MRI: Acquisition of a SQUID Magnetometer for Analysis of Advanced Materials

Technical Summary: Superconducting quantum interference device (SQUID) magnetometry is a non-destructive technique that reveals detailed information about the electron spin interactions in many types of materials. This project will involve a state-of-the-art SQUID magnetometer and Magnetic Property Measurement System (MPMS), which is a critical tool for characterizing several types of materials currently being investigated by researchers within the Laboratory for Surface Science & Technology (LASST) and other University of Maine (UMaine) laboratories. Specific measurement capabilities include DC and AC magnetic susceptibility, magnetoresistivity, van der Paaw conductivity, and Hall mobility. State-of-the-art MPMS capabilities will be especially valuable to several research programs at UMaine pertaining to (i) surface magnetism in nanoparticles, (ii) magnetic anisotropies in sedimentary rocks, (iii) electrical transport in physical and chemical sensing devices, (iv) optical properties of nanostructures in high magnetic fields, and (v) magnetic nanoparticle based biosensors. The MPMS will serve as a focal point for training undergraduates, graduate students, postdocs, and visiting scientists in magnetic materials, nanotechnology, biophysics, and materials science. This instrument is a critical tool for expanding the capacity of UMaine research into magnetic aspects of nanotechnology, biophysics, sensor technology, and materials science. As no SQUID magnetometer currently exists in the State of Maine, the instrumentation will provide access for research projects from interested parties throughout the state, including non-Ph.D. granting institutions and small Maine businesses. The instrument is relatively easy to operate and provides direct information on electron spin interactions, and thus it will be a powerful tool to teach physics and nanotechnology concepts to several different constituents participating in UMaine outreach activities, including K-12 students and teachers, the general public, under-represented groups, and industry partners.Layman Summary: Superconducting quantum interference device (SQUID) magnetometry is a non-destructive technique that reveals detailed information about the electron spin interactions in many types of materials. Knowledge of electron interactions in materials is extremely important in building the next generation of computers, electronics, and contrast agents in biological magnetic screening techniques (i.e. MRI). To gain the necessary information, a system with control over both the magnetic field strength and temperature is critical. To this end, a SQUID/Magnetic Property Measurement System (MPMS) is ideal for these measurements. This project will purchase a state-of-the-art MPMS system and will be especially valuable to several research programs at UMaine pertaining to surface magnetism in nanoparticles, magnetic anisotropies in sedimentary rocks, electrical transport in physical and chemical sensing devices, and magnetic nanoparticle based biosensors. The proposed MPMS will serve as a focal point for training undergraduates, graduate students, postdocs, and visiting scientists in magnetic materials, nanotechnology, biophysics, and materials science. As no SQUID magnetometer currently exists in the State of Maine, the instrumentation will provide access for research projects from interested parties throughout the state, including non-Ph.D. granting institutions and small Maine businesses. The instrument is relatively easy to operate and provides direct information on electron spin interactions, and thus it will be a powerful tool to teach physics and nanotechnology concepts to several different constituents participating in UMaine outreach activities, including K-12 students and teachers, the general public, under-represented groups, and industry partners

Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers

Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed

Designer Reagents for Mass Spectrometry-Based Proteomics: Clickable Cross-Linkers for Elucidation of Protein Structures and Interactions

We present novel homobifunctional amine-reactive clickable cross-linkers (CXLs) for investigation of three-dimensional protein structures and protein–protein interactions (PPIs). CXLs afford consolidated advantages not previously available in a simple cross-linker, including (1) their small size and cationic nature at physiological pH, resulting in good water solubility and cell-permeability, (2) an alkyne group for bio-orthogonal conjugation to affinity tags via the click reaction for enrichment of cross-linked peptides, (3) a nucleophilic displacement reaction involving the 1,2,3-triazole ring formed in the click reaction, yielding a lock-mass reporter ion for only clicked peptides, and (4) higher charge states of cross-linked peptides in the gas-phase for augmented electron transfer dissociation (ETD) yields. Ubiquitin, a lysine-abundant protein, is used as a model system to demonstrate structural studies using CXLs. To validate the sensitivity of our approach, biotin-azide labeling and subsequent enrichment of cross-linked peptides are performed for cross-linked ubiquitin digests mixed with yeast cell lysates. Cross-linked peptides are detected and identified by collision induced dissociation (CID) and ETD with linear quadrupole ion trap (LTQ)-Fourier transform ion cyclotron resonance (FTICR) and LTQ-Orbitrap mass spectrometers. The application of CXLs to more complex systems (e.g., in vivo cross-linking) is illustrated by Western blot detection of Cul1 complexes including known binders, Cand1 and Skp2, in HEK 293 cells, confirming good water solubility and cell-permeability

A Self-Consistent Microscopic Theory of Surface Superconductivity

The electronic structure of the superconducting surface sheath in a type-II superconductor in magnetic fields $H_{c2}<H<H_{c3}$ is calculated self-consistently using the Bogoliubov-de Gennes equations. We find that the pair potential $\Delta(x)$ exhibits pronounced Friedel oscillations near the surface, in marked contrast with the results of Ginzburg-Landau theory. The role of magnetic edge states is emphasized. The local density of states near the surface shows a significant depletion near the Fermi energy due to the development of local superconducting order. We suggest that this structure could be unveiled by scanning-tunneling microscopy studies performed near the edge of a superconducting sample.Comment: 12 pages, Revtex 3.0, 3 postscript figures appende

Catalysts for long-life closed-cycle CO2 lasers

Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin (IV) oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-LaRC on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) achievement of 98% to 100% conversion of a stoichiometric mixture of CO and O2 to CO2 for 318 hours (greater than 1 x 10 to the 6th power seconds), continuous, at a catalyst temperature of 60 C, and (2) development of a technique verified in a 30-hour test, to prevent isotopic scrambling when CO-18 and O-18(2) are reacted in the presence of a common-isotope Pt/Sn O-16(2) catalyst

A preliminary assessment of the state of harvest and collection technology for forest residues

To meet the 'Twenty in Ten Initiative' goals set in the 2007 State of the Union address, forest resources will be needed as feedstocks for lignocellulosic ethanol production. It has been estimated that 368 million dry tons can be produced annually in the U.S. from logging residues and fuel treatment thinnings. Currently, very little of this woody biomass is used for energy production due to the costs and difficulty in collecting and transporting this material. However, minimizing biomass costs (including harvest, handling, transport, storage, and processing costs) delivered to the refinery is necessary to develop a sustainable cellulosic ethanol industry. Achieving this goal requires a fresh look at conventional timber harvesting operations to identify ways of efficiently integrating energy wood collection and developing cost-effective technologies to harvest small-diameter trees. In conventional whole-tree logging operations, entire trees are felled and skidded from the stump to the landing. The residues (also called slash), consisting of tops and limbs, accumulate at the landing when trees are delimbed. This slash can be ground at the landing with a mobile grinder or transported to another central location with a stationary grinder. The ground material is transported via chip vans, or possibly large roll on/off containers, to the user facility. Cut-to-length harvesting systems are gaining popularity in some locations. In these operations, specialized harvesters that can fall, delimb, and cut logs to length are used. The small diameter tops and limbs accumulate along the machine's track. It can be left in the forest to dry or removed soon after harvest while logs are extracted. Removing slash during the same operation as the wood has been shown to be more efficient. However, leaving residue in the forest to dry reduces moisture content, which improves grinder performance, reduces dry matter loss during storage, and inhibits colonization of fungi that produce harmful spores. In recent years, new machines that are specially designed for collection of small diameter wood have been developed in the U.S. and Europe. Residue bundlers and balers improve transportation and handling efficiency by densifying the material and packaging it so that it can be handled with conventional equipment. An experimental integrated harvester/grinder can fall small diameter trees and feed them into a grinder. The ground material is collected in a bin that can be dumped into a chip van. The harvester head is also capable of delimbing and bucking (cut into sections) small timber to be used for pulp and posts. Limitations of these new technologies are their large capital costs and complexity, leading to high maintenance costs and the need for highly trained operators. To ensure that quality feedstock materials consistently enter the mouth of the refinery, the uniform format supply system concept proposes that feedstock diversity be managed at harvest, much like the current grain supply system. This allows for standardization of key infrastructure components and facilitation of a biomass commodity system. Challenges in achieving a uniform woody biomass supply include, but are not limited to, developing machines for efficient harvest of small-diameter trees in a range of topographies and conditions, developing machines and operating plans for grinding biomass as near to the stump as possible, developing cost-effective drying strategies to reduce losses and mold growth during wood chip storage, and quantifying environmental impacts of slash removal and fuel thinnings to aid landowner decisions and policy development

Reactivation of a tin oxide-containing catalyst

A method for the reactivation of a tin oxide-containing catalyst of a CO.sub.2 laser is provided. First, the catalyst is pretreated by a standard procedure. When the catalyst experiences diminished activity during usage, the heated zone surrounding the catalyst is raised to a temperature which is the operating temperature of the laser and 400.degree. C. for approximately one hour. The catalyst is exposed to the same laser gas mixture during this period. The temperature of the heated zone is then lowered to the operating temperature of the CO.sub.2 laser

Identification and characterization of a spontaneous ovarian carcinoma in Lewis rats

<p>Abstract</p> <p>Background</p> <p>Ovarian carcinoma is the fourth most common cause of death from cancer in women. Limited progress has been made toward improving the survival rate of patients with this disease in part because of the lack of a good animal model. We present here a model of spontaneous ovarian carcinoma arising in a normal Lewis rat.</p> <p>Methods</p> <p>A spontaneously occurring tumor of the left ovary was found in a normal Lewis rat during necropsy, which was sectioned for histological examination and placed into single cell suspension. Tumor cells were passaged <it>in vivo </it>by intraperitoneal injection into immunocompetent Lewis rats, and <it>in vitro </it>culture resulted in generation of a cell line. Tumor cells were examined by flow cytometry for expression of estrogen receptor α, progesterone receptor, androgen receptor, her-2/neu, epithelial cell adhesion molecule, and CA125. β-catenin expression and cellular localization was assessed by immunocytochemistry. RNA was harvested for gene expression profiling and studying the expression of cytokines.</p> <p>Results</p> <p>The tumor, designated FNAR, could be serially transplanted into Lewis rats and propagated as a cell line <it>in vitro</it>, maintaining the properties of the original tumor. The FNAR cells displayed striking morphologic similarities to human ovarian carcinoma, resembling the endometrioid carcinoma subtype of surface epithelial neoplasms. The cells expressed estrogen receptor α, progesterone receptor, androgen receptor, her-2/neu, epithelial cell adhesion molecule, CA125, and nuclear β-catenin. A gene expression profile showed upregulation of a number of genes that are also upregulated in human ovarian carcinoma.</p> <p>Conclusion</p> <p>This reliable model of ovarian carcinoma should be helpful in better understanding the biology of the disease as well as the development of novel treatment strategies.</p

Off-axis vortices in trapped Bose condensed gases: angular momentum and frequency splitting

We consider non centered vortices and their arrays in a cylindrically trapped Bose-Einstein condensate at zero temperature. We study the kinetic energy and the angular momentum per particle in the Thomas Fermi regime and their dependence on the distance of the vortices from the center of the trap. Using a perturbative approach with respect to the velocity-field of the vortices, we calculate to first order the frequency shift of the collective low-lying excitations due to the presence of an off-center vortex or a vortex array, and compare these results with predictions which would be obtained by the application of a simple sum-rule approach, previously found to be very successful for centered vortices. It turns out that the simple sum-rule approach fails for off-centered vortices.Comment: 11 pages, LaTeX, 3 figures. Perturbative approach adde

Glueballs in a Hamiltonian Light-Front Approach to Pure-Glue QCD

We calculate a renormalized Hamiltonian for pure-glue QCD and diagonalize it. The renormalization procedure is designed to produce a Hamiltonian that will yield physical states that rapidly converge in an expansion in free-particle Fock-space sectors. To make this possible, we use light-front field theory to isolate vacuum effects, and we place a smooth cutoff on the Hamiltonian to force its free-state matrix elements to quickly decrease as the difference of the free masses of the states increases. The cutoff violates a number of physical principles of light-front pure-glue QCD, including Lorentz covariance and gauge covariance. This means that the operators in the Hamiltonian are not required to respect these physical principles. However, by requiring the Hamiltonian to produce cutoff-independent physical quantities and by requiring it to respect the unviolated physical principles of pure-glue QCD, we are able to derive recursion relations that define the Hamiltonian to all orders in perturbation theory in terms of the running coupling. We approximate all physical states as two-gluon states, and use our recursion relations to calculate to second order the part of the Hamiltonian that is required to compute the spectrum. We diagonalize the Hamiltonian using basis-function expansions for the gluons' color, spin, and momentum degrees of freedom. We examine the sensitivity of our results to the cutoff and use them to analyze the nonperturbative scale dependence of the coupling. We investigate the effect of the dynamical rotational symmetry of light-front field theory on the rotational degeneracies of the spectrum and compare the spectrum to recent lattice results. Finally, we examine our wave functions and analyze the various sources of error in our calculation.Comment: 75 pages, 17 figures, 1 tabl