Hot-pressing behaviour of silicon carbide powders with additions of aluminium oxide

The hot-pressing behaviour of different silicon carbide powders (average particle sizes ranging from ～ 0.5 to 9 μm) with aluminium oxide additions ranging from 0.01 to 0.15 volume fractions was investigated. Using powders with an average particle size < 3 μm, densities ≥ 99% theoretical could be achieved at 1950° C (1 h) with 28 MN m^?2 for volume fractions of AI₂O₃ \(\bar > \) 0.02. A liquid phase forms at high temperatures which dissolves the silicon carbide particles to promote densification by a solution-reprecipitation mechanism.     

Sleeping Beauties in Psychology: Comparisons of "Hits" and "Missed Signals" in Psychological Journals.

Scientific publications tend to be forgotten quickly. A few works, however, are still cited 100 years and more after their publication. The author used bibliometric methods to compare "hits" (works noticed by the scientific community soon after their publication) with "missed signals" (works that went unnoticed until much later) by investigating 2 psychological journals founded in the 1890s: Zeitschrift für Psychologie and Psychological Review. All articles that were published in either of these journals up to 1920 and cited more than 25 times in the Web of Science up to the year 2000 were considered for inclusion in the analysis. It emerged that hits corresponded more closely to the focus of scientific attention at the time of publication than missed signals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vortex Matter in Superconductor / Ferromagnet Hybrids

No Heading Vortex pinning in type-II superconducting films can be effectively controlled by combining these films with different ferromagnetic nanostructures. In this article an overview is presented of divergent types of ferromagnetic pinning centers. The investigated hybrid structures consist of Pb films that are deposited on top of arrays of ferromagnetic dots with in-plane magnetization (IPM) or out-of-plane magnetization (OPM), ferromagnetic films with IPM or OPM that contain arrays of submicron holes (antidots), or continuous films with OPM and a magnetic domain structure. Interesting effects such as field-polarity dependent vortex pinning and the dependence of the pinning strength on the domain structure of the ferromagnet are observed. Our experiments demonstrate that vortex pinning in superconductors is strongly influenced by the magnetic properties of the different ferromagnetic pinning centers.PACS numbers: 74.25.Qt, 74.25.Ha, 74.78.Na     

Vortex matter in superconductor/ferromagnet hybrids

Vortex pinning in type-II superconducting films can be effectively controlled by combining these films with different ferromagnetic nanostructures. In this article an overview is presented of different types of ferromagnetic pinning centers. The investigated hybrid structures consist of Pb films that are deposited on top of arrays of ferromagnetic dots with in-plane magnetization (IMP) or out-of-plane magnetization (OPM), ferromagnetic films with IPM or OPM that contain arrays of submicron holes (antidots), or continuous films with OPM and a magnetic domain structure. Interesting effects such as field-polarity dependent vortex pinning and the dependence of the pinning strength on the domain structure of the ferromagnet are observed. Our experiments demonstrate that vortex pinning in superconductors is strongly influenced by the magnetic properties of the different ferromagnetic pinning centers.     

Compression pre-cracking to generate near threshold fatigue-crack-growth rates in two aluminum alloys

A test program was conducted to generate threshold and near-threshold data on two aluminum alloys: 2324-T39 and 7075-T7351, using compression pre-cracking constant-amplitude (CPCA) threshold testing procedures. Compact tension specimens were tested under stress ratios (R) of 0.1, 0.4, 0.7 or 0.8. Results were compared with either existing load-reduction data from the literature or with data that were generated using the load-reduction procedures. On the 2324 alloy, very little difference was observed between the load-reduction and CPCA test methods, although the CPCA test method consistently produced slightly lower thresholds or slightly faster crack-growth rates. But on the 2324 alloy, most of the load-reduction tests used extremely low initial ΔK values to grow the cracks under load reduction, which may explain the reason for the agreement. These low ΔK values were achieved by using compression pre-cracking to initiate a crack at the crack-starter notch. In contrast, the 7075 alloy showed very large differences between the CPCA and load-reduction results in the near-threshold and threshold regimes for R=0.1 and 0.4. Results under high R conditions (R=0.7) agreed very well between the two threshold test methods. An expression was also developed to generate fatigue-crack-growth-rate data using the CPCA threshold test method that would be unaffected by compressive yielding at the crack-starter notch and produce ‘steady-state’ constant-amplitude data in the near threshold regime.     

Parents' Personality and Infants' Temperament as Contributors to Their Emerging Relationship.

The authors examined the contributions of infant's temperament and parent's personality to their relationship. In Study 1, 102 infants, mothers, and fathers were studied when infants were 7 months; in Study 2, 112 infants and mothers were followed from 9 to 45 months. Infants' temperament (joy, fear, anger, and attention) was observed in standard temperament paradigms. Parents' personality measures encompassed the Big Five traits and Empathy in Study 1 and Mistrust, Manipulativeness, Aggression, Dependency, Entitlement, and Workaholism in Study 2. Parent-child relationship (shared positive affect and parental responsiveness in Studies 1 and 2 and parental tracking of the infant in Study 1) was observed in naturalistic contexts. In Study 1, mothers' Neuroticism, Empathy, and Conscientiousness and fathers' Agreeableness, Openness, and Extraversion related to the relationship with the infants. All measures of infant temperament also related to the emerging relationship. In Study 2, maternal Mistrust, Manipulativeness, Dependency, and Workaholism predicted the relationship with the child. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vacancy island creation and coalescence using automated scanning tunneling microscopy

We demonstrate that scanning tunneling microscope tip-surface crash events can be utilized as an efficient means for the creation of predefined island configurations for diffusion studies. Using this method, islands of varying size can be created and placed in close proximity, increasing the probability of initiating and observing coalescence events. Data obtained from crash initiated events on a Ag(111) surface are presented. Relaxation time exponents extracted from these data confirm that our method gives results consistent with previous, sputter-obtained island coalescence studies. We also describe an instrument-control routine developed for these measurements that utilizes commercial imaging and off-the-shelf automation software to automate the tracking of islands or other features by the microscope.     

Fusion: Expensive and Taking Forever?

The road map of fusion power is compared to the development and deployment of other energy technologies. A generic deployment model is presented, which describes the fastest deployment (of any new technology) achievable with the constraint that the industrial capacity that needs to be built up must be continuous and should not overshoot the replacement market in the final, saturated state. It is shown that the development needs an ‘investment’ phase to build up industrial capacity which takes several decades, during which growth is typically exponential, but net energy production is negligible. During the exponential growth the cost is dominated by the capital investment, which allows for a simple comparison of different energy technologies. Fusion is at the start of the exponential growth phase, while still having significant uncertainties concerning its technical feasibility. In comparison to e.g. solar PV and wind, fusion is ‘late’, lagging by some 50 years. To follow the same rate of development that fission, wind and PV have shown, fusion will need to have 3 DEMO reactors operational in the early 2050s, followed by 10 generation one (GEN1) plants in the early 2060s and 100 GEN2 plants in the early 2070s. For the cost development to be comparable, an estimated allowable cost for one DEMO reactor is ~20 G$. While these indicative numbers for the pace and cost of development are very challenging but perhaps not unthinkable for fusion, this analysis does point towards an emphasis on ‘simpler and cheaper’ reactor designs.     

Anion structural effects on interaction of rare earth element ions with Dowex 50W X8 cation exchange resin

The effect of the anion in the original rare earth element(REE) solution on the reversible ion exchange of Ce nitrate and Ce sulfate with the Dowex 50 W X8 was investigated using attenuated total reflection infrared(ATR-IR) spectroscopy, continuous flow reactor studies coupled with inductively coupled plasma mass spectroscopy(ICP-MS), and density functional theory(DFT). The simulated IR spectrum at the DFT B3 LYP/6-31 G(d) level was compared to the experimental results to characterize the IR spectrum, molecular interactions, and bonding of the ion exchanged species. The continuous liquid flow reactor studies show a capacity of 0.72 mmol/g sorbent for the Ce nitrateand 0.96 mmol/g sorbent for the Ce sulfate with the Dowex 50 W X8. The flow reactor studies reveal the type of solute anion(SO_4~((2-)) or NO_3~((-))) associated with the REE during cation exchange significantly affects the sorption capacity of the Dowex 50 W X8 ion exchange resin. The calculated REE binding energy(BE) and the DFT optimized structures suggest that the differences in sorption capacity is the result of the formation of different types of partially ionexchanged Ce_2~((3+))2 SO_4~((2-)) and Ce~((3+)) 3 NO_3~((-)). These results suggest that the solute anion affects the equilibrium constants of the Dowex resin by the formation of a charged layer capable of retaining the counterion. Modifying the sulfonic acid site(H+) in the Dowex 50 W X8 with the NH_4~+ counterion does not affect the sorption capacity and retention times of the Ce nitrate and Ce sulfate species. These results suggest that the counterions and co-ions having a finite size, may limit access to the Dowex sulfonate active site where the type of REE cation as a nitrate or sulfate in solution may significantly modify the sorption capacity of the ion exchange resin. Similar results are obtained during sorption with nitrates and sulfates of Sm and Yb.     

PCL Nanopillars Versus Nanofibers: A Contrast in Progenitor Cell Morphology,Proliferation, and Fate Determination

The role of nanotopography on the long‐term response of progenitor cells is explored using polycaprolactone (PCL) nanopillar and nanofiber surfaces seeded with plastic‐adherent rat multipotent mesenchymal stromal cells (MSCs). After 4 weeks in culture under normal expansion media conditions, MSCs cultured on nanofibers exhibit better adherence, increased proliferation, and maintain increasingly dense fibroblast‐like morphologies. In contrast, MSCs seeded on nanopillar surfaces display lowered adherence, reduced proliferation, and adopt highly elongated cellular morphologies. Immunofluorescent staining of MSCs on PCL nanopillars reveals the presence of two bone marker proteins, osteopontin and osteocalcin, providing evidence for surface induced differentiation into osteoblast‐like cells. Unlike the nanopillar topography, MSCs cultured on nanofiber and smooth PCL surfaces did not appear to undergo osteogenesis. Observed differences in cellular response to the PCL nanotopographies offer strategies to direct progenitor cell populations solely based upon submicron surface modifications. This study provides a foundation for future work exploring variations in PCL nanopillar topography with the goal of optimizing adherence and osteogenic response of MSCs.