The Narragansett Dawn

A newsletter edited by Princess Redwing and Ernest Hazard and published by the Narragansett Tribe of Indians in 1935 and 1936. It includes short articles by a variety of writers on the culture, history, and politics of the Narragansett Indians. It also includes religious and poetic writing, lessons in the Narragansett language, advice from community leaders, and a milestones section documenting births, deaths, and other life transitions

Thickness dependence of the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition

We have studied the effect of deposition rate and layer thickness on the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition on 4H-SiC substrates. The MgB2 film deposition rate depends linearly on the concentration of B2H6 in the inlet gas mixture. We found that the superconducting and normal-state properties of the MgB2 films are determined by the film thickness, not by the deposition rate. When the film thickness was increased, the transition temperature, Tc, increased and the residual resistivity, rho0, decreased. Above about 300 nm, a Tc of 41.8 K, a rho0 of 0.28 mikroOhm.cm, and a residual resistance ratio RRR of over 30 were obtained. These values represent the best MgB2 properties reported thus far.Comment: 10 pages, 4 figure

Critical Current Density and Resistivity of MgB2 Films

The high resistivity of many bulk and film samples of MgB2 is most readily explained by the suggestion that only a fraction of the cross-sectional area of the samples is effectively carrying current. Hence the supercurrent (Jc) in such samples will be limited by the same area factor, arising for example from porosity or from insulating oxides present at the grain boundaries. We suggest that a correlation should exist, Jc ~ 1/{Rho(300K) - Rho(50K)}, where Rho(300K) - Rho(50K) is the change in the apparent resistivity from 300 K to 50 K. We report measurements of Rho(T) and Jc for a number of films made by hybrid physical-chemical vapor deposition which demonstrate this correlation, although the "reduced effective area" argument alone is not sufficient. We suggest that this argument can also apply to many polycrystalline bulk and wire samples of MgB2.Comment: 11 pages, 3 figure

Assessing computational methods and science policy in systems biology

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2009.Includes bibliographical references (p. 109-112).In this thesis, I discuss the development of systems biology and issues in the progression of this science discipline. Traditional molecular biology has been driven by reductionism with the belief that breaking down a biological system into the fundamental biomolecular components will elucidate such phenomena. We have reached limitations with this approach due to the complex and dynamical nature of life and our inability to intuit biological behavior from a modular perspective [37]. Mathematical modeling has been integral to current system biology endeavors since detailed analysis would be invasive if performed on humans experimentally or in clinical trials [17]. The interspecies commonalities in systemic properties and molecular mechanisms suggests that certain behaviors transcend specie differentiation and therefore easily lend to generalizing from simpler organisms to more complex organisms such as humans [7, 17]. Current methodologies in mathematical modeling and analysis have been diverse and numerous, with no standardization to progress the discipline in a collaborative manner. Without collaboration during this formative period, successful development and application of systems biology for societal welfare may be at risk. Furthermore, such collaboration has to be standardized in a fundamental approach to discover generic principles, in the manner of preceding long-standing science disciplines. This study effectively implements and analyzes a mathematical model of a three-protein biochemical network, the Synechococcus elongatus circadian clock.(cont.) I use mass action theory expressed in kronecker products to exploit the ability to apply numerical methods-including sensitivity analysis via boundary value formulation (BVP) and trapiezoidal integration rule-and experimental techniques-including partial reaction fitting and enzyme-driven activations-when mathematically modeling large-scale biochemical networks. Amidst other applicable methodologies, my approach is grounded in the law of mass action because it is based in experimental data and biomolecular mechanistic properties, yet provides predictive power in the complete delineation of the biological system dynamics for all future time points. The results of my research demonstrate the holistic approach that mass action method-ologies have in determining emergent properties of biological systems. I further stress the necessity to enforce collaboration and standardization in future policymaking, with reconsiderations on current stakeholder incentive to redirect academia and industry focus from new molecular entities to interests in holistic understanding of the complexities and dynamics of life entities. Such redirection away from reductionism could further progress basic and applied scientific research to embetter our circumstances through new treatments and preventive measures for health, and development of new strains and disease control in agriculture and ecology [13].by Andrea R. Castillo.S.M.in Technology and Polic

Capacitance–voltage characterization of AlN/GaN metal–insulator–semiconductor structures grown on sapphire substrate by metalorganic chemical vapor deposition

Electrical characterization of AlN/GaN interfaces was carried out by the capacitance–voltage (C–V)(C–V) technique in materials grown by metalorganic chemical vapor deposition. The high-frequency C–VC–V characteristics showed clear deep-depletion behavior at room temperature, and the doping density derived from the slope of 1/C21/C2 plots under the deep depletion condition agreed well with the growth design parameters. A low value of interface state density DitDit of 1×1011 cm−2 eV−11×1011 cm−2 eV−1 or less around the energy position of Ec−0.8 eVEc−0.8 eV was demonstrated, in agreement with an average DitDit value estimated from photoassisted C–VC–V characteristics. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70376/2/JAPIAU-88-4-1983-1.pd

Photoelectrochemistry of Semiconductor Nanowire Arrays

This project supported research on the growth and photoelectrochemical characterization of semiconductor nanowire arrays, and on the development of catalytic materials for visible light water splitting to produce hydrogen and oxygen. Silicon nanowires were grown in the pores of anodic aluminum oxide films by the vapor-liquid-solid technique and were characterized electrochemically. Because adventitious doping from the membrane led to high dark currents, silicon nanowire arrays were then grown on silicon substrates. The dependence of the dark current and photovoltage on preparation techniques, wire diameter, and defect density was studied for both p-silicon and p-indium phosphide nanowire arrays. The open circuit photovoltage of liquid junction cells increased with increasing wire diameter, reaching 350 mV for micron-diameter silicon wires. Liquid junction and radial p-n junction solar cells were fabricated from silicon nano- and microwire arrays and tested. Iridium oxide cluster catalysts stabilized by bidentate malonate and succinate ligands were also made and studied for the water oxidation reaction. Highlights of this project included the first papers on silicon and indium phosphide nanowire solar cells, and a new procedure for making ligand-stabilized water oxidation catalysts that can be covalently linked to molecular photosensitizers or electrode surfaces

FDTD modeling of solar energy absorption in silicon branched nanowires

Thin film nanostructured photovoltaic cells are increasing in efficiency and decreasing the cost of solar energy. FDTD modeling of branched nanowire ‘forests’ are shown to have improved optical absorption in the visible and near-IR spectra over nanowire arrays alone, with a factor of 5 enhancement available at 1000 nm. Alternate BNW tree configurations are presented, achieving a maximum absorption of over 95% at 500 nm