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Articles 1501 - 1530 of 2524

Full-Text Articles in Physical Sciences and Mathematics

Origin Of The High-Energy Kink In The Photoemission Spectrum Of The High-Temperature Superconductor Bi₂Sr₂Cacu₂O₈, Susmita Basak, Tanmoy Das, Hsin Lin, J. Nieminen, M. Lindroos, R. Markiewicz, A. Bansil Apr 2012

Origin Of The High-Energy Kink In The Photoemission Spectrum Of The High-Temperature Superconductor Bi₂Sr₂Cacu₂O₈, Susmita Basak, Tanmoy Das, Hsin Lin, J. Nieminen, M. Lindroos, R. Markiewicz, A. Bansil

Hsin Lin

The high-energy kink or the waterfall effect seen in the photoemission spectra of cuprates is suggestive of the coupling of quasiparticles to a high-energy bosonic mode with implications for the mechanism of superconductivity. Recent experiments, however, indicate that this effect may be an artifact produced entirely by matrix element effects, i.e., by the way the photoemitted electron couples to incident photons in the emission process. In order to address this issue directly, we have carried out realistic computations of the photointensity in Bi₂Sr₂CaCu₂O₈ where the effects of the matrix element are included together with those of the corrections to the …

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Iron (Iii) Tosylate Catalyzed Synthesis Of Acylals (1,1-Diesters) From Aromatic Aldehydes, Ram Mohan, Anna Nord, '13 Apr 2012

Iron (Iii) Tosylate Catalyzed Synthesis Of Acylals (1,1-Diesters) From Aromatic Aldehydes, Ram Mohan, Anna Nord, '13

Ram S. Mohan

No abstract provided.

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Iron (Iii) Tosylate Catalyzed Synthesis Of Dihydropyrimidiones And Dihydropyrmidinothiones Via The Biginelli Reaction, Ram Mohan, Jacob Starcevich, '13, Thomas Laughlin, '14 Apr 2012

Iron (Iii) Tosylate Catalyzed Synthesis Of Dihydropyrimidiones And Dihydropyrmidinothiones Via The Biginelli Reaction, Ram Mohan, Jacob Starcevich, '13, Thomas Laughlin, '14

Ram S. Mohan

No abstract provided.

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The Development Of A Novel Therapeutic For The Treatment Of Sickle Cell Disease, Brian Brennan, Cody Wynn, '14 Apr 2012

The Development Of A Novel Therapeutic For The Treatment Of Sickle Cell Disease, Brian Brennan, Cody Wynn, '14

Brian B. Brennan

No abstract provided.

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Iron (Iii) Tosylate Catalyzed Synthesis Of Dihydrobenzopyrans, Ram Mohan, Stephen Whitfield, '14 Apr 2012

Iron (Iii) Tosylate Catalyzed Synthesis Of Dihydrobenzopyrans, Ram Mohan, Stephen Whitfield, '14

Ram S. Mohan

No abstract provided.

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Bismuth (Iii) Triflate Catalyzed Synthesis Of Homoallyl Allyl Ethers And Their Reactions, Ram Mohan, Brendan O'Donnell, '14 Apr 2012

Bismuth (Iii) Triflate Catalyzed Synthesis Of Homoallyl Allyl Ethers And Their Reactions, Ram Mohan, Brendan O'Donnell, '14

Ram S. Mohan

No abstract provided.

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Iron (Iii) Tosylate Catalyzed Acylation Of Alcohols And Phenols, Ram Mohan, Neil Baldwin, '13 Apr 2012

Iron (Iii) Tosylate Catalyzed Acylation Of Alcohols And Phenols, Ram Mohan, Neil Baldwin, '13

Ram S. Mohan

No abstract provided.

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A Multi-Channel, Multi-Mode Biopotential Measurment Device, Thushara Perera, Boxiang Liu, '14 Apr 2012

A Multi-Channel, Multi-Mode Biopotential Measurment Device, Thushara Perera, Boxiang Liu, '14

Thushara A. Perera

No abstract provided.

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Interaction Of Fish Aryl Hydrocarbon Receptor Paralogs (Ahr1 And Ahr2) With The Retinoblastoma Protein, Rebeka Merson, Sibel Karchner, Mark Hahn Apr 2012

Interaction Of Fish Aryl Hydrocarbon Receptor Paralogs (Ahr1 And Ahr2) With The Retinoblastoma Protein, Rebeka Merson, Sibel Karchner, Mark Hahn

Rebeka Rand Merson

The aryl hydrocarbon receptor (AHR) mediates the toxic effects of 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD) and related compounds. In some mammalian cell lines, TCDD induces G1 cell cycle arrest, which depends on an interaction between the AHR and the retinoblastoma tumor suppressor (RB). Mammals possess one AHR, whereas fishes possess two or more AHR paralogs that differ in the domains important for AHR-RB interactions in mammals. To test the hypothesis that fish AHR paralogs differ in their ability to interact with RB, we cloned RB cDNA from Atlantic killifish, Fundulus heteroclitus, and studied the interactions of killifish RB protein with killifish AHR1 and …

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The Retention And Persistence Support (Raps) Project: A Transition Initiative, Dawn Darlaston-Jones, L Cohen, S Haunold, L Pike, A Young, Neil Drew Apr 2012

The Retention And Persistence Support (Raps) Project: A Transition Initiative, Dawn Darlaston-Jones, L Cohen, S Haunold, L Pike, A Young, Neil Drew

Dawn Darlaston-Jones

The transition to university is often associated with stress, anxiety, and tension and in many cases can lead to students failing or withdrawing from university. Transition problems result in high social and economic costs to families and the community. The past decade has seen a proliferation of transition strategies across universities. Results from evaluations of these transition programmes suggest student retention rates are significantly higher among those students involved in these programmes. The emphasis now though is to develop school or department based programmes as these are more readily adapted to meet the specific needs of students than university wide …

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Support For Mum When Dad Works Away (Book Review), Dawn Darlaston-Jones Apr 2012

Support For Mum When Dad Works Away (Book Review), Dawn Darlaston-Jones

Dawn Darlaston-Jones

I was pleased to receive the invitation to review this booklet because it is a topic I am personally interested in and affected by. My partner is currently part of the FIFO workforce based on a mine site in the North West. His current work context involves a regular roster of 2 weeks on and 1 week off which allows the opportunity for greater structure and planning of family functions and events. However, in the past he has also spent much of his working life in construction in South East Asia, resulting in long irregular periods of time away from …

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Making Connections: The Relationship Between Epistemology And Research Methods, Dawn Darlaston-Jones Apr 2012

Making Connections: The Relationship Between Epistemology And Research Methods, Dawn Darlaston-Jones

Dawn Darlaston-Jones

The ability to identify the relationship between the epistemological foundation of research and the methods employed in conducting it is critical in order for research to be truly meaningful. Unfortunately this connection is often not taught in the research methods classes that most psychology students experience. Indeed the very names of these units emphasises the focus on methods and consequently the epistemology, theoretical frameworks and methodologies that influence the choice of methods remain ‘hidden’ from view. This paper brings into focus these hidden (or often overlooked and ignored) elements of research and illustrates the importance and relevance by drawing on …

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Dry Friction Due To Adsorbed Molecules, C. Daly, J. Zhang, J. Sokoloff Apr 2012

Dry Friction Due To Adsorbed Molecules, C. Daly, J. Zhang, J. Sokoloff

Christopher Daly

Using an adiabatic approximation method, which searches for Tomlinson model-like instabilities for a simple but still realistic model for two crystalline surfaces in the extremely light contact limit, with mobile molecules present at the interface, sliding relative to each other, we are able to account for the virtually universal occurrence of "dry friction." The model makes important predictions for the dependence of friction on the strength of the interaction of each surface with the mobile molecules.

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Architectural Control Points, C. Jason Woodard Apr 2012

Architectural Control Points, C. Jason Woodard

C. Jason Woodard

System designers and technology strategists have long recognized the concept of an architectural control point as a way to identify parts of a system that have particular strategic importance. Despite the vast body of work on system architecture in the engineering design literature, however, few authors have attempted to define architectural control points or study them systematically. Moreover, some industry participants have questioned whether architectural control is still a valuable or achievable goal in an era of increasingly open standards. This paper offers tentative definitions of architectural control, architectural control points, and architectural strategy. In a longer version of the …

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Modeling Architectural Strategy Using Design Structure Networks, C. Jason Woodard Apr 2012

Modeling Architectural Strategy Using Design Structure Networks, C. Jason Woodard

C. Jason Woodard

System architects face the formidable task of purposefully shaping an evolving space of complex designs. Their task s further complicated when they lack full control of the design process, and therefore must anticipate the behavior of other stakeholders, including the designers of component products and competing systems. This paper presents a conceptual tool called a design structure network (DSN) to help architects and design scientists reason effectively about these situations. A DSN is a graphical representation of a system’s design space. DSNs improve on existing representation schemes by providing a compact and intuitive way to express design options—the ability to …

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Highly Connected Monochromatic Subgraphs Of Multicoloured Graphs, H. Liu, R. Morris, N. Prince Apr 2012

Highly Connected Monochromatic Subgraphs Of Multicoloured Graphs, H. Liu, R. Morris, N. Prince

Noah Prince

We consider the following question of Bollobás: given an r-coloring of E(Kn), how large a k-connected subgraph can we find using at most s colors? We provide a partial solution to this problem when s=1 (and n is not too small), showing that when r=2 the answer is n−2k+2, when r=3 the answer is ⌊(n−k)/2⌋+1 or ⌈(n−k)/2⌉+1, and when r−1 is a prime power then the answer lies between n/(r−1)−11(k2−k)r and (n−k+1)/(r−1)+r. The case s≥2 is considered in a subsequent paper (Liu et al.[6]), where we also discuss some of the more glaring open problems relating to this question.

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A Novel Direct Method Of Fermi Surface Determination Using Constant Initial Energy Angle-Scanned Photoemission Spectroscopy, M. Lindroos, A. Bansil Apr 2012

A Novel Direct Method Of Fermi Surface Determination Using Constant Initial Energy Angle-Scanned Photoemission Spectroscopy, M. Lindroos, A. Bansil

Arun Bansil

We show that a constant initial energy, angle-scanned (CIE-AS) photoemission spectrum for emission from the Fermi energy (EF) contains Fermi surface (FS) signatures which originate from density of states type indirect transitions. Such previously unrecognized FS features in a CIE-AS spectrum would provide a robust and straightforward means of determining Fermi surfaces. Furthermore, the associated photointensity should yield a new window on k⊥, dispersion related issues in materials. Extensive simulations of CIE-AS spectra from low index faces of Cu are presented within the framework of the one-step photoemission model in order to delineate the nature of these new spectral features.

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X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr Apr 2012

X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr

Arun Bansil

We present results for realistic modeling of the x-ray absorption near edge structure (XANES) of the overdoped high-Tc superconductor La₂₋ₓSrₓCuO₄ in the hole doping range x = 0.20 - 0.30. Our computations are based on a real-space Green's function approach in which strong-correlation effects are taken into account in terms of a doping-dependent self-energy. The predicted O K-edge XANES is found to be in good accord with the corresponding experimental results in this overdoped regime. We find that the low energy spectra are dominated by the contribution of O atoms in the cuprate planes, with little contribution from apical O …

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Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil Apr 2012

Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil

Arun Bansil

We present angle-resolved photoemission spectra from the low-index faces of CuAl single crystals using 16.85- and 21.22-eV radiation, together with the computed bulk electronic structure of the alloy within the framework of the muffin-tin coherent-potential approximation (CPA). The d-band complex of Cu is found to suffer shifts of less than 0.1 eV on alloying, whereas the states of s-p symmetry are lowered in energy by as much as on the order of 1 eV. The dispersion curve of the uppermost valence band is measured and with the extrapolation of this curve to the Fermi energy (EF), the Fermi-surface radii along …

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Coherent-Potential And Average T-Matrix Approximations For Disordered Muffin-Tin Alloys: 1. Formalism, A. Bansil Apr 2012

Coherent-Potential And Average T-Matrix Approximations For Disordered Muffin-Tin Alloys: 1. Formalism, A. Bansil

Arun Bansil

The average density of states 〈ρ(E)〉 and the component charge density associated with an A(B) atom in the alloy, 〈ρA(B)(E)〉, are discussed for the disordered alloy AₓB₁₋ₓ within the framework of the muffintin Hamiltonian. A new version of the average t-matrix (ATA) is developed. The structure in the spectral density function, 〈ρ(k,E)〉, in the coherent-potential approximation (or the new ATA) is seen to result from not only the Bloch-type states in the medium of coherent-potential effective atoms tCP (or the average t-atoms 〈t〉) but also from non-Bloch-type impurity levels arising when a single A or B atom …

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Multiple-Scattering Theory Of Itinerant Electron Magnetism In Random Muffin-Tin Alloys, S. Kaprzyk, A. Bansil Apr 2012

Multiple-Scattering Theory Of Itinerant Electron Magnetism In Random Muffin-Tin Alloys, S. Kaprzyk, A. Bansil

Arun Bansil

We discuss the equilibrium electronic structure of a random binary alloy within the framework of a spin-dependent muffin-tin Hamiltonian. The disorder is treated on the basis of the single-site approximations (SSA), especially the average t-matrix and the coherent potential approximations. The local-spin-density (LSD) functional approach is employed to relate the electron and the spin densities with the atomic potentials, thus providing a fully self-consistent description of the ground-state properties of the random alloy. By using the atomic magnetic moments as expansion parameters, a Stoner-type linearized form of the full SSA-LSD formalism is developed. This analysis yields insights into the nature …

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Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil Apr 2012

Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil

Arun Bansil

We analyze how the coherence peaks observed in scanning tunneling spectroscopy (STS) of cuprate high-temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) assuming a short-range d-wave pairing interaction confined to the nearest-neighbor Cu dₓ2₋y2 orbitals. The resulting anomalous matrix elements of the Green’s function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and …

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Application Of Coherent-Potential Approximation To Disordered Muffin-Tin Alloys, A. Bansil Apr 2012

Application Of Coherent-Potential Approximation To Disordered Muffin-Tin Alloys, A. Bansil

Arun Bansil

I report implementation of the coherent-potential approximation for obtaining the electronic density of states and component charge densities in disordered muffin-tin alloys. Illustrative results for CuₓNi₁₋ₓ are presented. The extent to which the self-consistency in treating disorder influences the electronic spectrum is considered.

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Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil Apr 2012

Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil

Arun Bansil

We develop an analytical tool to extract bulk electronic properties of unconventional superconductors from inelastic neutron scattering spectra. We show that the upward and downward branches of the spin excitation spectra have distinct origins, with the upper branch representing a gapped spin-wave dispersion and the lower branch associated with Bogoliubov quasiparticle scattering on the Fermi surface. Combined, they produce an "hourglass" dispersion with 45 degrees rotation of the spectrum, as found experimentally. The downward dispersion can be inverted to reveal the Fermi momentum dispersion of the single-particle spectrum as well as the corresponding superconducting (SC) gap function, analogously to the …

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Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil Apr 2012

Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil

Arun Bansil

We have investigated band structures of a series of 28 ternary half-Heusler compounds MM'X of MgAgAs type, where M=(Lu, La, Sc, Y) and M'X=(PtBi, AuPb, PdBi, PtSb, AuSn, NiBi, PdSb). Our results show that the Z₂ topological order is due to a single band inversion at the Γ point. In native states, these half-Heusler compounds are identified as being topologically nontrivial semimetals, or nontrivial metals, or trivial insulators, which can be turned into insulating thin films on suitable substrates. Our analysis reveals a straightforward relationship which connects the band inversion strength (extent of deviation from the critical point) to the …

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Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti Apr 2012

Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti

Arun Bansil

High-resolution Compton scattering measurements on Be single crystals along three main crystallographic directions ([10.0], [11.0], and [00.1]) have been carried out using incident photon energies of 10, 29, and 56 keV to study the energy dependence of the scattering cross:section. The experimental Compton profiles are in good agreement with theoretical profiles employing the local density approximation-based band theory framework. Extensive comparisons between the computed and measured profiles, their first derivatives, and anisotropies defined as differences between various pairs of profiles show an excellent level of accord. The details related to the Fermi surface are clearly seen in the experimental Compton …

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One-Band Tight-Binding Model Parametrization Of The High-Tc Cuprates Including The Effect Of Kz Dispersion, R. Markiewicz, S. Sahrakorpi, M. Lindroos, Hsin Lin, A. Bansil Apr 2012

One-Band Tight-Binding Model Parametrization Of The High-Tc Cuprates Including The Effect Of Kz Dispersion, R. Markiewicz, S. Sahrakorpi, M. Lindroos, Hsin Lin, A. Bansil

Arun Bansil

We discuss the effects of interlayer hopping and the resulting kz dispersion in the cuprates within the framework of the one-band tight-binding model Hamiltonian. Specific forms of the dispersion relations in terms of the in-plane hopping parameters t, t′, t″, and t‴ and the effective interlayer hopping tz in La₂₋ₓSrₓCuO₄ (LSCO) and Nd₂₋ₓCeₓCuO₄ (NCCO) and the added intracell hopping tbi between the CuO₂ bilayers in Bi₂Sr₂CaCu₂O₈ (Bi2212) are presented. The values of the “bare” parameters are obtained via fits with the first-principles local-density-approximation- (LDA-) based band structures in LSCO, NCCO, and Bi2212. The corresponding “dressed” parameter sets which account for …

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Fermi Surface Evolution And Collapse Of The Mott Pseudogap In Nd2-Xcexcuo4±Δ, C. Kusko, R. Markiewicz, M. Lindroos, A. Bansil Apr 2012

Fermi Surface Evolution And Collapse Of The Mott Pseudogap In Nd2-Xcexcuo4±Δ, C. Kusko, R. Markiewicz, M. Lindroos, A. Bansil

Arun Bansil

Fermi surface (FS) maps and spectral intensities obtained recently in Nd₂₋ₓCeₓCuO₄±δ via high resolution ARPES measurements are analyzed using mean-field Hartree Fock and self-consistent renormalization computations within the framework of the one-band t-t′-t″-U Hubbard model Hamiltonian. We show that the remarkable observed crossover of the FS from small to large sheets reflects a reduction in the value of the effective Hubbard U with increasing electron doping and the collapse of the correlation induced Mott pseudogap just above optimal doping.

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Compton Profiles For Polycrystalline Cuxni1-X Alloys: Theory And Experiment, R. Benedek, R. Prasad, S. Manninen, B. Sharma, A. Bansil, P. Mijnarends Apr 2012

Compton Profiles For Polycrystalline Cuxni1-X Alloys: Theory And Experiment, R. Benedek, R. Prasad, S. Manninen, B. Sharma, A. Bansil, P. Mijnarends

Arun Bansil

We present experimental and theoretical Compton profiles, J(q), for a series of CuₓNi₁₋ₓ alloys. This is the first comprehensive study of Compton profiles in an alloy system. The experiments were carried out using 60-keV γ rays on five polycrystalline alloy samples with Cu concentrations x=0.40,0.50,0.55,0.60,0.65 and on pure Cu and pure Ni. Our computations of J(q) are based on the Korringa-Kohn-Rostoker coherent-potential approximation scheme for treating the average electronic spectrum of the alloy. The theory reproduces the main features of the observed Compton profiles. The experimental Compton profiles show a nearly linear dependence on concentration while the theoretically predicted Compton …

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Cuprocleav-1, A First Generation Photocage For Cu+, Shawn Burdette, Hannah Mbatia, H.M.Dhammika Bandara Mar 2012

Cuprocleav-1, A First Generation Photocage For Cu+, Shawn Burdette, Hannah Mbatia, H.M.Dhammika Bandara

Shawn C. Burdette

By utilizing thioether ligands, CuproCleav-1 stabilizes Cu+ complexes in aqueous solution and releases the guest metal ion upon photolysis of the nitrobenzyl group. The photocage has an apparent Kd of 54 pM for Cu+, and metal ion release has been demonstrated using the fluorescent sensor CS1.

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