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The relative-rate technique has been used to determine the rate coefficient for the reaction of C x F 2x+1 CH CH 2 (x = 1, 2, 3, 4 and 6) with ozone at (298 ± 2) K and (720 ± 5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospheric simulation chambers. The following rate coefficients, in units of 10 −19  cm 3 molecule −1 s −1 , were obtained: (3.01 ± 0.10) for CF 3 CH CH 2 , (2.11 ± 0.35) for C 2 F 5 CH CH 2 , (2.34 ± 0.42) for C 3 F 7 CH CH 2 , (2.05 ± 0.31) for C 4 F 9 CH CH 2 and (2.07 ± 0.39) for C 6 F 13 CH CH 2 , where uncertainties represent ±2σ statistical error. The atmospheric lifetime of C x F 2x+1 CH CH 2 due to reaction with ozone was estimated from the reported rate coefficients. Additionally, the gaseous products formed in these reactions were investigated in the presence of synthetic air simulating a clean atmosphere. Perfluoroaldehydes, C x F 2x+1 C(O)H (PFALs), formaldehyde, formic acid and CF 2 O were identified as reaction products in the investigated reactions. The identified products made possible to propose a reaction mechanism that justifies the observed products. The atmospheric implications of these results are discussed in terms of the potential contribution of the atmospheric degradation of these species to PFAL and PFCA burden. [ABSTRACT FROM AUTHOR]

Embryokines are molecules secreted by the mother that regulate embryonic development. Among these molecules in cattle are colony stimulating factor 2 (CSF2) and dickkopf-related protein 1 (DKK1). Here, we evaluated actions of CSF2 and DKK1 alone or in combination on characteristics of embryos produced in vitro in the presence of serum. A total of 70 beef cows from 4 farms were subjected to oocyte retrieval on 1 to 4 occasions. Within each farm, donors were randomly allocated to 1 of 4 treatment groups (vehicle, CSF2, DKK1, CSF2 + DKK1). Embryos from a given donor were always exposed to the same treatment. Treatments were added to the culture medium on d 5 after insemination, and blastocyst stage embryos were transferred to recipient females 2 d later. Treatment did not affect the percent of oocytes or cleaved embryos that developed to the blastocyst stage or the percent of recipients that became pregnant after embryo transfer. However, calves derived from embryos treated with DKK1 were smaller at birth, regardless of CSF2 treatment. Results indicate no effects of addition of CSF2 or DKK1 to culture of embryos produced in vitro with serum-containing medium on development to the blastocyst stage or competence to establish pregnancy after transfer to recipients. The fact that embryos cultured with DKK1 resulted in calves with reduced birth weight illustrates the potential ability of this embryokine to program postnatal phenotype. Results support the concept that properties of the offspring can be programmed as early as the preimplantation period. [ABSTRACT FROM AUTHOR]

A detailed description of a new pulsed supersonic uniform gas expansion system is presented together with the experimental validation of the setup by applying the CRESU (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique to the gas-phase reaction of OH radicals with 1-butene at ca. 23 K and 0.63 millibars of helium (carrier gas). The carrier gas flow, containing negligible mixing ratios of OH-precursor and 1-butene, is expanded from a high pressure reservoir (337 millibars) to a low pressure region (0.63 millibars) through a convergent-divergent nozzle (Laval type). The novelty of this experimental setup is that the uniform supersonic flow is pulsed by means of a Teflon-coated aerodynamic chopper provided with two symmetrical apertures. Under these operational conditions, the designed Laval nozzle achieves a temperature of (22.4 ± 1.4) K in the gas jet. The spatial characterization of the temperature and the total gas density within the pulsed uniform supersonic flow has also been performed by both aerodynamical and spectroscopic methods. The gas consumption with this technique is considerably reduced with respect to a continuous CRESU system. The kinetics of the OH+1-butene reaction was investigated by the pulsed laser photolysis/laser induced fluorescence technique. The rotation speed of the disk is temporally synchronized with the exit of the photolysis and the probe lasers. The rate coefficient (kOH) for the reaction under investigation was then obtained and compared with the only available data at this temperature. [ABSTRACT FROM AUTHOR]

Abstract: Relative rate coefficients for the gas-phase reaction of chlorine atoms (Cl) with tetrahydropyran (THP) have been determined by Fourier transform infrared (FTIR) spectroscopy and gas chromatography coupled to a mass spectrometer (GC–MS). The averaged rate coefficient is (2.21±0.32)×10−10 cm3 molecule−1 s−1 (with 2σ uncertainty) and was obtained using different reference compounds, Cl precursors, and bath gases at 740±5Torr and 298±2K. Products of the title reaction were identified and quantified by solid-phase microextraction (SPME) coupled to a GC–MS. Additionally, the first step of the reaction was theoretically studied by ab initio calculations. Reaction mechanism seems to proceed mainly by the H-abstraction from α and γ positions. THP tropospheric lifetime is estimated from the rate coefficient reported here. The atmospheric implications of the Cl reactivity are also discussed. [Copyright &y& Elsevier]

Investigates the kinetics and products of the gas-phase reactions of dimethylsulphide (DMS), dimethylsulphoxide and dimethylsulphone with bromine atoms and bromine oxide radicals in air. Use of on-line Fourier transform infrared spectroscopy; Oxidation of DMS by bromine atoms; Atmospheric chemistry; Rate constants.

The excitation LIF spectra of van der Waals complexes of o- and p-methylaniline and CF3Cl, CF3H, CH4 and CF4 in a supersonic free jet are reported. The spectra show a resolved structure characteristic due to the internal rotational transitions of the methyl group. The equilibrium geometries in the ground state of the complexes have been calculated at MP2/6-31+G* level of calculation and the intermolecular interaction have been discussed. [Copyright &y& Elsevier]

The UV fluorescence excitation and dispersed fluorescence spectra of jet-cooled p-methylaniline have been obtained for the S1←S0 transition. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes and with the help of computed vibrational frequencies. The structure of p-methylaniline in both the S0 and S1 states has been studied at ab initio quantum chemical calculations at MP2 and CIS levels of theory using the 6-31+G* basis sets. Both low- and high-resolution laser induced fluorescence spectra of p-methylaniline van der Waals complexes with CF3H, CH4 and CF4 have been characterised following jet-expansion investigations. The equilibrium geometries in the ground state of the complexes have been calculated at MP2/6-31+G* level of calculation and their rotational contour have been simulated for all the complexes studied. [Copyright &y& Elsevier]

The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled o-methylaniline have been obtained for the S1←S0 transition, in which some of the bands have been observed and assigned for the first time. The origin of the electronic transition appears at 34,328.4 cm−1. It was found that the spectra exhibit an important feature corresponding to the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31+G* and CIS/6-31+G* show that the optimised structure of o-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence of lone paired electrons on the N atom. Upon electronic excitation, the C&z.sbnd;N bond exhibits a partial double character, as in the case of other aniline derivatives. [Copyright &y& Elsevier]

The role of water vapor (H2O) and its hydrogen-bonded complexes in the gas-phase reactivity of organic compounds with hydroxyl (OH) radicals has been the subject of many recent studies. Contradictory effects have been reported at temperatures between 200 and 400 K. For the OH + acetaldehyde reaction, a slight catalytic effect of H2O was previously reported at temperatures between 60 and 118 K. In this work, we used Laval nozzle expansions to reinvestigate the impact of H2O on the OH-reactivity with acetaldehyde between 21.7 and 135.0 K. The results of this comprehensive study demonstrate that water, instead, slows down the reaction by factors of ∼3 (21.7 K) and ∼2 (36.2–89.5 K), and almost no effect of added H2O was observed at 135.0 K. [ABSTRACT FROM AUTHOR]

The reaction of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) with Cl atoms was studied for the first time experimentally and theoretically. Relative kinetic measurements were carried out at room temperature and 1 bar of synthetic air/N 2 in two different environmental chambers: a 300 L Teflon bag and a 16 L borosilicate glass cell. Reactants, reference compounds and products were monitored either by IR absorption or by GC-FID. Theoretical calculations were performed using the density functional theory method at BH&HLYP level of theory for twelve hydrogen abstraction pathways. The individual rate coefficients for the most favorable H-abstraction pathways were calculated by canonical variational theory using small curvature tunneling method at 298 K. An average experimental rate coefficient of (7.4 ± 0.6) × 10 −11 cm 3 molecule −1 s −1 was obtained at 298 K, in good agreement with the theoretical rate coefficient. The branching ratios for each reaction channel were evaluated theoretically from the individual rate coefficients of the identified channels. The H-atom abstracted on the –CH 2 group appeared to be the dominant channel with a small barrier height. Formaldehyde, acetic acid, HCl, CO 2 and CO were identified by IR as the major primary products. The obtained results are presented and discussed in terms of structure-reactivity relationships. A mechanism is suggested for the formation of the observed products. The atmospheric implications of the studied reaction are presented and more particularly, the lifetime of 4H4M2P towards Cl atoms is evaluated to be about 3 days. [ABSTRACT FROM AUTHOR]

The state-of-the-art materials for SOFCs are yttria-stabilized zirconia as electrolyte and lanthanum strontium cobalt ferrite as cathode. However, the formation of insulating phases between them requires the use of diffusion barriers, typically made of gadolinia doped ceria. The study of the stability of this layer during the fabrication and in operando is currently one of the major goals of the SOFC industry. In this work, the cation inter-diffusion at the cathode/barrier layer/electrolyte region is analysed for an anode-supported cell industrially fabricated by conventional techniques, assembled in a short-stack and tested under real operation conditions for 3000 h. A comprehensive study of this cell, and an equivalent non-operated one, is performed in order to understand the inter-diffusion mechanisms with possible effects on the final performance. The analyses evidence that the cation diffusion is occurring during the fabrication process. Despite the significant diffusion of Ce,Gd, Zr, Y and Sr cations, the formation of typically reported CGO-YSZ solid solution is not observed while the presence of isolated grains of SrZrO 3 is proved. All in all, this study presents new insights into the stability of the typically employed diffusion barriers for solid oxide cells that will guide future strategies to improve their performance and durability. [ABSTRACT FROM AUTHOR]

CdSe/ZnS core-shell quantum dots (QDs) have been immobilized onto solid substrates by matrix assisted pulsed laser evaporation (MAPLE). An UV KrF* ( λ = 248 nm, τFWHM ≅ 25 ns) excimer laser source was used for irradiations of the composite MAPLE targets. The targets were prepared by the dispersion of the CdSe/ZnS QDs in a solvent with high absorption at the incident laser radiation. The dependence of the surface morphology, crystalline structure, chemical composition, and functional properties of the laser transferred CdSe/ZnS QDs on the processing conditions as incident laser fluence value and ambient atmosphere inside the irradiation chamber was investigated. The possible physical mechanisms implied in the laser ablation process were identified. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid organic–inorganic semiconductor nanocomposites of layered zinc oxide/carboxylic acids were fabricated. Products are pure phases with structures constituted by double-layer sheets of the inorganic component sandwiched between self-assembled surfactant layers. The optical properties of the nanocomposites are found to be qualitatively similar to those of bulk zinc oxide. However, blue shifted absorption band edges and enhanced band-gap energies are observed. The photocatalytic activity of the products in the degradation of methylene blue indicates that the efficiency of the nanocomposites is comparable or even better than that of bulk oxide. [Copyright &y& Elsevier]

Abstract: The direct mixing of aqueous ferric chloride and o-phenylenediamine (OPD) solution at room temperature in the absence and presence of carbon nanotubes (CNTs) has been used to prepare poly(o-phenylenediamine) (POPD) micro-fibers and composites of the type CNTs/POPD having nanotubes incorporated in polymer fiber mass. Using surface enhanced infrared absorption (SEIRA) spectroscopy significant modifications in the low frequency range of the polymer spectrum are revealed when Au is used as metallic support. Similar variations are reported for the POPD samples prepared by the electropolymerization of OPD onto rough Au electrode. A covalent functionalization of CNTs with POPD and a doping process of POPD with radical anions of CNTs is proved by surface enhanced resonant Raman scattering and SEIRA spectroscopy. The X-ray diffraction (XRD) studies indicate a high crystallinity both for POPD and CNTs/POPD composites prepared by chemical or electrochemical methods. [Copyright &y& Elsevier]

We study the anisotropy of the spin and orbital magnetization of ultrathin Co layers characterized by structure inversion asymmetry, namely Pt/Co/AlOx trilayers with Co thicknesses between 0.6 and 2 nm. We use x-ray magnetic circular dichroism (XMCD) to probe the Co layer along two orthogonal measurement geometries. By combining transverse and collinear XMCD, we achieve a vector measurement of the Co spin and orbital magnetic moments. We find an enhanced and anisotropic orbital magnetic moment localized at the Co interface and verify the connection between the Co orbital moment anisotropy and the macroscopic magnetic anisotropy of the trilayer. These results provide a link between diverse interfacial phenomena originating from spin-orbit coupling, such as the Rashba effect and perpendicular magnetic anisotropy. Using simple considerations derived from tight-binding models, we show that the Rashba constant is proportional to the ratio between out-of-plane and in-plane orbital magnetic moments. [ABSTRACT FROM AUTHOR]

We report on the effect of cap layer material on the magnetic properties and aging of the Fe-NW (nanowire) arrays grown on oxidized vicinal Si (111) templates using atomic terrace low angle shadowing technique. We find that the Fe-NW arrays capped with metallic (Ag) layers do not show any sign of degradation with aging, whereas NW arrays capped with insulating dielectric (MgO) layers show degradation of the saturation magnetization and an out-of-plane unidirectional anisotropy. We find that this out-of-plane unidirectional anisotropy competes with the shape anisotropy which is still the dominant anisotropy. The origin of this additional anisotropy is explained on the basis of oxidation of Fe due to the presence of MgO that leads to the formation of an oxide interlayer. This oxide interlayer forms at the expense of NW materials, leading to reduction in the thickness of some of the Fe-NWs within the array, and orients their magnetic moments out-of-plane. The reduction in NW thickness and the presence of Fe-O interlayer facilitates stabilization of this anisotropy. Our model is supported by x-ray absorption spectroscopy studies performed as a function of aging, which suggests that the oxide interlayer thickness increases with aging. [ABSTRACT FROM AUTHOR]

• Various types of carbon nanoparticles are synthesized by different methods. • Structure, composition, optical properties and toxicity are directly compared. • Fluorescence origin is associated to carbon structure and oxygen functional groups. • All carbon nanoparticle types are compatible with normal human intestinal cells. • Anticancer activity of pristine nanoparticles is associated to functional groups. Given the potential applications of fluorescent carbon nanoparticles in biomedicine, the relationship between their chemical structure, optical properties and biocompatibility has to be investigated in detail. In this work, different types of fluorescent carbon nanoparticles are synthesized by acid treatment, sonochemical treatment, electrochemical cleavage and polycondensation. The particle size ranges from 1 to 6 nm, depending on the synthesis method. Nanoparticles that were prepared by acid or sonochemical treatments from graphite keep a crystalline core and can be classified as graphene quantum dots. The electrochemically produced nanoparticles do not clearly show the graphene core, but it is made of heterogeneous aromatic structures with limited size. The polycondensation nanoparticles do not have C C double bonds. The type of functional groups on the carbon backbone and the optical properties, both absorbance and photoluminescence, strongly depend on the nanoparticle origin. The selected types of nanoparticles are compatible with human intestinal cells, while three of them also show activity against colon cancer cells. The widely different properties of the nanoparticle types need to be considered for their use as diagnosis markers and therapeutic vehicles, specifically in the digestive system. [ABSTRACT FROM AUTHOR]

We fabricated planar arrays of Co nanowires (NWs) on oxidized step-bunched Si (111) templates using shallow angle deposition. These planar NW arrays exhibit ferromagnetic behavior at room temperature for NW widths down to 25 nm. The NWs possess polycrystalline character with hcp-crystal structure, and present a lightly oxidized interface when capped with MgO. The magnetic anisotropy of the NW array is dominated by the shape anisotropy, which keeps the magnetization in-plane with easy axis parallel to the wires. By reducing the inter-wire separation, we obtain NW arrays with reduced coercivity demonstrating the importance of magneto-static interactions in determining the magnetic properties of the NWs. [ABSTRACT FROM AUTHOR]

Planar nanowire (NW) arrays of Co grown on oxidized step-bunched Si(111) templates exhibit room temperature ferromagnetic behaviour for wire widths down to 25 nm. Temperature and thickness dependent magnetization studies on these polycrystalline NW arrays show that the magnetic anisotropy of the NW array is dominated by shape anisotropy, which keeps the magnetization in-plane with easy axis parallel to the wires. This shape related uniaxial anisotropy is preserved even at low temperatures (10 K). Thickness dependent studies reveal that the magnetization reversal is governed by the curling mode reversal for thick wires whereas thinner wires exhibit a more complex behaviour which is related to thermal effects and size distribution of the crystal grains that constitute the NWs. [ABSTRACT FROM AUTHOR]

The absolute rate constants for the gas-phase reactions of the NO3 radical with a series of aldehydes such as acetaldehyde, propanal, butanal, pentanal, hexanal and, heptanal were measured over the temperature range 298-433 K, using a discharge flow system and monitoring the NO3 radical by Laser Induced Fluorescence (LIF). The measured rate constants at 298 K for the reaction of NO3, in units of 10-14 cm3 molecule-1 s-1, were as follows: acetaldehyde 0.32 1 0.04, propanal 0.60 1 0.06, butanal 1.46 1 0.16, pentanal 1.75 1 0.06, hexanal 1.83 1 0.36, and heptanal 2.37 1 0.42. The proposed Arrhenius expressions are k1 = (6.2 1 7.5) x 10-11 exp [?(2826 1 866)/T] (cm3 molecule-1 s-1), k2 = (1.7 1 1.0) x 10-11 exp [?(2250 1 192)/T] (cm3 molecule-1 s1), k3 =(7.6 19.8) x 1011 exp [?(2466 1 505)/T] (cm3 molecule-1 s-1), k4 = (2.8 1 1.4) x 10-11 exp [?(2189 1 156)/T] (cm3 molecule-1s-1), k5 = (7.0 1 1.8) x 10-11 exp [?(2382 1 998)/T] (cm3 molecule-1 s-1), and k6 = (7.8 1 1.0) x 10-11 exp [?(2406 1 481)/T] (cm3 molecule-1 s-1). Tropospheric lifetimes for these aldehydes were calculated at night and during the day for typical NO3 and OH average concentrations and showed that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with the NO3 radical can be an important, if not dominant, loss process for these emitted organics and for NO3 radicals. [ABSTRACT FROM AUTHOR]