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Articles 1 - 30 of 98
Full-Text Articles in Physical Sciences and Mathematics
An Efficiently Excited Eu3+ Luminescent Site Formed In Eu,O-Codoped Gan, Takenori Iwaya, Shuhei Ichikawa, Volkmar Dierolf, Brandon Mitchell, Hayley Austin, Dolf Timmerman, Jun Tatebayashi, Yasufumi Fujiwara
An Efficiently Excited Eu3+ Luminescent Site Formed In Eu,O-Codoped Gan, Takenori Iwaya, Shuhei Ichikawa, Volkmar Dierolf, Brandon Mitchell, Hayley Austin, Dolf Timmerman, Jun Tatebayashi, Yasufumi Fujiwara
Physics & Engineering Faculty Publications
For the development of III-nitride-semiconductor-based monolithic micro-light-emitting diode (LED) displays, Eu,O-codoped GaN (GaN:Eu,O) is a promising material candidate for the red LEDs. The luminescence efficiency of Eu-related emission strongly depends on the local atomic structure of Eu ions. Our previous research has revealed that post-growth thermal annealing is an effective method for reconfiguring luminescent sites, leading to a significant increase in light output. We observed the preferential formation of a site with a peak at similar to 2.004 eV by the annealing process. In this study, we demonstrate that it is a previously unidentified independent site (OMVPE-X) using combined excitation-emission …
Quantum Logic Control And Precision Measurements Of Molecular Ions In A Ring Trap: An Approach For Testing Fundamental Symmetries, Yan Zhou, Joshua O. Island, Matt Grau
Quantum Logic Control And Precision Measurements Of Molecular Ions In A Ring Trap: An Approach For Testing Fundamental Symmetries, Yan Zhou, Joshua O. Island, Matt Grau
Physics Faculty Publications
This paper presents an experimental platform designed to facilitate quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin-precession coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame from parity-selective spin precession in a rotating frame. Moreover, the method is designed to support spatially and temporally coincident measurements on multiple ions prepared in states with different sensitivity to the new physics of interest. This provides powerful techniques to probe …
Determining Bond Strengths And Dissociation Dynamics Of Diatomic Metal-Containing Ions By Photofragment Imaging, Schuyler P. Lockwood
Determining Bond Strengths And Dissociation Dynamics Of Diatomic Metal-Containing Ions By Photofragment Imaging, Schuyler P. Lockwood
Doctoral Dissertations
Studies of simple metal ion – ligand complexes have primarily focused on understanding their roles in activating C-H and C-C bonds. However, data are often lacking on the fundamental properties of these species, which can have unusual bond orders and cluttered electronic structures with many states of multi-reference character, complicating their treatment in theoretical studies. Experimental work determining high-precision bond energies, ground state identities and excited state dynamics of a wider variety of metal-containing ions is needed to establish a robust set of well-characterized benchmark molecules. This work describes studies of the energetics and dynamics of several MX+ species, …
Characterization Of Particulate Size Distributions And Water-Soluble Ions Measured At A Broiler Farm, P. J. Silva, T. Cress, R. Drover, C. Michael, G. Docekal, P. Larkin, A. Godoy, D. A. Cavero, C. Sin, J. Waites, Rezaul Mamood, M. Cohron, K. L. Purvis-Roberts
Characterization Of Particulate Size Distributions And Water-Soluble Ions Measured At A Broiler Farm, P. J. Silva, T. Cress, R. Drover, C. Michael, G. Docekal, P. Larkin, A. Godoy, D. A. Cavero, C. Sin, J. Waites, Rezaul Mamood, M. Cohron, K. L. Purvis-Roberts
School of Natural Resources: Documents and Reviews
No abstract provided.
Formation Of Gaseous Peptide Ions From Electrospray Droplets: Competition Between The Ion Evaporation Mechanism And Charged Residue Mechanism., Elnaz Aliyari, Lars Konermann
Formation Of Gaseous Peptide Ions From Electrospray Droplets: Competition Between The Ion Evaporation Mechanism And Charged Residue Mechanism., Elnaz Aliyari, Lars Konermann
Chemistry Publications
The transfer of peptide ions from solution into the gas phase by electrospray ionization (ESI) is an integral component of mass spectrometry (MS)-based proteomics. The mechanisms whereby gaseous peptide ions are released from charged ESI nanodroplets remain unclear. This is in contrast to intact protein ESI, which has been the focus of detailed investigations using molecular dynamics (MD) simulations and other methods. Under acidic liquid chromatography/MS conditions, many peptides carry a solution charge of 3+ or 2+. Because of this pre-existing charge and their relatively small size, prevailing views suggest that peptides follow the ion evaporation mechanism (IEM). The IEM …
Toxic Effects Of Silver Ions On Early Developing Zebrafish Embryos Distinguished From Silver Nanoparticles, Martha S. Johnson, Preeyaporn Songkiatisak, Pavan Kumar Cherukuri, Xiao-Hong Nancy Xu
Toxic Effects Of Silver Ions On Early Developing Zebrafish Embryos Distinguished From Silver Nanoparticles, Martha S. Johnson, Preeyaporn Songkiatisak, Pavan Kumar Cherukuri, Xiao-Hong Nancy Xu
Chemistry & Biochemistry Faculty Publications
Currently, effects of nanomaterials and their ions, such as silver nanoparticles (Ag NPs) and silver ions (Ag+), on living organisms are not yet fully understood. One of the vital questions is whether nanomaterials have distinctive effects on living organisms from any other conventional chemicals (e.g., their ions), owing to their unique physicochemical properties. Due to various experimental protocols, studies of this crucial question have been inconclusive, which hinders rational design of effective regulatory guidelines for safely handling NPs. In this study, we chronically exposed early developing zebrafish embryos (cleavage-stage, 2 hours post-fertilization, hpf) to a dilution series of …
Efficient Removal Of Lead Ions From Aqueous Media Using Sustainable Sources On Marine Algae, Hannah Namkoong, Erik Biehler, Gon Namkoong, Tarek M. Abdel-Fattah
Efficient Removal Of Lead Ions From Aqueous Media Using Sustainable Sources On Marine Algae, Hannah Namkoong, Erik Biehler, Gon Namkoong, Tarek M. Abdel-Fattah
Electrical & Computer Engineering Faculty Publications
The goal of this project is to explore a new method to efficiently remove Pb(II) ions from water by processing Undaria pinnatifida into immobilized beads using sodium alginate and calcium chloride. The resulting biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Using immobilized U. pinnatifida, we investigated the effect of various factors on Pb(II) ion removal efficiency such as temperature, pH, ionic strength, time, and underlying biosorption mechanisms. For Pb(II) ion biosorption studies, Pb(II) ion biosorption data were obtained and analyzed using Langmuir and Freundlich adsorption models. It …
Mobile Protons Limit The Stability Of Salt Bridges In The Gas Phase: Implications For The Structures Of Electrosprayed Protein Ions., Lars Konermann, Elnaz Aliyari, Justin H Lee
Mobile Protons Limit The Stability Of Salt Bridges In The Gas Phase: Implications For The Structures Of Electrosprayed Protein Ions., Lars Konermann, Elnaz Aliyari, Justin H Lee
Chemistry Publications
Electrosprayed protein ions can retain native-like conformations. The intramolecular contacts that stabilize these compact gas-phase structures remain poorly understood. Recent work has uncovered abundant salt bridges in electrosprayed proteins. Salt bridges are zwitterionic BH+/A- contacts. The low dielectric constant in the vacuum strengthens electrostatic interactions, suggesting that salt bridges could be a key contributor to the retention of compact protein structures. A problem with this assertion is that H+ are mobile, such that H+ transfer can convert salt bridges into neutral B0/HA0 contacts. This possible salt bridge annihilation puts into question the …
Sulfolane-Induced Supercharging Of Electrosprayed Salt Clusters: An Experimental/Computational Perspective., Leanne M Martin, Lars Konermann
Sulfolane-Induced Supercharging Of Electrosprayed Salt Clusters: An Experimental/Computational Perspective., Leanne M Martin, Lars Konermann
Chemistry Publications
It is well-known that supercharging agents (SCAs) such as sulfolane enhance the electrospray ionization (ESI) charge states of proteins, although the mechanistic origins of this effect remain contentious. Only very few studies have explored SCA effects on analytes other than proteins or peptides. This work examines how sulfolane affects electrosprayed NaI salt clusters. Such alkali metal halide clusters have played a key role for earlier ESI mechanistic studies, making them interesting targets for supercharging investigations. ESI of aqueous NaI solutions predominantly generated singly charged [NanI(n-1)]+ clusters. The addition of sulfolane resulted in abundant …
The Effects Of Increasing Positively Charged Metal Ions Within Synovial Fluid, Kandisi Anyabwile
The Effects Of Increasing Positively Charged Metal Ions Within Synovial Fluid, Kandisi Anyabwile
Williams Honors College, Honors Research Projects
Osteoarthritis is a degenerative joint disease that affects 10% of men and 13% of women over age of 60. It is the degradation of the cartilage between two bones; obesity, age, overuse, or injury are major contributors to the development of this disease. The joint is incapsulated by the synovial sac filled with a viscous solution that aids in lubrication referred to as synovial fluid. If the synovial sac is ruptured due to injury, positive ions (K+, Na+, Ca2+, and Fe3+) may affect viscoelastic properties within the sac. The purpose of this …
Additive Modulation Of Dna-Dna Interactions By Interstitial Ions, Wei Meng, Raju Timsina, Abby Bull, Kurt Andresen, Xiangyun Qiu
Additive Modulation Of Dna-Dna Interactions By Interstitial Ions, Wei Meng, Raju Timsina, Abby Bull, Kurt Andresen, Xiangyun Qiu
Physics and Astronomy Faculty Publications
Quantitative understanding of biomolecular electrostatics, particularly involving multivalent ions and highly charged surfaces, remains lacking. Ion-modulated interactions between nucleic acids provide a model system in which electrostatics plays a dominant role. Using ordered DNA arrays neutralized by spherical cobalt3+ hexammine and Mg2+ ions, we investigate how the interstitial ions modulate DNA-DNA interactions. Using methods of ion counting, osmotic stress, and x-ray diffraction, we systematically determine thermodynamic quantities, including ion chemical potentials, ion partition, DNA osmotic pressure and force, and DNA-DNA spacing. Analyses of the multidimensional data provide quantitative insights into their interdependencies. The key finding of this study is that …
Laser Photoionization Spectroscopy Of Rydberg And Autoionization States Of Rare-Earth Atoms., Nafas Eshkabilov, Sh. R. Xaydarov, Anvar Kurbaniyazov
Laser Photoionization Spectroscopy Of Rydberg And Autoionization States Of Rare-Earth Atoms., Nafas Eshkabilov, Sh. R. Xaydarov, Anvar Kurbaniyazov
Scientific Journal of Samarkand University
Systematic studies of Rydberg and autoionization states of rare-earth atoms are carried out. The exact values of the ionization potentials of all lanthanides were determined, and the relationships between the ionization potential of atoms and the number of lost valence electrons during multistage laser photoionization were investigated. The physical mechanisms of the formation of spike and smooth, asymmetric autoionization resonances in near-threshold and long-range autoionization spectra of rare-earth atoms are established.
Gas Phase Protein Folding Triggered By Proton Stripping Generates Inside-Out Structures: A Molecular Dynamics Simulation Study., Alexander I M Sever, Lars Konermann
Gas Phase Protein Folding Triggered By Proton Stripping Generates Inside-Out Structures: A Molecular Dynamics Simulation Study., Alexander I M Sever, Lars Konermann
Chemistry Publications
The properties of electrosprayed protein ions continue to be enigmatic, owing to the absence of high-resolution structure determination methods in the gas phase. There is considerable evidence that under properly optimized conditions these ions preserve solution-like conformations and interactions. However, it is unlikely that these solution-like conformers represent the "intrinsic" structural preferences of gaseous proteins. In an effort to uncover what such intrinsically preferred conformers might look like, we performed molecular dynamics (MD) simulations of gaseous ubiquitin. Our work was inspired by recent gas phase experiments, where highly extended 13+ ubiquitin ions were transformed to compact 3+ species by proton …
Brown Carbon Production By Aqueous-Phase Interactions Of Glyoxal And So2, David O. De Haan, Kevin Jansen, Alec D. Rynaski, W. Ryan P. Sueme, Ashley K. Torkelson, Eric T. Czer, Alexander K. Kim, Michael A. Rafla, Audrey C. De Haan, Margaret A. Tolbert
Brown Carbon Production By Aqueous-Phase Interactions Of Glyoxal And So2, David O. De Haan, Kevin Jansen, Alec D. Rynaski, W. Ryan P. Sueme, Ashley K. Torkelson, Eric T. Czer, Alexander K. Kim, Michael A. Rafla, Audrey C. De Haan, Margaret A. Tolbert
Chemistry and Biochemistry: Faculty Scholarship
Oxalic acid and sulfate salts are major components of aerosol particles. Here, we explore the potential for their respective precursor species, glyoxal and SO2, to form atmospheric brown carbon via aqueous-phase reactions in a series of bulk aqueous and flow chamber aerosol experiments. In bulk aqueous solutions, UV- and visible-light-absorbing products are observed at pH 3–4 and 5–6, respectively, with small but detectable yields of hydroxyquinone and polyketone products formed, especially at pH 6. Hydroxymethanesulfonate (HMS), C2, and C3 sulfonates are major products detected by electrospray ionization mass spectrometry (ESI-MS) at pH 5. Past studies …
Generation And Reactions Of A Benzodehydrotropylium Ion-Co2(Co)6 Complex, Mariam A. Mehdi, Eric A.C. Bushnell, Sahar Nikoo, James W. Gauld, James R. Green
Generation And Reactions Of A Benzodehydrotropylium Ion-Co2(Co)6 Complex, Mariam A. Mehdi, Eric A.C. Bushnell, Sahar Nikoo, James W. Gauld, James R. Green
Chemistry and Biochemistry Publications
A series of 7-methylenedehydrobenzo[7]annulen-5-ol hexacarbonyldicobalt complexes were generated by Hosomi-Sakurai reactions of allylsilanes containing o-alkynylarylaldehyde-Co2(CO)6 complexes. One of cyclization products was converted into its corresponding dihydrobenzo[7]annulen-7-ol hexacarbonyldicobalt complex, an immediate precursor to a benzodehydrotropylium-Co2(CO)6. The cation was generated in situ and reacted with four nucleophiles, and its aromatic stabilization determined by computational methods.
Collaborative Learning Exercises For Teaching Protein Mass Spectrometry [Post-Print], Michelle Kovarik, Jill K. Robinson
Collaborative Learning Exercises For Teaching Protein Mass Spectrometry [Post-Print], Michelle Kovarik, Jill K. Robinson
Faculty Scholarship
A collaborative learning module for teaching protein mass spectrometry has been developed to overcome common obstacles to incorporating the modern topic of biological mass spectrometry into the undergraduate chemistry curriculum. Protein mass spectrometry data is provided to eliminate the need for expensive instrumentation, and an instructor’s manual gives necessary details for those unfamiliar with the topic. The first section provides background information on proteins and the field of proteomics. The second section describes the use of electrospray ionization to determine the molecular weight of a protein. The third section shows how to identify a protein using peptide mass mapping, and …
Substrate-Dependent Photoconductivity Dynamics In A High-Efficiency Hybrid Perovskite Alloy, Ali Moeed Tirmzi, Jeffrey A. Christians, Ryan P. Dwyer, David T. Moore, John A. Marohn
Substrate-Dependent Photoconductivity Dynamics In A High-Efficiency Hybrid Perovskite Alloy, Ali Moeed Tirmzi, Jeffrey A. Christians, Ryan P. Dwyer, David T. Moore, John A. Marohn
Faculty Publications
Films of (FA0.79MA0.16Cs0.05)0.97Pb(I0.84Br0.16)2.97 were grown over TiO2, SnO2, indium tin oxide (ITO), and NiO. Film conductivity was interrogated by measuring the in-phase and out-of-phase forces acting between the film and a charged microcantilever. We followed the films’ conductivity versus time, frequency, light intensity, and temperature (233−312 K). Perovskite conductivity was high and light-independent over ITO and NiO. Over TiO2 and SnO2, the conductivity was low in the dark,increased with light intensity, and persisted for 10’s of seconds after the light …
Oscillatory Behavior Of Hollow Grid Cathode Discharges, Roman Schrittwieser, Claudia-Teodora Teodorescu-Soare, Florin Enescu, Codrina Ionita, Dan-Gheorghe Dimitriu, Silviu Gurlui, Federico Mazzanti, Stefan-Andrei Irimiciuc, Bianca Hodoroaba, Turlough O'Hara, Ovidiu Vasilovici, Lidia Amarandi
Oscillatory Behavior Of Hollow Grid Cathode Discharges, Roman Schrittwieser, Claudia-Teodora Teodorescu-Soare, Florin Enescu, Codrina Ionita, Dan-Gheorghe Dimitriu, Silviu Gurlui, Federico Mazzanti, Stefan-Andrei Irimiciuc, Bianca Hodoroaba, Turlough O'Hara, Ovidiu Vasilovici, Lidia Amarandi
Conference Papers
Multiple complex space-charge structures in unmagnetized low-temperature plasmas arise from ionization phenomena near additional negatively or positively biased electrodes or due to local constraints. Because of their usually spherical form, such structures are called fireballs. If they appear inside hollow grids, they are called inverted fireballs or plasma bubbles. The temporal evolution of such structures is often accompanied by strong plasma instabilities. The dynamics of complex space-charge structures have been investigated by using single spherical grid cathode with an orifice. Langmuir probe and optical emission spectroscopy were used to diagnose the structures. Measurements delivered the axial profiles of the plasma …
Molecular Dynamics Simulation On Licl-H2o Interfacial Phenomenon For Liquid Desiccant Dehumidification, Xiaohui She, Yi Chen, Yuanhao Wang, Shifeng Wang, Yimo Luo
Molecular Dynamics Simulation On Licl-H2o Interfacial Phenomenon For Liquid Desiccant Dehumidification, Xiaohui She, Yi Chen, Yuanhao Wang, Shifeng Wang, Yimo Luo
Faculty of Science & Technology (THEi)
In this paper, molecular dynamics simulation was conducted to analyze the air-solution interface phenomenon of LiCl-H2O for liquid desiccant air dehumidification. Density profiles of ions in liquid desiccant aqueous solutions were plotted along the z axis, and distribution preferences of ions on the air-solution interface were studied. Besides, vapor pressure profiles above the solution surface were plotted, and the saturated vapor pressure was predicted and compared with the empirical data. It was found that water density remained stable in the bulk, and there was a sharp decrease on the air-solution interface. For the ions (Li+ and Cl-), a density peak …
Metallo-Polyelectrolytes As A Class Of Ionic Macromolecules For Functional Materials, Tianyu Zhu, Ye Sha, Jing Yan, Parasmani Pageni, Md Anisur Rahman, Yi Yan, Chuanbing Tang
Metallo-Polyelectrolytes As A Class Of Ionic Macromolecules For Functional Materials, Tianyu Zhu, Ye Sha, Jing Yan, Parasmani Pageni, Md Anisur Rahman, Yi Yan, Chuanbing Tang
Faculty Publications
The fields of soft polymers and macromolecular sciences have enjoyed a unique combination of metals and organic frameworks in the name of metallopolymers or organometallic polymers. When metallopolymers carry charged groups, they form a class of metal-containing polyelectrolytes or metallo-polyelectrolytes. This review identifies the unique properties and functions of metallo-polyelectrolytes compared with conventional organo-polyelectrolytes, in the hope of shedding light on the formation of functional materials with intriguing applications and potential benefits. It concludes with a critical perspective on the challenges and hurdles for metallo-polyelectrolytes, especially experimental quantitative analysis and theoretical modeling of ionic binding.
Effect Of Molten Salt Synthesis Processing Duration On The Photo- And Radioluminescence Of Uv- Visible- And X-Ray-Excitable La 2 Hf 2 O 7 :Eu 3+ Nanoparticles, Jose P. Zuniga, Santosh K. Gupta, Maya Abdou, Yuanbing Mao
Effect Of Molten Salt Synthesis Processing Duration On The Photo- And Radioluminescence Of Uv- Visible- And X-Ray-Excitable La 2 Hf 2 O 7 :Eu 3+ Nanoparticles, Jose P. Zuniga, Santosh K. Gupta, Maya Abdou, Yuanbing Mao
Chemistry Faculty Publications and Presentations
Ln 3+ -ion-doped nanomaterials possess excellent properties because of their high color purity, longer excited state lifetime, narrow emission, and large Stokes shifts. In this work, we studied the correlation between the luminescence properties of La 2 Hf 2 O 7 :Eu 3+ pyrochlore nanoparticles (NPs) synthesized by a molten salt synthesis (MSS) method at a relatively low temperature and several MSS processing durations (from 1 to 12 h). We synthesized these NPs with different sizes just by changing the MSS processing time without subjecting to high temperature. Raman spectroscopy confirmed the stabilization of the ideal pyrochlore structure of the …
All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website.
All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on an experimental approach which is based on an all-optical 6Liatom trap that--in contrast to magneto-optical traps--does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities …
Characterization Of The Effects Of Heavy Charged Particle Exposure On The Radiation Resistant Bacterium Deinococcus Radiodurans, Todd A. Bryant
Characterization Of The Effects Of Heavy Charged Particle Exposure On The Radiation Resistant Bacterium Deinococcus Radiodurans, Todd A. Bryant
Theses and Dissertations
Although not an extremophile, Deinococcus radiodurans has proven to have exceptional resistance to ionizing radiation, specifically via gamma and X-ray photons. To date, no known experiments have bombarded the bacterium with charged particles larger than hydrogen. This study explored the effects on the organism’s ability to survive high linear energy transfer heavy-charged particle exposures of oxygen ions. It also investigated the effects of low linear energy transfer ultraviolet radiation on various mutants. Two uvrB mutants were created to ascertain the importance of the gene in single-strand break repair following gamma irradiation and two recF mutants were created to explore the …
Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry
Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry
Theses and Dissertations
Deinococcus radiodurans is a robust bacterium that is known for its extraordinary resistance to ionizing radiation. In general, many of the investigations of this bacterium's resistance have revolved around low linear energy transfer radiation, such as gamma and electron radiation. This study explored Deinococcus radiodurans's ability to survive high linear energy transfer radiation, specifically proton and neutron radiation. Deinococcus radiodurans was dehydrated to reduce the effects of low linear energy transfer radiation. The bacteria were exposed to both neutron and proton radiation of varying amounts and rehydrated. The resulting colonies were counted and compared to colonies of non-irradiated control samples …
Crown Ether Effects On The Location Of Charge Carriers In Electrospray Droplets: Implications For The Mechanism Of Protein Charging And Supercharging., Haidy Metwally, Lars Konermann
Crown Ether Effects On The Location Of Charge Carriers In Electrospray Droplets: Implications For The Mechanism Of Protein Charging And Supercharging., Haidy Metwally, Lars Konermann
Chemistry Publications
"Native" electrospray ionization (ESI) mass spectrometry (MS) aims to transfer proteins from solution into the gas phase while maintaining solution-like structures and interactions. The ability to control the charge states of protein ions produced in these experiments is of considerable importance. Supercharging agents (SCAs) such as sulfolane greatly elevate charge states without significantly affecting the protein structure in bulk aqueous solution. The origin of native ESI supercharging remains contentious. According to one model, SCAs trigger unfolding within ESI droplets. In contrast, the "charge trapping model" envisions that SCAs impede the ejection of charge carriers (e.g., NH4+ or Na …
Improved Ultraviolet And Infrared Oscillator Strengths For Oh+, James N. Hodges, Dror M. Bittner, Peter F. Bernath
Improved Ultraviolet And Infrared Oscillator Strengths For Oh+, James N. Hodges, Dror M. Bittner, Peter F. Bernath
Chemistry & Biochemistry Faculty Publications
Molecular ions are key reaction intermediates in the interstellar medium. OH+ plays a central role in the formation of more complex chemical species and for estimating the cosmic ray ionization rate in astrophysical environments. Here, we use a recent analysis of a laboratory spectrum in conjunction with ab initio methods to calculate infrared and ultraviolet oscillator strengths. These new oscillator strengths include branch dependent intensity corrections, arising from the Herman–Wallis effect, that have not been included before. We estimate 10% total uncertainty in the UV and 6% total uncertainty in the IR for the oscillator strengths.
Characterization Of Laser-Generated Aluminum Plasma Using Ion Time-Of-Flight And Optical Emission Spectroscopy, Md. Haider A. Shaim, Hani E. Elsayed-Ali
Characterization Of Laser-Generated Aluminum Plasma Using Ion Time-Of-Flight And Optical Emission Spectroscopy, Md. Haider A. Shaim, Hani E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Laser plasma generated by ablation of an Al target in vacuum is characterized by ion time-of-flight combined with optical emission spectroscopy. A Q-switched Nd:YAG laser (wavelength λ = 1064 nm, pulse width τ ∼ 7 ns, and fluence F ≤ 38 J/cm2) is used to ablate the Al target. Ion yield and energy distribution of each charge state are measured. Ions are accelerated according to their charge state by the double-layer potential developed at the plasma-vacuum interface. The ion energy distribution follows a shifted Coulomb-Boltzmann distribution. Optical emission spectroscopy of the Al plasma gives significantly lower plasma temperature …
Single-Reference Coupled Cluster Theory For Multi-Reference Problems, Johannes T. Margraf, Ajith Perera, Jesse J. Lutz, Rodney J. Bartlett
Single-Reference Coupled Cluster Theory For Multi-Reference Problems, Johannes T. Margraf, Ajith Perera, Jesse J. Lutz, Rodney J. Bartlett
Faculty Publications
Coupled cluster (CC) theory is widely accepted as the most accurate and generally applicable approach in quantum chemistry. CC calculations are usually performed with single Slater-determinant references, e.g., canonical Hartree-Fock (HF) wavefunctions, though any single determinant can be used. This is an attractive feature because typical CC calculations are straightforward to apply, as there is no potentially ambiguous user input required. On the other hand, there can be concern that CC approximations give unreliable results when the reference determinant provides a poor description of the system of interest, i.e., when the HF or any other single determinant ground state has …
Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann
Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann
Chemistry Publications
Molecular dynamics (MD) simulations have become a key tool for examining the properties of electrosprayed protein ions. Traditional force fields employ static charges on titratable sites, whereas in reality, protons are highly mobile in gas-phase proteins. Earlier studies tackled this problem by adjusting charge patterns during MD runs. Within those algorithms, proton redistribution was subject to energy minimization, taking into account electrostatic and proton affinity contributions. However, those earlier approaches described (de)protonated moieties as point charges, neglecting charge solvation, which is highly prevalent in the gas phase. Here, we describe a mobile proton algorithm that considers the electrostatic contributions from …
Peptide Identification: Refining A Bayesian Stochastic Model, Theophilus Barnabas Kobina Acquah
Peptide Identification: Refining A Bayesian Stochastic Model, Theophilus Barnabas Kobina Acquah
Electronic Theses and Dissertations
Notwithstanding the challenges associated with different methods of peptide identification, other methods have been explored over the years. The complexity, size and computational challenges of peptide-based data sets calls for more intrusion into this sphere. By relying on the prior information about the average relative abundances of bond cleavages and the prior probability of any specific amino acid sequence, we refine an already developed Bayesian approach in identifying peptides. The likelihood function is improved by adding additional ions to the model and its size is driven by two overall goodness of fit measures. In the face of the complexities associated …