Persistent Monitoring by Multiple Unmanned Aerial Vehicles Using Bernstein Polynomials

Journal of Optimization Theory and Applications - A framework for monitoring a target modeled as Dubins car using multiple UAVs is proposed. The UAVs are subject to minimum and maximum speed,...     

Characterization of thermal diffusion in polymer solutions by thermal field-flow fractionation: Dependence on polymer and solvent parameters

The thermal diffusion coefficient D_T has been obtained for 17 polymer-solvent combinations, each of them spanning a range of polymer molecular weights, using thermal field-flow fractionation. The polymers examined include polystyrene, poly(alpha-methyl)styrene, polymethylmethacrylate, and polysioprene. The solvents include benzene, toluene, ethylbenzene, tetrahydrofuran, methylethylketone, ethylacetate, and cyclohexane. Although D_T was confirmed as essentially independent of polymer molecular weight, it was found to vary substantially with the chemical composition of polymer and solvent. The results were used to evaluate several thermal diffusion theories; the agreement with theory was generally found to be unsatisfactory. Attempts were then made to correlate the measured thermal diffusion coefficients with various physicochemical parameters of the polymers and solvent. A good correlation was found in which D_T increases with the thermal conductivity difference of the polymer and solvent and varies inversely with the activation energy of viscous flow of the solvent.     

Consistency of a myopic Bayesian algorithm for one-dimensional global optimization

A sequential Bayesian method for finding the maximum of a function based on myopically minimizing the expected dispersion of conditional probabilities is described. It is shown by example that an algorithm that generates a dense set of observations need not converge to the correct answer for some priors on continuous functions on the unit interval. For the Brownian motion prior the myopic algorithm is consistent; for any continuous function, the conditional probabilities converge weakly to a point mass at the true maximum.     

Amperometry of thiols in a flow-injection system with a nickel oxide electrode

The electrochemical oxidation of a series of thils on the surface of a nickel oxide electrode is investigated in a flow-injection system. The background electrolyte is 0.1 M NaOH containing 5 × 10^?65 M NiSO₄ and the injected sample volume is 25 μl. The net peak current is observed at +0.46 V vs. SCE for thiols dissolved in pH 3.0 phthalate buffer. The upper limit of linearity extends to 10^?3 M. The relative standard deviation for ten replicate measurements on 10^?4 M ethanethiol is 1.6%. The lower limits of detection are between 3 × 10^?5 and 2 × 10^?4 M for a series of thiols. Peak shapes indicate that thiolate oxidation mediated by a higher oxide layer on the electrode rather than mass transport or adsorption / rearrangement is the rate-determining step.     

Determination of polar organic compounds by potentiometry at an anodically pretreated nickel oxide electrode

The open-circuit potential drop of an oxidatively pretreated nickel electrode in 0.1 M NaOH was used to develop a technique for the determination of alcohols, amino acids, carbohydrates, etc., in aqueous solution. The electrode pretreatment consisted of the formation of nickel hydrated oxides on the electrode surface with an oxidation state > 2. Both electrochemical and chemical pre-oxidation of the electrode surface were examined. The analytical signal was the enhancement of the potential drop corresponding to analyte concentration. The analytical signal was linearly related to the logarithm of the analyte concentration. The limits of determination ranged from 1 mM for low-molecular-weight to 0.02 mM for alkyl polyether alcohols. The flow-injection technique allows convenient pretreatment and direct observation of the analytical signal. Interferences from chloride and calcium can be readily eliminated by excluding them during electrode pretreatment. Potentiometric measurements were correlated with amperometric anodic responses at the nickel oxide electrode, allowing an unusual direct comparison of the two methods.     

Hydride donor abilities and bond dissociation free energies of transition metal formyl complexes

The hydride complex [Pt(dmpe)2H]+ (dmpe = 1,2-bis(dimethylphosphino)ethane) reversibly transfers H- to the rhenium carbonyl complex [CpRe(PMe3)(NO)(CO)]+, giving the formyl CpRe(PMe3)(NO)(CHO). From the equilibrium constant for the hydride transfer (16.2), the DeltaGdegrees for the reaction was determined (-1.6 kcal/mol), as was the hydride-donating ability of the formyl (44.1 kcal/mol). The hydride-donating ability, DeltaGdegrees(H-), is defined as the energy required to release the hydride ion into solution by the formyl complex [i.e. M(CHO) right arrow M(CO)+ + H-]. Subsequently, the hydride-donating ability of a series of formyl complexes was determined, ranging from 44 to 55 kcal/mol. With use of this information, two rhenium carbonyl complexes, [CpRe(NO)(CO)2]+ and [Cp*Re(NO)(CO)2]+, were hydrogenated to formyls, employing [Pt(dmpp)2]2+ and Proton-Sponge. Finally, the E(1/2)(I/0) values for five rhenium carbonyl complexes were measured by cyclic voltammetry. Combined with the known DeltaGdegrees(H-) values for the complexes, the hydrogen atom donating abilities could be determined. These values were all found to be approximately 50 kcal/mol.     

KINETIC STUDIES OF THE TWO LIGHT REACTIONS IN PHOTOSYNTHESIS

Abstract— The decay kinetics of the photo-induced absorbance changes in red and green algae are very sensitive to the wavelength of the actinic light. A four to tenfold increase in half-decay time is noted in going from short wavelength (550–650 mμ) to long wavelength (> 700 mμ) excitation. The slow decay rates produced by long wavelength light can be enhanced with a steady background of short wavelength light. A relationship between initial decay rates and O₂ evolution rates is described. This relationship allows a direct correspondence between these spectroscopic studies and the 'red-drop' and 'enhancement' experiments of Emerson.     

PHOTOSYNTHESIS AS A RESOURCE FOR ENERGY AND MATERIALS*

Abstract— Photosynthesis, both natural and as a model process, is examined as a possible annually renewable resource for both material and energy. The conversion of carbohydrate from cane, beets and other sources through fermentation alcohol to hydrocarbon may again become economic in the light of improved fermentation technology. It may also be possible to produce material by direct fermentation of relatively labile carbohydrates in seaweed. Even the direct photosynthetic production of hydrocarbon from known sources (Hevea, etc.), or newly bred ones, seems possible in view of the large number of species and the new techniques of plant cell cloning which have already been successful on sugar cane. Finally, more distantly, synthetic systems constructed on the basis of our growing knowledge of the photosynthetic processes may produce fuel, fertilizer and power. Thus, from our current knowledge of the natural quantum conversion process in green plants we can envisage several photoelectron transfer processes. In a first one the excited sensitizer (chlorophyll) transfers its electron to an acceptor molecule such as an iron-sulfur complex which, in turn, could either reduce a carbon compound or pass that electron into a hydrogen-generating system leading to the evolution of molecular hydrogen. The remaining cation radical sensitizer would have to be neutralized through a chain of electron transfers which begins at another sensitized reaction (presumably by another kind of chlorophyll) through a quinone and other electron carriers. Finally, the last cation radical near the oxidation level of oxygen could be neutralized by electron transfer, ultimately from a water molecule (hydroxide or bicarbonate ion) involving a manganese catalyst. Some steps in this sequence of transfers have already been demonstrated in synthetic systems. However, the actual physical construction of such a complete system is a much more complex task.     

Dispersed fluorescence spectroscopy of jet-cooled HCF and DCF: Vibrational structure of the X 1A' state

We recorded dispersed fluorescence (DF) spectra following excitation of the pure bending levels 2(0) (n) and the combination states 1(0) (1)2(0) (n) and 2(0) (n)3(0) (1) in the A 1A"<--X 1A' system of HCF and DCF. Spectra were measured with a 0.3 m spectrograph equipped with a gated intensified charge coupled device (CCD) detector and obtained under jet-cooled conditions using a pulsed discharge source. The DF spectra reveal rich detail concerning the vibrational structure of the X state up to 10 000 cm(-1). For HCF, resonances among the nearly degenerate levels 1(1)2n, 2n+13(1), and 2n+2 produce a polyadlike structure in the spectrum, and the usual effective spectroscopic Hamiltonian (Dunham expansion) poorly reproduces the experimental term energies. In contrast, this Hamiltonian works well for the term energies of DCF. Density functional calculations of the ground state vibrational frequencies were performed; the results are in excellent agreement with the experimentally derived vibrational parameters. The search for perturbations involving the low-lying a 3A" state is described.