Low-crosstalk and low-loss waveguide crossings on InP with small dimensions

With the increasing scale of integration, resulting in a higher on-chip complexity, waveguide crossings with good performance are becoming increasingly important. Worst-case paths contain a high number of crossings, depending on the number of channels being processed, in switching matrices [11, multiwavelength add drop filters [2] (up to 151, and optical cross-connects [3]. Crossings with very low crosstalk and loss can be realized in fiber-matched waveguide structures as used in lithium niobate or silica-based technology [4,5]. In highly integrated semiconductor devices, crossings may contribute significantly to the loss and crosstalk performance. In this paper we present the results of a series of experiments for the design of high-performance semiconductor waveguide crossings.     

The construction of an accurate lower bound for the real parts of the eigenvalues of an M-matrix

Let A by an M-matrix, i.e., A is nonsingular, real, irreducible, and weakly diagonally dominant and has positive diagonal and nonpositive off-diagonal elements. Via the graph of A we construct a vector W such that AW is positive. This yields a lower bound of the spectrum, which is optimal in certain problems.     

Cube roots of integers. A conjecture about Heron's method in Metrika III. 20

Did Heron (or his teachers) use sequences of differences to find an approximate value of the cube root of an integer? I venture a conjecture of his heuristics and a couple of possible mathematical proofs of his method.     

Phenol photodegradation on platinized-TiO2 photocatalysts related to charge-carrier dynamics

Three commercial TiO2 compounds (Degussa P25, Sachtleben UV100, and Millenium PC50) and their platinized forms have been studied by the time-resolved microwave conductivity (TRMC) method to follow their charge-carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge-carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidenced.     

Determination of drug protein-binding by high-performance liquid chromatography using a chemically bonded bovine albumin stationary phase

A liquid chromatographic method for the determination of the degree of protein-binding of drugs has been established, using a stationary phase to which bovine serum albumin has been bonded chemically. In a structurally heterogeneous group of compounds, results of the method correlate well with protein-binding data obtained by equilibrium dialysis (r = 0.89, n = 23, p less than 0.001). Within a series of analogous piperazines a good correlation is found (r = 0.981, n = 11, p less than 0.001). The chromatographic method allows automation of the measurement of protein-binding of large series of compounds with protein-binding ranging between 10 and 99%. The method is not expensive and is less time consuming than equilibrium dialysis. Only 1 mg of technical-grade material is required to determine the protein-binding, and radioactive labelling of the material is not necessary.