Evaluation of Biotic and Treatment Factors Relaying to Bacterial Control of Zebra Mussels (open access)

Evaluation of Biotic and Treatment Factors Relaying to Bacterial Control of Zebra Mussels

Testing over the last quarter has indicated the following regarding control of zebra mussels with bacterium Pseudomonas fluorescens strain CL0145A: (1) the concentration of bacteria suspended in water is directly correlated with mussel kill; (2) the ratio of bacterial mass per mussel, if too low, could limit mussel kill; a treatment must be done at a high enough ratio so that mussels do not deplete all the suspended bacteria before the end of the desired exposure period; (3) bacteria appear to lose almost all their toxicity after suspension for 24 hr in highly oxygenated water; (4) in a recirculating pipe system, the same percentage mussel kill will be achieved irrespective of whether all the bacteria are applied at once or divided up and applied intermittently in smaller quantities over a 10-hr period. Since this is the fourth quarterly report, a summation of all test results over the last twelve months is provided as a table in this report. The table includes the above-mentioned fourth-quarter results.
Date: April 30, 2002
Creator: Molloy, Daniel P.
Object Type: Report
System: The UNT Digital Library
Export Administration Act of 2001: Side-by-Side of S. 149 and H.R. 2541 (open access)

Export Administration Act of 2001: Side-by-Side of S. 149 and H.R. 2541

None
Date: April 30, 2002
Creator: Fergusson, Ian F.
Object Type: Report
System: The UNT Digital Library
Federal Student Aid: Additional Management Improvements Would Clarify Strategic Direction and Enhance Accountability (open access)

Federal Student Aid: Additional Management Improvements Would Clarify Strategic Direction and Enhance Accountability

A letter report issued by the General Accounting Office with an abstract that begins "The Department of Education's Office of Federal Student Aid (FSA) administers more than $53 billion in financial aid for more than 8.1 million students. Since 1990, GAO has included student financial aid on its high-risk list. To address these and other long-standing management weaknesses, Congress established FSA as a performance-based organization (PBO) within Education in 1998. To develop and implement a strategic direction, FSA set three strategic goals, created indicators to measure progress toward these goals, and developed a tool to link employees' day-to-day activities to these goals. The goals are to (1) increase customer satisfaction, (2) increase employee satisfaction, and (3) reduce unit cost. FSA's efforts have generally improved customer and employee satisfaction scores. FSA has begun to implement some human capital practices to better organize its services and manage its employees. But gaps exist, and FSA has not yet implemented performance management initiatives to develop and assess its employees. To better serve customers, FSA reorganized to reflect its different customers--students, schools, and financial partners. To encourage accountability, FSA is linking staff bonuses to FSA's strategic goals. Education continues to clarify FSA's level of independence …
Date: April 30, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Final Report of FY 1999, 2000, and 2001 Activities: Continued Development of an Integrated Sounding System in Support of the DOE/ARM Experimental Program (open access)

Final Report of FY 1999, 2000, and 2001 Activities: Continued Development of an Integrated Sounding System in Support of the DOE/ARM Experimental Program

OAK B188 FINAL REPORT OF FY 1999, 2000, AND 2001 ACTIVITIES: CONTINUED DEVELOPMENT OF AN INTEGRATED SOUNDING SYSTEM IN SUPPORT OF THE DOE/ARM EXPERIMENTAL PROGRAM The basic goals of the research are to develop and test algorithms and deploy instruments that improve measurements of atmospheric quantities relevant to radiative transfer and climate research. Primary among these atmospheric variables are integrated amounts of water vapor and cloud liquid, as well as profiles of temperature, water vapor and cloud liquid. A primary thrust of this research is to combine data from instruments available to ARM to maximize their importance in radiative transfer and climate research. To gather data relevant to these studies, participation in field experiments, especially intensive operating periods, as well as the subsequent analysis and dissemination of collected data, is of primary importance. Examples of relevant experiments include several Water Vapor Intensive Operating Periods at the Southern Great Plains Cloud And Radiation Testbed site, experiments in the Tropical Western Pacific such as PROBE and Nauru'99, and experiments at the North Slope of Alaska/Adjacent Arctic Ocean site. This final report describes our analyses of data taken during these field experiments.
Date: April 30, 2002
Creator: Ed R. Westwater CIRES, University of Colorado /NOAA Environmental Technology Laboratory 325 Broadway MS R/E/ET1 Boulder, Colorado 80305
Object Type: Report
System: The UNT Digital Library
Food Safety: Continued Vigilance Needed to Ensure Safety of School Meals (open access)

Food Safety: Continued Vigilance Needed to Ensure Safety of School Meals

Testimony issued by the General Accounting Office with an abstract that begins "The national school lunch and breakfast programs provide inexpensive or free meals to more than 27 million children each day. During the 1990s, nearly 300 outbreaks of foodborne illness at the nation's schools sickened 16,000 students. The rise in the number of school outbreaks mirrors a rise in the number of outbreaks in the overall population, according to the Centers for Disease Control and Prevention (CDC). Because the CDC data include outbreaks attributable to food brought from home or other sources, GAO could not determine the extent to which food served in the school meal programs caused reported outbreaks. Data from 1998 and 1999 do show, however, that most of the outbreaks during those years were caused by foods served through the school meal program. Foods contaminated with salmonella and Norwalk-like viruses were the most common causes of outbreaks. GAO found that the Department of Agriculture has not developed security measures to protect foods served at schools from deliberate contamination. The existing food safety system is a patchwork of protections that fall short in addressing existing and emerging food safety threats."
Date: April 30, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
FUEL-FLEXIBLE GASIFICATION-COMBUSTION TECHNOLOGY FOR PRODUCTION OF H2 AND SEQUESTRATION-READY CO2 (open access)

FUEL-FLEXIBLE GASIFICATION-COMBUSTION TECHNOLOGY FOR PRODUCTION OF H2 AND SEQUESTRATION-READY CO2

Further development of a combustion Large Eddy Simulation (LES) code for the design of advanced gaseous combustion systems is described in this sixth quarterly report. CFD Research Corporation (CFDRC) is developing the LES module within the parallel, unstructured solver included in the commercial CFD-ACE+ software. In this quarter, in-situ adaptive tabulation (ISAT) for efficient chemical rate storage and retrieval was implemented and tested within the Linear Eddy Model (LEM). ISAT type 3 is being tested so that extrapolation can be performed and further improve the retrieval rate. Further testing of the LEM for subgrid chemistry was performed for parallel applications and for multi-step chemistry. Validation of the software on backstep and bluff-body reacting cases were performed. Initial calculations of the SimVal experiment at Georgia Tech using their LES code were performed. Georgia Tech continues the effort to parameterize the LEM over composition space so that a neural net can be used efficiently in the combustion LES code. A new and improved Artificial Neural Network (ANN), with log-transformed output, for the 1-step chemistry was implemented in CFDRC's LES code and gave reasonable results. This quarter, the 2nd consortium meeting was held at CFDRC. Next quarter, LES software development and testing will …
Date: April 30, 2002
Creator: Rizeq, George; West, Janice; Frydman, Arnaldo; Subia, Raul; Zamansky, Vladimir; Wiltowski, Tomasz et al.
Object Type: Report
System: The UNT Digital Library
''Green'' Biopolymers for Improved Decontamination of Metals from Surfaces: Sorptive Characterization and Coating Properties (open access)

''Green'' Biopolymers for Improved Decontamination of Metals from Surfaces: Sorptive Characterization and Coating Properties

The proposed research aimed to develop a fundamental understanding of important biological and physical chemical parameters for effective decontamination of metal surfaces using environmentally benign aqueous-based biopolymer solutions. Understanding how heavy metal-chelating biopolymers coat and interact with contaminated surfaces will benefit the development of novel, safe, easy-to-apply decontamination methodologies for removal of radionuclides and heavy metals. The benefits of these methodologies include the following: decreased exposure hazards for workers; decreased secondary waste generation; increased efficiency of decontamination; positive public appeal and development of novel, nature-friendly business opportunities; and lower cost of cleanup to the government. We proposed to use aqueous biopolymer solutions to coat a contaminated metal surface (i.e., steel), solubilize the heavy metals (e.g., uranium) from the surface, and bind the heavy metals into the biopolymer. The biopolymer coating (containing the immobilized hazardous metal contaminants) was to be removed as a viscous film, as a dry powder, or by washing. This ''apply, wait, and remove'' procedure will reduce the amount of worker time spent in decontamination activities.
Date: April 30, 2002
Creator: Davison, Brian H.
Object Type: Report
System: The UNT Digital Library
Group Purchasing Organizations: Pilot Study Suggests Large Buying Groups Do Not Always Offer Hospitals Lower Prices (open access)

Group Purchasing Organizations: Pilot Study Suggests Large Buying Groups Do Not Always Offer Hospitals Lower Prices

A statement of record issued by the General Accounting Office with an abstract that begins "This testimony discusses group purchasing organizations (GPO) for medical devices and supplies used in hospitals. By pooling the purchases of their member hospitals, these specialized firms negotiate lower prices from vendors. GAO found that a hospital's use of a GPO contract did not guarantee that the hospital saved money: GPOs' prices were not always lower and were often higher than prices paid by hospitals negotiating directly with vendors. GAO studied price savings with respect to: (1) whether hospitals using GPO contracts received better prices than hospitals that did their own contracting, (2) the size of the hospital, and (3) size of the GPO. This data raises questions about whether GPOs, specially large GPOs, achieve consistent price savings."
Date: April 30, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING (open access)

HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

In this semiannual report we summarize the progress obtained in the first six months with the support of DoE contract No.DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has made significant progress in the development of GaN vertical cavity surface-emitting lasers (VCSELs) as well as light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV). The Rensselaer team has developed target specifications for some of the key parameters for the proposed solid-state lighting system, including a luminous flux requirement matrix for various lighting applications, optimal spectral power distributions, and the performance characteristics of currently available commercial LEDs for eventual comparisons to the devices developed in the scope of this project.
Date: April 30, 2002
Creator: Fini, Dr. Paul T. & Nakamura, Prof. Shuji
Object Type: Report
System: The UNT Digital Library
HORIZON SENSING (PROPOSAL No.51) (open access)

HORIZON SENSING (PROPOSAL No.51)

Real-time horizon sensing on continuous mining machines is becoming an industry tool. Installation and testing of production-grade HS systems has been ongoing this quarter at Monterey Coal Company (EXXON), FMC Trona, Twentymile Coal Company (RAG America), and SASOL Coal. Detailed monitoring of system function, user experience, and mining benefits is ongoing. All horizon sensor components have finished MSHA (U.S.) and IEC (International) certification.
Date: April 30, 2002
Creator: Stolarczyk, Larry G.
Object Type: Report
System: The UNT Digital Library
In-situ calibration: migrating control system IP module calibration from the bench to the storage ring (open access)

In-situ calibration: migrating control system IP module calibration from the bench to the storage ring

The Control System for the Advanced Light Source (ALS) at Lawrence Berkeley National Lab (LBNL) uses in-house designed IndustryPack(registered trademark) (IP) modules contained in compact PCI (cPCI) crates with 16-bit analog I/O to control instrumentation. To make the IP modules interchangeable, each module is calibrated for gain and offset compensation. We initially developed a method of verifying and calibrating the IP modules in a lab bench test environment using a PC with LabVIEW. The subsequent discovery that the ADCs have significant drift characteristics over periods of days of installed operation prompted development of an ''in-situ'' calibration process--one in which the IP modules can be calibrated without removing them from the cPCI crates in the storage ring. This paper discusses the original LabVIEW PC calibration and the migration to the proposed in-situ EPICS control system calibration.
Date: April 30, 2002
Creator: Weber, Jonah M. & Chin, Michael
Object Type: Article
System: The UNT Digital Library
INCREASING HEAVY OIL RESERVES IN THE WILMINGTON OIL FIELD THROUGH ADVANCED RESERVOIR CHARACTERIZATION AND THERMAL PRODUCTION TECHNOLOGIES (open access)

INCREASING HEAVY OIL RESERVES IN THE WILMINGTON OIL FIELD THROUGH ADVANCED RESERVOIR CHARACTERIZATION AND THERMAL PRODUCTION TECHNOLOGIES

The project involves using advanced reservoir characterization and thermal production technologies to improve thermal recovery techniques and lower operating and capital costs in a slope and basin clastic (SBC) reservoir in the Wilmington field, Los Angeles Co., Calif. Through December 2001, project work has been completed on the following activities: data preparation; basic reservoir engineering; developing a deterministic three dimensional (3-D) geologic model, a 3-D deterministic reservoir simulation model and a rock-log model; well drilling and completions; and surface facilities on the Fault Block II-A Tar Zone (Tar II-A). Work is continuing on research to understand the geochemistry and process regarding the sand consolidation well completion technique, final reservoir tracer work, operational work and research studies to prevent thermal-related formation compaction in the Tar II-A steamflood area, and operational work on the Tar V steamflood pilot and Tar II-A post-steamflood projects. During the First Quarter 2002, the project team developed an accelerated oil recovery and reservoir cooling plan for the Tar II-A post-steamflood project and began implementing the associated well work in March. The Tar V pilot steamflood project will be converted to post-steamflood cold water injection in April 2002. The Tar II-A post-steamflood operation started in February 1999 and …
Date: April 30, 2002
Creator: Hara, Scott
Object Type: Report
System: The UNT Digital Library
INEEL Advanced Radiotherapy Research Program Annual Report 2001 (open access)

INEEL Advanced Radiotherapy Research Program Annual Report 2001

This report summarizes the major activities and accomplishments of the Idaho National Engineering and Environmental Laboratory (INEEL) Advanced Radiotherapy Research Program for calendar year 2001. Applications of supportive research and development, as well as technology deployment in the fields of chemistry, radiation physics and dosimetry, and neutron source design and demonstration are described. Contributions in the fields of physics and biophysics include development of advanced patient treatment planning software, feasibility studies of accelerator neutron source technology for Neutron Capture Therapy (NCT), and completion of major modifications to the research reactor at Washington State University to produce an epithermal-neutron beam for NCT research applications.
Date: April 30, 2002
Creator: Venhuizen, James R.
Object Type: Report
System: The UNT Digital Library
LOWER TEMPERATURE ELECTROLYTE AND ELECTRODE MATERIALS (open access)

LOWER TEMPERATURE ELECTROLYTE AND ELECTRODE MATERIALS

LSGM electrolyte and LSCF cathode materials were synthesized via solid state reaction and wet-chemical method. From these materials, symmetrical cells were fabricated for electrochemical characterizations.
Date: April 30, 2002
Creator: Huang, Keqin
Object Type: Report
System: The UNT Digital Library
Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system? (open access)

Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system?

Cold bubbling springs in the Separation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium and carbon isotopes and CO{sub 2}/{sup 3}He. This suggests the presence of fresh basaltic magma in the volcanic plumbing system. Currently there is no evidence to link this system directly to the uplift, which started in 1998. To the contrary, all geochemical evidence suggests that there is a long-lived geothermal system in the Separation Creek area, which has not significantly changed since the early 1990s. There was no archived helium and carbon data, so a definite conclusion regarding the strong mantle signature observed in these tracers cannot yet be drawn. There is a distinct discrepancy between the yearly magma supply required to explain the current uplift (0.006 km{sup 3}/yr) and that required to explain the discharge of CO{sub 2} from the system (0.0005 km{sup 3}/yr). This discrepancy may imply that the chemical signal associated with the increase in magma supply has not reached the surface yet. With respect to this the small changes observed at upper Mesa Creek require further attention, due to the recent volcanic vent in that area it may be the location were the …
Date: April 30, 2002
Creator: van Soest, M.C.; Kennedy, B.M.; Evans, W.C. & Mariner, R.H.
Object Type: Article
System: The UNT Digital Library
Marmousi-2: An Updated Model for the Investigation of AVO in Structurally Complex Areas (open access)

Marmousi-2: An Updated Model for the Investigation of AVO in Structurally Complex Areas

We have created an elastic version of the IFF Marmousi model for use in AVO analysis in the presence of complex structure. The model is larger, includes larger offsets, lies in deeper water, includes surface streamer, multicomponent OBC and VSP acquisition, and contains more hydrocarbons than its predecessor. In addition to AVO analysis, we believe these data will be suitable for calibrating emerging technologies including converted wave tomography and vector seismic processing.
Date: April 30, 2002
Creator: Martin, G.S.; Marfurt, K.J. & Larsen, S.
Object Type: Article
System: The UNT Digital Library
Mass Transit: FTA's New Starts Commitments for Fiscal Year 2003 (open access)

Mass Transit: FTA's New Starts Commitments for Fiscal Year 2003

A letter report issued by the General Accounting Office with an abstract that begins "Since the early 1970's, the federal government has provided a large share of the nation's capital investment in urban mass transportation. Much of this funding has come through the Federal Transit Administration's (FTA) New Starts Program, which helps pay for rail, bus, and trolley projects. The Transportation Equity Act for the 21st Century authorized about $6 billion in "guaranteed" funding for the New Starts program through fiscal year 2003. FTA's evaluation process assigns candidate projects individual ratings for project justification and local financial commitments. The process also assigns an overall rating intended to reflect the project's merit. FTA recommended four projects for funding commitments for fiscal year 2003 in its New Starts report and budget proposal. FTA evaluated 50 proposed projects for fiscal year 2003 and developed ratings for 31 of them. Twenty-seven of these projects were rated as "highly recommended" or "recommended." Although FTA has faced transit budget crunches for years, the agency will end the act's authorization period with $310 million in unused commitment authority. Proposals to limit the amount of New Starts funds would allow more projects to receive such funding, but could …
Date: April 30, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Meteorological and air quality impacts of increased urban albedo and vegetative cover in the Greater Toronto Area, Canada (open access)

Meteorological and air quality impacts of increased urban albedo and vegetative cover in the Greater Toronto Area, Canada

The study described in this report is part of a project sponsored by the Toronto Atmospheric Fund, performed at the Lawrence Berkeley National Laboratory, to assess the potential role of surface property modifications on energy, meteorology, and air quality in the Greater Toronto Area (GTA), Canada. Numerical models were used to establish the possible meteorological and ozone air-quality impacts of increased urban albedo and vegetative fraction, i.e., ''cool-city'' strategies that can mitigate the urban heat island (UHI), significantly reduce urban energy consumption, and improve thermal comfort, particularly during periods of hot weather in summer. Mitigation is even more important during critical heat wave periods with possible increased heat-related hospitalization and mortality. The evidence suggests that on an annual basis cool-city strategies are beneficial, and the implementation of such measures is currently being investigated in the U.S. and Canada. We simulated possible scenari os for urban heat-island mitigation in the GTA and investigated consequent meteorological changes, and also performed limited air-quality analysis to assess related impacts. The study was based on a combination of mesoscale meteorological modeling, Lagrangian (trajectory), and photochemical trajectory modeling to assess the potential meteorological and ozone air-quality impacts of cool-city strategies. As available air-quality and emissions data …
Date: April 30, 2002
Creator: Taha, Haider; Hammer, Hillel & Akbari, Hashem
Object Type: Report
System: The UNT Digital Library
Microstructures of GaN and In{sub x}Ga{sub 1-x}N films grown by MOCVD on free-standing GaN templates (open access)

Microstructures of GaN and In{sub x}Ga{sub 1-x}N films grown by MOCVD on free-standing GaN templates

We summarize structural properties of thick HVPE GaN templates from the point of view of their application as substrates for growth of nitride layers. This is followed by the results of optical and structural studies, mostly transmission electron microscopy, of nitride layers grown by MOCVD on top of the HVPE substrates. The results indicate high structural quality of these layers with a low density of threading dislocations (in the range of 10{sup 6} cm{sup -2}). Convergent beam electron diffraction studies showed that the MOCVD GaN films have Ga-polarity, the same polarity as the HVPE GaN substrates. Structural studies of an InGaN layer grown on top of the MOCVD GaN film showed the presence of two layers, which differed in lattice parameter and composition. The upper layer, on the top of the structure had a c-lattice parameter about 2% larger than that of GaN and contained 10.3 {+-} 0.8% of In. Values measured for the thinner, intermediate layer adjacent to the GaN layer were about 2 .5 times lower.
Date: April 30, 2002
Creator: Jasinski, J.; Liliental-Weber, Z.; Huang, D.; Reshchikov, M. A.; Yun, F.; Morkoc, H. et al.
Object Type: Article
System: The UNT Digital Library
Military Training: Limitations Exist Overseas but Are Not Reflected in Readiness Reporting (open access)

Military Training: Limitations Exist Overseas but Are Not Reflected in Readiness Reporting

A letter report issued by the General Accounting Office with an abstract that begins "Rigorous, realistic training is key to military readiness. All U.S. military forces conduct frequent training exercises to hone and maintain their war-fighting skills. Combat units stationed outside the continental United States are able to meet many of their training requirements but face constraints in such areas as (1) maneuver operations, (2) live ordnance practice, and (3) night and low altitude flying. Training constraints cause adverse effects, including (1) requiring workarounds that can breed bad habits affecting combat performance; (2) requiring military personnel to be away from home more often; and (3) preventing training from being accomplished. To address these concerns, military commands and services are negotiating with host governments to lessen restrictions on existing training areas, but such actions are often done at an individual-service level and sometimes create unforeseen problems for other services and for existing training capabilities."
Date: April 30, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
NOx Control Options and Integration for US Coal Fired Boilers Quarterly Progress Report: January-March 2002 (open access)

NOx Control Options and Integration for US Coal Fired Boilers Quarterly Progress Report: January-March 2002

This is the seventh Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-00NT40753. The goal of the project is to develop cost effective analysis tools and techniques for demonstrating and evaluating low NOx control strategies and their possible impact on boiler performance for firing US coals. The Electric Power Research Institute (EPRI) is providing co-funding for this program. This program contains multiple tasks and good progress is being made on all fronts. A series of field tests for RRI at the Ameren Sioux Unit No.1 have demonstrated that RRI can provide up to 30% NOx reduction over the use of over fire air in large scale (480MW) cyclone fired utility boilers. The field tests and modeling results are in good agreement. Final data analysis has been completed for tests performed at Eastlake Power Station of a real-time waterwall corrosion monitoring system. The tests demonstrated that corrosion could be measured accurately in real-time in normal boiler operations, and an assessment of waterwall wastage could be made without impacting boiler availability. Detailed measurements of soot volume fraction have been performed for a coal burner in a pilot scale test furnace. The measured values are in good agreement with the expected trends for …
Date: April 30, 2002
Creator: Bockelie, Mike; Cremer, Marc; Davis, Kevin; Senior, Connie; Hurt, Bob; Eddings, Eric et al.
Object Type: Report
System: The UNT Digital Library
Nuclear Energy Policy (open access)

Nuclear Energy Policy

None
Date: April 30, 2002
Creator: Holt, Mark & Behrens, Carl E.
Object Type: Report
System: The UNT Digital Library
A possible evolutionary origin for the Mn4 cluster of the photosynthetic water oxidation complex from natural MnO2 precipitates in the early ocean (open access)

A possible evolutionary origin for the Mn4 cluster of the photosynthetic water oxidation complex from natural MnO2 precipitates in the early ocean

The photosynthetic water oxidation complex consists of a cluster of 4 Mn atoms bridged by O atoms, associated with Ca2+ and Cl- and incorporated into protein. The structure is similar in higher plants and algae, as well as in cyanobacteria of more ancient lineage, dating back more than 2.5 Ga on Earth. It has been proposed that the proto-enzyme derived from a component of a natural early marine manganese precipitate that contained a CaMn4O9 cluster. A variety of MnO2 minerals is found in nature. Three major classes are spinels, sheet-like layered structures and 3-dimensional networks that contain parallel tunnels. These relatively open structures readily incorporate cations (Na+, Li+, Mg2+, Ca2+, Ba2+, H+ and even Mn2+) and water. The minerals have different ratios of Mn(III) and Mn(IV) octahedrally coordinated to oxygens. Using X-ray spectroscopy we compare the chemical structures of Mn in the minerals with what is known about the arrangement in the water-oxidation complex to define the parameters of a structural model for the photosynthetic catalytic site. This comparison provides for the structural model a set of candidate Mn4 clusters -- some previously proposed and considered and others entirely novel.
Date: April 30, 2002
Creator: Sauer, Kenneth & Yachandra, Vittal K.
Object Type: Article
System: The UNT Digital Library
Predicting sporadic Grid data transfers. (open access)

Predicting sporadic Grid data transfers.

The increasingly common practice of (1) replicating datasets and (2) using resources as distributed data stores in Grid environments has lead to the problem of determining which replica can be accessed most efficiently. Due to diverse performance characteristics and load variations of several components in the end-to-end path linking these various locations, selecting a replica location from among many requires accurate prediction information of end-to-end data transfer times between the sources and sinks. In this paper, we present a prediction system that is based on combining end-to-end application throughput observations and network load variations, drawing from their merits of capturing whole system performance and variations in load patterns respectively. We develop a set of regression models to derive predictions that characterize the effect of network load variations on file transfer times. We apply these techniques to the GridFTP data movement tool, part of the Globus Toolkit{sup TM}, and observe performance gains of up to 10% in prediction accuracy when compared to approaches based on past system behavior in isolation.
Date: April 30, 2002
Creator: Vazhkudai, S. & Schopf, J. M.
Object Type: Article
System: The UNT Digital Library