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Showing papers by "Alcatel-Lucent published in 1990"


Journal ArticleDOI
TL;DR: Block copolymers are macromolecules composed of sequences, or blocks, of chemically distinct repeat units that make possible the sequential addition of monomers to various carbanion-ter­ minated ("living") linear polymer chains.
Abstract: Block copolymers are macromolecules composed of sequences, or blocks, of chemically distinct repeat units. The development of this field originated with the discovery of termination-free anionic polymerization, which made possible the sequential addition of monomers to various carbanion-ter­ minated ("living") linear polymer chains. Polymerization of just two dis­ tinct monomer types (e.g. styrene and isoprene) leads to a class of materials referred to as AB block copolymers. Within this class, a variety of molec­ ular architectures is possible. For example, the simplest combination, obtained by the two-step anionic polymerization of A and B monomers, is an (A-B) dioblock copolymer. A three-step reaction provides for the preparation of (ABA) or (BAB) triblock copolymer. Alternatively, "living" diblock copolymers can be reacted with an n-functional coupling agent to produce (A-B)n star-block copolymers, where n = 2 constitutes a triblock copolymer. Several representative (A-B)n block copolymer architectures

3,475 citations


Journal ArticleDOI
TL;DR: In this article, a series of terminally substituted alkyl thiols, X(CH 2 ) 15 SH (X=CH 3, CH 2 OH, CO 2 H, CO2 CH 3, and CONH 2 ), have been prepared by adsorption from solution onto evaporated gold substrates.
Abstract: Monolayers of a series of terminally substituted alkyl thiols, X(CH 2 ) 15 SH (X=CH 3 , CH 2 OH, CO 2 H, CO 2 CH 3 , and CONH 2 ), have been prepared by adsorption from solution onto evaporated gold substrates. The structures habe been characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ellipsometry, and temperature-programmed desorption (TPD). The IR data shows the monolayer films to be densely packed, crystalline-like structures with all-trans conformation alkyl chains exhibiting average tilt angles of the chain axis in a range of 28-40° from the surface normal and an approximate 55° twist of the chain axis away from a configuration with the CCC plane perpendicular to the surface plane

1,525 citations


Journal ArticleDOI
TL;DR: In this article, the effect of varying the solution pH on the surface structure was studied by measuring the SiH stretch vibrations with infrared absorption spectroscopy, and the surface was found to be very homogeneous with low defect density (<0.5%) and narrow vibrational linewidth.
Abstract: Aqueous HF etching of silicon surfaces results in the removal of the surface oxide and leaves behind silicon surfaces terminated by atomic hydrogen. The effect of varying the solution pH on the surface structure is studied by measuring the SiH stretch vibrations with infrared absorption spectroscopy. Basic solutions ( pH=9–10) produce ideally terminated Si(111) surfaces with silicon monohydride ( 3/4 SiH) oriented normal to the surface. The surface is found to be very homogeneous with low defect density (<0.5%) and narrow vibrational linewidth (0.95 cm−1 ).

1,250 citations


Journal ArticleDOI
TL;DR: In this article, the authors report the characterization of series of oxygen deficient Ba2YCu3Ox samples for 7 ≥ x ≥ 6 prepared by Zr gettered annealing at 440°C.
Abstract: We report the characterization of series of oxygen deficient Ba2YCu3Ox samples for 7 ≥ x ≥ 6 prepared by Zr gettered annealing at 440°C. Measurements include complete crystal structure analysis at 5 K by powder neutron diffraction, electron microscopy study of the oxygen ordering, and magnetic measurements of the superconducting transitions, with particular attention to the transition widths. The results show for the first time that the 90 K and 60 K plateaus in Tc as a function of oxygen stoichiometry are associated with plateaus in the effective valence of the plane coppers. We also correlate the disappearance of superconductivity for x

884 citations


Journal ArticleDOI
TL;DR: In this article, a partially deuterated poly(ethylene-propylene) and poly(ethylethylene) diblock copolymer containing 55% by volume PEP was characterized above and below the order-disorder transition (ODT) by small-angle neutron scattering (SANS) and rheological measurements, respectively.
Abstract: The thermodynamic and dynamic properties of a partially deuterated poly(ethylene‐propylene)–poly(ethylethylene)(PEP–PEE) diblock copolymer containing 55% by volume PEP were characterized above and below the order–disorder transition (ODT) by small‐angle neutron scattering (SANS) and rheological measurements, respectively. Both experimental techniques produced unambiguous evidence of composition fluctuations well above TODT(T−TODT≲50 °C) in the disordered state, which increase in magnitude as the weak first‐order transition is approached. Based on the SANS results, which are nearly predicted by a recent fluctuation theory, we conclude that the (equilibrium) instantaneous morphology in the disordered state closely resembles a spinodally decomposed binary mixture. Below TODT, long‐range order can be obtained by the application of a shear field as evidenced by the resulting highly anisotropic (one‐dimensional) SANS pattern. As the ODT is approached in the shear‐oriented ordered state, an isotropic scattering ...

375 citations


Journal ArticleDOI
TL;DR: In this article, the influence of temperature on the infrared spectra of a docosylthiol (C22) monolayer on a gold substrate was investigated and it was found that this adsorbate exhibits a complex phase state at 300 K in which gauche conformations concentrated at the chain termina figure prominently.
Abstract: The influences of temperature on the infrared spectra of a docosylthiol (C22) monolayer on a gold substrate are reported. The data suggest that this adsorbate exhibits a complex phase state at 300 K in which gauche conformations concentrated at the chain termina figure prominently. The detailed temperature dependence of the spectral band intensities is found to be very similar in many regards to that of bulk hydrocarbon crystals. At low temperature, band splittings are observed which suggest the lowest energy structure for this adsorbate is one containing two chains per unit cell. A simple lattice argument, consistent with steric models and low‐energy electron diffraction data, is presented to explain these observations.

351 citations


Journal ArticleDOI
TL;DR: The linear dynamic mechanical properties of nearly symmetric 55:45 PEP-PEE diblock copolymers and their corresponding homopolymers are described in this article, showing the influence of composition fluctuations on the rheological properties around the microphase separation transition and confirming the first-order nature of this transition.
Abstract: The linear dynamic mechanical properties of nearly symmetric 55:45 PEP-PEE diblock copolymers and the corresponding homopolymers are described. The results show the influence of composition fluctuations on the rheological properties around the microphase separation transition and confirms the first-order nature of this transition for hearly symmetric samples dynamic shear measurements obtained after a temperature quench from just above to just below the microphase separation temperature demonstrate the ability to supercool the disordered material and provide a measure of the subsequent ordering kinetics

347 citations




Journal ArticleDOI
TL;DR: In this paper, self-assembled monolayers of a series of terminally substituted alkyl thiols and disulfides chemisorbed on an Au(111) single-crystal surface were used as substrates for subsequent temperature-programmed desorption (TPD) studies.
Abstract: Self-assembled monolayers of a series of terminally substituted alkyl thiols and disulfides chemisorbed on an Au(111) single-crystal surface were used as substrates for subsequent temperature-programmed desorption (TPD) studies. The monolayers studied were derived from adsorbates of the general structure HS(CH 2 ) 15 X or (S(CH 2 ) 15 X 1 ) (where X=CH 3 , CO 2 CH 3 , CH 2 OH, CO 2 H, and CONH 2 ). The adsorption of n-hexane, methanol, and water on these materials as well as on the clean Au(111) surface was examined. The data reveal complex behavior for the adsorption of secondary overlayers on these dense molecular solids especially in those substrate-adsorbate pairings capable of forming interlayer hydrogen bonds. It is also found that certain correlations can be made between the TPD data, a microscopic measurement, and the macroscopic wetting properties as defined by contact angle data

258 citations


Journal ArticleDOI
01 Oct 1990
TL;DR: The proposed formalism is applied to the problems of selecting an optimal architecture and the prediction of learning curves and the Gibbs distribution on the ensemble of networks with a fixed architecture is derived.
Abstract: A general statistical description of the problem of learning from examples is presented. Learning in layered networks is posed as a search in the network parameter space for a network that minimizes an additive error function of a statistically independent examples. By imposing the equivalence of the minimum error and the maximum likelihood criteria for training the network, the Gibbs distribution on the ensemble of networks with a fixed architecture is derived. The probability of correct prediction of a novel example can be expressed using the ensemble, serving as a measure to the network's generalization ability. The entropy of the prediction distribution is shown to be a consistent measure of the network's performance. The proposed formalism is applied to the problems of selecting an optimal architecture and the prediction of learning curves. >

Journal ArticleDOI
01 Jan 1990-Nature
TL;DR: In this article, the authors reported the successful synthesis and preliminary physical characterization of superconducting (La, Sr)2CaCu2O6, which is a uniquely simple double-layer superconductor.
Abstract: STARTING with the pioneering work of Bednorz and Muller1, many copper-oxide-based superconductors with high transition temperatures (Tc) have been discovered. All contain layers of copper-oxygen squares, pyramids or octahedra as their electronically active structural components2,3. One structure type, first reported for La2SrCu2O6 and La2CaCu2O6 (ref. 4), has stood as an enigma since the beginning of high-Tc research. This crystal structure4-7 (Fig. 1) is the least complex of all the structures with the double layers of copper oxide pyramids common to the compounds with highest Tc, yet despite considerable effort, both published8,9 and unpublished, it has not until now been made superconducting. Here we report the successful synthesis and preliminary physical characterization of superconducting (La, Sr)2CaCu2O6. The highest transition temperature observed is 60 K at the composition La1.6Sr0.4CaCu2O6. This is a uniquely simple double-layer superconductor, which, like its single-layer analogue (La, Sr)2CuO4, becomes superconducting through the introduction of carriers in an unambiguous manner—by straightforward atomic substitution without the intervention of charge reservoir layers with flexible valence states.

Journal ArticleDOI
TL;DR: In this article, the planarization of 1-4 μm thick liquid epoxy films over 25-200 μm wide isolated trenches on a silicon substrate during spin coating is determined by photochemically hardening the film and measuring the film profiles over the trenches with a profilometer.
Abstract: The planarization, that is leveling, of 1–4 μm thick liquid epoxy films over 25–200 μm wide isolated trenches on a silicon substrate during spin coating is determined by photochemically hardening the film and measuring the film profiles over the trenches with a profilometer. The profiles are quantitatively described by a simple lubrication theory that takes advantage of the thinness of the film compared to the feature width, the narrowness of the feature width compared with the distance of the feature from the substrate center, and the rapidity of change in the film profile compared to the overall rate of centrifugally driven film thinning. For a fixed ratio of film thickness to trench depth hf/d, the experimental data fall on a single curve when planarization is plotted against a dimensionless parameter Ω2≡ρω2w3r0/γhf, where ρ is the density of the liquid film, ω is the substrate angular velocity, w is the trench width, r0 is the radial position of the trench, and γ is the film surface tension. For a fix...

Journal ArticleDOI
TL;DR: A method that has been developed for the assessment and quantification of loudness perception in normal-hearing and hearing-impaired persons is described, named LGOB, which stands for loudness growth in 1/2-octave bands.
Abstract: In this paper, a method that has been developed for the assessment and quantification of loudness perception in normal‐hearing and hearing‐impaired persons is described. The method has been named LGOB, which stands for loudness growth in 1/2‐octave bands. The method uses 1/2‐octave bands of noise, centered at 0.25, 0.5, 1.0, 2.0, and 4.0 kHz, with subjective levels between a subject’s threshold of hearing and the ‘‘too loud’’ level. The noise bands are presented to the subject, randomized over frequency and level, and the subject is asked to respond with a loudness rating (one of: VERY SOFT, SOFT, OK, LOUD, VERY LOUD, TOO LOUD). Subject responses (normal and hearing‐impaired) are then compared to the average responses of a group of normal‐hearing subjects. This procedure allows one to estimate the subject’s loudness growth relative to normals, as a function of frequency and level. The results may be displayed either as isoloudness contours or as recruitment curves. In its present form, the measurements take less than 30 min. The signal presentation and analysis is done using a PC and a PC plug‐in board having a digital to analog converter.

Journal ArticleDOI
K. Tai1, L. Yang1, Y. H. Wang, J. D. Wynn1, A.Y. Cho1 
TL;DR: In this article, the series resistance of a p-type semiconductor distributed Bragg reflectors (DBR) consisting of ten pairs of quarter-wavelength GaAs (high refractive index)/Al0.7Ga0.3As (low index) layers was reduced by inserting an intermediate Al0.35Ga 0.65As layer.
Abstract: Modifications to reduce the series resistance in p‐type semiconductor distributed Bragg reflectors (DBR) consisting of ten pairs of quarter‐wavelength GaAs (high refractive index)/Al0.7Ga0.3As (low index) layers were made by inserting an intermediate Al0.35Ga0.65As layer or a 200 A superlattice of GaAs(10 A)/Al0.7Ga0.3As (10 A) at the GaAs/Al0.7Ga0.3As heterointerfaces. The specific DBR series resistance was reduced by two orders of magnitude to about 6.2×10−5 Ω cm2. These modifications did not alter the optical reflectivity and nearly identical reflection spectra were measured.


Journal ArticleDOI
TL;DR: In this paper, a model that describes the kinetics of diffusion across the terraces, as well as the filling of step sites, is proposed to estimate the diffusion barrier and prefactor.
Abstract: The microscopic diffusion of CO on stepped Pt(111) crystal surfaces has been investigated with pulsed molecular beam–time‐resolved surface infrared methods. Following a rapid exposure to CO, we record the time evolution of the CO surface vibrational spectra as the CO diffuse from the initial random distribution to the thermodynamically favored step sites. The data are simulated with a model that describes the kinetics of diffusion across the terraces, as well as the filling of step sites. We critically evaluate this model and the general experimental approach by extending our previous measurements of CO diffusion on Pt(28(111)–(110)) to a surface with higher step density, Pt(l2(111)–(110)), with varying coverages. The model describes both sets of data with the same parameters, confirming the original determination of the diffusion barrier (ΔET) and prefactor (AT) for microscopic surface hopping of CO/Pt(111). This further provides a quantitative means to estimate systematic errors. We report ΔET=4.0±0.7...

Patent
Karl Schrodi1, Gert Eilenberger1, Stefan Wahl1, Bodo Pfeiffer1, Bozo Cesar1 
20 Dec 1990
TL;DR: In this paper, the successive cells of one and the same connection are routed to the output by as many different paths as possible; however, mutual overtaking of successive cells must be avoided or corrected.
Abstract: To be able to load an ATM switching network as efficiently as possible, the successive cells of one and the same connection are routed to the output by as many different paths as possible; however, mutual overtaking of successive cells must be avoided or corrected. Each cell is held at the output until it is certain that no older cell can be buffered in the switching network. Before the cell is passed on, a check is made to determine whether the cells received from the switching network later include an older cell which must be passed on before that cell. At the input end, consecutive numbers ("Sequence Numbers") are allocated to the cells. A buffer (1) at the output end is operated, at least in part (1 . . . d), in the manner of a shift register, thereby introducing a predetermined delay. Prior to the output of a cell, at least the shift-register-like portion of the buffer is examined as to whether a cell written in later is to be put out earlier: if so, the two cells are interchanged.

Patent
31 May 1990
TL;DR: In this paper, a computer is provided with the facility to display in map form spatially-time-varying data associated with respective nodes, and the user is also provided with a tool so that he/she may either manually or automatically play through the data.
Abstract: A computer is provided with the facility to display in map form spatially-time-varying data associated with respective nodes. Specifically, responsive to a user inputting a specific command, the computer displays a plurality of symbols representing respective ones of the nodes in which the symbols share a common characteristic, the size of which is varied commensurate with changes in the data associated with their respective nodes. In addition, the user is provided with a tool so that he/she may either manually or automatically play through the data. The user is also provided with a number of other tools to control the display of the symbols and/or data, such as, for example, a tool which changes the size of the symbols so that smaller symbols are not obscured by larger symbols.

Journal ArticleDOI
TL;DR: A model low-molecular-weight polymer mixture was studied as a function of temperature near the critical point by small-angle neutron scattering (SANS) and dynamic light scattering (DLS), which reveal a crossover in the static susceptibility from mean-field to non-mean-field behavior.
Abstract: A model low-molecular-weight polymer mixture was studied as a function of temperature near the critical point by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). SANS measurements reveal a crossover in the static susceptibility from mean-field to non-mean-field behavior at {ital T}{sub {ital x}}{approx equal}{Tc}+30 {degree}C, in quantitative agreement with the Ginzburg criterion. This crossover behavior is also reflected in the DLS experiments, which reveal mode-coupled critical dynamics far into the mean-field regime.

Proceedings Article
01 Oct 1990
TL;DR: The learning time of a simple neural network model is obtained through an analytic computation of the eigenvalue spectrum for the Hessian matrix, which describes the second order properties of the cost function in the space of coupling coefficients as mentioned in this paper.
Abstract: The learning time of a simple neural network model is obtained through an analytic computation of the eigenvalue spectrum for the Hessian matrix, which describes the second order properties of the cost function in the space of coupling coefficients. The form of the eigenvalue distribution suggests new techniques for accelerating the learning process, and provides a theoretical justification for the choice of centered versus biased state variables.

Patent
23 Nov 1990
TL;DR: A metal housing for an electrical connector, such as a standardized HE12 connector, comprises two half-housings enclosing a connector plug adapted to be inserted into a socket as discussed by the authors.
Abstract: A metal housing for an electrical connector such as a standardized HE12 connector comprises two half-housings enclosing a connector plug adapted to be inserted into a socket. Each half-housing comprises a half-hinge and an orifice having a contour which is open when the two half-housings are open to enable insertion of cables and which is closed when the two half-housings are closed. Fork-shape projections in each half-housing constitute two insulation-displacement contacts for establishing an electrical connection between the half-housing and the screening braid of each cable and to prevent the cable being pulled out. Tangs in each half-housing are inserted in insulation displacement contacts when the two half-housings are closed to constitute electrical screens preventing electromagnetic interference between nearby contacts. A captive screw constitutes both a rotation spindle for the hinge and means for fixing the housing to a nut fixed to the chassis. The housing protects the connector against electromagnetic interference.

Patent
17 Apr 1990
TL;DR: In this article, a group of subscribers serviced from a center has a common remote distribution unit located in its vicinity, and the subscribers are connected to this remote transmission unit by individual lines, preferably optical waveguides.
Abstract: A group of subscribers serviced from a center has a common remote distribution unit located in its vicinity. The subscribers are connected to this remote distribution unit by individual lines, preferably optical waveguides. A single optical waveguide connects the center to the remote distribution unit. Subscriber-assigned signals with subscriber-assigned wavelengths and signals to be distributed to all subscribers in the direction from the center to the subscribers are transmitted as a multiplexed optical signal, using wavelength-division multiplexing, to the remote distribution unit. The optical signal containing the signals to be distributed is separated out at the remote distribution unit and is distributed by optical means to the subscribers. The subscriber-assigned signals are also separated in the remote distribution unit into individual signals and are transmitted to the subscribers over individual lines. In the opposite direction from the subscribers to the center, the signals to be transmitted from the subscribers to the center are also transmitted over the individual lines with subscriber-assigned wavelength to the remote distribution unit where they are grouped into an optical multiplexed signal and are transmitted to the center over an optical waveguide. A suitable selection of the wavelengths makes possible a simple multiplexed formation and multiplexed resolution of the various signals.

Journal ArticleDOI
TL;DR: La solution solide de la perovskite BaSn 1−x Sb x O 3 existe pour 0.0≤x≤0.2 et est essentiellement independante de the temperature entre 300 et 5 K.
Abstract: La solution solide de la perovskite BaSn 1−x Sb x O 3 existe pour 0.0≤x≤0.2. Sa meilleure conductivite electrique survient pour x voisin de 0.15 et est essentiellement independante de la temperature entre 300 et 5 K. Les materiaux, bien que conducteurs, ne deviennent pas supraconducteurs aux temperatures aussi basses que 0.05 K. On propose que la difference entre la liaison metal 5s-oxygene 2p et la liaison metal 6s-oxygene 2p dans les solides rend compte de ce comportement

Journal ArticleDOI
TL;DR: The energy gap is measured in a series of cuprate crystals and it is found that the energy gap scales predominantly with the in-plane Cu-O distance, scaling as {delta} log{Delta}/{delta] log{ital d}{similar to}{minus}6.
Abstract: We have measured the insulating energy gap \ensuremath{\Delta} and the exchange interaction J in a series of cuprate crystals, including T'-phase ${\mathit{M}}_{2}$${\mathrm{CuO}}_{4}$ (M=Pr, Nd, Sm, Eu, and Gd), ${\mathit{T}}^{\mathrm{*}}$-phase La,Tb,${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{4}$, and T-phase ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$. We find that the energy gap scales predominantly with the in-plane Cu-O distance, scaling as \ensuremath{\delta} log\ensuremath{\Delta}/ \ensuremath{\delta} logd\ensuremath{\sim}-6. Furthermore, contrary to simple expectations, the energy gap increases with decreasing Cu-O distance, suggesting that Coulomb and other repulsive energies dominate the effects of band hybridization. Using a three-band Hubbard-model expression, our studies of \ensuremath{\Delta} and J in the cuprates allow us to estimate that the hopping energy t scales with Cu-O distance as \ensuremath{\delta} logt/\ensuremath{\delta} logd\ensuremath{\sim}-4.

Patent
26 Oct 1990
TL;DR: In this article, the authors propose an approach to reconnect a communications network such as a DS3 telephone-type network when a span of DS3 channels is rendered inoperative, such as by cutting, within the 1.5 second time frame necessary to prevent disablement of local offices.
Abstract: The present invention provides an approach to reconnect a communications network such as a DS3 telephone-type network when a span of DS3 channels is rendered inoperative, such as by cutting, within the 1.5 second time frame necessary to prevent disablement of local offices. This is accomplished by preplanning a restoration connection for each possible operating link failure in each span using spare capacity. A dedicated (DS3) communication loop is used to inform all nodes in the network substantially simultaneously to implement their portion of a plan associated with the failed span. After the restoration occurs for a given failed span, the concept can be extended to start planning for further failures or can be designed to restore further failures on a real time basis.

Journal ArticleDOI
TL;DR: In this paper, the stability of steady state solutions to Doi's kinetic equation for rigid rod-like polymers in an arbitrary flow field was studied, and it was found that for a certain range of concentration, the addition of flow to an isotropic phase can induce a transition to the nematic phase, if the flow rate exceeds a certain critical value.
Abstract: In this paper we study the stability of steady state solutions to Doi’s kinetic equation for rigid rod‐like polymers in an arbitrary flow field. It is found that for a certain range of concentration, the addition of flow to an isotropic phase can induce a transition to the nematic phase, if the flow rate exceeds a certain critical value. This critical flow rate decreases as concentration is increased. For phase transitions occurring in weak flow, exact solutions to this problem are calculated. Unlike the ‘‘free energy’’ approach, these calculations are not restricted to potential flows.

Journal ArticleDOI
TL;DR: Results from the study of the development of the optical conductivity as electrons are added to the Cu-O planes indicate an electron-hole symmetry that is not anticipated by standard charge-transfer insulator models.
Abstract: We have studied the development of the optical conductivity as electrons are added to the Cu-O planes in ${\mathrm{Pr}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ by varying x(0\ensuremath{\le}x\ensuremath{\le}0.2). In the metallic phases, contributions to the optical conductivity below 3 eV arise from three sources: mobile carriers, mid-infrared excitations, and charge-transfer excitations. The mobile carrier spectral weight grows roughly linearly with x, while the mid-infrared band appears to evolve at low doping via a transfer of spectral weight from the charge-transfer band. Comparing these results with hole doping in ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ indicates an electron-hole symmetry that is not anticipated by standard charge-transfer insulator models.

Journal ArticleDOI
TL;DR: The primary intermediate in the reaction of oxygen with cytochrome c oxidase was generated by photodissociating carbon monoxide in a continuous flow rapid mixing apparatus and the presence of the primary intermediate was confirmed by a comparison of the iron-dioxygen stretching frequency with that obtained in the reacting enzyme.
Abstract: The primary intermediate in the reaction of oxygen with cytochrome c oxidase was generated by photodissociating carbon monoxide in a continuous flow rapid mixing apparatus. The presence of the primary intermediate was confirmed by a comparison of the iron-dioxygen stretching frequency with that obtained in the reaction of oxygen with the mixed-valence enzyme. For both of these preparations, the Fe-O2 stretching mode is detected at 568 cm-1, the same frequency as that found in oxyhemoglobin and oxymyoglobin. These data illustrate that the primary intermediate may be generated and detected at room temperature in the fully reduced enzyme and that the oxidation state of cytochrome a does not affect the structure of the iron-dioxygen complex. By following the changes in the intensity of the Fe-O2 stretching mode in the resonance Raman spectrum as a function of time, the first-order rate constant for the decay of the primary intermediate was found to be 3.5 x 10(4) s-1 (t1/2 = 20 microseconds).

Proceedings ArticleDOI
M.A. Henrion1, K.J. Schrodi, D. Boettle, M. De Somer, M. Dieudonne 
28 May 1990
TL;DR: A new ATM based switching architecture for asynchronous communications based on the advantageous combination of a multiple-path self-routing principle with an internal transfer mode using multi-slot cells is described.
Abstract: Being the communication core of future broadband products, the ATM based switching network architecture must comply with a challenging set of future safe requirements and objectives, which are tentatively defined first. After some period of research work, a number of different solutions for fast packet switching or ATM switching are still proposed. It is thus interesting to discuss the respective attributes of key architecture options for asynchronous switch fabrics. As an illustration, the paper then describes a new ATM based switching architecture for asynchronous communications based on the advantageous combination of a multiple-path self-routing principle with an internal transfer mode using multi-slot cells. These principles are the foundation for a flexible and fault tolerant switching network configuration built with two Weis of standard switching components: the Switch Module board equivalent to a 128 x 128 single-stage matrix operating at 150 Mbit/s, and the Integrated Switching Element LSI circuit realizing an elementary, fully featured, 32 x 32 switching matrix.