Texas Digital Library
University of Houston-Clear Lake: UHCL Institutional RepositoryNot a member yet
4292 research outputs found
Sort by
Determination of Aliphatic Organo-Phosphorus Compounds in Environmental Samples by Integrated Pulsed Amperometric Detection-Ion Chromatography
No full textGlyphosate (N-(phosphonomethyl) glycine) is globally the most commonly used herbicidal active ingredient. Public concerns have elicited environmental agencies to monitor the persistence and occurrence of glyphosate. Recent environmental assessments quantify its annual mean concentration well within the parts per trillion range for US natural water sources. The environmental metabolites of glyphosate, aminomethyl phosphonic acid (AMPA), and the herbicidal active ingredient glufosinate are also frequently analyzed alongside glyphosate due to their similar chemical structures. However, their determination is labor intensive and not amenable to typical analytical methods due to the polyprotic and photo-inactive properties of these compounds. These compounds are typically analyzed by derivatization-based single residue methods (SRMs), where a few analytes undergo quantitative analysis by Liquid Chromatography-Tandem Mass Spectrometry method only (LC-MS/MS). The United States Geological Survey (USGS) has developed a method for glyphosate determination using online SPE-LC-MS/MS. Yet, studies utilizing similar LC-MS/MS methods have suggested that derivatizing steps are susceptible to salt-associated matrix effects. Ion Chromatography-Integrated Amperometric Detection (IC-IPAD) offers simple, direct analysis of aliphatic organo-phosphorus compound without derivatization steps. In this study, an offline SPE-IC-IPAD method was developed and validated for the determination of glyphosate and other aliphatic organophosphorus compounds in environmental water samples. The linear range was found to be 3-750 µg/L (R squared = 0.9973, 0.9998, 0.9983) and the limits of detection (LOD) were found to be 0.950, 0.402, and 0.252 µg/L for glyphosate, glufosinate, and AMPA in reagent water, respectively. The offline solid phase extraction (SPE) method provided excellent recovery values (104-131%) by standard addition of spiked glyphosate in Horsepen Bayou. Although our SPE-IC-PAD method was not able to detect glyphosate, glufosinate, and AMPA in several surface water samples collected within the Houston area, a satisfactory recovery value of 96.8% was achieved for certified reference material containing glyphosate. Further, our study on optimal sample storge conditions suggested that glyphosate is stable in acidified surface water for 36 days. Our study recommends acidified or refrigerated conditions following sample collection intended for glyphosate determination. Optimal method development parameters and development strategies were also discussed with the intention to further lower LOD values and improve precision in natural water matrices
Inventory of STS-7 Mission Documents
No full textThis subseries consists of memos, mission reports, flight rules, payload analysis, safety summary, photo distribution plan, mission management team minutes, fact sheets, press information, etc. related to STS-7. The material is arranged chronologically and runs from February 1980 to June 1983
Application of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for Differentiating Sources of Fecal Pollution
No full textSince the passage of the Marine Mammal Protection Act in 1973, pinniped populations in coastal waters of the United States have increased exponentially. These high populations of large mammals could contribute to fecal contamination of recreational waters. Enterococci species counts are used to assess the degree of fecal contamination and elevated counts of this fecal indicator bacteria (FIB) force managers to close beaches; however, contribution of pinnipeds to high Enterococci counts is not known. This may reflect the high cost of methods of tracking the source of microbial contamination. Matrix Assisted Laser Desorption Ionization – Time of Flight Mass Spectrometry (MALDI-TOF MS) is a time and cost-effective way to identify bacteria through protein mass spectra analysis. MALDI-TOF can distinguish strains of bacteria of the same species but has not been evaluated as a tool for tracking Enterococci isolated from pinnipeds. In this study, Enterococci isolates were cultured from fresh seal scat samples taken from a pen housing Harbor seals. Enterococci were isolated by plating serial dilutions onto Rapid Enterococci ChromoSelect agar to generate a library of isolates from captive seals. Libraries of Enterococci were also generated from dog scat and a composite sample of human waste from a wastewater treatment plant, respectively. These isolates were identified with a MALDI-TOF system and cluster analysis was performed of all Enterococci isolates showed overall clusters between Enterococci isolated from a single source. Cluster analysis of isolates from harbor seal and dog scat reliably identified as E. faecalis with Bruker MALDI Biotyper system (> 2.3) was performed for source discrimination comparison. 22 E. faecalis isolates clustered into four separate MTUs, with two MTUs being harbor seal-specific. The distinct source-dependent MALDI-TOF MS clusters suggest that MALDI-TOF MS may be a valuable tool in microbial source tracking
Finding Aid for the Ellington Field Research Collection,1912-1998 (#2016-0003)
No full textThe Ellington Field Research Collection contains organizational histories, newspaper articles, manuscript drafts, photographs, memos, correspondence, copied items, newsletter issues, and miscellaneous materials, compiled as research materials by NASA Johnson Space Center historian William Larsen for author and NASA summer fellow Erik Carlson to write the NASA publication Ellington Field: A Short History, 1917-1962, in February 1999. It appears that Larsen had begun a manuscript for this history, but Carlson finished it and it was published under Carlson’s name. The materials in the collection pertain to the history and operation of Ellington Field (also known as Ellington Air Force Base) near Houston, Texas. The field has been used since 1962 by NASA Johnson Space Center for test flights and other aviation-based research related to human space flight
Finding Aid for the Allan DuPont Papers (HSF-55)
No full textThe Allan DuPont Papers is composed of internal NASA presentations, professional presentations, memos, and other related documentation, from NASA employee Allan DuPont’s time working in the Guidance, Navigation and Control (GNC) Subsystem at NASA Johnson Space Center in Houston, Texas, from 1963 to 2016. The majority of the collection consists PowerPoint-style presentation slide pages (printouts and transparencies). Topics within the collection include Rendezvous Proximity Operations & Capture Rendezvous (RPOC) between the International Space Station and various service vehicles; the Japanese H-II Transfer Vehicle; the European Space Agency Automated Transfer Vehicle; detailing of the development, testing and integration of the H-II Transfer vehicle and Automated Transfer Vehicle with NASA and the ISS; and other topics
Inventory of Flight Director's Presentation Files
No full textThis subseries consists of a chronological run of presentation charts generated by members of the Flight Director's Office of the Mission Operations Directorate. "Flight Directors are in charge of the flight control team. All decisions regarding the safe and expedient conduct of the flight are the flight director's responsibility. Since the main objective of the STS is to serve STS users, a prime FD responsibility is to accommodate user requirements and objectives whenever possible within safety and resource constraints. The FD has the final authority on time critical decisions affecting flight safety, including situations involving conflicting requirements between STS operations and payload operations" (MOD Orientation Manual, December 15, 1985). These concerns of the flight directors' are apparent in the subjects of the presentations in this subseries. A large number of them deal with safety and risk assessment issues, flight rules, and mission techniques. The material is dated from August 1983 through December 1987 (bulk dates 1986 - 1987)
Inventory of (Shuttle Program Office) Presentation Material
No full textThis subseries consists of 23 linear feet (46 boxes) of presentation material, most of which was produced by or for the Shuttle Program Office at JSC. It includes Congressional briefing material, presentations to the program director, presentations made to dignitaries and groups visiting JSC, program status briefings and more. This material runs from May 1969 (Phase A feasibility studies) through September 1988. Subject areas covered include design, cost, management, and operations of the Space Shuttle system
Inventory of Schnyer Documents
No full textThese documents are copies from the files of Mr. Dan Schnyer of NASA Headquarters. Mr. Schnyer is the former Director of Transportation Systems, Advanced Manned Missions Program Office of Manned Spaceflight. These copies were made by Dr. John Mauer, contract historian for the Shuttle Chronology, while conducting an oral history interview with Mr. Schnyer on October 20, 1984.The interview transcript is among the documents in this collection. The documents cover the early planning for a space transportation system during the period from 1964 to 1971. They consist of copies of correspondence, reports, briefing charts and drawings. The documents are arranged chronologically and preceded by a copy of the interview transcript
Inventory of Office of Space and Terrestrial Applications (OSTA) Photographs
No full textOSTA-1, the first scientific cargo carried on the Space Shuttle, was sponsored by NASA's Office of Space and Terrestrial Applications. The pallet, located in the Shuttle cargo bay, housed seven experiment packages including the Shuttle Imaging Radar (SIR), the Shuttle Multispectral Infra-red Radiometer (SMIRR), the Night / Day Optical Survey of Lightning
(NOSL), the Ocean Color Experiment (OCE), and the Feature Identification and Location Experiment (FILE), all terrestrial observation experiments. The seventh package calibrated a planned Spacelab experiment. This subseries consists of one linear foot of 8x10 photos showing pallet and experiment equipment and components, as well as OSTA pallet models and integration hardware. The folders are arranged alphabetically by subject and range in date from 1978 to 1981
Inventory of Boeing Documents
No full textThis subseries consists of reports and briefing charts generated by the Boeing Corporation between 1963 and 1980. The documents are organized chronologically