Geochemical zoning and early differentiation in the moon

The volatile elements (e.g., Rb, Pb, Tl, Bi, Cs) seem to have been depleted at the time of lunar accretion. Accordingly, it may be assumed that the moon initially accreted from refractory material. The good correlation between volatile/involatile element ratios (e.g., Cs/U, K/La, K/Zr) in both highland and maria samples means that element distribution in lunar crustal rocks is not governed by volatility differences. This and other evidence encourages the view that the moon was accreted homogeneously. A consequence of homogeneous accretion theories is that very efficient large-scale element fractionation is required to account both for the high near-surface concentrations of refractory elements (e.g., Th, U, REE, Zr, Ba, etc.) and for the Ca-Al-rich crust

Nanoindentation-based mechanical spectroscopy of wood cell walls

Mechanical spectroscopy is the assessment of a mechanical index, such as the viscoelastic Young’s modulus or the plastic flow stress, across a broad spectrum of time scale, deformation rate, temperature, or moisture content. In addition to providing thorough mechanical characterization, which is useful to predict material performance over a wide range of conditions, mechanical spectroscopy also provides information about the microphysical processes which are causally linked to the properties. Recently, broadband nanoindentation creep (BNC) has been developed to measure viscoplastic properties across 4-6 decades of strain rate and broadband nanoindentation viscoelasticity (BNV) to measure viscoelastic properties across greater than 4 decades of time scale. The capabilities to perform variable-temperature BNC and BNV at temperatures between 20 and 200°C have also been developed, and the relative humidity (RH) during the test can be controlled between dry air and 95%. In validation studies on polymers, the data generated from BNC, BNV, and the more typical dynamic nanoindentation technique all agreed with conventional viscoplastic and viscoelastic measurements. Furthermore, the nanoindentation results revealed the same information about the microphysical processes causally linked to the polymer properties. Wood possesses hierarchy of structure ranging from individual wood polymers to cells to growth rings. The development of new forest products is hindered by the lack of fundamental understanding of how molecular-scale modifications affect properties of bulk wood and wood composites. Nanoindentation-based mechanical spectroscopy is well suited to probe the individual cell wall layers and provide new information about how modifications of wood polymers affect bulk wood properties. Results will be presented from BNC and dynamic nanoindentation performed on the S2 secondary wood cell walls, which are anisotropic composites consisting of semicrystalline cellulose microfibrils embedded in a matrix of hemicelluloses and lignin. Experiments were performed in multiple orientations to study anisotropic effects and over a wide range of humidity conditions. A sampling of the dynamic nanoindentation results are shown in Figure 1. The experiments were performed in the S2 secondary cell wall layer in latewood loblolly pine on a longitudinal plane, which means the stiff cellulose microfibrils were oriented perpendicular to the indentation direction. Storage modulus (Figure 1a) as a function of frequency and humidity showed over a factor of three decrease from 0% to 88% RH. Interestingly, tan delta (Figure 1b) as a function of frequency and humidity showed a peak (arrows) in value at approximately 10 s-1 in the experiments at 78% RH and 25 s-1 at 88% RH. These peaks were attributed to a moisture-induced glass transition in the hemicelluloses of the S2 secondary wood cell wall. The moisture-induced glass transition in hemicelluloses’ is of particular interest because it is hypothesized that percolated networks of softened hemicelluloses create diffusion channels for ion transport through wood cell walls. Because the fungal decay of wood requires ion transport through wood cell walls, a chemical treatment that prevents the hemicelluloses’ glass transition may also be an effective non-toxic wood treatment to protect wood products against decay. Nanoindentation-based mechanical spectroscopy can now be used as a tool in wood science research to study the effects of chemical modifications on the moisture-induced glass transition in hemicelluloses

Success Strategies of Small Business Owners

In the United States, 20% of newly established small businesses, including small businesses in the life insurance industry, fail within 2 years, and over 50% of them fail during the first 5 years. The purpose of this multiple case study was to identify and explore the strategies that life insurance brokerage owners use to sustain business operations beyond 5 years. Porter\u27s 5 forces model served as the conceptual framework for exploring this subject matter. Owners of 3 separate small life insurance brokerage firms in Texas, who sustained their businesses beyond 5 years, participated in semistructured interviews. A secondary source of data was relevant company documents. Methodological triangulation and member checking assured the reliability and validity of the interpretations. Through thematic analysis and supporting software, 5 themes emerged: exceptional customer service, relationship-building, efficient promotional strategies, regular training of salespersons, and hiring the right employees. The application of the findings of the study could contribute to positive social change by reducing unemployment and thereby catalyzing an economic environment supporting employees, families, and communities