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Chemistry & Biochemistry Faculty Publications

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Articles 301 - 330 of 339

Full-Text Articles in Chemistry

Atmospheric Effects Of Energetic Particle Precipitation In The Arctic Winter 1978-1979 Revisted, L. A. Holt, C. E. Randall, V. L. Harvey, E. E. Remsberg, G. P. Stiller, B. Funke, P. F. Bernath, K. A. Walker Jan 2012

Atmospheric Effects Of Energetic Particle Precipitation In The Arctic Winter 1978-1979 Revisted, L. A. Holt, C. E. Randall, V. L. Harvey, E. E. Remsberg, G. P. Stiller, B. Funke, P. F. Bernath, K. A. Walker

Chemistry & Biochemistry Faculty Publications

[1] The Limb Infrared Monitor of the Stratosphere (LIMS) measured polar stratospheric enhancements of NO2 mixing ratios due to energetic particle precipitation (EPP) in the Arctic winter of 1978–1979. Recently reprocessed LIMS data are compared to more recent measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) to place the LIMS measurements in the context of current observations. The amount of NOx (NO + NO2) entering the stratosphere that has been created by EPP in the mesosphere and lower thermosphere (EPP-NOx) has been quantified …

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First Remote Sensing Observations Of Trifluoromethane (Hfc-23) In The Upper Troposphere And Lower Stratosphere, Jeremy J. Harrison, Christopher D. Boone, Alexander T. Brown, Nicholas D. C. Allen, Geoffrey C. Toon, Peter F. Bernath Jan 2012

First Remote Sensing Observations Of Trifluoromethane (Hfc-23) In The Upper Troposphere And Lower Stratosphere, Jeremy J. Harrison, Christopher D. Boone, Alexander T. Brown, Nicholas D. C. Allen, Geoffrey C. Toon, Peter F. Bernath

Chemistry & Biochemistry Faculty Publications

This work reports the first remote sensing measurements of atmospheric HFC-23 (CHF3) using solar occultation measurements made by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and the Jet Propulsion Laboratory Mark IV (MkIV) balloon interferometer. A total of 8809 ACE occultations measured between 2004 and 2010 have been processed, along with 24 MkIV occultations measured between 1989 and 2007. ACE data (yearly averages over the 10-25 km altitude range) in the tropics/subtropics (40°S-40°N) reveal a trend of 4.0 ± 1.6% per year in the growth of HFC-23 for 2004-2009 (or 3.9 ± 1.2% per year for 2004-2010), …

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Analysis Of Iasi Tropospheric O₃ Data Over The Arctic During Polarcat Campaigns In 2008, M. Pommier, C. Clerbaux, K. S. Law, G. Ancellet, P. Bernath, P.-F. Coheur, J. Hadji-Lazaro, D. Hurtmans, P. Nédélec, J.-D. Paris, F. Ravetta, T. B. Ryerson, H. Schlager, A. J. Weinheimer Jan 2012

Analysis Of Iasi Tropospheric O₃ Data Over The Arctic During Polarcat Campaigns In 2008, M. Pommier, C. Clerbaux, K. S. Law, G. Ancellet, P. Bernath, P.-F. Coheur, J. Hadji-Lazaro, D. Hurtmans, P. Nédélec, J.-D. Paris, F. Ravetta, T. B. Ryerson, H. Schlager, A. J. Weinheimer

Chemistry & Biochemistry Faculty Publications

Ozone data retrieved in the Arctic region from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp-A European satellite are presented. They are compared with in situ and lidar observations obtained during a series of aircraft measurement campaigns as part of the International Polar Year POLARCAT activities in spring and summer 2008. Different air masses were sampled during the campaigns including clean air, polluted plumes originating from anthropogenic sources, forest fire plumes from the three northern continents, and stratospheric-influenced air masses. The comparison between IASI O3 [0–8 km], [0–12 km] partial columns and …

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Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopic Observations: 2. Using Isotopic Diagnostics To Understand The Mid And Upper Tropospheric Moist Bias In The Tropics And Subtropics, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Sandrine Bony, Jeonghoon Lee, Derek Brown, Christophe Sturm Jan 2012

Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopic Observations: 2. Using Isotopic Diagnostics To Understand The Mid And Upper Tropospheric Moist Bias In The Tropics And Subtropics, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Sandrine Bony, Jeonghoon Lee, Derek Brown, Christophe Sturm

Chemistry & Biochemistry Faculty Publications

Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic …

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Tunable Gold Nanostructures With Nanocapsules As Template Reaction Vessels, Balasubramanian Ramjee, Srujana Prayakarao, Sangbum Han, Wei Cao Jan 2012

Tunable Gold Nanostructures With Nanocapsules As Template Reaction Vessels, Balasubramanian Ramjee, Srujana Prayakarao, Sangbum Han, Wei Cao

Chemistry & Biochemistry Faculty Publications

Hollow, polymeric, thiol-ene resorcinarene nanocapsules can act as template reaction vessels for the synthesis of gold nanoshells or spherical aggregates of gold nanoparticles depending on the reaction conditions. The spherical nanoparticle aggregates were evaluated as catalysts in the biphasic reduction of 4-nitrophenol.

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Fourier Transform Mass Spectrometry For The Molecular Level Characterization Of Natural Organic Matter: Instrument Capabilities, Applications, And Limitations, Rachel L. Sleighter, Patrick G. Hatcher, Goran Nikolić (Ed.) Jan 2011

Fourier Transform Mass Spectrometry For The Molecular Level Characterization Of Natural Organic Matter: Instrument Capabilities, Applications, And Limitations, Rachel L. Sleighter, Patrick G. Hatcher, Goran Nikolić (Ed.)

Chemistry & Biochemistry Faculty Publications

No abstract provided.

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Characterization Of Heterogeneities And Domains In Aquatic And Sedimentary Organic Matter By 1 H Spin Diffusion: Potential For Elucidating The Formation Mechanisms, Jingdong Mao, Xiaoyan Cao Jan 2011

Characterization Of Heterogeneities And Domains In Aquatic And Sedimentary Organic Matter By 1 H Spin Diffusion: Potential For Elucidating The Formation Mechanisms, Jingdong Mao, Xiaoyan Cao

Chemistry & Biochemistry Faculty Publications

Although the information on domains and heterogeneities of natural organic matter (NOM) can provide insights into its formation mechanisms, the appropriate solid-state NMR technique for measuring them is still lacking. The traditional technique requires mobility differences in NOM whereas NOM components are primarily rigid. We introduced a new 1H spin diffusion technique, 1H-13C two-dimensional heteronuclear correlation (2D HETCOR) NMR with 1H spin diffusion, for characterization of domains and heterogeneities in aquatic and sedimentary organic matter. It was achieved by collecting a series of 2D HETCOR spectra with a variable mixing time, tm', and …

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Fossil And Contemporary Aerosol Particulate Organic Carbon In The Eastern United States: Implications For Deposition And Inputs To Watersheds, Andrew S. Wozniak, James E. Bauer, Rebecca M. Dickhut Jan 2011

Fossil And Contemporary Aerosol Particulate Organic Carbon In The Eastern United States: Implications For Deposition And Inputs To Watersheds, Andrew S. Wozniak, James E. Bauer, Rebecca M. Dickhut

Chemistry & Biochemistry Faculty Publications

Atmospheric particulate matter samples were collected from mid-Atlantic and northeastern U. S. (Virginia and New York, respectively) sites to assess the fossil versus contemporary sources contributing to aerosol organic carbon (OC) and the implications for its deposition to watersheds. Mean particulate matter total OC (TOC) deposition rates (wet + dry deposition) were calculated to be 1.6 and 2.4 mg C m-2 d-1 for the Virginia and New York sites, respectively. Wet deposition of particulate TOC was determined to be the dominant depositional mode, accounting for >65% (Virginia) and >80% (New York) of total aerosol TOC deposition. Isotopic mass …

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A Mini-Electrodialysis System For Desalting Small Volume Saline Samples For Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Hongmei Chen, Aron Stubbins, Patrick G. Hatcher Jan 2011

A Mini-Electrodialysis System For Desalting Small Volume Saline Samples For Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Hongmei Chen, Aron Stubbins, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

An affordable, commercially available mini-electrodialysis (mini-ED) system has been evaluated for the efficient desalting of small volume samples of seawater before analysis by electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Mini-ED FT-ICR mass spectra were compared with spectra for samples that were treated by C18 solid phase extraction, a commonly used method for rapid sample preparation for this type of analysis. In this comparison, it is clear that mini-ED provides more representative molecular information, compared with C18 isolation, and recovers the overwhelming majority of peaks from salt-free samples, indicating that it adequately represents the …

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Fourier Transform Emission Spectroscopy Of Yh And Yd: Observation Of New A¹Δ And B¹Π Electronic States, R. S. Ram, G. Li, P. F. Bernath Jan 2011

Fourier Transform Emission Spectroscopy Of Yh And Yd: Observation Of New A¹Δ And B¹Π Electronic States, R. S. Ram, G. Li, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

The emission spectra of YH and YD molecules have been investigated in the 3600–12 000 cm−1 region using a Fourier transform spectrometer. Molecules were formed in an yttrium hollow cathode lamp operated with a continuous flow of a mixture of Ne and Ar gases, and YH and YD were observed together in the same spectra. A group of bands observed near 1 μm have been identified as 0-0 and 1-1 bands of the A1Δ-X1Σ+ and B1Π-X1Σ+ transitions of YH and the 0-0 bands of the same two transitions …

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Ace-Fts Measurements Of Trace Species In The Characterization Of Biomass Burning Plumes, K. A. Tereszchuk, G. González Abad, C. Clerbaux, D. Hurtmans, P.-F. Coheur, P. F. Bernath Jan 2011

Ace-Fts Measurements Of Trace Species In The Characterization Of Biomass Burning Plumes, K. A. Tereszchuk, G. González Abad, C. Clerbaux, D. Hurtmans, P.-F. Coheur, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

To further our understanding of the effects of biomass burning emissions on atmospheric composition, we report measurements of trace species in biomass burning plumes made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the SCISAT-1 satellite. An extensive set of 15 molecules, C2H2, C2H6, CH3OH, CH4, CO, H2CO, HCN, HCOOH, HNO3, NO, NO2, N2O5, O-3, OCS and SF6 are used in our analysis. Even though most biomass burning smoke is typically confined to the …

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Effluent Organic Nitrogen (Eon): Bioavailability And Photochemical And Salinity-Mediated Release, Deborah A. Bronk, Quinn N. Roberts, Marta P. Sanderson, Elizabeth A. Canuel, Patrick G. Hatcher, Rajaa Mesfioui, Katherine C. Filippino, Margaret R. Mulholland, Nancy G. Love Jan 2010

Effluent Organic Nitrogen (Eon): Bioavailability And Photochemical And Salinity-Mediated Release, Deborah A. Bronk, Quinn N. Roberts, Marta P. Sanderson, Elizabeth A. Canuel, Patrick G. Hatcher, Rajaa Mesfioui, Katherine C. Filippino, Margaret R. Mulholland, Nancy G. Love

Chemistry & Biochemistry Faculty Publications

The goal of this study was to investigate three potential ways that the soluble organic nitrogen (N) fraction of wastewater treatment plant (WWTP) effluents, termed effluent organic N (EON), could contribute to coastal eutrophication - direct biological removal, photochemical release of labile compounds, and salinity-mediated release of ammonium (NH4+). Effluents from two WWTPs were used in the experiments. For the bioassays, EON was added to water from four salinities (∼0 to 30) collected from the James River (VA) in August 2008, and then concentrations of N and phosphorus compounds were measured periodically over 48 h. Bioassay results, based …

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Sequence And Structural Analysis Of The Chitinase Insertion Domain Reveals Two Conserved Motifs Involved In Chitin Binding, Hai Li, Lesley H. Greene Jan 2010

Sequence And Structural Analysis Of The Chitinase Insertion Domain Reveals Two Conserved Motifs Involved In Chitin Binding, Hai Li, Lesley H. Greene

Chemistry & Biochemistry Faculty Publications

Background: Chitinases are prevalent in life and are found in species including archaea, bacteria, fungi, plants, and animals. They break down chitin, which is the second most abundant carbohydrate in nature after cellulose. Hence, they are important for maintaining a balance between carbon and nitrogen trapped as insoluble chitin in biomass. Chitinases are classified into two families, 18 and 19 glycoside hydrolases. In addition to a catalytic domain, which is a triosephosphate isomerase barrel, many family 18 chitinases contain another module, i.e., chitinase insertion domain. While numerous studies focus on the biological role of the catalytic domain in chitinase activity, …

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Analytical Chemistry 2.0, David Harvey Jan 2010

Analytical Chemistry 2.0, David Harvey

Chemistry & Biochemistry Faculty Publications

No abstract provided.

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Theoretical Studies Of 2,3 -Sigmatropic Rearrangements Of Allylic Selenoxides And Selenimides, Craig A. Bayse, Sonia Antony Sep 2009

Theoretical Studies Of 2,3 -Sigmatropic Rearrangements Of Allylic Selenoxides And Selenimides, Craig A. Bayse, Sonia Antony

Chemistry & Biochemistry Faculty Publications

Density-functional theory is used to model the endo and exo transition states for [2,3]-sigmatropic rearrangement of allylic aryl-selenoxides and -selenimides. The endo transition state is generally preferred for selenoxides if there is no substitution at the 2 position of the allyl group. Based upon the relative energies of the endo and exo transition states, enantioselectivity of rearrangements is expected to be greatest for molecules with substitutions at the 1- or (E)-3- position of the allyl group. Ortho substitution of a nitro group on the ancillary selenoxide phenyl ring reduces the activation barriers, increases the difference between the endo and exo …

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Come For The Content, Stay For The Community, Hilary J. Eppley Jan 2009

Come For The Content, Stay For The Community, Hilary J. Eppley

Chemistry & Biochemistry Faculty Publications

No abstract provided.

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Electrospray And Photoionization Mass Spectrometry For The Characterization Of Organic Matter In Natural Waters: A Qualitative Assessment, William C. Hockaday, Jeremiah M. Pucell, Alan G. Marshall, Jeffery A. Baldock, Patrick G. Hatcher Jan 2009

Electrospray And Photoionization Mass Spectrometry For The Characterization Of Organic Matter In Natural Waters: A Qualitative Assessment, William C. Hockaday, Jeremiah M. Pucell, Alan G. Marshall, Jeffery A. Baldock, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Fourier-transform ion cyclotron resonance mass spectrometry (MS) has demonstrated potential to revolutionize the fields of limnology and chemical oceanography by identifying the individual molecular components of organic matter in natural waters. The use of MS for this purpose is made possible by the electrospray technique which successfully ionizes polar, nonvolatile organic molecules. Another recently developed ion source, atmospheric pressure photoionization (APPI), extends MS capabilities to less polar molecules. This article presents early results on the application of APPI MS to natural organic matter. We compare APPI MS and electrospray MS data for dissolved organic matter from Lake Drummond (Virginia, USA). …

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Zeolite Activation Of Organometallics: Revisiting Substitution Kinetics Of [Mo(Co)6] With Chemisorbed Pme3 In Dehydrated Na56Y Zeolite, Anthony L. Fernandez, Jianbin Hao, Roberta L. Parkes, Anthony J. Poë, Eduardo J.S. Vichi Jan 2008

Zeolite Activation Of Organometallics: Revisiting Substitution Kinetics Of [Mo(Co)6] With Chemisorbed Pme3 In Dehydrated Na56Y Zeolite, Anthony L. Fernandez, Jianbin Hao, Roberta L. Parkes, Anthony J. Poë, Eduardo J.S. Vichi

Chemistry & Biochemistry Faculty Publications

Reactions of [Mo(CO)6] under vacuum in α-cages of Na56Y zeolite fully loaded with chemisorbed PMe3 form cis-[Mo(CO)4(PMe3)2] but mixtures of [Mo(CO)5(PMe3)] and cis-[Mo(CO)4(PMe3)2] are formed under CO. Reactions under vacuum exhibit low enthalpic and very negative entropic factors (ΔH = 71.4 ± 3.5 kJ mol-1 and ΔS = -102 ± 11 J K-1 mol-1) compared with much higher enthalpic and positive entropic factors for CO dissociative reactions with P(n-Bu) …

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Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher Jan 2008

Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

The analysis of dissolved organic matter ( DOM) by Fourier transform ion cyclotron resonance mass spectrometry ( FTICR- MS) has gained wide interest recently, driven primarily by its ultrahigh resolving power and mass accuracy. Accurate calibration of mass spectra is a key step to successfully decipher the DOM components. We propose a simple and accurate method to internally calibrate the peaks in the complex spectra without the need to add a calibrant. Mass spectra of DOM samples from the Dismal Swamp, Virginia, and the lower Chesapeake Bay display the presence of naturally occurring fatty acids which can be readily recognized …

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Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper Jan 2008

Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

An analytical system was developed to determine photochemically produced carbon dioxide in marine waters. Our system was designed to measure low levels of carbon dioxide by maintaining a closed system to prevent atmospheric contamination during sample preparation, irradiation, and analysis. To detect low levels of photoproduced carbon dioxide in seawater, background dissolved inorganic carbon (DIC) was removed before irradiation. To strip out DIC, samples were acidified to pH 3.0 (converting DIC to carbon dioxide) and bubbled with low carbon dioxide air. The pH was then readjusted back to the original value, and the resulting low-DIC seawater samples were transferred pneumatically …

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Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper Jan 2008

Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

A new approach for parameterizing dissolved organic matter ( DOM) ultraviolet-visible absorption spectra is presented. Two distinct spectral slope regions ( 275-295 nm and 350-400 nm) within log-transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water ( Atlantic Ocean). On the basis of DOM size-fractionation studies ( ultrafiltration and gel filtration chromatography), the slope of the 275-295- nm region and the ratio of these slopes (SR; 275-295- nm slope : 350-400- nm slope) were related to DOM molecular weight ( MW) and …

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Technical Note: Molecular Characterization Of Aerosol-Derived Water Soluble Organic Carbon Using Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, A. S. Wozniak, J. E. Bauer, R. L. Sleighter, R. M. Dickhut, Patrick Hatcher Jan 2008

Technical Note: Molecular Characterization Of Aerosol-Derived Water Soluble Organic Carbon Using Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, A. S. Wozniak, J. E. Bauer, R. L. Sleighter, R. M. Dickhut, Patrick Hatcher

Chemistry & Biochemistry Faculty Publications

Despite the acknowledged relevance of aerosol-derived water-soluble organic carbon (WSOC) to climate and biogeochemical cycling, characterization of aerosol WSOC has been limited. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was utilized in this study to provide detailed molecular level characterization of the hi(,h molecular weight (HMW; m/z>223) component of aerosol-derived WSOC collected from rural sites in Virginia and New York, USA. More than 3000 peaks were detected by ESI FT-ICR MS within a m/z range of 223-600 for each sample. Approximately 86% (Virginia) and 78% (New York) of these peaks were assigned molecular formulas …

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Lignin Degradation In Wood-Feeding Insects, Scott M. Geib, Timothy R. Filley, Patrick G. Hatcher, Kelli Hoover, John E. Carlson, Maria Del Mar Jimenez-Gasco, Akiko Nakagawa-Izumi, Rachel L. Sleighter, Ming Tien Jan 2008

Lignin Degradation In Wood-Feeding Insects, Scott M. Geib, Timothy R. Filley, Patrick G. Hatcher, Kelli Hoover, John E. Carlson, Maria Del Mar Jimenez-Gasco, Akiko Nakagawa-Izumi, Rachel L. Sleighter, Ming Tien

Chemistry & Biochemistry Faculty Publications

The aromatic polymer lignin protects plants from most forms of microbial attack. Despite the fact that a significant fraction of all lignocellulose degraded passes through arthropod guts, the fate of lignin in these systems is not known. Using tetramethylammonium hydroxide thermochemolysis, we show lignin degradation by two insect species, the Asian longhorned beetle (Anoplophora glabripennis) and the Pacific dampwood termite (Zootermopsis angusticollis). In both the beetle and termite, significant levels of propyl side-chain oxidation (depolymerization) and demethylation of ring methoxyl groups is detected; for the termite, ring hydroxylation is also observed. In addition, culture-independent fungal gut …

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Elliptical Micro-Ring Organic Lasers, P. R. Korade, John Ballato, R, V. Gregory Jan 2007

Elliptical Micro-Ring Organic Lasers, P. R. Korade, John Ballato, R, V. Gregory

Chemistry & Biochemistry Faculty Publications

Multimode laser action was observed from optically excited 2,5-dioctyloxy poly(para-phenylene-vinylene), DOO-PPV, micro-rings coaxially deposited around glass optical fibres of elliptical cross-section. The laser emission was found to be dependent upon the incident angle of the excitation and exhibited linewidths of approximately 1.2 Å, quality factors (Q) exceeding 5000, and thresholds below 0.3 μJ pulse. Such elliptical organic micro-ring lasers offer increased tailorability in emission properties over more conventional analogues of circular cross-section. Also discussed is the potential for such low-threshold lasers to serve as integrated sources for fibre lasers and amplifiers.

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The Shape Of Pulverized Bituminous Vitrinite Coal Particles, Jonathan P. Mathews, Patrick G. Hatcher, Alan W. Scaroni Jan 2007

The Shape Of Pulverized Bituminous Vitrinite Coal Particles, Jonathan P. Mathews, Patrick G. Hatcher, Alan W. Scaroni

Chemistry & Biochemistry Faculty Publications

The shape of pulverized bituminous coal particles (vitrinites) was determined by optical and laser light scattering. Vitrain samples were collected from obvious tree remains located in the ceilings of two Appalachian coal mines. Wet sieving produced narrow size cuts. The particles were determined to be oblong or blocky in shape, with average length-to-width ratio of 1.7 and sphericity of 0.78. They were analogous in shape to a square ended, rectangular "house brick". The two bituminous coals and different size cuts of each coal had essentially the same shape parameters. Characteristic heating times and terminal velocities were higher by 22 and …

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In Vivo Imaging Of Transport And Biocompatibility Of Single Silver Nanoparticles In Early Development Of Zebrafish Embryos, Kerry J. Lee, Prakash D. Nallathamby, Lauren M. Browning, Christopher J. Osgood, Xiao-Hong Nancy Xu Jan 2007

In Vivo Imaging Of Transport And Biocompatibility Of Single Silver Nanoparticles In Early Development Of Zebrafish Embryos, Kerry J. Lee, Prakash D. Nallathamby, Lauren M. Browning, Christopher J. Osgood, Xiao-Hong Nancy Xu

Chemistry & Biochemistry Faculty Publications

Real-time study of the transport and biocompatibility of nanomaterials in early embryonic development at single-nanoparticle resolution can offer new knowledge about the delivery and effects of nanomaterials in vivo, and provide new insights into molecular transport mechanisms in developing embryos. In this study, we directly characterized the transport of single silver nanoparticles into an in vivo model system (zebrafish embryos) and investigated their effects on early embryonic development at single-nanoparticle resolution in real time. We designed highly purified and stable (not aggregated and no photodecomposition) nanoparticles and developed single-nanoparticle optics and in vivo assays to enable the study. We …

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The Application Of Electrospray Ionization Coupled To Ultrahigh Resolution Mass Spectrometry For The Molecular Characterization Of Natural Organic Matter, Rachel L. Sleighter, Patrick G. Hatcher Jan 2007

The Application Of Electrospray Ionization Coupled To Ultrahigh Resolution Mass Spectrometry For The Molecular Characterization Of Natural Organic Matter, Rachel L. Sleighter, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Mass spectrometry has recently played a key role in the understanding of natural organic matter (NOM) by providing molecular-level details about its composition. NOM, a complex assemblage of organic molecules present in natural waters and soils/sediments, has the ability to bind and transport anthropogenic materials. An improved understanding of its composition is crucial in order to understand how pollutants interact with NOM and how NOM cycles through global carbon cycles. In the past, low-resolution (> 3000) mass analyzers have offered some insights into the structure of NOM, but emerging ultrahigh resolution (> 200000) techniques such as electrospray ionization (ESI) coupled …

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Open-Ocean Carbon Monoxide Photoproduction, Aron Stubbins, Günther Uher, Cliff S. Law, Kenneth Mopper, Carol Robinson, Robert C. Upstill-Goddard Jan 2006

Open-Ocean Carbon Monoxide Photoproduction, Aron Stubbins, Günther Uher, Cliff S. Law, Kenneth Mopper, Carol Robinson, Robert C. Upstill-Goddard

Chemistry & Biochemistry Faculty Publications

Sunlight-initiated photolysis of chromophoric dissolved organic matter (CDOM) is the dominant source of carbon monoxide (CO) in the open-ocean. A modelling study was conducted to constrain this source. Spectral solar irradiance was obtained from two models (GCSOLAR and SMARTS2). Water-column CDOM and total light absorption were modelled using spectra collected along a Meridional transect of the Atlantic ocean using a 200-cm pathlength liquid waveguide UV-visible spectrophotometer. Apparent quantum yields for the production of CO (AQYCO) from CDOM were obtained from a parameterisation describing the relationship between CDOM light absorption coefficient and AQYCO and the CDOM spectra collected. …

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Effects Of Salinity Changes On The Photodegradation And Ultraviolet-Visible Absorbance Of Terrestrial Dissolved Organic Matter, E. C. Minor, J. Pothen, B. J. Dalzell, H. Abdulla, K. Mopper Jan 2006

Effects Of Salinity Changes On The Photodegradation And Ultraviolet-Visible Absorbance Of Terrestrial Dissolved Organic Matter, E. C. Minor, J. Pothen, B. J. Dalzell, H. Abdulla, K. Mopper

Chemistry & Biochemistry Faculty Publications

We performed laboratory studies to determine the effects of salinity on the photodegradation of dissolved organic matter (DOM) from the Great Dismal Swamp, Virginia, an important source of terrestrial DOM to the lower Chesapeake Bay. Samples were created by mixing Great Dismal Swamp water (ionic strength approximate to 0 mol L-1) with modified artificial seawater solutions of differing salinities while keeping the final dissolved organic carbon (DOC) concentration constant. These samples were then irradiated for 24 h in a light box providing ultraviolet (UV) light similar to that of natural sunlight. Light absorbance and DOC concentrations decreased after …

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Effect Of Humic Substance Photodegradation On Bacterial Growth And Respiration In Lake Water, Alexandre M. Anesio, William Granéli, George R. Aiken, David J. Kieber, Kenneth Mopper Jan 2005

Effect Of Humic Substance Photodegradation On Bacterial Growth And Respiration In Lake Water, Alexandre M. Anesio, William Granéli, George R. Aiken, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-μm pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H2O2 photoproduction. The H2 …

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