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Western University

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2017

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Articles 1 - 30 of 52

Full-Text Articles in Physical Sciences and Mathematics

Changes In Enzyme Structural Dynamics Studied By Hydrogen Exchange-Mass Spectrometry: Ligand Binding Effects Or Catalytically Relevant Motions?, Courtney S Fast, Siavash Vahidi, Lars Konermann Dec 2017

Changes In Enzyme Structural Dynamics Studied By Hydrogen Exchange-Mass Spectrometry: Ligand Binding Effects Or Catalytically Relevant Motions?, Courtney S Fast, Siavash Vahidi, Lars Konermann

Chemistry Publications

It is believed that enzyme catalysis is facilitated by conformational dynamics of the protein scaffold that surrounds the active site, yet the exact nature of catalytically relevant protein motions remains largely unknown. Hydrogen/deuterium exchange (HDX) mass spectrometry (MS) reports on backbone H-bond fluctuations. HDX/MS thus represents a promising avenue for probing the relationship between enzyme dynamics and catalysis. A seemingly straightforward strategy for such studies involves comparative measurements during substrate turnover and in the resting state. We examined the feasibility of this approach using rabbit muscle pyruvate kinase (rM1-PK) which catalyzes the conversion of phosphoenolpyruvate and Mg-ADP to pyruvate and …

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Effect Of Counter Ions On The Self-Assembly Of Polystyrene-Polyphosphonium Block Copolymers, Benjamin Hisey, Jasmine V. Buddingh, Elizabeth R. Gillies, Paul J. Ragogna Dec 2017

Effect Of Counter Ions On The Self-Assembly Of Polystyrene-Polyphosphonium Block Copolymers, Benjamin Hisey, Jasmine V. Buddingh, Elizabeth R. Gillies, Paul J. Ragogna

Chemistry Publications

The ability to manipulate block copolymers on the nanoscale has led to many scientific and technological advances. These include nano-scale ordered bulk and thin films and also solution phase components, these are promising materials for making smaller ordered electronics, selective membranes, and also biomedical applications. The ability to manipulate block copolymer material architectures on such small scales has risen from thorough investigations into the properties that affect the architectures. Polyelectrolytes are an important class of polymers that are used to make amphiphilic block copolymers. In this context the authors synthesized polystyrene-b-polyphosphonium block copolymers with different anions coordinated to …

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1,6-Diphenyl-1,3,5-Hexatriene (Dph) As A Novel Matrix For Maldi Ms Imaging Of Fatty Acids, Phospholipids, And Sulfatides In Brain Tissues., Hanadi Ibrahim, Kristina Jurcic, Jasmine S-H Wang, Shawn N Whitehead, Ken K-C Yeung Dec 2017

1,6-Diphenyl-1,3,5-Hexatriene (Dph) As A Novel Matrix For Maldi Ms Imaging Of Fatty Acids, Phospholipids, And Sulfatides In Brain Tissues., Hanadi Ibrahim, Kristina Jurcic, Jasmine S-H Wang, Shawn N Whitehead, Ken K-C Yeung

Chemistry Publications

1,6-Diphenyl-1,3,5-hexatriene (DPH) is a commonly used fluorescence probe for studying cell membrane-lipids due to its affinity toward the acyl chains in the phospholipid bilayers. In this work, we investigated its use in matrix-assisted laser desorption/ionization (MALDI) as a new matrix for mass spectrometry imaging (MSI) of mouse and rat brain tissue. DPH exhibits very minimal matrix-induced background signals for the analysis of small molecules (below m/z of 1000). In the negative ion mode, DPH permits the highly sensitive detection of small fatty acids (m/z 200-350) as well as a variety of large lipids up to m/z of 1000, including lyso-phospholipid, …

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Tip-Enhanced Raman Spectroscopy Of Amyloid Β At Neuronal Spines., Mohammadali Tabatabaei, Fabiana A Caetano, Farshid Pashee, Stephen S G Ferguson, François Lagugné-Labarthet Nov 2017

Tip-Enhanced Raman Spectroscopy Of Amyloid Β At Neuronal Spines., Mohammadali Tabatabaei, Fabiana A Caetano, Farshid Pashee, Stephen S G Ferguson, François Lagugné-Labarthet

Chemistry Publications

The early stages of Alzheimer's disease pathogenesis are thought to occur at the synapse level, since synapse loss can be directly correlated with memory dysfunction. Considerable evidence has suggested that amyloid beta (Aβ), a secreted proteolytic derivative of amyloid precursor protein, appears to be a critical factor in the early 'synaptic failure' that is observed in Alzheimer's disease pathogenesis. The identification of Aβ at neuronal spines with high spatial resolution and high surface specificity would facilitate unraveling the intricate effect of Aβ on synapse loss and its effect on neighboring neuronal connections. Here, tip-enhanced Raman spectroscopy was used to map …

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Tip-Enhanced Raman Spectroscopy Of Amyloid Β At Neuronal Spines., Mohammadali Tabatabaei, Fabiana A Caetano, Farshid Pashee, Stephen S G Ferguson, François Lagugné-Labarthet Nov 2017

Tip-Enhanced Raman Spectroscopy Of Amyloid Β At Neuronal Spines., Mohammadali Tabatabaei, Fabiana A Caetano, Farshid Pashee, Stephen S G Ferguson, François Lagugné-Labarthet

Chemistry Publications

The early stages of Alzheimer's disease pathogenesis are thought to occur at the synapse level, since synapse loss can be directly correlated with memory dysfunction. Considerable evidence has suggested that amyloid beta (Aβ), a secreted proteolytic derivative of amyloid precursor protein, appears to be a critical factor in the early 'synaptic failure' that is observed in Alzheimer's disease pathogenesis. The identification of Aβ at neuronal spines with high spatial resolution and high surface specificity would facilitate unraveling the intricate effect of Aβ on synapse loss and its effect on neighboring neuronal connections. Here, tip-enhanced Raman spectroscopy was used to map …

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Would You Like To Motivate Software Testers? Ask Them How, Ronnie Santos, Cleyton Magalhaes, Jorge Correia-Neto, Fabio Queda Silva, Luiz Fernando Capretz, Rodrigo Souza Nov 2017

Would You Like To Motivate Software Testers? Ask Them How, Ronnie Santos, Cleyton Magalhaes, Jorge Correia-Neto, Fabio Queda Silva, Luiz Fernando Capretz, Rodrigo Souza

Electrical and Computer Engineering Publications

Considering the importance of software testing to the development of high quality and reliable software systems, this paper aims to investigate how can work-related factors influence the motivation of software testers. Method. We applied a questionnaire that was developed using a previous theory of motivation and satisfaction of software engineers to conduct a survey-based study to explore and understand how professional software testers perceive and value work-related factors that could influence their motivation at work. Results. With a sample of 80 software testers we observed that software testers are strongly motivated by variety of work, creative tasks, recognition for their …

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Cytochrome C As A Peroxidase: Activation Of The Precatalytic Native State By H, Victor Yin, Gary S Shaw, Lars Konermann Nov 2017

Cytochrome C As A Peroxidase: Activation Of The Precatalytic Native State By H, Victor Yin, Gary S Shaw, Lars Konermann

Chemistry Publications

In addition to serving as respiratory electron shuttle, ferri-cytochrome c (cyt c) acts as a peroxidase; i.e., it catalyzes the oxidation of organic substrates by H2O2. This peroxidase function plays a key role during apoptosis. Typical peroxidases have a five-coordinate heme with a vacant distal coordination site that permits the iron center to interact with H2O2. In contrast, native cyt c is six-coordinate, as the distal coordination site is occupied by Met80. It thus seems counterintuitive that native cyt c would exhibit peroxidase activity. The current work scrutinizes the origin of this …

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Would You Like To Motivate Software Testers? Ask Them How, Ronnie Santos, Cleyton Magalhaes, Jorge S. Correia-Neto, Fabio Q. B. Silva Dr., Luiz Fernando Capretz, Rodrigo E. C. Souza Nov 2017

Would You Like To Motivate Software Testers? Ask Them How, Ronnie Santos, Cleyton Magalhaes, Jorge S. Correia-Neto, Fabio Q. B. Silva Dr., Luiz Fernando Capretz, Rodrigo E. C. Souza

Electrical and Computer Engineering Publications

Considering the importance of software testing to the development of high quality and reliable software systems, this paper aims to investigate how can work-related factors influence the motivation of software testers. Method. We applied a questionnaire that was developed using a previous theory of motivation and satisfaction of software engineers to conduct a survey-based study to explore and understand how professional software testers perceive and value work-related factors that could influence their motivation at work. Results. With a sample of 80 software testers we observed that software testers are strongly motivated by variety of work, creative tasks, recognition for their …

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Dendritic Plasmonics For Mid-Infrared Spectroscopy, Francois Lagugne-Labarthet, Gregory Q. Wallace, Hayden C. Foy, Scott M. Rosendahl Nov 2017

Dendritic Plasmonics For Mid-Infrared Spectroscopy, Francois Lagugne-Labarthet, Gregory Q. Wallace, Hayden C. Foy, Scott M. Rosendahl

Chemistry Publications

Metallic nanostructures that exhibit tailored optical resonances spanning from the near to mid-infrared spectral range are of particular interest for spectroscopic and optical measurements in these spectral domains that can benefit from localized surface-enhancement effects. Plasmon resonances shifted in the near or mid-infrared range could be used to further enhance the excitation and/or the emission of an optical process. Surface-enhanced infrared absorption (SEIRA) is one of such processes and can particularly benefit from plasmon-enhanced local fields yielding an increase in sensitivity towards the detection of an analyte. Herein, we have fabricated a series of gold dendritic nanostructures, prepared by electron-beam …

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Finding An Effective Classification Technique To Develop A Software Team Composition Model, Abdul Rehman Gilal, Jafrezal Jaafar, Luiz Fernando Capretz, Mazni Omar, Shuib Basri Oct 2017

Finding An Effective Classification Technique To Develop A Software Team Composition Model, Abdul Rehman Gilal, Jafrezal Jaafar, Luiz Fernando Capretz, Mazni Omar, Shuib Basri

Electrical and Computer Engineering Publications

Ineffective software team composition has become recognized as a prominent aspect of software project failures. Reports from results extracted from different theoretical personality models have produced contradicting fits, validity challenges, and missing guidance during software development personnel selection. It is also believed that the technique/s used while developing a model can impact the overall results. Thus, this study aims to: 1) discover an effective classification technique to solve the problem, and 2) develop a model for composition of the software development team. The model developed was composed of three predictors: team role, personality types, and gender variables; it also contained …

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Thermo-Responsive Self-Immolative Nanoassemblies: Direct And Indirect Triggering, Bo Fan, John F. Trant, Gauvin Hemery, Olivier Sandre, Elizabeth R. Gillies Oct 2017

Thermo-Responsive Self-Immolative Nanoassemblies: Direct And Indirect Triggering, Bo Fan, John F. Trant, Gauvin Hemery, Olivier Sandre, Elizabeth R. Gillies

Chemistry Publications

A thermo-responsive end-cap based on a retro-Diels-Alder and subsequent furan elimination reaction was developed. It was used to cap poly(ethyl glyoxylate), allowing end-to-end depolymerization upon thermal triggering. Using block copolymers, thermo-responsive micelles and vesicles were prepared and shown to disassemble upon heating. Thermal degradation could also be triggered indirectly by magnetic field hyperthermia after incorporation of iron oxide nanoparticles into the assemblies.

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Aluminum Complexes Of N2o23‒ Formazanate Ligands Supported By Phosphine Oxide Donors, Ryan Maar, Amir Rabiee Kenaree, Ruizhong Zhang, Yichen Tao, Benjamin D. Katzman, Viktor N. Staroverov, Zhifeng Ding, Joe Gilroy Sep 2017

Aluminum Complexes Of N2o23‒ Formazanate Ligands Supported By Phosphine Oxide Donors, Ryan Maar, Amir Rabiee Kenaree, Ruizhong Zhang, Yichen Tao, Benjamin D. Katzman, Viktor N. Staroverov, Zhifeng Ding, Joe Gilroy

Chemistry Publications

The synthesis and characterization of a new family of phosphine-oxide-supported aluminum formazanate complexes (7a, 7b, 8a, 9a) are reported. X-ray diffraction studies revealed that the aluminum atoms in the complexes adopt an octahedral geometry in the solid state. The equatorial positions are occupied by an N2O23‒ formazanate ligand, and the axial positions are occupied by L-type phosphine oxide donors. UV-vis absorption spectroscopy revealed that the complexes were strongly absorbing (ε ~ 30,000 M‒1 cm‒1) between 500 and 700 nm. The absorption maxima in this region were simulated using …

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Boron Difluoride Adducts Of A Flexidentate Pyridine-Substituted Formazanate Ligand: Property Modulation Via Protonation And Coordination Chemistry, Stephanie M. Barbon, Jasmine V. Buddingh, Ryan R. Maar, Joe Gilroy Sep 2017

Boron Difluoride Adducts Of A Flexidentate Pyridine-Substituted Formazanate Ligand: Property Modulation Via Protonation And Coordination Chemistry, Stephanie M. Barbon, Jasmine V. Buddingh, Ryan R. Maar, Joe Gilroy

Chemistry Publications

The synthesis and characterization of a flexidentate pyridine-substituted formazanate ligand and its boron difluoride adducts, formed via two different coordination modes of the title ligand, are described. The first adduct adopted a structure that was typical of other boron difluoride adducts of triarylformazanate ligands and contained a free pyridine subsituent, while the second was formed via chelation of nitrogen atoms from the formazanate backbone and the pyridine substituent. Stepwise protonation of the pydridine-functionalized adduct, which is essentially non-emissive, resulted in a significant increase in the fluorescence quantum yield up to a maximum of 18%, prompting study of this adduct as …

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Photonic Band Structure Of Diamond Colloidal Crystals In A Cholesteric Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston Sep 2017

Photonic Band Structure Of Diamond Colloidal Crystals In A Cholesteric Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston

Physics and Astronomy Publications

In this paper, we demonstrate the presence of a photonic band gap for a diamond lattice structure made of particles with normal anchoring inside a cholesteric liquid crystal. As is typical for liquid crystals (LCs), there is considerable contrast between the dielectric constant parallel ε∥ and perpendicular ε⊥ to the director, with ε∥/ε⊥∼4 here. It is shown that the size of the photonic band gap is directly related to the size of colloidal particles and the contrast between the dielectric constant in the particles and the extreme values of ε in the LC medium (one needs either ε in the …

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Zr-Doped Tio2 As A Thermostabilizer In Plasmon-Enhanced Dye-Sensitized Solar Cells, Anastasia Pasche, Bernd Grohe, Silvia Mittler, Paul A. Charpentier Sep 2017

Zr-Doped Tio2 As A Thermostabilizer In Plasmon-Enhanced Dye-Sensitized Solar Cells, Anastasia Pasche, Bernd Grohe, Silvia Mittler, Paul A. Charpentier

Physics and Astronomy Publications

Harvesting solar energy is a promising solution toward meeting the world’s evergrowing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic–inorganic solar cells with tremendous potential for commercial application, but they are plagued by in efficiency due to their poor sunlight absorption. Plasmonic silver nanoparticles (AgNPs) have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance can cause thermal damage resulting in cell deterioration. Hence, the influence of Zr-doped TiO2 on the efficiency of plasmon-enhanced DSSCs was studied, showing that 5 mol.% Zr-doping of the photoactive TiO2 material can improve the photovoltaic performance of DSSCs by …

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Addressing A Common Misconception: Ammonium Acetate As Neutral Ph "Buffer" For Native Electrospray Mass Spectrometry., Lars Konermann Sep 2017

Addressing A Common Misconception: Ammonium Acetate As Neutral Ph "Buffer" For Native Electrospray Mass Spectrometry., Lars Konermann

Chemistry Publications

Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pKa ± 1 pH unit. NH4+ and CH3-COO- are …

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Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann Aug 2017

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 …

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Calcium-Mediated Control Of S100 Proteins: Allosteric Communication Via An Agitator/Signal Blocking Mechanism., Yiming Xiao, Gary S Shaw, Lars Konermann Aug 2017

Calcium-Mediated Control Of S100 Proteins: Allosteric Communication Via An Agitator/Signal Blocking Mechanism., Yiming Xiao, Gary S Shaw, Lars Konermann

Chemistry Publications

Allosteric proteins possess dynamically coupled residues for the propagation of input signals to distant target binding sites. The input signals usually correspond to "effector is present" or "effector is not present". Many aspects of allosteric regulation remain incompletely understood. This work focused on S100A11, a dimeric EF-hand protein with two hydrophobic target binding sites. An annexin peptide (Ax) served as the target. Target binding is allosterically controlled by Ca2+ over a distance of ∼26 Å. Ca2+ promotes formation of a [Ca4 S100 Ax2] complex, where the Ax peptides are accommodated between helices III/IV and III'/IV'. …

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Vacuum Birefringence, The Photon Anomalous Magnetic Moment And The Neutron Star Rx J1856.5−3754, Sree Ram Valluri, J.W. Mielniczuk, Farrukh Chishtie, D. Lamm, S. Auddy Aug 2017

Vacuum Birefringence, The Photon Anomalous Magnetic Moment And The Neutron Star Rx J1856.5−3754, Sree Ram Valluri, J.W. Mielniczuk, Farrukh Chishtie, D. Lamm, S. Auddy

Physics and Astronomy Publications

We analyse the spectrum of the Hamiltonian of a photon propagating in a strong magnetic field B ∼ Bcr, where Bcr=m2e≃4.4×1013" role="presentation">Bcr=m2e≃4.4×1013 G is the Schwinger critical field. We show that the anomalous magnetic moment of a photon in the one-loop approximation is a non-decreasing function of the magnetic field B in the range 0 ≤ B ≤ 30 Bcr. We provide a numerical representation of the expression for the anomalous magnetic moment in terms of special functions. We find that the anomalous magnetic moment μγ of a photon for B = 30 B …

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Nitrogen And Carbon Isotopic Dynamics Of Subarctic Soils And Plants In Southern Yukon Territory And Its Implications For Paleoecological And Paleodietary Studies, Farnoush Tahmesabi, Fred J. Longstaffe, Grant Zazula, Bruce Bennett Aug 2017

Nitrogen And Carbon Isotopic Dynamics Of Subarctic Soils And Plants In Southern Yukon Territory And Its Implications For Paleoecological And Paleodietary Studies, Farnoush Tahmesabi, Fred J. Longstaffe, Grant Zazula, Bruce Bennett

Earth Sciences Publications

We examine here the carbon and nitrogen isotopic compositions of bulk soils (8 topsoil and 7 subsoils, including two soil profiles) and five different plant parts of 79 C3 plants from two main functional groups: herbs and shrubs/subshrubs, from 18 different locations in grasslands of southern Yukon Territory, Canada (eastern shoreline of Kluane Lake and Whitehorse area). The Kluane Lake region in particular has been identified previously as an analogue for Late Pleistocene eastern Beringia. All topsoils have higher average total nitrogen δ15N and organic carbon δ13C than plants from the same sites with a …

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(Co)Polymers Containing Boron Difluoride 3-Cyanoformazanate Complexes: Emission Enhancement Via Random Copolymerization, Joe Gilroy, Samantha Novoa Aug 2017

(Co)Polymers Containing Boron Difluoride 3-Cyanoformazanate Complexes: Emission Enhancement Via Random Copolymerization, Joe Gilroy, Samantha Novoa

Chemistry Publications

Ring-opening metathesis polymerization was used to produce polymers bearing an asymmetrically substituted boron difluoride 3-cyanoformazanate complex. The polymers were found to retain many of the unique characteristics of molecular boron difluoride complexes of 3-cyanoformazanates, including intense light absorption at ca. 560 nm and reversible electrochemical reductions implicating the radical anion and dianion forms of the formazanate complexes in the repeating unit of the polymer backbone. The polymers were also found to be emissive, with emission maxima centred at ca. 665 nm. The monomer employed in this study had a fluorescence quantum yield of 30%, while homopolymers were weakly emissive and …

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A Vision For Canadian Space Exploration, Ilaria Caiazzo, Sarah C. Gallagher, Jeremy Heyl Aug 2017

A Vision For Canadian Space Exploration, Ilaria Caiazzo, Sarah C. Gallagher, Jeremy Heyl

Physics and Astronomy Publications

We propose a sustained and balanced program in space exploration to fuel innovation in the space sector, support Canada's world-leading space researchers, inspire the next generation of scientists and innovators, and create thousands of highly skilled, well-paying jobs for Canadians. During the next decade we recommend a total investment of approximately $1B, increasing to $1.3B in each decade that follows, including a regular flagship mission that Canada would lead and a constellation of smaller missions, either led by Canada or in collaboration with international partners.

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Evolution Of Delayed Dispersal And Subsequent Emergence Of Helping, With Implications For Cooperative Breeding., Geoff Wild, Judith Korb Aug 2017

Evolution Of Delayed Dispersal And Subsequent Emergence Of Helping, With Implications For Cooperative Breeding., Geoff Wild, Judith Korb

Applied Mathematics Publications

Cooperative breeding occurs when individuals help raise the offspring of others. It is widely accepted that help displayed by cooperative breeders emerged only after individuals' tendency to delay dispersal had become established. We use this idea as a basis for two inclusive-fitness models: one for the evolution of delayed dispersal, and a second for the subsequent emergence of helpful behavior exhibited by non-breeding individuals. We focus on a territorial species in a saturated environment, and allow territories to be inherited by non-breeding individuals who have delayed dispersal. Our first model predicts that increased survivorship and increased fecundity both provide an …

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New Biotite And Muscovite Isotopic Reference Materials, Usgs57 And Usgs58, For Δ2h Measurements–A Replacement For Nbs 30, Haiping Qi, Tyler B. Coplen, Matthias Gehre, Torsten W. Vennemann, Willi A. Brand, Heike Geilmann, Gerald Olack, Ilya N. Bindeman, Jim Palandri, Li Huang, Fred J. Longstaffe Jul 2017

New Biotite And Muscovite Isotopic Reference Materials, Usgs57 And Usgs58, For Δ2h Measurements–A Replacement For Nbs 30, Haiping Qi, Tyler B. Coplen, Matthias Gehre, Torsten W. Vennemann, Willi A. Brand, Heike Geilmann, Gerald Olack, Ilya N. Bindeman, Jim Palandri, Li Huang, Fred J. Longstaffe

Earth Sciences Publications

The advent of continuous-flow isotope-ratio mass spectrometry (CF-IRMS) coupled with a high temperature conversion (HTC) system enabled faster, more cost effective, and more precise δ2H analysis of hydrogen-bearing solids. Accurate hydrogen isotopic analysis by on-line or off-line techniques requires appropriate isotopic reference materials (RMs). A strategy of two-point calibrations spanning δ2H range of the unknowns using two RMs is recommended. Unfortunately, the supply of the previously widely used isotopic RM, NBS 30 biotite, is exhausted. In addition, recent measurements have shown that the determination of δ2H values of NBS 30 biotite on the VSMOW-SLAP …

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Self-Healing Polyphosphonium Ionic Networks, Elizabeth Gillies, Tyler J. Cuthbert, Joshua J. Jadischke, John R. De Bruyn, Paul J. Ragogna, Elizabeth R. Gillies Jul 2017

Self-Healing Polyphosphonium Ionic Networks, Elizabeth Gillies, Tyler J. Cuthbert, Joshua J. Jadischke, John R. De Bruyn, Paul J. Ragogna, Elizabeth R. Gillies

Chemistry Publications

Self healing, ionically crosslinked networks were prepared from poly(acrylic acid) (PAA) and poly(triethyl(4-vinylbenzyl)phosphonium chloride (P-Et-P) and their properties were studied. Three different ratios of PAA/P-Et-P were incorporated into the networks by varying the addition orders of the components. Swelling of the networks increased with increasing NaCl concentration when they were immersed in aqueous solution. All networks retained their structural integrity in 0.1 M NaCl. Studies of the rheological and tensile properties of the networks swelled in 0.1 M NaCl showed that PAA>P-Et-Pexhibited high elongation and viscoelastic properties suitable for self-healing with a relaxation time of ~30 …

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Soft Sides Of Software, Luiz Fernando Capretz, Faheem Ahmed, Fabio Queda Silva Jul 2017

Soft Sides Of Software, Luiz Fernando Capretz, Faheem Ahmed, Fabio Queda Silva

Electrical and Computer Engineering Publications

Software is a field of rapid changes: the best technology today becomes obsolete in the near future. If we review the graduate attributes of any of the software engineering programs across the world, life-long learning is one of them. The social and psychological aspects of professional development is linked with rewards. In organizations, where people are provided with learning opportunities and there is a culture that rewards learning, people embrace changes easily. However, the software industry tends to be short-sighted and its primary focus is more on current project success; it usually ignores the capacity building of the individual or …

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Structurally Diverse Boron-Nitrogen Heterocycles From An N2o23− Formazanate Ligand, Stephanie Barbon, Viktor Staroverov, Joe Gilroy Jun 2017

Structurally Diverse Boron-Nitrogen Heterocycles From An N2o23− Formazanate Ligand, Stephanie Barbon, Viktor Staroverov, Joe Gilroy

Chemistry Publications

Five new compounds comprised of unprecedented boron-nitrogen heterocycles have been isolated from a single reaction of a potentially tetradentate N2O23− formazanate ligand with BF3­•OEt2 and NEt3. Optimized yields for each product were obtained through variation of experimental conditions and rationalized in terms of relative Gibbs free energies of the products as determined by electronic structure calculations. Chemical reduction of two of these compounds resulted in the formation of a stable anion, radical anion, and diradical dianion. Structural and electronic properties of this new family of redox-active heterocycles were characterized using UV-vis …

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Structurally Diverse Boron-Nitrogen Heterocycles From An N2o23− Formazanate Ligand, Stephanie M. Barbon, Viktor N. Staroverov, Joe Gilroy Jun 2017

Structurally Diverse Boron-Nitrogen Heterocycles From An N2o23− Formazanate Ligand, Stephanie M. Barbon, Viktor N. Staroverov, Joe Gilroy

Chemistry Publications

Five new compounds comprised of unprecedented boron-nitrogen heterocycles have been isolated from a single reaction of a potentially tetradentate N2O23− formazanate ligand with BF3­•OEt2 and NEt3. Optimized yields for each product were obtained through variation of experimental conditions and rationalized in terms of relative Gibbs free energies of the products as determined by electronic structure calculations. Chemical reduction of two of these compounds resulted in the formation of a stable anion, radical anion, and diradical dianion. Structural and electronic properties of this new family of redox-active heterocycles were characterized using UV-vis …

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Catalytic Acceptorless Dehydrogenation Of Amines With Ru(PR2nR′2) And Ru(Dppp) Complexes, James M. Stubbs, Richard J. Hazlehurst, Paul D. Boyle, Johanna M. Blacquiere May 2017

Catalytic Acceptorless Dehydrogenation Of Amines With Ru(PR2nR′2) And Ru(Dppp) Complexes, James M. Stubbs, Richard J. Hazlehurst, Paul D. Boyle, Johanna M. Blacquiere

Chemistry Publications

[Ru(Cp)(PPh2NBn2)(MeCN)]PF6 (1; PPh2NBn2 = 1,5-benzyl-3,7-phenyl-1,5-diaza-3,7-diphosphacyclooctane) and [Ru(Cp)(dppp)(MeCN)]PF6 (2; dppp = 1,3-bis(diphenylphosphino)propane) are both active toward the acceptorless dehydrogenation of benzylamine (BnNH2) and N-heterocycles. The two catalysts have similar activities but different selectivities for dehydrogenation products. Independent synthesis of a [Ru(Cp)(PPh2NBn2)(NH2Bn)]PF6 adduct (3) reveals the presence of a hydrogen bond between the bound amine and the pendent base of the PPh2NBn2 ligand. Preliminary mechanistic studies reveal that the benzylamine adduct is not an on-cycle catalyst intermediate.

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Heterogeneous Colloidal Particles Immersed In A Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston May 2017

Heterogeneous Colloidal Particles Immersed In A Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston

Physics and Astronomy Publications

In this paper, we explore anisotropic interactions between particles with heterogeneous boundary conditions inside both nematic and cholesteric liquid crystals. The results show that when particles are put at different distances and angles with respect to each other, new types of defect structures are produced, depending on the relative distances and directions. In a cholesteric liquid crystal, the value of the pitch affects the defect structures and induced forces. Moreover, it was observed that it is energetically favorable for the particles to remain in a plane parallel to the far-field director in a nematic liquid crystal, while for particles immersed …

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