Correcting the polarization effect in low frequency Dielectric Spectroscopy

We demonstrate a simple and robust methodology for measuring and analyzing the polarization impedance appearing at interface between electrodes and ionic solutions, in the frequency range from 1 to $10^6$ Hz. The method assumes no particular behavior of the electrode polarization impedance and it only makes use of the fact that the polarization effect dies out with frequency. The method allows a direct and un-biased measurement of the polarization impedance, whose behavior with the applied voltages and ionic concentration is methodically investigated. Furthermore, based on the previous findings, we propose a protocol for correcting the polarization effect in low frequency Dielectric Spectroscopy measurements of colloids. This could potentially lead to the quantitative resolution of the $\alpha$-dispersion regime of live cells in suspension

Effect of pump-probe detuning on the Faraday rotation and ellipticity signals of mode-locked spins in InGaAs quantum dots

We have studied the Faraday rotation and ellipticity signals in ensembles of singly-charged (In,Ga)As/GaAs quantum dots by pump-probe spectroscopy. For degenerate pump and probe we observe that the Faraday rotation signal amplitude first grows with increasing the time separation between pump and probe before a decay is observed for large temporal separations. The temporal behavior of the ellipticity signal, on the other hand, is regular: its amplitude decays with the separation. By contrast, for detuned pump and probe the Faraday rotation and ellipticty signals both exhibit similar and conventional behavior. The experimental results are well described in the frame of a recently developed microscopic theory [Phys. Rev. B 80, 104436 (2009)]. The comparison between calculations and experimental data allows us to provide insight into the spectral dependence of the electron spin precession frequencies and extract the electron g-factor dependence on energy.Comment: 9 pages, 7 figure

Biological Control of Sheep Parasites using Duddingtonia flagrans: Trials on Commercial Farms in Sweden

Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned

Third-Generation W(CNAr)₆ Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)

Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to the isocyanide functionality results in W(CNDippAr)₆ oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp)₆. Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr)₆ compounds with naphthalene-based fused-ring (CN-1-(2-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^(CC)Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDippCCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^(CC)Ar)₆ complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr)₆ complexes. Notably, W(CN-1-(2-iPr)-Naph)₆ exhibits the longest excited-state lifetime of all W(CNAr)₆ complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants

Third-Generation W(CNAr)₆ Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)

Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to the isocyanide functionality results in W(CNDippAr)₆ oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp)₆. Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr)₆ compounds with naphthalene-based fused-ring (CN-1-(2-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^(CC)Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDippCCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^(CC)Ar)₆ complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr)₆ complexes. Notably, W(CN-1-(2-iPr)-Naph)₆ exhibits the longest excited-state lifetime of all W(CNAr)₆ complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants

Characterization of different fruit wines made from cacao, cupuassu, gabiroba, jaboticaba and umbu

The main aim of this work was to produce fruit wines from pulp of gabiroba, cacao, umbu, cupuassu and jaboticaba and characterize them using gas chromatography–mass spectrometry for determination of minor compounds and gas chromatography-flame ionization detection for major compounds. Ninety-nine compounds (C6 compounds, alcohols, monoterpenic alcohols, monoterpenic oxides, ethyl esters, acetates, volatile phenols, acids, carbonyl compounds, sulfur compounds and sugars) were identified in fruit wines. The typical composition for each fruit wine was evidenced by principal component analysis and Tukey test. The yeast UFLA CA 1162 was efficient in the fermentation of the fruit pulp used in this work. The identification and quantification of the compounds allowed a good characterization of the fruit wines. With our results, we conclude that the use of tropical fruits in the production of fruit wines is a viable alternative that allows the use of harvest surpluses and other underused fruits, resulting in the introduction of new products into the market.Conselho Nacional de Desenvolvimento Científico e Tecnológico do Brasil (CNPq) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The prolate-to-oblate shape transition of phospholipid vesicles in response to frequency variation of an AC electric field can be explained by the dielectric anisotropy of a phospholipid bilayer

The external electric field deforms flaccid phospholipid vesicles into spheroidal bodies, with the rotational axis aligned with its direction. Deformation is frequency dependent: in the low frequency range (~ 1 kHz), the deformation is typically prolate, while increasing the frequency to the 10 kHz range changes the deformation to oblate. We attempt to explain this behaviour with a theoretical model, based on the minimization of the total free energy of the vesicle. The energy terms taken into account include the membrane bending energy and the energy of the electric field. The latter is calculated from the electric field via the Maxwell stress tensor, where the membrane is modelled as anisotropic lossy dielectric. Vesicle deformation in response to varying frequency is calculated numerically. Using a series expansion, we also derive a simplified expression for the deformation, which retains the frequency dependence of the exact expression and may provide a better substitute for the series expansion used by Winterhalter and Helfrich, which was found to be valid only in the limit of low frequencies. The model with the anisotropic membrane permittivity imposes two constraints on the values of material constants: tangential component of dielectric permittivity tensor of the phospholipid membrane must exceed its radial component by approximately a factor of 3; and the membrane conductivity has to be relatively high, approximately one tenth of the conductivity of the external aqueous medium.Comment: 17 pages, 6 figures; accepted for publication in J. Phys.: Condens. Matte

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table