The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

/pdf/the-environmental-protection-agency-3gx4opzrjm.pdf

The Environmental Protection Agency

The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.

https://journals.sagepub.com/doi/pdf/10.1366/11-06574

Laser-induced breakdown spectroscopy (LIBS), part II: review of instrumental and methodological approaches to material analysis and applications to different fields.

Nitric Oxide Donors: Chemical Activities and Biological Applications

Aquatic surface chemistry: Edited by Werner Stumm. Wiley, New York. 1987. $69.95 (ISBN 0471822951)

Supercritical fluids posses properties that make them attractive as media for chemical reactions. Conducting chemical reactions at supercritical conditions affords opportunities to manipulate the reaction environment (solvent properties) by manipulating pressure, to enhance the solubilities of reactants and products, to eliminate interphase transport limitations on reaction rates, and to integrate reaction and separation unit operations. Supercritical conditions may be advantageous for reactions involved in fuels processing, biomass conversion, biocatalysis, homogeneous and heterogeneous catalysis, environmental control, polymerization, materials synthesis, and chemical synthesis. Moreover, supercritical fluids can be used profitably in fundamental chemical investigations of intermolecular interactions and their influence on chemical processes. Work on chemical reactions in and with supercritical fluids is reviewed. We discuss both fundamental studies and applications of reactions at supercritical conditions, with focus on work published after 1985.

/pdf/reactions-at-supercritical-conditions-applications-and-1qoeqkmmtb.pdf

Reactions at supercritical conditions: Applications and fundamentals

There have been relatively few detailed studies of PAH photochemical degradation mechanisms and products at solid/air interfaces under controlled conditions. Results from mechanistic studies on par...

Photochemical oxidation of phenanthrene sorbed on silica gel

Porous silica surfaces are shown to slowly catalyze the oxidation of adsorbed polycyclic aromatic hydrocarbons (PAH) to the corresponding radical cation via Lewis acid sites present on the surface. When a good electron acceptor such as methyl viologen dication (MV ++ ) is co-adsorbed on silica surface, a red-shifted structureless absorption band characteristic of a ground-state charge transfer (CT) complex formed between the PAH and MV ++ is observed. Oxygen efficiently competes with MV ++ for the trapped electrons on the active sites of silica surface causing a significant decrease in the concentration of ground-state CT complex. The rate of this electron transfer process is enhanced dramatically at the solid/liquid interface when solution of PAH in a non-polar solvent is added to dry silica containing adsorbed MV ++ . Room temperature electron paramagnetic resonance (EPR) spectra of PAHs adsorbed on silica show a broad unresolved signal ( g =2.0031–2.0045) due to PAH ⋅+ radical cation which disappears in the presence of air but can be restored upon evacuation of the sample. The EPR measurements of mixed samples containing PAH and MV ++ co-adsorbed on silica show a composite signal with hyperfine structure that may be due to presence of two paramagnetic species corresponding to MV ⋅+ and possibly PAH radical cation.

Surface catalyzed electron transfer from polycyclic aromatic hydrocarbons (PAH) to methyl viologen dication: evidence for ground-state charge transfer complex formation on silica gel

Supercritical carbon dioxide: behavior of .pi.* and .beta. solvatochromic indicators in media of different densities

The photochemistry of anthracene ( 1 ) was studied on dry surfaces of silica, CabOSil (fumes silica) and alumina (neutral) at low coverages (less than 11% of a monolayer). The adsorption of 1 onto these surfaces from cyclohexane obeys a Freundlich adsorption isotherm, demonstrating a distribution of adsorption sites for interactions between 1 and the surface. Photolysis of 1 ( λ ex =350 nm) adsorbed on silica, CabOSil or alumina, under deaerated conditions, proceeds slowly to give the anthracene-9,10-photodimer ( 2 ) as the only product. Diffuse reflectance and fluorescence spectroscopy show that a novel process, involving the formation of a stable ground state pair between two molecules of 1 takes place on all three surfaces at coverages of more than 1% of a monolayer. We propose a dimerization mechanism involving a singlet excimer formed from the stable ground state pairs. Photolysis at the solid-air interface, on the other hand, is considerably faster and proceeds to give 2 and photo-oxidation products of 1 . The primary oxidation product is anthracene-9,10-endoperoxide ( 3 ) which undergoes thermal decomposition on the surface to give 9,10-anthraquinone ( 4 ), 9,10-dihydro-9,10-dihydroxyanthracene ( 5 ), bianthronyl ( 6 ), 9-hydroxyanthrone ( 7 ) and 10,10′-dihydroxy-9,9′,10,10′-tetrahydro-9,9′-bianthryl ( 8 ) as the secondary products. Photo-oxidation is mediated by the addition of singlet molecular oxygen to ground state 1 .

Photodecomposition of anthracene on dry surfaces: products and mechanism

Photolysis of pyrene at the solid/air interface of unactivated and activated silica gel proceeds slowly to give mainly oxidized pyrene products. We have identified 1-hydroxypyrene, 1,6-pyrenedione, and 1,8-pyrenedione among the main reaction products. The remaining minor products show molecular weights and spectral properties consistent with oxygenated pyrenes. Furthermore, small amounts of 1,1‘-bipyrene dimer are also formed at higher surface coverages (2 × 10-5 mol/g). When photolysis is carried out at 5 × 10-5 mol/g pyrene, photodegradation rate drops sharply and pyrene loss becomes insignificant. No significant change in the product distribution is observed when the photolysis is carried out on unactivated or activated silica. Photodegradation rate is slightly faster on activated silica compared to unactivated silica. Mechanistic studies indicate that the precursor to photoproduct formation is pyrene cation radical which is postulated to be formed by electron transfer from pyrene excited state to oxyg...

Photochemistry of pyrene on unactivated and activated silica surfaces

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Michael E. Sigman

Author Tools

Chat about Author