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Articles 31 - 60 of 151
Full-Text Articles in Physics
The Icecube Realtime Alert System, Karen Andeen, Icecube Collaboration
The Icecube Realtime Alert System, Karen Andeen, Icecube Collaboration
Physics Faculty Research and Publications
Although high-energy astrophysical neutrinos were discovered in 2013, their origin is still unknown. Aiming for the identification of an electromagnetic counterpart of a rapidly fading source, we have implemented a realtime analysis framework for the IceCube neutrino observatory. Several analyses selecting neutrinos of astrophysical origin are now operating in realtime at the detector site in Antarctica and are producing alerts for the community to enable rapid follow-up observations. The goal of these observations is to locate the astrophysical objects responsible for these neutrino signals. This paper highlights the infrastructure in place both at the South Pole site and at IceCube …
Astrophysical Neutrinos And Cosmic Rays Observed By Icecube, Karen Andeen, Icecube Collaboration
Astrophysical Neutrinos And Cosmic Rays Observed By Icecube, Karen Andeen, Icecube Collaboration
Physics Faculty Research and Publications
The core mission of the IceCube neutrino observatory is to study the origin and propagation of cosmic rays. IceCube, with its surface component IceTop, observes multiple signatures to accomplish this mission. Most important are the astrophysical neutrinos that are produced in interactions of cosmic rays, close to their sources and in interstellar space. IceCube is the first instrument that measures the properties of this astrophysical neutrino flux and constrains its origin. In addition, the spectrum, composition, and anisotropy of the local cosmic-ray flux are obtained from measurements of atmospheric muons and showers. Here we provide an overview of …
Search For Annihilating Dark Matter In The Sun With 3 Years Of Icecube Data, Karen Andeen
Search For Annihilating Dark Matter In The Sun With 3 Years Of Icecube Data, Karen Andeen
Physics Faculty Research and Publications
We present results from an analysis looking for darkmatter annihilation in the Sun with the IceCube neutrino telescope. Gravitationally trapped dark matter in the Sun’s core can annihilate into Standard Model particles making the Sun a source of GeV neutrinos. IceCube is able to detect neutrinos with energies>100GeVwhile its low-energy infill array DeepCore extends this to >10GeV. This analysis uses data gathered in the austral winters between May 2011 and May 2014, corresponding to 532 days of livetime when the Sun, being below the horizon, is a source of up-going neutrino events, easiest to discriminate against the dominant background …
All-Sky Search For Time-Integrated Neutrino Emission From Astrophysical Sources With 7 Yr Of Icecube Data, Karen Andeen
All-Sky Search For Time-Integrated Neutrino Emission From Astrophysical Sources With 7 Yr Of Icecube Data, Karen Andeen
Physics Faculty Research and Publications
Since the recent detection of an astrophysical flux of high-energy neutrinos, the question of its origin has not yet fully been answered. Much of what is known about this flux comes from a small event sample of high neutrino purity, good energy resolution, but large angular uncertainties. In searches for point-like sources, on the other hand, the best performance is given by using large statistics and good angular reconstructions. Track-like muon events produced in neutrino interactions satisfy these requirements. We present here the results of searches for point-like sources with neutrinos using data acquired by the IceCube detector over 7 …
First Search For Dark Matter Annihilations In The Earth With The Icecube Detector, Karen Andeen, Icecube Collaboration
First Search For Dark Matter Annihilations In The Earth With The Icecube Detector, Karen Andeen, Icecube Collaboration
Physics Faculty Research and Publications
We present the results of the first IceCube search for dark matter annihilation in the center of the Earth. Weakly interacting massive particles (WIMPs), candidates for dark matter, can scatter off nuclei inside the Earth and fall below its escape velocity. Over time the captured WIMPs will be accumulated and may eventually self-annihilate. Among the annihilation products only neutrinos can escape from the center of the Earth. Large-scale neutrino telescopes, such as the cubic kilometer IceCube Neutrino Observatory located at the South Pole, can be used to search for such neutrino fluxes. Data from 327 days of detector livetime during …
The Contribution Of Fermi-2lac Blazars To Diffuse Tev-Pev Neutrino Flux, Karen Andeen
The Contribution Of Fermi-2lac Blazars To Diffuse Tev-Pev Neutrino Flux, Karen Andeen
Physics Faculty Research and Publications
The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the …
The Iron-Type Nitrile Hydratase Activator Protein Is A Gtpase, Natalie Gumataotao, Karunagala Pathiranage Wasantha Lankathilaka, Brian Bennett, Richard C. Holz
The Iron-Type Nitrile Hydratase Activator Protein Is A Gtpase, Natalie Gumataotao, Karunagala Pathiranage Wasantha Lankathilaka, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
The Fe-type nitrile hydratase activator protein from Rhodococcus equi TG328-2 (ReNHase TG328-2) was successfully expressed and purified. Sequence analysis and homology modeling suggest that it is a G3E P-loop guanosine triphosphatase (GTPase) within the COG0523 subfamily. Kinetic studies revealed that the Fe-type activator protein is capable of hydrolyzing GTP to GDP with a kcat value of 1.2 × 10−3 s−1 and a Km value of 40 μM in the presence of 5 mM MgCl2 in 50 mM 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid at a pH of 8.0. The addition of divalent metal ions, such as Co(II), …
A Cobalt-Containing Eukaryotic Nitrile Hydratase, Salette Martinez, Xinhang Yang, Brian Bennett, Richard C. Holz
A Cobalt-Containing Eukaryotic Nitrile Hydratase, Salette Martinez, Xinhang Yang, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Nitrile hydratase (NHase), an industrially important enzyme that catalyzes the hydration of nitriles to their corresponding amides, has only been characterized from prokaryotic microbes. The putative NHase from the eukaryotic unicellular choanoflagellate organism Monosiga brevicollis (MbNHase) was heterologously expressed in Escherichia coli. The resulting enzyme expressed as a single polypeptide with fused α- and β-subunits linked by a seventeen-histidine region. Size-exclusion chromatography indicated that MbNHase exists primarily as an (αβ)2 homodimer in solution, analogous to the α2β2 homotetramer architecture observed for prokaryotic NHases. The NHase enzyme contained its full complement of Co(III) …
Multiple States Of Nitrile Hydratase From Rhodococcus Equi Tg328-2: Structural And Mechanistic Insights From Electron Paramagnetic Resonance And Density Functional Theory Studies, Natalia Stein, Natalie Gumataotao, Natalia Hajnas, Rui Wu, Karunagala Pathiranage Wasantha Lankathilaka, Uwe Bornscheuer, Dali Liu, Adam T. Fiedler, Richard C. Holz, Brian Bennett
Multiple States Of Nitrile Hydratase From Rhodococcus Equi Tg328-2: Structural And Mechanistic Insights From Electron Paramagnetic Resonance And Density Functional Theory Studies, Natalia Stein, Natalie Gumataotao, Natalia Hajnas, Rui Wu, Karunagala Pathiranage Wasantha Lankathilaka, Uwe Bornscheuer, Dali Liu, Adam T. Fiedler, Richard C. Holz, Brian Bennett
Physics Faculty Research and Publications
Iron-type nitrile hydratases (NHases) contain an Fe(III) ion coordinated in a characteristic “claw setting” by an axial cysteine thiolate, two equatorial peptide nitrogens, the sulfur atoms of equatorial cysteine-sulfenic and cysteine-sulfinic acids, and an axial water/hydroxyl moiety. The cysteine-sulfenic acid is susceptible to oxidation, and the enzyme is traditionally prepared using butyric acid as an oxidative protectant. The as-prepared enzyme exhibits a complex electron paramagnetic resonance (EPR) spectrum due to multiple low-spin (S = 1/2) Fe(III) species. Four distinct signals can be assigned to the resting active state, the active state bound to butyric acid, an …
Magnetization Reversal In Ferromagnetic Spirals Via Domain Wall Motion, Ryan D. Schumm, Andrew Kunz
Magnetization Reversal In Ferromagnetic Spirals Via Domain Wall Motion, Ryan D. Schumm, Andrew Kunz
Physics Faculty Research and Publications
Domain wall dynamics have been investigated in a variety of ferromagnetic nanostructures for potential applications in logic, sensing, and recording. We present a combination of analytic and simulated results describing the reliable field driven motion of a domain wall through the arms of a ferromagnetic spiral nanowire. The spiral geometry is capable of taking advantage of the benefits of both straight and circular wires. Measurements of the in-plane components of the spirals' magnetization can be used to determine the angular location of the domain wall, impacting the magnetoresistive applications dependent on the domain wall location. The spirals' magnetization components are …
Teaching The Basics Of Reactive Oxygen Species And Their Relevance To Cancer Biology: Mitochondrial Reactive Oxygen Species Detection, Redox Signaling, And Targeted Therapies, Balaraman Kalyanaraman, Gang Cheng, Micael Hardy, Olivier Ouari, Brian Bennett, Jacek Zielonka
Teaching The Basics Of Reactive Oxygen Species And Their Relevance To Cancer Biology: Mitochondrial Reactive Oxygen Species Detection, Redox Signaling, And Targeted Therapies, Balaraman Kalyanaraman, Gang Cheng, Micael Hardy, Olivier Ouari, Brian Bennett, Jacek Zielonka
Physics Faculty Research and Publications
Reactive oxygen species (ROS) have been implicated in tumorigenesis (tumor initiation, tumor progression, and metastasis). Of the many cellular sources of ROS generation, the mitochondria and the NADPH oxidase family of enzymes are possibly the most prevalent intracellular sources. In this article, we discuss the methodologies to detect mitochondria-derived superoxide and hydrogen peroxide using conventional probes as well as newly developed assays and probes, and the necessity of characterizing the diagnostic marker products with HPLC and LC-MS in order to rigorously identify the oxidizing species. The redox signaling roles of mitochondrial ROS, mitochondrial thiolperoxidases, and transcription factors in response to …
Increasing Tetrahydrobiopterin In Cardiomyocytes Adversely Affects Cardiac Redox State And Mitochondrial Function Independently Of Changes In No Production, Savitha Sethumadhavan, Jennifer Whitsett, Brian Bennett, Irina A. Ionova, Galen M. Pieper, Jeannette Vasquez-Vivar
Increasing Tetrahydrobiopterin In Cardiomyocytes Adversely Affects Cardiac Redox State And Mitochondrial Function Independently Of Changes In No Production, Savitha Sethumadhavan, Jennifer Whitsett, Brian Bennett, Irina A. Ionova, Galen M. Pieper, Jeannette Vasquez-Vivar
Physics Faculty Research and Publications
Tetrahydrobiopterin (BH4) represents a potential strategy for the treatment of cardiac remodeling, fibrosis and/or diastolic dysfunction. The effects of oral treatment with BH4 (Sapropterin™ or Kuvan™) are however dose-limiting with high dose negating functional improvements. Cardiomyocyte-specific overexpression of GTP cyclohydrolase I (mGCH) increases BH4 several-fold in the heart. Using this model, we aimed to establish the cardiomyocyte-specific responses to high levels of BH4. Quantification of BH4 and BH2 in mGCH transgenic hearts showed age-based variations in BH4:BH2 ratios. Hearts of mice (months) have lower BH4:BH2 ratios …
Potentially Diagnostic Electron Paramagnetic Resonance Spectra Elucidate The Underlying Mechanism Of Mitochondrial Dysfunction In The Deoxyguanosine Kinase Deficient Rat Model Of A Genetic Mitochondrial Dna Depletion Syndrome, Brian Bennett, Daniel Helbling, Hui Meng, Jason Jarzembowski, Aron M. Geurts, Marisa W. Friederich, Johan L.K. Van Hove, Michael W. Lawlor, David P. Dimmock
Potentially Diagnostic Electron Paramagnetic Resonance Spectra Elucidate The Underlying Mechanism Of Mitochondrial Dysfunction In The Deoxyguanosine Kinase Deficient Rat Model Of A Genetic Mitochondrial Dna Depletion Syndrome, Brian Bennett, Daniel Helbling, Hui Meng, Jason Jarzembowski, Aron M. Geurts, Marisa W. Friederich, Johan L.K. Van Hove, Michael W. Lawlor, David P. Dimmock
Physics Faculty Research and Publications
A novel rat model for a well-characterized human mitochondrial disease, mitochondrial DNA depletion syndrome with associated deoxyguanosine kinase (DGUOK) deficiency, is described. The rat model recapitulates the pathologic and biochemical signatures of the human disease. The application of electron paramagnetic (spin) resonance (EPR) spectroscopy to the identification and characterization of respiratory chain abnormalities in the mitochondria from freshly frozen tissue of the mitochondrial disease model rat is introduced. EPR is shown to be a sensitive technique for detecting mitochondrial functional abnormalities in situ and, here, is particularly useful in characterizing the redox state changes and oxidative stress that can result …
Selection And Control Of Individual Domain Walls In Nanowire Arrays Via Asymmetric Depinning Fields, Andrew Kunz, H. Henry Le, Demetrious Kutzke, Jesse Vogeler-Wunsch
Selection And Control Of Individual Domain Walls In Nanowire Arrays Via Asymmetric Depinning Fields, Andrew Kunz, H. Henry Le, Demetrious Kutzke, Jesse Vogeler-Wunsch
Physics Faculty Research and Publications
Artificially inscribed notches are often used to pin domain walls (DWs) in ferromagnetic nanowires. The process of selecting and moving the trapped DW in nanowire arrays is an important step for potential applications. The chirality of a DW leads to a pair of pinning positions at the inscribed notches, which can be modeled by a symmetric double well. The depinning field depends on the side of the well, the DW is trapped with respect to the applied field direction, and the DWs can also be transitioned between the two wells without depinning. We demonstrate how manipulating the double well improves …
Inhibition Of The Dape-Encoded N-Succinyl- ʟ, ʟ-Diaminopimelic Acid Desuccinylase From Neisseria Meningitidis By ʟ-Captopril, Anna Starus, Boguslaw Nocek, Brian Bennett, James A. Larrabee, Daniel L. Shaw, Wisath Sae-Lee, Marie T. Russo, Danuta M. Gillner, Magdalena Makowska-Grzyska, Andzrej Joachimiak, Richard C. Holz
Inhibition Of The Dape-Encoded N-Succinyl- ʟ, ʟ-Diaminopimelic Acid Desuccinylase From Neisseria Meningitidis By ʟ-Captopril, Anna Starus, Boguslaw Nocek, Brian Bennett, James A. Larrabee, Daniel L. Shaw, Wisath Sae-Lee, Marie T. Russo, Danuta M. Gillner, Magdalena Makowska-Grzyska, Andzrej Joachimiak, Richard C. Holz
Physics Faculty Research and Publications
Binding of the competitive inhibitor ʟ-captopril to the dapE-encoded N-succinyl-ʟ, ʟ-diaminopimelic acid desuccinylase from Neisseria meningitidis (NmDapE) was examined by kinetic, spectroscopic, and crystallographic methods. ʟ-Captopril, an angiotensin-converting enzyme (ACE) inhibitor, was previously shown to be a potent inhibitor of the DapE from Haemophilus influenzae (HiDapE) with an IC50 of 3.3 μM and a measured Ki of 1.8 μM and displayed a dose-responsive antibiotic activity toward Escherichia coli. ʟ-Captopril is also a competitive inhibitor of NmDapE with a Ki of 2.8 μM. To examine the nature of the interaction …
Correlations Between The Electronic Properties Of Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) And Its Structure: Effects Of Heme Oxidation State And Active Site Ligation, Natalia Stein, Daniel Love, Evan T. Judd, Sean J. Elliot, Brian Bennett, A. Andrew Pacheco
Correlations Between The Electronic Properties Of Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) And Its Structure: Effects Of Heme Oxidation State And Active Site Ligation, Natalia Stein, Daniel Love, Evan T. Judd, Sean J. Elliot, Brian Bennett, A. Andrew Pacheco
Physics Faculty Research and Publications
The electrochemical properties of Shewanella oneidensis cytochrome c nitrite reductase (ccNiR), a homodimer that contains five hemes per protomer, were investigated by UV–visible and electron paramagnetic resonance (EPR) spectropotentiometries. Global analysis of the UV–vis spectropotentiometric results yielded highly reproducible values for the heme midpoint potentials. These midpoint potential values were then assigned to specific hemes in each protomer (as defined in previous X-ray diffraction studies) by comparing the EPR and UV–vis spectropotentiometric results, taking advantage of the high sensitivity of EPR spectra to the structural microenvironment of paramagnetic centers. Addition of the strong-field ligand cyanide led to a 70 mV …
Conformational Dynamics Of Metallo-Β-Lactamase Ccra During Catalysis Investigated By Using Deer Spectroscopy, Mahesh Aitha, Lindsay Moritz, Indra D. Sahu, Omar Sanyurah, Zahilyn Roche, Robert Mccarrick, Gary A. Lorigan, Brian Bennett, Michael W. Crowder
Conformational Dynamics Of Metallo-Β-Lactamase Ccra During Catalysis Investigated By Using Deer Spectroscopy, Mahesh Aitha, Lindsay Moritz, Indra D. Sahu, Omar Sanyurah, Zahilyn Roche, Robert Mccarrick, Gary A. Lorigan, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
Previous crystallographic and mutagenesis studies have implicated the role of a position-conserved hairpin loop in the metallo-β-lactamases in substrate binding and catalysis. In an effort to probe the motion of that loop during catalysis, rapid-freeze-quench double electron–electron resonance (RFQ-DEER) spectroscopy was used to interrogate metallo-β-lactamase CcrA, which had a spin label at position 49 on the loop and spin labels (at positions 82, 126, or 233) 20–35 Å away from residue 49, during catalysis. At 10 ms after mixing, the DEER spectra show distance increases of 7, 10, and 13 Å between the spin label at position 49 and the …
Epr Methods For Biological Cu(Ii): L-Band Cw And Nars, Brian Bennett, Jason M. Kowalski
Epr Methods For Biological Cu(Ii): L-Band Cw And Nars, Brian Bennett, Jason M. Kowalski
Physics Faculty Research and Publications
Abstract: Copper has many roles in biology that involve the change of coordination sphere and/or oxidation state of the copper ion. Consequently, the study of copper in heterogeneous environments is an important area in biophysics. EPR is a primary technique for the investigation of paramagnetic copper, which is usually the isolated Cu(II) ion, but sometimes as Cu(II) in different oxidation states of multitransition ion clusters. The gross geometry of the coordination environment of Cu(II) can often be determined from a simple inspection of the EPR spectrum, recorded in the traditional X-band frequency range (9–10 GHz). Identification and quantitation of the …
Dilution Of Dipolar Interactions In A Spin-Labeled, Multimeric Metalloenzyme For Deer Studies, Mahesh Aitha, Timothy K. Richmond, Zhenxin Hu, Alyssa Hetrick, Raquel Reese, Althea Gunther, Robert Mccarrick, Brian Bennett, Michael W. Crowder
Dilution Of Dipolar Interactions In A Spin-Labeled, Multimeric Metalloenzyme For Deer Studies, Mahesh Aitha, Timothy K. Richmond, Zhenxin Hu, Alyssa Hetrick, Raquel Reese, Althea Gunther, Robert Mccarrick, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
The metallo-β-lactamases (MβLs), which require one or two Zn(II) ions in their active sites for activity, hydrolyze the amide bond in β-lactam-containing antibiotics, and render the antibiotics inactive. All known MβLs contain a mobile element near their active sites, and these mobile elements have been implicated in the catalytic mechanisms of these enzymes. However little is known about the dynamics of these elements. In this study, we prepared a site-specific, double spin-labeled analog of homotetrameric MβL L1 with spin labels at positions 163 and 286 and analyzed the sample with DEER (double electron electron resonance) spectroscopy. Four unique distances were …
A Deep Chandra Acis Survey Of M83, Knox S. Long, Kip D. Kuntz, William P. Blair, Leith Godfrey, Paul P. Plucinsky, Roberto Soria, Christopher Stockdale, P. Frank Winkler
A Deep Chandra Acis Survey Of M83, Knox S. Long, Kip D. Kuntz, William P. Blair, Leith Godfrey, Paul P. Plucinsky, Roberto Soria, Christopher Stockdale, P. Frank Winkler
Physics Faculty Research and Publications
We have obtained a series of deep X-ray images of the nearby galaxy M83 using Chandra, with a total exposure of 729 ks. Combining the new data with earlier archival observations totaling 61 ks, we find 378 point sources within the D25 contour of the galaxy. We find 80 more sources, mostly background active galactic nuclei (AGNs), outside of the D25 contour. Of the X-ray sources, 47 have been detected in a new radio survey of M83 obtained using the Australia Telescope Compact Array. Of the X-ray sources, at least 87 seem likely to be supernova remnants …
Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) Does Not Disproportionate Hydroxylamine To Ammonia And Nitrite, Despite A Strongly Favorable Driving Force, Matthew Youngblut, Daniel J. Pauly, Natalia Stein, Daniel Walters, John A. Conrad, Graham R. Moran, Brian Bennett, A. Andrew Pacheco
Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) Does Not Disproportionate Hydroxylamine To Ammonia And Nitrite, Despite A Strongly Favorable Driving Force, Matthew Youngblut, Daniel J. Pauly, Natalia Stein, Daniel Walters, John A. Conrad, Graham R. Moran, Brian Bennett, A. Andrew Pacheco
Physics Faculty Research and Publications
Cytochrome c nitrite reductase (ccNiR) from Shewanella oneidensis, which catalyzes the six-electron reduction of nitrite to ammonia in vivo, was shown to oxidize hydroxylamine in the presence of large quantities of this substrate, yielding nitrite as the sole free nitrogenous product. UV–visible stopped-flow and rapid-freeze-quench electron paramagnetic resonance data, along with product analysis, showed that the equilibrium between hydroxylamine and nitrite is fairly rapidly established in the presence of high initial concentrations of hydroxylamine, despite said equilibrium lying far to the left. By contrast, reduction of hydroxylamine to ammonia did not occur, even though disproportionation of hydroxylamine to …
Electron Cooling In A Young Radio Supernova: Sn 2012aw, Naveen Yadav, Alak Ray, Christopher Stockdale, Poonam Chandrasiri, Randall Smith, Rupak Roy, Vikram Dwarkadas, Firoza Sutaria, David Pooley
Electron Cooling In A Young Radio Supernova: Sn 2012aw, Naveen Yadav, Alak Ray, Christopher Stockdale, Poonam Chandrasiri, Randall Smith, Rupak Roy, Vikram Dwarkadas, Firoza Sutaria, David Pooley
Physics Faculty Research and Publications
We present the radio observations and modeling of an optically bright Type II-P supernova (SN), SN 2012aw which exploded in the nearby galaxy Messier 95 (M95) at a distance of 10 Mpc. The spectral index values calculated using C, X, and K bands are smaller than the expected values for the optically thin regime. During this time, the optical bolometric light curve stays in the plateau phase. We interpret the low spectral-index values to be a result of electron cooling. On the basis of comparison between the Compton cooling timescale and the synchrotron cooling timescale, we find that …
Homoleptic Nickel(Ii) Complexes Of Redox-Tunable Pincer-Type Ligands, Jeewantha S. Hewage, Sarath Wanniarachchi, Tyler James Morin, Brendan J Liddle, Megan Banaszynski, Sergey V. Lindeman, Brian Bennett, James R. Gardinier
Homoleptic Nickel(Ii) Complexes Of Redox-Tunable Pincer-Type Ligands, Jeewantha S. Hewage, Sarath Wanniarachchi, Tyler James Morin, Brendan J Liddle, Megan Banaszynski, Sergey V. Lindeman, Brian Bennett, James R. Gardinier
Physics Faculty Research and Publications
Different synthetic methods have been developed to prepare eight new redox-active pincer-type ligands, H(X,Y), that have pyrazol-1-yl flanking donors attached to an ortho-position of each ring of a diarylamine anchor and that have different groups, X and Y, at the para-aryl positions. Together with four previously known H(X,Y) ligands, a series of 12 Ni(X,Y)2 complexes were prepared in high yields by a simple one-pot reaction. Six of the 12 derivatives were characterized by single-crystal X-ray diffraction, which showed tetragonally distorted hexacoordinate nickel(II) centers. The nickel(II) complexes exhibit two quasi-reversible one-electron oxidation waves in their cyclic voltammograms, with …
An Early And Comprehensive Millimetre And Centimetre Wave And X-Ray Study Of Sn 2011dh: A Non-Equipartition Blast Wave Expanding Into A Massive Stellar Wind, Assaf Horesh, Christopher Stockdale, Derek B. Fox, Dale A. Frail, John Carpenter, S. R. Kulkarni, Eran O. Ofek, Avishay Gal-Yam, Mansi M. Kasliwal, Iair Arcavi, Robert Quimby, S. Bradley Cenko, Peter E. Nugent, Joshua S. Bloom, Nicholas M. Law, Dovi Poznanski, Evgeny Gorbikov, David Polishook, Ofer Yaron, Stuart Ryder, Kurt W. Weiler, Franz Bauer, Schuyler D. Van Dyk, Stefan Immler, Nino Panagia, Dave Pooley, Namir Kassim
An Early And Comprehensive Millimetre And Centimetre Wave And X-Ray Study Of Sn 2011dh: A Non-Equipartition Blast Wave Expanding Into A Massive Stellar Wind, Assaf Horesh, Christopher Stockdale, Derek B. Fox, Dale A. Frail, John Carpenter, S. R. Kulkarni, Eran O. Ofek, Avishay Gal-Yam, Mansi M. Kasliwal, Iair Arcavi, Robert Quimby, S. Bradley Cenko, Peter E. Nugent, Joshua S. Bloom, Nicholas M. Law, Dovi Poznanski, Evgeny Gorbikov, David Polishook, Ofer Yaron, Stuart Ryder, Kurt W. Weiler, Franz Bauer, Schuyler D. Van Dyk, Stefan Immler, Nino Panagia, Dave Pooley, Namir Kassim
Physics Faculty Research and Publications
Only a handful of supernovae (SNe) have been studied in multiwavelengths from the radio to X-rays, starting a few days after the explosion. The early detection and classification of the nearby Type IIb SN 2011dh/PTF 11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at one of the youngest phase ever of a core-collapse SN (days 3–12 after the explosion) in the radio, millimetre and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding …
Moving Difference (Mdiff) Non-Adiabatic Rapid Sweep (Nars) Epr Of Copper(Ii), James S. Hyde, Brian Bennett, Aaron W. Kittell, Jason M. Kowalski, Jason Walter Sidabras
Moving Difference (Mdiff) Non-Adiabatic Rapid Sweep (Nars) Epr Of Copper(Ii), James S. Hyde, Brian Bennett, Aaron W. Kittell, Jason M. Kowalski, Jason Walter Sidabras
Physics Faculty Research and Publications
Non-adiabatic rapid sweep (NARS) EPR spectroscopy has been introduced for application to nitroxide-labeled biological samples (Kittell et al., 2011). Displays are pure absorption, and are built up by acquiring data in spectral segments that are concatenated. In this paper we extend the method to frozen solutions of copper-imidazole, a square planar copper complex with four in-plane nitrogen ligands. Pure absorption spectra are created from concatenation of 170 5-gauss segments spanning 850 G at 1.9 GHz. These spectra, however, are not directly useful since nitrogen superhyperfine couplings are barely visible. Application of the moving difference (MDIFF) algorithm to the digitized NARS …
Responses Of Mn2+ Speciation In Deinococcus Radiodurans And Escherichia Coli To Γ-Radiation By Advanced Paramagnetic Resonance Methods, Ajay Sharma, Elena K. Gaidamakova, Vera Y. Matrosova, Brian Bennett, Michael J. Daly, Brian M. Hoffman
Responses Of Mn2+ Speciation In Deinococcus Radiodurans And Escherichia Coli To Γ-Radiation By Advanced Paramagnetic Resonance Methods, Ajay Sharma, Elena K. Gaidamakova, Vera Y. Matrosova, Brian Bennett, Michael J. Daly, Brian M. Hoffman
Physics Faculty Research and Publications
The remarkable ability of bacterium Deinococcus radiodurans to survive extreme doses of γ-rays (12,000 Gy), 20 times greater than Escherichia coli, is undiminished by loss of Mn-dependent superoxide dismutase (SodA). D. radiodurans radiation resistance is attributed to the accumulation of low-molecular-weight (LMW) “antioxidant” Mn2+–metabolite complexes that protect essential enzymes from oxidative damage. However, in vivo information about such complexes within D. radiodurans cells is lacking, and the idea that they can supplant reactive-oxygen-species (ROS)–scavenging enzymes remains controversial. In this report, measurements by advanced paramagnetic resonance techniques [electron-spin-echo (ESE)-EPR/electron nuclear double resonance/ESE envelope modulation (ESEEM)] reveal differential details …
Sample Preparation For Service At The National Biomedical Epr Center, Brian Bennett
Sample Preparation For Service At The National Biomedical Epr Center, Brian Bennett
Physics Faculty Research and Publications
No abstract provided.
Application Of Local Transverse Field For Domain Wall Control In Ferromagnetic Nanowire Arrays, Andrew Kunz, Jesse Vogeler-Wunsch
Application Of Local Transverse Field For Domain Wall Control In Ferromagnetic Nanowire Arrays, Andrew Kunz, Jesse Vogeler-Wunsch
Physics Faculty Research and Publications
In ferromagnetic nanowire arrays, where each wire contains multiple domain walls, it will be necessary to select an individual domain wall (DW) to move. In the field driven DW case, the field is typically applied globally affecting all of the domain walls in the system. We present micromagnetic simulation results demonstrating selectivity and control of an individual DW in such an array of nanowires using a combination of global and locally generated magnetic fields. Arranging the orientation of the local field allows for selectivity of a specific DW and its controllable movement to a new location.
Structural And Kinetic Studies On Metallo-Β-Lactamase Imp-1, Dionne H. Griffin, Timothy K. Richmond, Carlo Sanchez, Abraham Jon Moller, Robert M. Breece, David L. Tierney, Brian Bennett, Michael W. Crowder
Structural And Kinetic Studies On Metallo-Β-Lactamase Imp-1, Dionne H. Griffin, Timothy K. Richmond, Carlo Sanchez, Abraham Jon Moller, Robert M. Breece, David L. Tierney, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
In an effort to probe for metal binding to metallo-β-lactamase (MβL) IMP-1, the enzyme was overexpressed, purified, and characterized. The resulting enzyme was shown to bind 2 equiv of Zn(II), exhibit significant catalytic activity, and yield EXAFS results similar to crystallographic data previously reported. Rapid kinetic studies showed that IMP-1 does not stabilize a nitrocefin-derived reaction intermediate; rather, the enzyme follows a simple Michaelis mechanism to hydrolyze nitrocefin. Metal-substituted and metal-reconstituted analogues of IMP-1 were prepared by directly adding metal ion stocks to metal-free enzyme, which was generated by dialysis versus EDTA. UV–vis studies on IMP-1 containing 1 equiv of …
Using Sterics To Promote Reactivity In Fac-Re(Co)3 Complexes Of Some ‘Non-Innocent’ Nnn-Pincer Ligands, Sarath Wanniarachchi, Brendan J Liddle, John Toussaint, Sergey Lindeman, Brian Bennett, James R. Gardinier
Using Sterics To Promote Reactivity In Fac-Re(Co)3 Complexes Of Some ‘Non-Innocent’ Nnn-Pincer Ligands, Sarath Wanniarachchi, Brendan J Liddle, John Toussaint, Sergey Lindeman, Brian Bennett, James R. Gardinier
Physics Faculty Research and Publications
Two new redox active ligands based on di(2-(3-organopyrazolyl)-p-tolyl)amine have been prepared in order to investigate potential effects of steric bulk on the structures, electronic properties, or reactivity of tricarbonylrhenium(I) complexes. Replacing the hydrogens at the 3-pyrazolyl positions with alkyl groups causes significant distortion to the ligand framework due to potential interactions between these groups when bound to a fac-Re(CO)3 moiety. The distortions effectively increase the nucleophilic character of the central amino nitrogen and ligand-centered reactivity of the metal complexes.