginal particle size effects on the compressive strength are rationalized based on the relative variation of the relative density, pore aspect ratio, and interlamellae bridge density in between the sintered alumina scaffolds processed from 0.3 μm and 0.9 μm particle sizes. This study also suggests that particle size variation within a range of submicrometer to few micrometers (typical particle size range used in ceramic processing) can be uniquely employed to systematically modify the microstructure of the ice-templated sintered ceramic scaffolds, without significantly altering their uniaxial compressive response; which can be useful to optimize the structure-property relationships of the ice-templated scaffolds for the structural, biomedical and functional applications

Comparitive Study of Plain Foundations with Shell Foundations

The spread footing for columns transmitting heavy load to weak Soils tends to be massive, if rafts are provided. Shell foundation can serve as better replacement to plain foundation as economic alternative where heavy super structural loads are to be transmitted to weaker soils. The substitution of shell foundations for spread footings and rafts can therefore lead to considerable saving in concrete and reinforcing steel.The sector of spherical dome, in inverted positions can serve as rafts for structures such as water tanks

Microscale experiments in chemistry - the need of the new millenium 5. Organic qualitative analysis and mixture separation on microscale

This article does not have an abstract

Microscale experiments in chemistry - the need of the new millenium 2. Experiments which bring theory closer to laboratories

This article does not have an abstract

Fluselenamyl: A novel benzoselenazole derivative for PET detection if amyloid plaques (Aβ) in Alzheimer\u27s disease

Fluselenamyl (5), a novel planar benzoselenazole shows traits desirable of enabling noninvasive imaging of Aβ pathophysiology in vivo; labeling of both diffuse (an earlier manifestation of neuritic plaques) and fibrillar plaques in Alzheimer’s disease (AD) brain sections, and remarkable specificity for mapping Aβ compared with biomarker proteins of other neurodegenerative diseases. Employing AD homogenates, [(18)F]-9, a PET tracer demonstrates superior (2–10 fold higher) binding affinity than approved FDA tracers, while also indicating binding to high affinity site on Aβ plaques. Pharmacokinetic studies indicate high initial influx of [(18)F]-9 in normal mice brains accompanied by rapid clearance in the absence of targeted plaques. Following incubation in human serum, [(18)F]-9 indicates presence of parental compound up to 3h thus indicating its stability. Furthermore, in vitro autoradiography studies of [(18)F]-9 with AD brain tissue sections and ex vivo autoradiography studies in transgenic mouse brain sections show cortical Aβ binding, and a fair correlation with Aβ immunostaining. Finally, multiphoton- and microPET/CT imaging indicate its ability to penetrate brain and label parenchymal plaques in transgenic mice. Following further validation of its performance in other AD rodent models and nonhuman primates, Fluselenamyl could offer a platform technology for monitoring earliest stages of Aβ pathophysiology in vivo

An orbital-free molecular dynamics study of melting in K_20, K_55, K_92, K_142, Rb_55 and Cs_55 clusters

The melting-like transition in potasium clusters K_N, with N=20, 55, 92 and 142, is studied by using an orbital-free density-functional constant-energy molecular dynamics simulation method, and compared to previous theoretical results on the melting-like transition in sodium clusters of the same sizes. Melting in potasium and sodium clusters proceeds in a similar way: a surface melting stage develops upon heating before the homogeneous melting temperature is reached. Premelting effects are nevertheless more important and more easily established in potasium clusters, and the transition regions spread over temperature intervals which are wider than in the case of sodium. For all the sizes considered, the percentage melting temperature reduction when passing from Na to K clusters is substantially larger than in the bulk. Once those two materials have been compared for a number of different cluster sizes, we study the melting-like transition in Rb_55 and Cs_55 clusters and make a comparison with the melting behavior of Na_55 and K_55. As the atomic number increases, the height of the specific heat peaks decreases, their width increases, and the melting temperature decreases as in bulk melting, but in a more pronounced way.Comment: LaTeX file. 6 pages with 17 pictures. Final version with minor change

Facile method for trimethylsilylation of alcohols using hexamethyldisilazane and ammonium thiocyanate under neutral conditions

A highly efficient method for trimethylsilylation of primary, secondary, tertiary, allylic, and a variety of sugar-derived alcohols using hexamethyldisilazane in the presence of a catalytic amount of ammonium thiocyanate under neutral conditions is reported

Password based Doorlock Security System using 8051

Many times we forgot to carry the key of our home. Or sometimes we come out of our home and door latch closes by mistake. In these cases it is really difficult to get inside the house. This project is designed to solve this purpose. Main concept behind this project is of a door-latch opening using a password entered through keypad. As well as turning on the Buzzer when password is entered wrong for multiple times. User can change this password anytime he/she wish using a keypad