Pump-noise transfer in dual-pump fiber-optic parametric amplifiers: walk-off effects

Transfer of intensity noise from pumps to signal in dual-pump fiber-optic parametric amplifiers is simulated numerically for a realistic configuration in which both pumps are amplified and filtered before they enter the fiber. The walk-off effects induced by different group velocities of pumps, signal, and idler are fully taken into account. It is found that the optical signal-to-noise ratio can be as low as 15 dB when the amplifier length is close to 0.5 km, but it can be improved by 3 dB or so by use of longer fibers.     

Decoding the Fucose Migration Product during Mass-Spectrometric analysis of Blood Group Epitopes

Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin-dependent leukocyte adhesion or pathogen-receptor interactions. Mass-spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose-containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion-mobility spectrometry, radical-directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density-functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with an α(1→6) glycosidic bond as the most likely product.     

Crystallization studies of poly(trimethylene terephthalate) using thermal analysis and far‐infrared spectroscopy

Crystallization of poly(trimethylene terephthalate) (PTT) by annealing was examined using density measurement, differential scanning calorimetry, and far‐infrared spectroscopy (FIR). Crystallinity, measured by density, increased slowly up to the T_a of 185 °C and increases rapidly once T_a exceeds 185 °C. It was found that thermally induced crystallization is mainly temperature‐dependent above T_a = 185 °C and temperature‐ and time‐dependent below T_a = 60 °C. Two melting transitions, T and T, were observed for those samples annealed above 120 °C. No significant change in T was observed as a function of T_a while T showed strong dependency on T_a. Digital subtraction of the amorphous contribution from the semicrystalline FIR spectra provided characteristic spectra of amorphous and crystalline PTT. The bands at 373, 282, and 92 cm^?1 were assigned to the crystalline phase, while the bands at 525, 406, and 351 cm^?1 were attributed to the amorphous phase. It was shown that FIR spectroscopy can be used as a means to estimate the degree of crystallinity of PTT. The band ratio of 373 and 501 cm^?1 was plotted against crystallinity measured by density and reasonably good correlation was obtained. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1675–1682, 2007     

Symbolic-numeric Gaussian cubature rules

It is well known that Gaussian cubature rules are related to multivariate orthogonal polynomials. The cubature rules found in the literature use common zeroes of some linearly independent set of products of basically univariate polynomials. We show how a new family of multivariate orthogonal polynomials, so-called spherical orthogonal polynomials, leads to symbolic-numeric Gaussian cubature rules in a very natural way. They can be used for the integration of multivariate functions that in addition may depend on a vector of parameters and they are exact for multivariate parameterized polynomials. Purely numeric Gaussian cubature rules for the exact integration of multivariate polynomials can also be obtained.We illustrate their use for the symbolic-numeric solution of the partial differential equations satisfied by the Appell function F₂, which arises frequently in various physical and chemical applications. The advantage of a symbolic-numeric formula over a purely numeric one is that one obtains a continuous extension, in terms of the parameters, of the numeric solution. The number of symbolic-numeric nodes in our Gaussian cubature rules is minimal, namely m for the exact integration of a polynomial of homogeneous degree 2m−1.In Section 1 we describe how the symbolic-numeric rules are constructed, in any dimension and for any order. In Sections 2, 3 and 4 we explicit them on different domains and for different weight functions. An illustration of the new formulas is given in Section 5 and we show in Section 6 how numeric cubature rules can be derived for the exact integration of multivariate polynomials. From Section 7 it is clear that there is a connection between our symbolic-numeric cubature rules and numeric cubature formulae with a minimal (or small) number of nodes.     

Relaxations for two-level multi-item lot-sizing problems

We consider several variants of the two-level lot-sizing problem with one item at the upper level facing dependent demand, and multiple items or clients at the lower level, facing independent demands. We first show that under a natural cost assumption, it is sufficient to optimize over a stock-dominant relaxation. We further study the polyhedral structure of a strong relaxation of this problem involving only initial inventory variables and setup variables. We consider several variants: uncapacitated at both levels with or without start-up costs, uncapacitated at the upper level and constant capacity at the lower level, constant capacity at both levels. We finally demonstrate how the strong formulations described improve our ability to solve instances with up to several dozens of periods and a few hundred products.     

Unique viscoelastic behaviors of colloidal nanocrystalline cellulose aqueous suspensions

Unique rheological and phase behaviors of rod-like nanocrystalline cellulose (NCC) suspensions in aqueous media are revealed in the present article. Specifically, the NCC aqueous suspension remained isotropic in a wide NCC concentration range in which the suspension underwent transition from dilute solution to gel, and the relative viscosity of the NCC suspension could be well fitted by the Sato-Teramoto theory in the full concentration range tested. Correspondingly, both zero-shear viscosity and complex viscosity increased monotonically with NCC concentration, and no maximum value was observed along the curves of zero-shear viscosity or complex viscosity versus NCC concentration, indicating a deviation from the lyotropic system. However, a shear-induced birefringence phenomenon was observed, indicating the NCC suspension formed a temporary ordered structure in the external force field but was unable to form an anisotropic (liquid crystalline) phase. The Cox-Merz rule was not applicable for the NCC suspension as a result of oriented domains, i.e., rod-like NCC particles. Moreover, time-concentration superposition was successfully applied to both the storage and loss modulus, attributed to the isotropic feature of the NCC suspension in the tested concentration range. The reason why this NCC suspension remained isotropic could be because of the strong electrostatic repulsions between NCC particles and the weak tendency or driving force of anisotropy formation as a result of the small aspect ratio of NCC particles, Na⁺ counterions and large amounts of negative charges along the NCC particles. The results suggested that not all the rod-like particles were able to form an anisotropic phase in aqueous suspension, but dominated by various factors.     

Online preconcentration for the determination of lead, cadmium and copper by slotted tube atom trap (STAT)-flame atomic absorption spectrometry

An online sensitivity enhancement by using atom trapping in flame atomic absorption spectrophotometry was examined for increasing the residence time of the analyte atoms in the light path. For this purpose, various parameters of quartz tubes of the slotted tube atom trap were tested. The studied parameters include the internal diameter, the length of the upper slot and the wall thickness of quartz tube. The best sensitivities as high as 7-fold, 13-fold and 3-fold enhancement were achieved by the tubes having an internal diameter of 6 mm, an upper slot length of 1.0 cm and the wall thickness of 1.5 mm for lead, cadmium and copper, respectively. The limits of quantitation were found to be 30 ng mL(-1) for Pb and 3 ng mL(-1) for Cd and 30 ng mL(-1) for Cu by the optimized method. The achieved technique was applied to determine the concentrations of Pb, Cd and Cu in different plant leaves taken around cement and textile industries.     

Synthesis and Optical Characterization of Red-Emitting BaTa<Subscript>2</Subscript>O<Subscript>6</Subscript>:Eu<Superscript>3+</Superscript> Phosphors

Undoped and Eu³⁺ doped BaTa₂O₆ phosphors were synthesized via solid state reaction method and characterized by using XRD, SEM-EDS and photoluminescence (PL) analyses. The XRD results revealed that the crystal structure of BaTa₂O₆ allowed up to 10 mol% levels of Eu³⁺ ions due to the TTB characteristic network of adjacent octahedrals. SEM-EDS analyses confirmed the formation of BaTa₂O₆ structure and EuTaO₄ secondary phase. BaTa₂O_6:Eu³⁺ phosphors exhibited orange and red emissions at 592.2 nm and 615.7 nm in the visible region respectively. The Commission Internationale d’Eclairage (CIE) chromaticity coordinates of the BaTa₂O_6:Eu³⁺ phosphors that excited at λ _ex = 400 nm ranged from orangish-red to pinkish-red depending on increasing Eu³⁺ concentration.     

Photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one in different solutions

A number of photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one have been measured for the first time including the prompt and P-type delayed fluorescence, and triplet-triplet absorption. Decay parameters, for the triplet-state of this molecule, have also been measured in different quenching conditions. The results are discussed and compared for those of similar molecules.     

Polyhedral analysis for the two-item uncapacitated lot-sizing problem with one-way substitution

We consider a production planning problem for two items where the high quality item can substitute the demand for the low quality item. Given the number of periods, the demands, the production, inventory holding, setup and substitution costs, the problem is to find a minimum cost production and substitution plan. This problem generalizes the well-known uncapacitated lot-sizing problem. We study the projection of the feasible set onto the space of production and setup variables and derive a family of facet defining inequalities for the associated convex hull. We prove that these inequalities together with the trivial facet defining inequalities describe the convex hull of the projection if the number of periods is two. We present the results of a computational study and discuss the quality of the bounds given by the linear programming relaxation of the model strengthened with these facet defining inequalities for larger number of periods.