Crystal and molecular structure of 1,4-diphenyl-2,3-dioxabicyclo[2,2,1] heptane,C17H16O2

The crystal structure of 1,4-diphenyl-2,3-dioxabicyclo [2,2,1] heptane has been determined from three-dimensional counter data and refined by full-matrix least-squares procedures. This endoperoxide compound crystallizes from ethanol in space groupP2₁/c with cell constantsa = 11.797(1),b = 9.051(8),c = 12.472(1) Å, = 93.78(1) °,Z = 4,D _x = 1.261, andD _m = 1.274 g cm^–3. The final residual for 2238 observed reflections is 0.063. The molecular structure possesses both an unusually long peroxide bond, 1.501(2) Å, and adjoining C-O bonds, 1.459(2) Å. This observation confirms a previously made conjecture that the forcedcis coplanarity of the C-O-O-C torsion angle would permit repulsive antisymmetric vicinal orbital interactions between the oxygen centers, destabilizing the peroxide bond relative to that normally encountered as the commonly observedgauche conformation.     

Macrocycle-Derived Functional Xanthenes and Progress Towards Concurrent Detection of Glucose and Fructose

The detection of saccharides in biological media is of great current importance for the monitoring of disease states. We have previously reported that solutions of boronic acid-functionalized macrocycles form acyclic oligomeric materials in situ. The oligomers contain fluorescent xanthene moieties. Current efforts are aimed at modulating the spectroscopic responses of these materials for the analysis of specific sugars. We describe conditions whereby the xanthene boronic acids exhibit high colorimetric fructose selectivity. In contrast, at physiological levels selective glucose monitoring can be achieved via fluorescence. Additionally, we describe a method which exhibits promise for detecting both glucose and fructose at dual wavelengths in the UV-Vis region. Mechanistic rationale for each of these findings is presented.     

Synthesis,crystal structure and catalytic activity for H2O2 disproportionation of the manganese(II) coordination polymer {[Mn(O2C(CF2)8CO2)(phen)2]H2O}n (phen = 1,10-phenanthroline)

The title polymeric complex {[Mn(O₂C(CF₂)₈CO₂)(phen)₂]H₂O}_n was synthesized through the reaction of 1,10-phenanthroline, perfluorosebacic acid and MnCO₃ · H₂O. The molecular structure was characterized by X-ray diffraction, elemental analysis, thermal gravimetry, IR and UV–Vis spectroscopy and its catalytic activity has been studied. X-ray structure analysis shows that each Mn(II) ion is octahedrally coordinated by two bidentate phenanthroline ligands and the carboxylate oxygen atoms from two symmetry related perfluorosebacate ligands, which are coordinated in cisoid positions. The structure consists of polymeric chains, with the perfluorosebacato ligand bridging the Mn(II) ions in a monodentate fashion. Crystallographic characterization shows a supramolecular structure involving hydrogen bonds, π–π and π-ring interactions. The catalytic results indicated that the complex has reasonably good activity towards the disproportionation of hydrogen peroxide into water and dioxygen in methanol and it does not exhibit saturation kinetics with the substrate. The initial reaction rates and their temperature and base dependencies were investigated by monitoring the dioxygen evolution. Kinetic studies revealed a first-order dependence on the catalyst concentration. Activation parameters have been calculated at 301 K.     

Fourier optics analysis of grating sensors with tilt errors

Dynamic diffraction gratings can be microfabricated with precision and offer extremely sensitive displacement measurements and light intensity modulation. The effect of pure translation of the moving part of the grating on diffracted order intensities is well known. This study focuses on the parameters that limit the intensity and the contrast of the interference. The effects of grating duty cycle, mirror reflectivities, sensor tilt and detector size are investigated using Fourier optics theory and Gaussian beam optics. Analytical findings reveal that fringe visibility becomes <0.3 when the optical path variation exceeds half the wavelength within the grating interferometer. The fringe visibility can be compensated by monitoring the interfering portion of the diffracted order light only through detector size reduction in the expense of optical power. Experiments were conducted with a grating interferometer that resulted in an eightfold increase in fringe visibility with reduced detector size, which is in agreement with theory. Findings show that diffraction grating readout principle is not limited to translating sensors but also can be used for sensors with tilt or other deflection modes.     

Spectral amplitude and phase measurement of ultrafast pulses using all-optical differential tomography

We demonstrate a simple, all-optical, fiber-based method for characterizing the spectral amplitude and phase of ultrafast pulses using a differential tomographic measurement realized via four-wave mixing. The technique is applied to subpicosecond pulses in the C-band of the telecommunication spectrum. Characterization of amplified pulses and propagation through dispersive media is demonstrated and compared with autocorrelation measurements and calculated predictions. We show how our approach can be extended to larger bandwidths in similar systems, extending tomographic reconstruction of coherent fields to nearly an octave of bandwidth while maintaining a robust, waveguide-based geometry.     

Selling to the “Newsvendor” with a forecast update: Analysis of a dual purchase contract

We consider a supply chain in which a manufacturer sells to a procure-to-stock retailer facing a newsvendor problem with a forecast update. Under a wholesale price contract, the retailer waits as long as she can and optimally places her order after observing the forecast update. We show that the retailer’s wait-and-decide strategy, induced by the wholesale price contract, hinders the manufacturer’s ability to (1) set the wholesale price and maximize his profit, (2) hedge against excess inventory risk, and (3) reduce his profit uncertainty. To mitigate the adverse effect of wholesale price contract, we propose the dual purchase contract, through which the manufacturer provides a discount for orders placed before the forecast update. We characterize how and when a dual purchase contract creates strict Pareto improvement over a wholesale price contract. To do so, we establish the retailer’s optimal ordering policy and the manufacturer’s optimal pricing and production policies. We show how the dual purchase contract reduces profit variability and how it can be used as a risk hedging tool for a risk averse manufacturer. Through a numerical study, we provide additional managerial insights and show, for example, that market uncertainty is a key factor that defines when the dual purchase contract provides strict Pareto improvement over the wholesale price contract.     

A fuzzy goal programming method with imprecise goal hierarchy

Two most widely used approaches to treating goals of different importance in goal programming (GP) are: (1) weighted GP, where importance of goals is modelled using weights, and (2) preemptive priority GP, where a goal hierarchy is specified implying infinite trade-offs among goals placed in different levels of importance. These approaches may be too restrictive in modelling of real life decision making problems. In this paper, a novel fuzzy goal programming method is proposed, where the hierarchical levels of the goals are imprecisely defined. The imprecise importance relations among the goals are modelled using fuzzy relations. An additive achievement function is defined, which takes into consideration both achievement degrees of the goals and degrees of satisfaction of the fuzzy importance relations. Examples are given to illustrate the proposed method.     

Vibrational Spectra and Structural-Dynamic Models of Phenyldichlorarsine and Phenyldichlorophosphine

Vibrational spectra of phenyldichlorarsine and phenyldichlorophosphine are analyzed for free molecules and in water solutions within the framework of the ab initio methods. Characteristic spectral parameters of compounds are determined for their subsequent use in ecological monitoring.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 58–61, March, 2005.     

Transient heat conduction with uniform heat generation in a slab subjected to convection and radiation cooling

A finite difference scheme with fourth order Runge-Kutta method is employed to determine the unsteady state temperature distribution in a plane slab with uniform heat generation. The plane slab is insulated on one face and subjected to convective and radiative cooling at the other face. The plane slab has a uniform initial temperature and the ambient environment as well as the fluid temperatures are assumed to be constant. Heat conduction is considered to be one dimensional. Results are presented in dimensionless charts over a wide range of parameters.

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Instationäre Wärmeleitung mit gleichförmiger Wärmeerzeugung in einer Platte bei Kühlung durch Konvektion und Abstrahlung

Zusammenfassung Zur Ermittlung der instationären Temperaturverteilung in einer Platte mit gleichförmiger Wärmeerzeugung wird ein Differenzverfahren vierter Ordnung nach Runge-Kutta angewendet. Die ebene Platte ist einseitig isoliert und wird auf der anderen Seite durch Konvektion und Abstrahlung gekühlt. Zu Beginn befindet sich die Platte gleichförmig auf einer bestimmten Anfangstemperatur, die Temperaturen der umgebenden Objekte sowie des Fluids sind ebenfalls konstant. Der Wärmeleitungsvorgang sei eindimensional. Die Ergebnisse sind in dimensionsloser Form für einen weiten Parameterbereich in Diagrammform dargestellt.

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Nomenclature Bi Biot number - c specific heat - h heat transfer coefficient - k thermal conductivity - L half thickness of plate - Nr Radiation number - T absolute temperature - t time - F _o dimensionless time - T _e environment temperature - T _f fluid temperature - T _i initial plate temperature - u internal energy generation number - u internal energy generation - x space coordinate - x* dimensionless space coordinate Greek symbols thermal diffusivity - emissivity - dimensionless temperature - density - Stephan-Boltzman constant