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Several caspases have been implicated in the pathogenesis of Huntington's disease (HD); however, existing caspase inhibitors lack the selectivity required to investigate the specific involvement of individual caspases in the neuronal cell death associated with HD. In order to explore the potential role played by caspase-2, the potent but non-selective canonical Ac-VDVAD-CHO caspase-2 inhibitor 1 was rationally modified at the P(2) residue in an attempt to decrease its activity against caspase-3. With the aid of structural information on the caspase-2, and -3 active sites and molecular modeling, a 3-(S)-substituted-l-proline along with four additional scaffold variants were selected as P(2) elements for their predicted ability to clash sterically with a residue of the caspase-3 S(2) pocket. These elements were then incorporated by solid-phase synthesis into pentapeptide aldehydes 33a-v. Proline-based compound 33h bearing a bulky 3-(S)-substituent displayed advantageous characteristics in biochemical and cellular assays with 20- to 60-fold increased selectivity for caspase-2 and ∼200-fold decreased caspase-3 potency compared to the reference inhibitor 1. Further optimization of this prototype compound may lead to the discovery of valuable pharmacological tools for the study of caspase-2 mediated cell death, particularly as it relates to HD.

The high upper critical field characteristic of the recently discovered iron-based superconducting chalcogenides opens the possibility of developing a new type of non-oxide high-field superconducting wires. In this work, we utilize a buffered metal template on which we grow a textured FeSe$_{0.5}$Te$_{0.5}$ layer, an approach developed originally for high temperature superconducting coated conductors. These tapes carry high critical current densities (>1$\times10^{4}$A/cm$^{2}$) at about 4.2K under magnetic field as high as 25 T, which are nearly isotropic to the field direction. This demonstrates a very promising future for iron chalcogenides for high field applications at liquid helium temperatures. Flux pinning force analysis indicates a point defect pinning mechanism, creating prospects for a straightforward approach to conductor optimization., Accepted for publication in Appl. Phys. Lett

We report angle-resolved photoemission spectroscopy (ARPES) and a set of in situ scanning tunneling microscopy (STM) measurements on a narrow-terrace-width vicinal Cu(111) crystal surface, Cu(775), whose vicinal cut lies close to the transition between terrace and step modulation. These measurements show sharp zone-folding (or umklapp) features with a periodicity in ${k}_{\ensuremath{\parallel}}$, indicating that the predominant reference plane is that of Cu(775), i.e., that the surface is predominately step-modulated. Our measurements also show variation in umklapp intensity with photon energy, which is consistent with prior ARPES experiments on other vicinal Cu(111) surfaces and in agreement with our designation of the state as being step-modulated. The measurements also show a weak terrace-modulated state, which, based on several characteristics, we attribute to the presence of terrace widths larger than the ideal terrace width. By measuring the intensity ratio of the two distinct surface-state modulations from photoemission and the terrace-width distribution from STM, we derive a value for the terrace width at which the surface state switches between the two modulations.

Electron emission from the negative electron affinity (NEA) surface of hydrogen terminated, boron doped diamond in the [100] orientation is investigated using angle resolved photoemission spectroscopy (ARPES). ARPES measurements using 16 eV synchrotron and 6 eV laser light are compared and found to show a catastrophic failure of the sudden approximation. While the high energy photoemission is found to yield little information regarding the NEA, low energy laser ARPES reveals for the first time that the NEA results from a novel Franck-Condon mechanism coupling electrons in the conduction band to the vacuum. The result opens the door to the development of a new class of NEA electron emitter based on this effect.

If you treasure semantic precision, you might name the volcano that erupted (figuratively speaking!) in 1973: Coloring Problems in Geometrically Defined Hypergraphs.

This issue of SRN focuses on photoelectron spectroscopy, a technique that is flourishing at many synchrotron facilities worldwide. In a nutshell, it is a simple technique making use of the photoelectric effect and benefiting from the bright light available at synchrotrons. In the past two decades, one of its branches, angle-resolved photoemission (ARPES), has gained tremendous popularity due to its ability to provide insights into the physics of strongly correlated materials such as, for example, the high Tc superconductors. Its success rests on advances in instrumentation which, over the course of many years, have led to dramatic improvements in resolution in both energy and momentum.

Throughout, \(\mathbb{Z}\), \(\mathbb{Q}\), and \(\mathbb{R}\) denote the usual rings of integers, rational numbers, and real numbers, respectively. If X is a set and n is a positive integer, X n denotes, as usual, the set of n-tuples with entries from X.

We present a combined analysis of neutron scattering and photoemission measurements on superconducting FeSe{sub 0.5}Te{sub 0.5}. The low-energy magnetic excitations disperse only in the direction transverse to the characteristic wave vector (1/2,0,0) whereas the electronic Fermi surface near (1/2,0,0) appears to consist of four incommensurate pockets. While the spin resonance occurs at an incommensurate wave vector compatible with nesting, neither spin-wave nor Fermi-surface-nesting models can describe the magnetic dispersion. We propose that a coupling of spin and orbital correlations is key to explaining this behavior. If correct, it follows that these nematic fluctuations are involved in the resonance and could be relevant to the pairing mechanism.

Superconducting thin films of ${\text{Fe}}_{1.08}\text{Te}:{\text{O}}_{x}$ have been epitaxially grown on ${\text{SrTiO}}_{3}$ substrates by pulsed-laser deposition in controlled oxygen atmosphere. Although the bulk ${\text{Fe}}_{1.08}\text{Te}$ is not superconducting, thin films with oxygen are superconducting with an onset and a zero resistance transition temperature around 12 and 8 K, respectively. Oxygen was found to be crucial to the superconducting properties of these films, suggesting that the oxygen incorporation can induce superconductivity in FeTe thin films. A metal-insulator transition is found at about 60 K, lower than that of bulk $(\ensuremath{\sim}70\text{ }\text{K})$. From magnetoresistive measurements, we obtained the irreversibility line and the upper critical field.

We present carbon K emission spectra of diamond excited with high-resolution undulator radiation. The valence-band emission spectra are shown to be strongly dependent on the excitation energy, up to 20--30 eV above the C K edge. It is proposed that the dependence is indicative of the resonant inelastic scattering description of these emission spectra, i.e., the absorption-emission process should be described as a single scattering event where the momenta of the photoelectron and the valence hole in the final state are related by momentum conservation.

The use of synchrotron radiation in the study of the electronic properties of magnetic systems is now becoming widespread. New compact spin detectors have allowed extensive studies of both the valence bands and core levels of clean ferromagnetic surfaces, adsorbates on the same surfaces, and thin films. Photon energy dependencies allow the identification of two dimensional magnetic states in both surface and interface regions. The core level studies allow information to be obtained about the local magnetic structure. The development of new techniques for the study of magnetic properties dependent on the polarization of the light is also discussed. Thus in certain experiments the use of circularly polarized light has an advantage that no spin detector is required.

The X1 undulator on the X-ray ring of the NSLS at Brookhaven is an extremely bright source of soft X-ray photons. On the recently completed spectroscopy beamline X1B we have attempted to utilise the intrinsically narrow beam size and divergence to maximise the intensity throughput in a spherical grating monochromator (SGM). The high power density of the undulator radiation requires the use of water cooled mirrors, entrance slit and grating. Calculations predict that simple side cooled copper pads attached to optical elements will be sufficiently effective that resolution degradation due to thermal deformation of figure error will be negligible in the SGM design. This is confirmed by attainment of resolution superior to other SGMs and the BESSY SX700-II monochromator over the energy range 300–540 eV (C1s−1, N1s−1 and Ols−1). At a resolution comparable to the best so far obtained for the nitrogen N 1s π∗ excitation (401 eV) on other monochromators we have demonstrated an intensity increase, at the sample, of more than three orders of magnitude. The design consideration upon which beamline X1B is based are highly relevant to the construction of soft X-ray monochromators at future synchrotron radiation sources such as the ALS (Berkeley). Elettra (Trieste) and BESSYII (Berlin).

Inverse photoemission is used to examine the adsorbate-induced unoccupied band structure of the c(2\ifmmode\times\else\texttimes\fi{}2)CO/Cu(001) adsorption system. As in an earlier study we observe two adsorbate-induced peaks above the Fermi level. By comparing with a simple tight-binding model we associate one unoccupied adsorbate band with the molecular 2\ensuremath{\pi} level and another band with a substrate surface band interacting with the molecular 5\ensuremath{\sigma} level.

A beamline has been established at the National Synchrotron Light Source to perform angle‐resolved photoemission experiments on magnetic surfaces with spin sensitivity. The system has two novel features: it uses a miniature electron‐spin polarization analyzer and it also uses synchrotron radiation from an undulator rather than a bending magnet.

The layout and first data on the performance of the soft x‐ray undulator beam line on the x‐ray ring at Brookhaven are described. The undulator (X1) has 35 periods of 8 cm, resulting in a tuning range for the fundamental of about 200–700 eV at the nominal ring energy of 2.5 GeV. The monochromator is based on the Dragon concept with spherical grating, movable exit slit but with water‐cooled optical elements in order to deal with the maximum flux of ca. 400 W. This system represents one of the next generation of soft x‐ray undulator beam lines which will figure prominently at new synchrotron radiation facilities such as ALS, ELETTRA and BESSY II. During the first performance tests absorption spectra of simple molecules at the C, N, and O K edges have been recorded with resolution and flux so far unattained in the soft x‐ray region.

Laser-based photoemission with photons of energy 6 eV is used to examine the fine details of the very low-energy electron dispersion and associated dynamics in the nodal region of optimally doped Bi2212. A ``kink'' in the dispersion in the immediate vicinity of the Fermi energy is associated with scattering from an optical phonon previously identified in Raman studies. The identification of this phonon as the appropriate mode is confirmed by comparing the scattering rates observed experimentally with the results of calculated scattering rates based on the properties of the phonon mode.

We demonstrate angle-resolved, tunable, two-photon photoemission (2PPE) to map a bulk unoccupied band, viz. the Cu $sp$ band 0 to 1 eV below the vacuum level, in the vicinity of the $L$ point. This short-lived bulk band is seen due to the strong optical pump rate, and the observed transition energies and their dispersion with photon energy $\ensuremath{\hbar}\ensuremath{\omega}$, are in excellent agreement with tight-binding band-structure calculations. The variation of the final-state energy with $\ensuremath{\hbar}\ensuremath{\omega}$ has a measured slope of $\ensuremath{\sim}1.64$ in contrast to values of 1 or 2 observed for 2PPE from two-dimensional states. This unique variation illustrates the significant role of the perpendicular momentum $\ensuremath{\hbar}{k}_{\ensuremath{\perp}}$ in 2PPE.

The normal function of Syk in epithelium of the developing or adult breast is not known, however, Syk suppresses tumor growth, invasion, and metastasis in breast cancer cells. Here, we demonstrate that in the mouse mammary gland, loss of one Syk allele profoundly increases proliferation and ductal branching and invasion of epithelial cells through the mammary fat pad during puberty. Mammary carcinomas develop by one year. Syk also suppresses proliferation and invasion in vitro. siRNA or shRNA knockdown of Syk in MCF10A breast epithelial cells dramatically increased proliferation, anchorage independent growth, cellular motility, and invasion, with formation of functional, extracellular matrix-degrading invadopodia. Morphological and gene microarray analysis following Syk knockdown revealed a loss of luminal and differentiated epithelial features with epithelial to mesenchymal transition and a gain in invadopodial cell surface markers CD44, CD49F, and MMP14. These results support the role of Syk in limiting proliferation and invasion of epithelial cells during normal morphogenesis, and emphasize the critical role of Syk as a tumor suppressor for breast cancer. The question of breast cancer risk following systemic anti-Syk therapy is raised since only partial loss of Syk was sufficient to induce mammary carcinomas.

The combination of spin‐polarization detection with core‐level photoemission to give spin‐polarized electron spectroscopy for chemical analysis provides new information on the oxidation of an iron surface. During the initial stage of oxidation the predominant phase is of a ferrimagnetic γ‐Fe2O3 form. The observed antiferromagnetic coupling of this oxide with the iron substrate is attributed to the superexchange interaction mediated by an oxygen ion. This provides evidence for a site exchange mechanism during the initial oxidation. Annealing transforms this oxide into an antiferromagnetic FexO form which is also present at the initial stage.

We measure the electronic structure of low-coverage Co on a Cu(775) stepped substrate using high-resolution photoemission spectroscopy with the particular goal of relating the electronic dispersion to the coverage-dependent surface structure. In particular, we follow the evolution of the electronic dispersion of the $sp$-like Cu surface state and the position of the band minimum as a function of Co coverage. On the bare Cu(775) surface, we observe band folding of this state due to the stepped surface-superlattice array. In addition, we determine that the reference plane, as measured by the position of the band minimum of this state, changes dramatically after addition of just 0.03 ML Co. At 0.06 ML, we observe the formation of a second surface state at a binding energy of $0.68\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. This feature is attributed to a quantum-well state hybridized with the substrate.

Angle-resolved photoemission and optical spectroscopy are used to probe the electronic structure of the one-dimensional Mott insulator ${\mathrm{Sr}}_{2}\mathrm{Cu}{\mathrm{O}}_{3+\ensuremath{\delta}}$, both at half-filling and with small concentrations of excess oxygen doping. Spin-charge separation can be seen as evidenced by the existence of spinon and holon branches in the photoemission spectra. Optical studies reveal no significant doping dependence, while photoemission studies show a large energy shift in the spinon and holon states with respect to the main valence band states which remain nearly unaffected. The results suggest the excess dopant carriers are incorporated solely within the one-dimensional Hubbard band which is electronically isolated from the rest of the states in the system.

Recent angle resolved photoemission \cite{yang-nature-08} and scanning tunneling microscopy \cite{kohsaka-nature-08} measurements on underdoped cuprates have yielded new spectroscopic information on quasiparticles in the pseudogap phase. New features of the normal state such as particle-hole asymmetry, maxima in the energy dispersion and accompanying drops in the spectral weight of quasiparticles agree with the ansatz of Yang \textit{et al.} for the single particle propagator in the pseudogap phase. The coherent quasiparticle dispersion and reduced asymmetry in the tunneling density of states in the superconducting state can also be described by this propagator., Comment: updated version, 6 pages, 7 figures, 1 table, EPL 86 (2009) 37002 (https://www.epletters.net)

Spin polarized photoemission studies of different adsorbates on an Fe (001) substrate show the interaction between the adsorbate and the substrate d bands. Studies of the adsorption of oxygen reveal exchange split adsorbate bands indicative of both a magnetic moment on the adsorbate atom and also a strong adsorbate p z substrate d z 2 bond. The oxygen p z bands show a large variation in exchange splitting across the surface zone, an observation that is not predicted in first principles calculations of this system. Spin Polarised Auger Electron Spectroscopy studies of sulfur adsorbed on the same surface provide some indication of the magnetic moment on the adsorbate. It is found to be of the order of 0.1 μB. Studies of carbon monoxide adsorption in two different configurations, vertical and tilted, reveal little or no exchange splitting in the molecular 5σ orbital suggesting that the interaction of this orbital with the substrate d bands is much weaker.

Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

We present an angle-resolved photoemission spectroscopy (ARPES) study of a Mott-Hubbard-type bismuth cobaltate system across a metal-insulator transition. By varying the amount of Pb substitution, and by doping with Sr or Ba cation, a range of insulating to metallic properties is obtained. We observe a systematic change in the spectral weight of the coherent and incoherent parts, accompanied by an energy shift of the incoherent part. The band dispersion also shows the emergence of a weakly dispersing state at the Fermi energy with increasing conductivity. These changes correspond with the changes in the temperature-dependent resistivity behavior. We address the nature of the coherent-incoherent parts in relation to the peak-dip-hump feature seen in cuprates superconductors.

New developments in instrumentation have recently allowed photoemission measurements to be performed with very high energy and momentum resolution.[1] This has allowed detailed studies of the self-energy corrections to the lifetime and mass renormalization of excitations in the vicinity of the Fermi level. These developments come at an opportune time. Indeed the discovery of high temperature superconductivity in the cuprates and related systems is presenting a range of challenges for condensed matter physics.[2] Does the mechanism of high T{sub c} superconductivity represent new physics? Do we need to go beyond Landau's concept of the Fermi liquid?[3] What, if any, is the evidence for the presence or absence of quasiparticles in the excitation spectra of these complex oxides? The energy resolution of the new instruments is comparable to or better than the energy or temperature scale of superconductivity and the energy of many collective excitations. As such, photoemission has again become recognized as an important probe of condensed matter. Studies of the high T{sub c} superconductors and related materials are aided by the observation that they are two dimensional. To understand this, we note that the photoemission process results in both an excited photoelectron and a photohole in the final state.more » Thus the experimentally measured photoemission peak is broadened to a width reflecting contributions from both the finite lifetime of the photohole and the momentum broadening of the outgoing photoelectron.« less

Photoemission studies show the presence of a high-energy anomaly in the observed band dispersion for two families of cuprate superconductors, Bi2Sr2CaCu2O8+delta and La 2-x BaxCuO4. The anomaly, which occurs at a binding energy of approximately 340 meV, is found to be anisotropic and relatively weakly doping dependent. Scattering from short range or nearest neighbor spin excitations is found to supply an adequate description of the observed phenomena.

We investigate the nature of oxygen dopant-induced electronic states in the high-temperature Bi2Sr2CaCu2O8+x superconductor by measuring photoemission spectra of underdoped, optimally doped, and overdoped samples using a wide photon energy range (15-100 e

Very high energy resolution photoemission experiments on high quality samples of optimally doped Bi2Sr2CaCu2O8+delta show new features in the low-energy electronic excitations. A marked change in the binding energy and temperature dependence of the near-n

We present the design and parameters of an energy recovery linac (ERL) facility, which is under construction in the Collider-Accelerator Department at BNL. This R&D facility has the goal of demonstrating CW operation of an ERL with an average beam current in the range of 0.1 - 1 ampere and with very high efficiency of energy recovery. The possibility of a future upgrade to a two-pass ERL is also being considered. The heart of the facility is a 5-cell 703.75 MHz super-conducting RF linac with strong Higher Order Mode (HOM) damping. The flexible lattice of the ERL provides a test-bed for exploring issues of transverse and longitudinal instabilities and diagnostics of intense CW electron beams. This ERL is also perfectly suited for a far-IR FEL. We present the status and plans for construction and commissioning of this facility.

We report angle-resolved photoemission and two-photon photoemission measurements of occupied and unoccupied states of clean stepped Cu(775) surfaces using tunable synchrotron and ultrafast femtosecond laser sources.

The element-specific valence- and conduction-band densities of states for the high-dielectric-material $\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$ have been measured using soft x-ray emission and absorption spectroscopies. Ti ${L}_{\ensuremath{\alpha},\ensuremath{\beta}}$, Cu ${L}_{\ensuremath{\alpha},\ensuremath{\beta}}$, and O $K$ soft x-ray emission spectra of $\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$ were measured with monochromatic photon excitation on selected energies above the Ti and Cu ${L}_{2,3}$ and O $K$ absorption edges, respectively. X-ray absorption spectra were recorded at the same edges. The electronic structure was also calculated using density functional theory employing the full-potential linearized augmented plane-wave method. Excellent agreement is seen between the results of these calculations and the measured x-ray emission and absorption spectra. This agreement is particularly good at the O $K$ edge where the resonant behavior of the x-ray emission spectrum can be attributed directly to $\ensuremath{\sigma}$- and $\ensuremath{\pi}$-state emission from valence-band O $2p$ states when in resonance with ${\ensuremath{\pi}}^{*}$ and ${\ensuremath{\sigma}}^{*}$ conduction-band O $2p$ states. Resonant inelastic x-ray scattering is observed at the Ti ${L}_{2,3}$ absorption edge and is compared to previous studies of Ti containing perovskite compounds. The role of Cu $3d$ states in determining the band gap of this material is discussed.

We present a method for extracting the electron-boson spectral function a 2 Fsvd from infrared and photoemission data. This procedure is based on inverse theory and will be shown to be superior to previous techniques. Numerical implementation of the algorithm is presented in detail and then used to accurately determine the doping and temperature dependence of the spectral function in several families of high-Tc superconductors. Principal limitations of extracting a 2 Fsvd from experimental data will be pointed out. We directly compare the IR and angular-resolved photoemission spectroscopy a 2 Fsvd and discuss the resonance structure in the spectra in terms of existing theoretical models.

The bulk-representative low-energy spectrum of Sr2RuO4 can be directly measured by angle- resolved photoemission. We find that the quasiparticle spectral line shape of Sr2RuO4 is sensitive to both temperature and momentum. Along the � 0; 0� -� �; 0� direction, bothandbands develop a sharp quasiparticle peak near kF at low temperatures, but as the temperature increases the spectra quickly lose coherent weight and become broad backgrounds above � 130 K, which is the metal-nonmetal crossover temperature, TM ,i n thec-axis resistivity. However, spectra along the � 0; 0� -� �; � � direction evolve smoothly across TM. A simple transport model can describe both in-plane and c-axis resistivity in terms of the quasiparticle line shape. Comparisons are also made to the cuprates, with implications for two dimensionality, magnetic fluctuations, and superconductivity.

We report a new approach to the generation of high-current, high-brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron-volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating proper of the “gun” through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: 1. Reduction of the number of primary electrons by the large SEY, i.e. a very low laser power in a photocathode producing the primaries. 2. Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons.3. Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. 4. Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. 5. Production of high average currents, up to ampere class. 6. Encapsulated design, making the “load-lock” systems unnecessary. Section

High-resolution photoemission has been used to study the electronic structure of the charge-density wave (CDW) and superconducting dichalcogenide, 2H-NbSe2. From the extracted self-energies, important components of the quasiparticle interactions have been identified. In contrast to previously studied TaSe2, the CDW transition does not affect the electronic properties significantly. The electron-phonon coupling is identified as a dominant contribution to the quasiparticle self-energy and is shown to be very anisotropic (k dependent) and much stronger than in TaSe2.

We report a new approach to the generation of high‐current, high‐brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron‐volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating region proper of the “gun” through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: 1. Reduction of the required number of primary electrons by the large SEY, i.e. we can utilize a very low laser power in a photocathode producing the primaries. 2. Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons.3. Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. 4. Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. 5. Production of high average currents, up to ampere class. 6. Encapsulated design, making the “load‐lock” systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier.

We report an angle-resolved photoemission study of d-derived quantum well (QW) states in ultrathin silver films grown on V(100). Distinct d-derived QW states were observed for film thicknesses between 1 and 5 ML. Using a line shape analysis we conclude that for thicker films the d electrons are almost completely confined within the silver overlayer, suggesting a high reflectivity at the vanadium-silver interface. The energies of the QW states were found to be in good agreement with tight-binding calculations as well as with a phase accumulation model analysis. The calculations indicate a strong influence of the vanadium substrate on the energy of d-band QW states for the single-monolayer film.

The tethered aminohydroxylation of cyclic allylic carbamates is described using catalytic amounts of potassium osmate. The mechanism of reaction involves formation of an imido-osmium complex which adds intramolecularly to alkenes with complete control of both regio- and stereoselectivity: the formation of syn-aminodiol motifs is now straightforward using this chemistry. Proof of the mechanism was obtained with an X-ray crystal structure of an azaglycolate osmate ester intermediate.

Angle-resolved-photoemission studies of the dispersion of the quantum-well states in copper thin films deposited on a Co(001) substrate reveal that hybridization in the interface leads to a large increase in the effective mass of the electrons. These observations have implications for theories of the oscillatory exchange coupling in the related magnetic multilayers, particularly where Fermi-surface spanning vectors away from the center of the zone are invoked as in the case of the short-period oscillation in the Co/Cu(001) multilayers.

The properties of an interacting electron system depend on the electron correlations and the effective dimensionality. For example, Coulomb repulsion between electrons may inhibit, or completely block, conduction by intersite electron hopping, thereby determining whether a material is a metal or an insulator1. Furthermore, correlation effects increase as the number of effective dimensions decreases; in three-dimensional systems, the low-energy electronic states behave as quasiparticles, whereas in one-dimensional systems, even weak interactions break the quasiparticles into collective excitations2. Dimensionality is particularly important for exotic low-dimensional materials where one- or two-dimensional building blocks are loosely connected into a three-dimensional whole. Here we examine two such layered metallic systems with angle-resolved photoemission spectroscopy and electronic transport measurements, and we find a crossover in the number of effective dimensions—from two to three—with decreasing temperature. This is apparent from the observation that, in the direction perpendicular to the layers, the materials have an insulating character at high temperatures but become metal-like at low temperatures, whereas transport within the layers remains metallic over the whole temperature range. We propose that this change in effective dimensionality correlates with the presence of coherent quasiparticles within the layers.

Flow charts are one of the standard means of representing actions or algorithms in many domains. However, applying flow charts in dynamically changing environments, like clinical treatment planning, reveals their limitations. Flow charts do not include the temporal dimension in their design, do not allow complex paths through many components, and scale very badly. These are only some of the requirements for a means of communicating clinical therapy plans. As an alternative, a plan-representation language called Asbru was designed, which overcomes all the limitations of flow charts. It is, however, impossible for a domain expert to work with Asbru directly. Therefore, a visualisation called AsbruView is presented here, which uses three-dimensional diagrams and metaphors — running tracks and traffic signs — to make the parts of Asbru easily understandable and usable. Even very complex clinical plans are easy to understand with AsbruView.

We present O K-edge absorption and emission spectra for \ensuremath{\alpha}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$ and ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ obtained using a high-resolution-undulator soft-x-ray radiation source. The occupied and the unoccupied O p densities of states are obtained and compared with the valence-band photoemission results. While these results confirm that \ensuremath{\alpha}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$ can be classified as a charge transfer or an intermediate-type insulator, they suggest that ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ is more likely of the Mott-Hubbard type. The excitation-energy dependence of the emission spectra is also discussed.

We develop a framework which unifies seemingly different extension (or "joinability") problems for bipartite quantum states and channels. This includes well known extension problems such as optimal quantum cloning and quantum marginal problems as special instances. Central to our generalization is a variant of the Choi-Jamiolkowski isomorphism between bipartite states and dynamical maps which we term the "homocorrelation map": while the former emphasizes the preservation of the positivity constraint, the latter is designed to preserve statistical correlations, allowing direct contact with entanglement. In particular, we define and analyze state-joining, channel-joining, and local-positive joining problems in three-party settings exhibiting collective UxUxU symmetry, obtaining exact analytical characterizations in low dimension. Suggestively, we find that bipartite quantum states are limited in the degree to which their measurement outcomes may agree, while quantum channels are limited in the degree to which their measurement outcomes may disagree. Loosely speaking, quantum mechanics enforces an upper bound on the extent of positive correlation across a bipartite system at a given time, as well as on the extent of negative correlation between the state of a same system across two instants of time. We argue that these general statistical bounds inform the quantum joinability limitations, and show that they are in fact sufficient for the three-party UxUxU-invariant setting.

High-resolution photoemission is used to study the electronic structure of the cuprate superconductor, ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$, as a function of hole doping and temperature. A kink observed in the band dispersion in the nodal line in the superconducting state is associated with coupling to a resonant mode observed in neutron scattering. From the measured real part of the self-energy it is possible to extract a coupling constant which is largest in the underdoped regime, then decreasing continuously into the overdoped regime.

High resolution spin-resolved photoemission is used to probe the properties of a Gd(0001) surface state. The state shows both a spin-mixing behavior reflecting the exchange of magnons with the local moments and a reduction of the exchange splitting with increasing temperature. The surface state polarization at low T suggests that the surface layer has an enhanced Tc of 365K or greater. Measurements of the photoemission linewidths show that at low temperatures, the lifetime of a majority spin photohole is predominantly limited by electron-phonon scattering and that of a minority spin photohole by electron-magnon scattering. Since similar behavior may be expected for bulk states close to the Fermi level, the transport properties of this material will also be determined by different decay mechanisms in the two channels.

The temperature dependence of angle-resolved photoemission from quantum-well states in ultrathin films of Ag on V(100) has been examined for films from 1--8 ML thickness within the temperature range 45--600 K. Contrary to bulk solids, the photoemission peaks shift to higher binding energy as the temperature is increased. The temperature dependence of the peak widths is linear, consistent with the expected behavior for electron-phonon coupling, but the coupling parameter \ensuremath{\lambda} is found to show a strong oscillatory dependence on film thickness, with some values many times larger than those found for bulk silver. The observations are explained in terms of the influence on both the initial and final states in the photoemission process of the static and dynamic movements of the surface-vacuum interface barrier induced by temperature changes.