Linear Spectrograms Using Electrooptic Modulators

Accurate intensity and phase measurement of high-speed optical pulses is becoming more important with the ever increasing data rates of fiber links. Linear spectrograms employing electroabsorption modulators have proven to be useful in making these measurements. In this letter, we investigate and compare the use of electrooptic Mach-Zehnder and phase modulators in linear spectrograms     

Incompatibility of macroscopic local realism with quantum mechanics in measurements with macroscopic uncertainties

We show that quantum mechanics predicts a contradiction with local hidden variable theories for photon number measurements which have limited resolving power, to the point of imposing an uncertainty in the photon number result which is macroscopic in absolute terms. We show how this can be interpreted as a failure of a new premise, macroscopic local realism.     

Continuous variable tripartite entanglement and Einstein-Podolsky-Rosen correlations from triple nonlinearities

We develop three-mode generalizations of the Einstein-Podolsky-Rosen paradox, allowing us to define inequalities which may be used to indicate continuous-variable tripartite entanglement. We use these inequalities and an appropriate version of the previously developed van Loock-Furusawa inequalities to theoretically compare the continuous-variable tripartite entanglement available from the use of three concurrent x ⁽²⁾ nonlinearities and from three independent squeezed states mixed on beamsplitters. The text was submitted by the authors in English.     

First-order strong variation algorithm for optimal control problems involving parabolic systems

This paper considers the optimal control of a system governed by a parabolic partial differential equation with first boundary conditions. For this system, a condition of extremality is defined, which is proven to be a necessary condition for optimality. For non-extremal controls, a method of constructing a new control that has an improved criterion value is discussed. It is shown that if a sequence of controls, each constructed from the previous control in the manner discussed, converges, then the limit is extremal.     

Implicit Scaling of Linear Least Squares Problems

We consider the solution of weighted linear least squares problems by Householder transformations with implicit scaling, that is, with the weights stored separately. By holding inverse weights, the constrained case can be accommodated. The error analysis of the weighted and unconstrained case is readily extended and we show that iterative refinement may be applied.     

Mediated Inner-Sphere Electron Transfer Induces Homogeneous Reduction of CO2 via Through-Space Electronic Conjugation**

The electrocatalytic reduction of CO₂ is an appealing method for converting renewable energy sources into value-added chemical feedstocks. We report a co-electrocatalytic system for the reduction of CO₂ to CO comprised of a molecular Cr complex and dibenzothiophene-5,5-dioxide (DBTD) as a redox mediator, which achieves high activity (TOF=1.51–2.84×10⁵ s^?1) and quantitative selectivity. Under aprotic or protic conditions, DBTD produces a co-electrocatalytic response with 1 by coordinating trans to the site of CO₂ binding and mediating electron transfer from the electrode with quantitative efficiency for CO. This assembly is reliant on through-space electronic conjugation between the π frameworks of DBTD and the bpy fragment of the catalyst ligand, with contributions from dispersive interactions and weak sulfone coordination.     

A Method to Combine Residual Stress Measurements from XRD and IHD using Series Expansion

Experimental Mechanics - It is common practice to use various residual stress measurement methods to complement each other and fully define a through-thickness stress distribution. Incremental...     

Chemical diffusion and crystalline nucleation during oxidation of ferrous iron-bearing magnesium aluminosilicate glass

Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM) have been used to evaluate the mechanism and kinetics of oxidation of a Fe²⁺-doped MgO---Al₂O₃---SiO₂ glass (with nominal composition along the enstatite-cordierite-liquid divariant) which was heat treated in air under the time and temperature ranges 10–150 h and 700–800°C, respectively. The results clearly demonstrate that oxidation occurs by a cation diffusion process: specifically, the divalent cations diffuse from the interior of the glass to the free surface where they subsequently react with environmental oxygen to form a two-phase, MgO---(Mg, Fe)₃O₄ crystalline layer which covers the (divalent cation-depleted) glass. Oxidation of some Fe²⁺ within the glass occurs via the inward flux of electron holes (a counterflux to the divalent cation diffusion required to maintain charge neutrality of the glass); this internal oxidation results in the fine-scale ( 1–5 nm), homogeneous nucleation of crystalline (Mg, Fe)₃O₄ within the divalent cation-depleted layer of the glass. Chemical diffusion of an oxygen species is thus demonstrated to be a slower, parallel kinetic process which is not required for oxidation to occur in this material. A first-order analysis of oxidation kinetics in the glass is presented.