Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects (open access)

Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects

This report summarizes the work done during the eighth quarter of the project.
Date: January 18, 2005
Creator: Virkar, Anil V.
Object Type: Report
System: The UNT Digital Library
Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects (open access)

Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects

This report summarizes the work done during the seventh quarter of the project. Effort was directed in three areas: (1) Further development of the model on the role of connectivity on ionic conductivity of porous bodies, including the role of grain boundaries and space charge region, and estimation of the polarization resistance. (2) Fabrication of cells with cathodes formed by infiltration. () Testing of cells to isolate the possible effect of space charge.
Date: January 18, 2005
Creator: Virkar, Anil V.
Object Type: Report
System: The UNT Digital Library
Activity Estimates of Various Radionuclides in Saltstone Vapor Phase (open access)

Activity Estimates of Various Radionuclides in Saltstone Vapor Phase

Savannah River National Laboratory estimated activities of various radionuclides in vapor phase associated with saltstone. These radionuclides, as well as the estimated activity and concentration of each in the gases phase are listed. Some of the activities are so low they should be considered zero. In particular, activity of the antimony and tin isotopes in the gas phase correspond to less than a molecule of gas per 340 m3 of vapor volume. Equilibrium calculations of the partitioning of each radionuclide between vapor and dissolved phases were done using the Geochemists Workbench (R). The conceptual model used was that 1 curie of each constituent was available to partition between vapor and dissolved phases. The overall assumption is that exposure would come from a single release of the vapor phase from a saltstone vault.
Date: January 18, 2005
Creator: MILES, DENHAM
Object Type: Report
System: The UNT Digital Library
Basic Data Report for Drillhole SNL-5 (C-3002) (open access)

Basic Data Report for Drillhole SNL-5 (C-3002)

SNL-5 (permitted by the New Mexico State Engineer as C-3002) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation in an area north of the Waste Isolation Pilot Plant (WIPP) site where data are sparse and where a pumping or monitoring well for the northern pumping test is needed. SNL-5 is located in the southeast quarter of section 6, T22S, R31E, in eastern Eddy County, New Mexico. SNL-5 was drilled to a total depth of 687 ft below ground level (bgl), based on driller's measurements. Below the caliche pad, SNL-5 encountered the Mescalero caliche, Gatu?a, Dewey Lake, and Rustler Formations. Two intervals of the Rustler were cored: (1) from the lower Forty-niner Member through the Magenta Dolomite and into the upper Tamarisk Member; and (2) from the lower Tamarisk Member through the Culebra Dolomite and into the upper Los Meda?os Members. Geophysical logs were acquired from the open hole to a depth of ~672 ft. No water was observed to flow into the open drillhole until the Culebra was penetrated. includes horizontal beds and laminae near the base, and the uppermost part shows some inclined bedding. The mudstone unit shows …
Date: January 18, 2005
Creator: Powers, Dennis W. & Services, Washington Regulatory and Environmental
Object Type: Report
System: The UNT Digital Library
Bead and Process for Removing Dissolved Metal Contaminants (open access)

Bead and Process for Removing Dissolved Metal Contaminants

A bead is provided which comprises or consists essentially of activated carbon immobilized by crosslinked poly (carboxylic acid) binder, sodium silicate binder, or polyamine binder. The bead is effective to remove metal and other ionic contaminants from dilute aqueous solutions. A method of making metal-ion sorbing beads is provided, comprising combining activated carbon, and binder solution (preferably in a pin mixer where it is whipped), forming wet beads, and heating and drying the beads. The binder solution is preferably poly(acrylic acid) and glycerol dissolved in water and the wet beads formed from such binder solution are preferably heated and crosslinked in a convection oven.
Date: January 18, 2005
Creator: Summers, Bobby L., Jr.; Bennett, Karen L. & Foster, Scott A.
Object Type: Patent
System: The UNT Digital Library
CRACK TIP OPENING DISPLACEMENT AND ANGLE FOR A GROWING CRACK IN CARBON STEEL (open access)

CRACK TIP OPENING DISPLACEMENT AND ANGLE FOR A GROWING CRACK IN CARBON STEEL

The crack tip opening displacements and angles (CTOD/CTOA) are calculated with finite element method based on the test data of a set of constraint-dependent J-R curves for A285 carbon steel. The values of the CTOD/CTOA are initially high at initiation, but rapidly decrease to a nearly constant value. When the common practice is adopted by using only the constant part of CTOD/CTOA as the fracture criterion, the crack growth behavior is shown to be severely underestimated. However, with a bilinear form of CTOD/CTOA fracture criterion which approximates the initial non-constant portion, the experimental load vs. crack extension curves can be closely predicted. Furthermore, it is demonstrated that the CTOD/CTOA is crack tip constraint dependent. The values of CTOD/CTOA for specimens with various ratios of crack length to specimen width (a/W) are reflected by the J-R curves and their slopes.
Date: January 18, 2005
Creator: LAM, POH-SANG
Object Type: Article
System: The UNT Digital Library
Development of a Rotary Microfilter for SRS HLW Applications (open access)

Development of a Rotary Microfilter for SRS HLW Applications

The processing rate of Savannah River Site (SRS) high-level waste decontamination processes are limited by the flow rate of the solid-liquid separation. The baseline process, using a 0.1 micron cross-flow filter, produces approximately 0.02 gpm/sq. ft. of filtrate under expected operating conditions. Savannah River National Laboratory (SRNL) personnel identified the rotary microfilter as a technology that could significantly increase filter flux, with throughput improvements of as much as 10X for that specific operation. With funding from the U. S. Department of Energy Office of Cleanup Technology, SRNL personnel are evaluating and developing the rotary microfilter for radioactive service at SRS. This work includes pilot-scale and actual waste testing to evaluate system reliability, the impact of radiation on system components, the filter flux for a variety of waste streams, and relative performance for alternative filter media. Personnel revised the design for the disks and filter unit to make them suitable for high-level radioactive service.
Date: January 18, 2005
Creator: MICHAEL, POIRIER
Object Type: Report
System: The UNT Digital Library
Development of an Experimental Database and Theories for Prediction of Thermodynamic Properties of Aqueous (open access)

Development of an Experimental Database and Theories for Prediction of Thermodynamic Properties of Aqueous

Construction of models of geochemical and microbial activity in aqueous solutions, using theoretical predictions constrained by experimental data.
Date: January 18, 2005
Creator: Shock, E. L.
Object Type: Report
System: The UNT Digital Library
Develpoment of a one-meter plasma source for heavy ion beam chargeneutralization (open access)

Develpoment of a one-meter plasma source for heavy ion beam chargeneutralization

Highly ionized plasmas are being employed as a medium for charge neutralizing heavy ion beams in order to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length {approx} 0.1-1 m would be suitable for achieving a high level of charge neutralization. A radio frequency (RF) source was constructed at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization. Pulsing the source enabled operation at pressures {approx} 10{sup -6} Torr with plasma densities of 10{sup 11} cm{sup -3}. Near 100% ionization was achieved. The plasma was 10 cm in length, but future experiments require a source 1 m long. The RF source does not easily scale to the length. Consequently, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. A 1 m long section of the drift tube inner surface of NTX will …
Date: January 18, 2005
Creator: Efthimion, Philip C.; Gilson, Erik P.; Grisham, Larry; Davidson, Ronald C.; Yu, Simon; Waldron, William et al.
Object Type: Article
System: The UNT Digital Library
Drift compression and final focus options for heavy ionfusion (open access)

Drift compression and final focus options for heavy ionfusion

A drift compression and final focus lattice for heavy ion beams should focus the entire beam pulse onto the same focal spot on the target. The authors show that this requirement implies that the drift compression design needs to satisfy a self-similar symmetry condition. For un-neutralized beams, the Lie symmetry group analysis is applied to the warm-fluid model to systematically derive the self-similar drift compression solutions. For neutralized beams, the 1D Vlasov equation is solved explicitly and families of self-similar drift compression solutions are constructed. To compensate for the deviation from the self-similar symmetry condition due to the transverse emittance, four time-dependent magnets are introduced in the upstream of the drift compression such that the entire beam pulse can be focused onto the same focal spot.
Date: January 18, 2005
Creator: Qin, Hong; Davidson, Ronald C.; Barnard, John J. & Lee, Edward P.
Object Type: Article
System: The UNT Digital Library
Dynamics of neutralized electrons and the focusability of intenseion beams in HIF accelerating structures (open access)

Dynamics of neutralized electrons and the focusability of intenseion beams in HIF accelerating structures

In most of the proposals for HIF reactors, beams propagate ballistically through the containment chamber. To get the required final radius ({approx} 3 mm), the charge of the beam must be neutralized to some extent. Several neutralization schemes are possible, as co-injection of negative-ions beams, inclusion of external sources of electrons, or it can be provided by electrons coming from ionization of the background gas. In this work, we study the role of the electron dynamic on the neutralization and final radius of the beam. This is done by performing fully-electromagnetic PIC simulations of the beam ballistic transport using the BPIC code[1]. In agreement with previous works we found that the evolution of an isolated beam is well described as a bidimensional adiabatic compression, and the beam neutralization degree and final radius can be estimated from the initial electron transversal temperature. When a background gas is present the evolution differs significantly from an adiabatic compression. Even for low gas densities, the continuous electrons flow coming from gas ionization limits efficiently the compressional heating, thus reducing the final radius. Aspects of beam neutralization by background gas ionization are discussed.
Date: January 18, 2005
Creator: Lifschitz, A. F.; Maynard, G. & Vay, J.-V.
Object Type: Article
System: The UNT Digital Library
Energy Loss, Range, and Electron Yield Comparisons of the CRANGEIon-Material Interaction code (open access)

Energy Loss, Range, and Electron Yield Comparisons of the CRANGEIon-Material Interaction code

We present comparisons of the CRANGE code to other well-known codes, SRIM and ASTAR, and to experimental results for ion-material interactions such as energy loss per unit length, ion range, and ion induced electron yield. These ion-material interaction simulations are relevant to the electron cloud effect in heavy ions accelerators for fusion energy and high energy density physics. Presently, the CRANGE algorithms are most accurate at energies above 1.0 MeV/amu. For calculations of energy loss per unit length of a potassium ion in stainless steel, results of CRANGE and SRIM agree to within ten percent above 1.0 MeV/amu. For calculations of the range of a helium ion in aluminum, results of CRANGE and ASTAR agree to within two percent above 1.0 MeV/amu. Finally, for calculations of ion induced electron yield for hydrogen ions striking gold, results of CRANGE agree to within ten percent with measured electron yields above 1.0 MeV/amu.
Date: January 18, 2005
Creator: Stoltz, P. H.; Veitzer, S. A.; Cohen, R. H.; Molvik, A. W. & J.-L., Vay
Object Type: Article
System: The UNT Digital Library
Experimental evaluation of a negative ion source for a heavy ionfusion negative ion driver (open access)

Experimental evaluation of a negative ion source for a heavy ionfusion negative ion driver

Negative halogen ions have recently been proposed as a possible alternative to positive ions for heavy ion fusion drivers because electron accumulation would not be a problem in the accelerator, and if desired, the beams could be photodetached to neutrals [1,2,3]. To test the ability to make suitable quality beams, an experiment was conducted at Lawrence Berkeley National Laboratory using chlorine in an RF-driven ion source. Without introducing any cesium (which is required to enhance negative ion production in hydrogen ion sources) a negative chlorine current density of 45 mA/cm{sup 2} was obtained under the same conditions that gave 57 mA/cm{sup 2} of positive chlorine, suggesting the presence of nearly as many negative ions as positive ions in the plasma near the extraction plane. The negative ion spectrum was 99.5% atomic chlorine ions, with only 0.5% molecular chlorine, and essentially no impurities. Although this experiment did not incorporate the type of electron suppression technology that is used in negative hydrogen beam extraction, the ratio of co-extracted electrons to Cl{sup -} was as low as 7 to 1, many times lower than the ratio of their mobilities, suggesting that few electrons are present in the near-extractor plasma. This, along with the …
Date: January 18, 2005
Creator: Grisham, L. R.; Hahto, S. K.; Hahto, S. T.; Kwan, J. W. & Leung, K. N.
Object Type: Article
System: The UNT Digital Library
Fiber Laser Front Ends for High-Energy Short Pulse Lasers (open access)

Fiber Laser Front Ends for High-Energy Short Pulse Lasers

We are developing an all fiber laser system optimized for providing input pulses for short pulse (1-10ps), high energy ({approx}1kJ) glass laser systems. Fiber lasers are ideal solutions for these systems as they are highly reliable and once constructed they can be operated with ease. Furthermore, they offer an additional benefit of significantly reduced footprint. In most labs containing equivalent bulk laser systems, the system occupies two 4'x8' tables and would consist of 10's if not a 100 of optics which would need to be individually aligned and maintained. The design requirements for this application are very different those commonly seen in fiber lasers. High energy lasers often have low repetition rates (as low as one pulse every few hours) and thus high average power and efficiency are of little practical value. What is of high value is pulse energy, high signal to noise ratio (expressed as pre-pulse contrast), good beam quality, consistent output parameters and timing. Our system focuses on maximizing these parameters sometimes at the expense of efficient operation or average power. Our prototype system consists of a mode-locked fiber laser, a compressed pulse fiber amplifier, a ''pulse cleaner'', a chirped fiber Bragg grating, pulse selectors, a transport …
Date: January 18, 2005
Creator: Dawson, J W; Liao, Z M; Mitchell, S; Messerly, M; Beach, R; Jovanovic, I et al.
Object Type: Article
System: The UNT Digital Library
Method and Appartus for Calibrating a Linear Variable Differential Transformer (open access)

Method and Appartus for Calibrating a Linear Variable Differential Transformer

A calibration apparatus for calibrating a linear variable differential transformer (LVDT) having an armature positioned in au LVDT armature orifice, and the armature able to move along an axis of movement. The calibration apparatus includes a heating mechanism with an internal chamber, a temperature measuring mechanism for measuring the temperature of the LVDT, a fixture mechanism with an internal chamber for at least partially accepting the LVDT and for securing the LVDT within the heating mechanism internal chamber, a moving mechanism for moving the armature, a position measurement mechanism for measuring the position of the armature, and an output voltage measurement mechanism. A method for calibrating an LVDT, including the steps of powering the LVDT; heating the LVDT to a desired temperature; measuring the position of the armature with respect to the armature orifice; and measuring the output voltage of the LVDT.
Date: January 18, 2005
Creator: Pokrywka, Robert J.
Object Type: Patent
System: The UNT Digital Library
Micro-Raman spectroscopy Detects Individual Neoplastic and Normal Hematopoietic Cells (open access)

Micro-Raman spectroscopy Detects Individual Neoplastic and Normal Hematopoietic Cells

Current methods for identifying neoplastic cells and discerning them from their normal counterparts are often non-specific, slow, biologically perturbing, or a combination, thereof. Here, we show that single-cell micro-Raman spectroscopy averts these shortcomings and can be used to discriminate between unfixed normal human lymphocytes and transformed Jurkat and Raji lymphocyte cell lines based on their biomolecular Raman signatures. We demonstrate that single-cell Raman spectra provide a highly reproducible biomolecular fingerprint of each cell type. Characteristic peaks, mostly due to different DNA and protein concentrations, allow for discerning normal lymphocytes from transformed lymphocytes with high confidence (p << 0.05). Spectra are also compared and analyzed by principal component analysis (PCA) to demonstrate that normal and transformed cells form distinct clusters that can be defined using just two principal components. The method is shown to have a sensitivity of 98.3% for cancer detection, with 97.2% of the cells being correctly classified as belonging to the normal or transformed type. These results demonstrate the potential application of confocal micro-Raman spectroscopy as a clinical tool for single cell cancer detection based on intrinsic biomolecular signatures, therefore eliminating the need for exogenous fluorescent labeling.
Date: January 18, 2005
Creator: Chan, J. W.; Taylor, D.; Zwerdling, T.; Lane, S. M.; Ihara, K. & Huser, T.
Object Type: Article
System: The UNT Digital Library
Rotating Aperture System (open access)

Rotating Aperture System

A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.
Date: January 18, 2005
Creator: Rusnak, Brian; Hall, James M.; Shen, Stewart & Wood, Richard L.
Object Type: Patent
System: The UNT Digital Library
Scoria Cone Construction Mechanism, Lathrop Wells Volcano, Southern Nevada (open access)

Scoria Cone Construction Mechanism, Lathrop Wells Volcano, Southern Nevada

Scoria cones are commonly assumed to have been constructed by the accumulation of ballistically-ejected clasts from discrete and relatively coarse-grained Strombolian bursts and subsequent avalanching such that the cone slopes are at or near the angle of repose for loose scoria. The cone at the hawaiitic Lathrop Wells volcano, southern Nevada, contains deposits that are consistent with the above processes during early cone-building phases; these early deposits are composed mainly of coarse lapilli and fluidal bombs and are partially welded, indicating relatively little cooling during flight. However, the bulk of the cone is comprised of relatively fine-grained (ash and lapilli), planar beds with no welding, even within a few tens of meters of the vent. This facies is consistent with deposition by direct fallout from sustained eruption columns of relatively well-fragmented material, primarily mantling cone slopes and with a lesser degree of avalanching than is commonly assumed. A laterally extensive fallout deposit (up to 20 km from the vent) is inferred to have formed contemporaneously with these later cone deposits. This additional mechanism for construction of scoria cones may also be important at other locations, particularly where the magmas are relatively high in volatile content and where conditions promote the …
Date: January 18, 2005
Creator: Valentine, G.; Krier, D.; Perry, F. & Heiken, G.
Object Type: Report
System: The UNT Digital Library
Simulations of neutralized final focus (open access)

Simulations of neutralized final focus

In order to drive an inertial fusion target or study high energy density physics with heavy ion beams, the beam radius must be focused to < 3 mm and the pulse length must be compressed to < 10 ns. The conventional scheme for temporal pulse compression makes use of an increasing ion velocity to compress the beam as it drifts and beam space charge to stagnate the compression before final focus. Beam compression in a neutralizing plasma does not require stagnation of the compression, enabling a more robust method. The final pulse shape at the target can be programmed by an applied velocity tilt. In this paper, neutralized drift compression is investigated. The sensitivity of the compression and focusing to beam momentum spread, plasma, and magnetic field conditions is studied with realistic driver examples. Using the 3D particle-in-cell code, we examine issues associated with self-field generation, stability, and vacuum-neutralized transport transition and focusing.
Date: January 18, 2005
Creator: Welch, D. R.; Rose, D. V.; Genoni, T. C.; Yu, S. S. & Barnard, J. J.
Object Type: Article
System: The UNT Digital Library
Towards p-type doping of ZnO by ion implantation (open access)

Towards p-type doping of ZnO by ion implantation

Zinc oxide is a very attractive material for a range of optoelectronic devices including blue light-emitting diodes and laser diodes. Though n-type doping has been successfully achieved, p-type doing of ZnO is still a challenge that must be overcome before p-n junction devices can be realized. Ion implantation is widely used in the microelectronics industry for selective area doping and device isolation. Understanding damage accumulation and recrystallization processes is important for achieving selective area doping. In this study, As (potential p-type dopant) ion implantation and annealing studies were carried out. ZnO samples were implanted with high dose (1.4 x 10{sup 17} ions/cm{sup 2}) 300 keV As ions at room temperature. Furnace annealing of samples in the range of 900 C to 1200 C was employed to achieve recrystallization of amorphous layers and electrical activation of the dopant. Rutherford backscattering/channeling spectrometry, transmission electron microscopy and cathodolumiescence spectroscopy were used to monitor damage accumulation and annihilation behavior in ZnO. Results of this study have significant implications for p-type doing of ZnO by ion implantation.
Date: January 18, 2005
Creator: Coleman, V; Tan, H H; Jagadish, C; Kucheyev, S; Phillips, M & Zou, J
Object Type: Article
System: The UNT Digital Library
Unsymmetric ordering using a constrained Markowitz scheme (open access)

Unsymmetric ordering using a constrained Markowitz scheme

We present a family of ordering algorithms that can be used as a preprocessing step prior to performing sparse LU factorization. The ordering algorithms simultaneously achieve the objectives of selecting numerically good pivots and preserving the sparsity. We describe the algorithmic properties and challenges in their implementation. By mixing the two objectives we show that we can reduce the amount of fill-in in the factors and reduce the number of numerical problems during factorization. On a set of large unsymmetric real problems, we obtained the median reductions of 12% in the factorization time, of 13% in the size of the LU factors, of 20% in the number of operations performed during the factorization phase, and of 11% in the memory needed by the multifrontal solver MA41-UNS. A byproduct of this ordering strategy is an incomplete LU-factored matrix that can be used as a preconditioner in an iterative solver.
Date: January 18, 2005
Creator: Amestoy, Patrick R.; S., Xiaoye & Pralet, Stephane
Object Type: Article
System: The UNT Digital Library
Yucca Mountain Feature, Event, and Process (FEP) Analysis (open access)

Yucca Mountain Feature, Event, and Process (FEP) Analysis

A Total System Performance Assessment (TSPA) model was developed for the U.S. Department of Energy (DOE) Yucca Mountain Project (YMP) to help demonstrate compliance with applicable postclosure regulatory standards and support the License Application (LA). Two important precursors to the development of the TSPA model were (1) the identification and screening of features, events, and processes (FEPs) that might affect the Yucca Mountain disposal system (i.e., FEP analysis), and (2) the formation of scenarios from screened in (included) FEPs to be evaluated in the TSPA model (i.e., scenario development). YMP FEP analysis and scenario development followed a five-step process: (1) Identify a comprehensive list of FEPs potentially relevant to the long-term performance of the disposal system. (2) Screen the FEPs using specified criteria to identify those FEPs that should be included in the TSPA analysis and those that can be excluded from the analysis. (3) Form scenarios from the screened in (included) FEPs. (4) Screen the scenarios using the same criteria applied to the FEPs to identify any scenarios that can be excluded from the TSPA, as appropriate. (5) Specify the implementation of the scenarios in the computational modeling for the TSPA, and document the treatment of included FEPs. This …
Date: January 18, 2005
Creator: Freeze, G.
Object Type: Report
System: The UNT Digital Library
Aging and Gene Expression in the Primate Brain (open access)

Aging and Gene Expression in the Primate Brain

It is well established that gene expression levels in many organisms change during the aging process, and the advent of DNA microarrays has allowed genome-wide patterns of transcriptional changes associated with aging to be studied in both model organisms and various human tissues. Understanding the effects of aging on gene expression in the human brain is of particular interest, because of its relation to both normal and pathological neurodegeneration. Here we show that human cerebral cortex, human cerebellum, and chimpanzee cortex each undergo different patterns of age-related gene expression alterations. In humans, many more genes undergo consistent expression changes in the cortex than in the cerebellum; in chimpanzees, many genes change expression with age in cortex, but the pattern of changes in expression bears almost no resemblance to that of human cortex. These results demonstrate the diversity of aging patterns present within the human brain, as well as how rapidly genome-wide patterns of aging can evolve between species; they may also have implications for the oxidative free radical theory of aging, and help to improve our understanding of human neurodegenerative diseases.
Date: February 18, 2005
Creator: Fraser, Hunter B.; Khaitovich, Philipp; Plotkin, Joshua B.; Paabo, Svante & Eisen, Michael B.
Object Type: Article
System: The UNT Digital Library
Architecture and High-Resolution Structure of Bacillus thuringiensis and Bacillus cereus Spore Coat Surfaces (open access)

Architecture and High-Resolution Structure of Bacillus thuringiensis and Bacillus cereus Spore Coat Surfaces

We have utilized atomic force microscopy (AFM) to visualize the native surface topology and ultrastructure of Bacillus thuringiensis and Bacillus cereus spores in water and in air. AFM was able to resolve the nanostructure of the exosporium and three distinctive classes of appendages. Removal of the exosporium exposed either a hexagonal honeycomb layer (B. thuringiensis) or a rodlet outer spore coat layer (B. cereus). Removal of the rodlet structure from B. cereus spores revealed an underlying honeycomb layer similar to that observed with B. thuringiensis spores. The periodicity of the rodlet structure on the outer spore coat of B. cereus was {approx}8 nm, and the length of the rodlets was limited to the cross-patched domain structure of this layer to {approx}200 nm. The lattice constant of the honeycomb structures was {approx}9 nm for both B. cereus and B. thuringiensis spores. Both honeycomb structures were composed of multiple, disoriented domains with distinct boundaries. Our results demonstrate that variations in storage and preparation procedures result in architectural changes in individual spore surfaces, which establish AFM as a useful tool for evaluation of preparation and processing ''fingerprints'' of bacterial spores. These results establish that high-resolution AFM has the capacity to reveal species-specific assembly …
Date: February 18, 2005
Creator: Plomp, Marco; Leighton, Terrance J.; Wheeler, Katherine E. & Malkin, Alexander J.
Object Type: Article
System: The UNT Digital Library