An Empirical Testing of the Economic Base Theory

Most central cities must at present bargain with other units of their regions and the nation for the residents and industry they need; and their bargaining power is so weak as to threaten their viability unless aid from state and federal governments is supplied. Both in order to serve the disadvantaged residents they do attract, and to cultivate their attractiveness to other residents and to industry, cities must re-define “urban renewal” as consisting of large investments in the development of human, land, and transportation potentialities. Such investments must, as all investments, come from “surpluses” which are controlled by the states and the nation, not the cities.     

Effect of composition on the matrix transformation of the Co-Re-Cr-Ta-C alloys

Neutron diffraction measurement was performed in-situ at high temperatures on Co-Re-Ta-C alloys with and without Cr addition. This included alloys containing different C content with the C/Ta ratio varying between 0.5 and 1.0. The Co-Re-solid solution matrix of the experimental alloys is polymorphic (like in pure cobalt) and transformed from low temperature hexagonal ? phase to high temperature cubic γ phase on heating. This transformation is reversible and show hysteresis. The main alloying addition, Re, stabilizes the ? Co-phase and increases the transformation temperature to above 1273 K. The onset of the \(\varepsilon \rightleftharpoons \gamma\) transformation during heating and cooling was found to differ depending on the alloy composition. In alloys without Cr addition the transformation was not completed on cooling and the high temperature γ phase was partly retained at room temperature in metastable state with the amount depending on the cooling rate from high temperature. The diffraction and microstructural results showed that Cr is ? stabilizer (similar as Re) but the role of Ta is not clear. The C/Ta ratio has no direct effect on the matrix phase transformation. Nevertheless, it influences indirectly by determining the amount of Ta which is freely available in the matrix.     

Molecular Weight Patterns of Nägeli Amylodextrins

This research was designed to assess the utility of a four-column high performance size-exclusion chromatography (HPSEC) system to characterize starch-based carbohydrates of different sizes. Corn starches with varying amounts of amylose were treated with 16% sulfuric acid to create Nägeli amylodextrins. During treatment, sub-samples were taken at various intervals from 0–100 days. The washed, dried sub-samples were chromatographically analyzed using four Shodex lonpak columns linked in series. Chromatograms showed the progressive depolymerization of starch. Pullulan molecular weight standards were used to estimate amylodextrin molecular weights (MW). Number-average MWs of amylodextrins decreased as the original starches' amylopectin content decreased. A single HPSEC system can be effectively used to characterize carbohydrates ranging in size from starch to amylodextrins; and to monitor the acid (or enzyme) depolymerization of starches.     

Genetic Deficiency and Pharmacological Stabilization of Mast Cells Ameliorate Pressure Overload-Induced Maladaptive Right Ventricular Remodeling in Mice

Although the response of the right ventricle (RV) to the increased afterload is an important determinant of the patient outcome, very little is known about the underlying mechanisms. Mast cells have been implicated in the pathogenesis of left ventricular maladaptive remodeling and failure. However, the role of mast cells in RV remodeling remains unexplored. We subjected mast cell-deficient WBB6F1-KitW/W-v (Kit^W/Kit^W-v) mice and their mast cell-sufficient littermate controls (MC^+/+) to pulmonary artery banding (PAB). PAB led to RV dilatation, extensive myocardial fibrosis, and RV dysfunction in MC^+/+ mice. In PAB Kit^W/Kit^W-v mice, RV remodeling was characterized by minimal RV chamber dilatation and preserved RV function. We further administered to C57Bl/6J mice either placebo or cromolyn treatment starting from day 1 or 7 days after PAB surgery to test whether mast cells stabilizing drugs can prevent or reverse maladaptive RV remodeling. Both preventive and therapeutic cromolyn applications significantly attenuated RV dilatation and improved RV function. Our study establishes a previously undescribed role of mast cells in pressure overload-induced adverse RV remodeling. Mast cells may thus represent an interesting target for the development of a new therapeutic approach directed specifically at the heart.     

Molecular hydrogen and spiltover hydrogen storage on high surface area carbon sorbents

A series of templated carbons with various high surface areas (2033–3798 m²/g) have been prepared using various microporous zeolites as hard templates. Molecular hydrogen storage and spiltover hydrogen storage on these templated carbons were investigated and compared with superactivated carbon AX-21 and other reported porous carbon sorbents at 298 K and 100 atm. Two relationships between the surface areas of these carbons and their hydrogen capacities were obtained. The relationship between molecular hydrogen capacity and surface area showed a 0.23 wt.% H₂/1000 m²/g of carbon sorbent at 298 K and 100 atm, indicating that merely increasing surface areas of the carbon sorbents cannot achieve a significant molecular hydrogen capacity at ambient temperature. Spiltover hydrogen storage was achieved by doping Pt nanoparticles (as dissociative hydrogen source) on these carbons (spiltover hydrogen receptor). Our first result on the relationship between the spiltover hydrogen capacity and surface area showed 0.4 wt.% H₂/1000 m²/g of carbon sorbent at 298 K and 100 atm, which indicated that storage via spillover can lead to an average of 70% enhancement compared to molecular hydrogen storage.     

The effect of physiologically relevant additives on the rheological properties of concentrated Pluronic copolymer gels

The high concentration triblock copolymer poly(ethylene oxide)₉₉-poly(propylene oxide)₆₉-poly(ethylene oxide)₉₉ (Pluronic F127) aqueous solutions with the addition of different components commonly used in physiologically relevant applications were characterized by rheological measurements, differential scanning calorimetry (DSC) and small angle X-ray/neutron scattering. The sol-gel transition temperature, as well as the storage modulus of the F127 solution depend both on the concentration of polymer and of clay. Above the gel transition, the storage modulus of the solutions increased with clay concentration. Yield strain is independent of polymer and clay concentrations. Two different kinds of inorganic salts, sodium chloride (NaCl) and calcium chloride (CaCl₂) were added into the polymer and polymer-clay solutions. The sol-gel transition temperature decreased noticeably, but the storage modulus decreased only a small amount with increasing concentration of inorganic salts. Addition of salts to polymer-clay solutions resulted in precipitation of the clays which decreased the modulus. No effect on the mechanical properties was observed with the addition of common serum proteins. However, addition of 0.5-10% glucose decreased the transition temperature between 3° and 7°, without significantly affecting the modulus. The depression of the transition temperature by glucose was similar to that found with salts and indicated that the mechanism, namely competition for water, may be similar.     

Thermophysical Properties of ZrB2 and ZrB2–SiC Ceramics

Thermophysical properties were investigated for zirconium diboride (ZrB₂) and ZrB₂–30 vol% silicon carbide (SiC) ceramics. Thermal conductivities were calculated from measured thermal diffusivities, heat capacities, and densities. The thermal conductivity of ZrB₂ increased from 56 W (m K)⁻¹ at room temperature to 67 W (m K)⁻¹ at 1675 K, whereas the thermal conductivity of ZrB₂–SiC decreased from 62 to 56 W (m K)⁻¹ over the same temperature range. Electron and phonon contributions to thermal conductivity were determined using electrical resistivity measurements and were used, along with grain size models, to explain the observed trends. The results are compared with previously reported thermal conductivities for ZrB₂ and ZrB₂–SiC.     

Ta2O5/Nb2O5 and Y2O3 Co-doped Zirconias for Thermal Barrier Coatings

Zirconia doped with 3.2–4.2 mol% (6–8 wt%) yttria (3–4YSZ) is currently the material of choice for thermal barrier coating topcoats. The present study examines the ZrO₂-Y₂O₃-Ta₂O₅/Nb₂O₅ systems for potential alternative chemistries that would overcome the limitations of the 3–4YSZ. A rationale for choosing specific compositions based on the effect of defect chemistry on the thermal conductivity and phase stability in zirconia-based systems is presented. The results show that it is possible to produce stable (for up to 200 h at 1000°–1500°C), single (tetragonal) or dual (tetragonal + cubic) phase chemistries that have thermal conductivity that is as low (1.8–2.8W/m K) as the 3–4YSZ, a wide range of elastic moduli (150–232 GPa), and a similar mean coefficient of thermal expansion at 1000°C. The chemistries can be plasma sprayed without change in composition or deleterious effects to phase stability. Preliminary burner rig testing results on one of the compositions are also presented.