Theoretical Studies of the Structure and Stability of Metal Chalcogenide CrnTem (1≤n≤6, 1≤m≤8) clusters

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, CrnTem clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr6Te8 which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation energy indicating energetic stability. The high electron affinity shows that the stability of Cr6Te8 cluster can be enhanced by adding charge donating ligands including PEt3 to form stable Cr6Te8(PEt3)6 clusters as seen in experiments. The other cluster of interest was Cr4Te6 in which energetic stability was accompanied with electronic inertness marked by its large HOMO-LUMO gap, non-magnetic ground state and high fragmentation energy

Coexisting Sickle Cell Anemia and Sarcoidosis: A Management Conundrum!

Sickle cell disease and Sarcoidosis are conditions that are more common in the African American population. In this report we share an unfortunate patient who had hepatic sarcoidosis but could not receive steroids since that precipitated acute liver failure. We have discussed potential therapy options but we need more options that improve mortality

CHARACTERIZATION OF MICROSATELLITE LOCI AND PILOT POPULATION GENETIC ANALYSIS IN HICKORY SHAD, ALOSA MEDIOCRIS

The hickory shad (Alosa mediocris) is a relatively understudied species of the anadromous fish sub-family Alosinae. This study, the first population genetic analysis of this species, employed 12 neutral microsatellite loci to estimate genetic diversity and population structure in tributaries of lower Chesapeake Bay, Virginia including James River and its tributaries (Appomattox and Chickahominy Rivers), Rappahannock River, and Pamunkey River. Genetic variation was extremely low. Estimates of observed heterozygosity were lower than expected heterozygosity. Significant population structure was detected among the six samples (FST = 0.093, p = 0.01). Effective population sizes were low (Ne ranged from 2 to 134). The lack of genetic diversity, especially compared to that of the American shad, was striking and could be the result of a bottleneck that took place more than thirty years ago which may plausibly account for the low genetic variation observed across all populations

Trade Liberalization, Poverty, Income Inequality in India

This paper is a study on the impact of India's trade liberalization as part of its economic reforms and structural adjustment programs initiated during the 1990s on poverty and income inequality. Major reforms: 1. Trade liberalization 2. Financial liberalization 3. Privatization 3. Tax reforms 4. Inflation control measures 5. Foreign investment 6. Agriculture developmen

FORMATION OF CARBON NANOSPRINGS VIA PRECURSOR CONSTRAINED FIBER MICROBUCKLING

Flexible carbon nanosprings and wavy nanofibers can be used in micro and nanoelectromechanical system devices, deployable structures, flexible displays, energy storage, catalysis, nanocomposites and a multitude of other uses. A novel method to produce wavy and helical carbon nanofibers (CNFs) is presented here. The CNFs with controlled geometry were fabricated via pyrolysis of electrospun polyacrylonitrile (PAN) nanofibers as the precursor. The waviness/helicity of nanofibers was achieved by subjecting the precursor nanofibers to constraint buckling inside a thermally shrinking matrix. The much higher tendency of the matrix to shrink, compared to PAN nanofibers, was achieved by controlling the microstructure and crystallinity of the precursors. The formation of the wavy/helical geometry was explained quantitatively via mechanistic models, by minimizing the total mechanical energy stored in the PAN-matrix system during the matrix shrinkage. Despite its simplicity in considering elastic deformations only, the model provided reasonably quantitative matching with the experiments. Compared to existing methods in generating wavy/helical nanofibers, such as chemical vapor deposition growth methods, our method provides a more controllable geometry which is suitable for large scale production of aligned buckled CNFs

The Effect of Different Surface Treatments on The Bond Strength of Zirconia

Objectives: The purpose of the study was to evaluate the influence of various surface treatment methods on the resin bond durability of zirconia. Methods: Hundred KATANA Zirconia STML (n=20) specimens were sectioned and sintered in an induction furnace (CEREC SpeedFire, Dentsply Sirona, Germany). Specimen surfaces were ground finished with 800 grit silicon carbide abrasive with cooling water and cleaned in an alcohol bath ultrasonically before cementation for 5 min, and thoroughly washed again with running distilled water. Specimens in Group 1 had no surface treatment, Group 2 was air-abraded with 50 μm aluminum oxide, Group 3 was air abraded with glass bead particles, Group 4 specimens were immersed in Zircos E etching solution for 2 h and Group 5 specimens were immersed in 48% Hydrofluoric acid solution heated at 25oC for 30 min. Cylindrical composite resin specimens (2.1 mm in diameter, 3 mm in height) were bonded to the zirconia samples with self-adhesive resin cement Panavia V5 (PV5, after application of ceramic primer) following manufacturers’ instructions. A load of 1000 g was applied to the composite cylinders during bonding in an alignment apparatus, then light cured for 80 s. Each main group was divided into two subgroups (n = 10/each). Half of the samples were tested for SBS after 48 h in distilled water at 37o C (100-percent humidity), 10 then subjected to 10,000 thermo cycles and the other half were tested after 10,000 thermo cycles. Shear bond strength was determined using a universal testing machine at a crosshead speed of 0.5 mm/m expressed in MPa. The fractured surfaces of specimens were inspected with a stereo microscope and classified as adhesive, cohesive, or mixed failures. One-way ANOVA test and paired t- test was applied for statistical analysis. Results: All four surface treatment methods tested were significantly different from each other and with the control group (no surface treatment). Mean shear bond strength values for group1 8.316(SD 1.953), group 2 14.976(SD 3.189), group 3 9.286(SD 0.985), group 4 4.831(SD 0.468), and group 5 14.796(SD 0.829). The mean shear bond strength values for all the groups decreased significantly after thermocycling. Conclusions: According to the results of this in vitro study, air abrasion and heated hydrofluoric acid proved to be better methods for surface treatment of zirconia as compared to other methods. Newly launched zirconia etching solution containing hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and phosphoric acid (H3PO4) performed poorly as surface treatment agents in increasing the bond strength of zirconia

Assessment of the Wear Effects of Alumina-Nanofluids on Heat-Exchanger Materials

Nanofluids are nano-size-powder suspensions in liquids that are mainly studied for their abnormal thermal transport properties, and hence as enhanced alternatives to ordinary cooling fluids. The tribological effects of nanofluids are, however, largely unknown, in particular their likely wear and/or erosion effects, because of their interaction with cooling-system (heat-exchanger) materials. The thesis presents research to establish methodologies for testing and evaluating surface-change by nanofluid impact. The work is presented on development of novel test rigs and testing methodologies, and on the use of typical surface analysis tools for assessment of wear and erosion that may be produced by nanofluids; prediction of such effects in cooling systems is discussed. Two new tests rigs were designed and developed: a multiple nozzle test rig and a parallel flow test rig. A main purpose of this research work was to assess the use of these new test rigs to evaluate nanofluid wear, and the ad-hoc newly proposed testing methodologies are discussed. Experimental results are presented on typical nanofluids (as 2%-volume of alumina nanopowders in 50/50 water/ethylene glycol solution, and in distilled water) which are jet-impinged (on aluminum and copper specimens) with 3.5 m/s to 15.5 m/s jet-speeds and in a 1 m/s parallel-flow (along the test specimen surface) during long test periods. The obtained surface modifications were assessed by roughness measurements, by weighing of removed-material, and by optical-microscopy. The results are presented on the observed substantially different surface modifications when same tests are conducted in aluminum and copper, and by both the base fluids and its alumina-nanofluids. The likely mechanisms of early erosion and abrasion, and the possibility of extrapolating the test-rig results and methodologies to typical cooling systems are discussed

Indirect Additive Manufacturing of Ceramics

Additive manufacturing of ceramics has gained a lot of impetus recently due to its ability to do away with the costs of machining ceramics. In this study, the feasibility of two popular methods: indirect selective laser sintering (SLS) and vat photopolymerization was studied. The focus of this research is on feedstock material preparation of these two processes. Firstly, temperature induced phase separation (TIPS) was used to prepare three different powders containing varied amounts of polyamide and alumina composite microspheres. Flowability versus sinterability of the feedstock composite powder was studied. The results showed that as the fraction of polyamide in the composite powder increased, the flowability of the powder increased, however the sinterability decreased. Inferentially, a fine balance of flowability versus sinterability must be maintained in order to produce dense crack free alumina 3D parts by indirect SLS. Secondly, vat photopolymerization was chosen to produce 3D alumina parts using the commercial vat photopolymerization printer (Nobel Superfine, XYZprinting). Four green bodies using a photopolymerizable ceramic suspension were created. All were subjected to the same parameters of thermal processing. A quantitative study of the amount of open and closed pores and their dependence on the size of the sintered parts was done. The lowest porosity was observed in the smallest cubes (5 mm). Finally, green bodies using the vat photopolymerization technique were created using three monomodal and three bimodal ceramic suspensions consisting of varying volumes of alumina particles in an in-house photopolymerizable resin. A quantitative study of the apparent solid and bulk densities of the specimens was done. The sample containing 0.3 μm particles achieved the highest density among the monomodal suspensions. The sample containing 0.3 μm & 0.8 μm particles achieved the highest density among the bimodal suspensions. This work demonstrated that adding a small amount of a finer ceramic powder as dopant to a larger sized ceramic powder significantly improved the sinterability of the green part. The promising nature of vat photopolymerization of ceramics presents great opportunities for the production of high density ceramics using a bottom-up 3D printer by optimizing the fractions of different components of a photopolymerizable ceramic suspension

Embodied Interactions for Spatial Design Ideation: Symbolic, Geometric, and Tangible Approaches

Computer interfaces are evolving from mere aids for number crunching into active partners in creative processes such as art and design. This is, to a great extent, the result of mass availability of new interaction technology such as depth sensing, sensor integration in mobile devices, and increasing computational power. We are now witnessing the emergence of maker culture that can elevate art and design beyond the purview of enterprises and professionals such as trained engineers and artists. Materializing this transformation is not trivial; everyone has ideas but only a select few can bring them to reality. The challenge is the recognition and the subsequent interpretation of human actions into design intent