Ample divisors in the moduli space of 0-genus pointed curves

In this paper we give bounds for the ample cone of the boundary divisors in the moduli space of 0-genus stable pointed curves.     

Solar heterogeneous and homogeneous photocatalysis as a pre-treatment option for biotreatment

In this paper, we present pilot-scale solar Photo-Fenton and TiO₂ treatment of a model compound (α-methylphenylglycine) dissolved in 500 mg/l concentration in water. Not only contaminant disappearance and mineralisation were evaluated, but also enhancement of biodegradability. The solar photoreactors, composed of 4.16 m² of compound parabolic collectors, had a total volume of 82 l (44.6 l illuminated). Treatment was successful with both Advanced Oxidation Processes (AOPs) tested, but photo-Fenton was shown to be by far more efficient from the kinetic and practical point of view. To find out the conditions for biocompatibility using the AOPs as a pre-treatment, waste water after certain degradation time, unacclimated municipal sludge and mineral nutrients were placed together and evaluated by the Zahn-Wellens (Z-W) test. Biodegradability was enhanced (70% biodegradable) by both AOPs, but photo-Fenton was demonstrated to be more efficient, requiring a treatmen time one order of magnitude shorter than TiO₂. Hydrogen peroxide management for reduced consumption and elimination prior to discharging water to the biotreatment step is also discussed in detail.     

Global existence of solutions to one-dimensional viscous quantum hydrodynamic equations

The existence of global-in-time weak solutions to the one-dimensional viscous quantum hydrodynamic equations is proved. The model consists of the conservation laws for the particle density and particle current density, including quantum corrections from the Bohm potential and viscous stabilizations arising from quantum Fokker-Planck interaction terms in the Wigner equation. The model equations are coupled self-consistently to the Poisson equation for the electric potential and are supplemented with periodic boundary and initial conditions. When a diffusion term linearly proportional to the velocity is introduced in the momentum equation, the positivity of the particle density is proved. This term, which introduces a strong regularizing effect, may be viewed as a classical conservative friction term due to particle interactions with the background temperature. Without this regularizing viscous term, only the nonnegativity of the density can be shown. The existence proof relies on the Faedo-Galerkin method together with a priori estimates from the energy functional.     

Characterization of the aerosol produced by infrared femtosecond laser ablation of polyacrylamide gels for the sensitive inductively coupled plasma mass spectrometry detection of selenoproteins

A 2D high repetition rate femtosecond laser ablation strategy (2-mm wide lane) previously developed for the detection of selenoproteins in gel electrophoresis by inductively coupled plasma mass spectrometry was found to increase signal sensitivity by a factor of 40 compared to conventional nanosecond ablation (0.12-mm wide lane) [G. Ballihaut, F. Claverie, C. Pécheyran, S. Mounicou, R. Grimaud and R. Lobinski, Sensitive Detection of Selenoproteins in Gel Electrophoresis by High Repetition Rate Femtosecond Laser Ablation-Inductively Coupled Plasma Mass Spectrometry, Anal. Chem. 79 (2007) 6874–6880]. Such improvement couldn't be explained solely by the difference of amount of material ablated, and then, was attributed to the aerosol properties. In order to validate this hypothesis, the characterization of the aerosol produced by nanosecond and high repetition rate femtosecond laser ablation of polyacrylamide gels was investigated. Our 2D high repetition rate femtosecond laser ablation strategy of 2-mm wide lane was found to produce aerosols of similar particle size distribution compared to nanosecond laser ablation of 0.12-mm wide lane, with 38% mass of particles < 1 µm. However, at high repetition rate, when the ablated surface was reduced, the particle size distribution was shifted toward thinner particle diameter (up to 77% for a 0.12-mm wide lane at 285 µm depth). Meanwhile, scanning electron microscopy was employed to visualize the morphology of the aerosol. In the case of larger ablation, the fine particles ejected from the sample were found to form agglomerates due to higher ablation rate and then higher collision probability. Additionally, investigations of the plasma temperature changes during the ablation demonstrated that the introduction of such amount of polyacrylamide gel particles had very limited impact on the ICP source (ΔT~ 25 ± 5 K). This suggests that the cohesion forces between the thin particles composing these large aggregates were weak enough to have negligible impact on the ICPMS detection.     

Analytical speciation of mercury in fish tissues by reversed phase liquid chromatography-inductively coupled plasma mass spectrometry with Bi as internal standard

In this work, the quantification of two mercury species (Hg²⁺ and CH₃Hg⁺) in fish tissues has been revisited. The originality of our approach relies on the use of Bi³⁺ as internal standard (IS) and on the modification of typical extraction conditions. The IS (125 μl, 1000 μg l⁻¹ Bi³⁺) was added to the aliquot of fresh fish tissue (400-500 mg). A high-speed blender and ultrasound-assisted homogenization/extraction was carried out in the presence of perchloric acid (1.5 ml, 0.6 mol l⁻¹), l-cysteine (500 μl, 0.75 mol l⁻¹) and 500 μl toluene:methanol (1:1). Perchloric acid was used for protein denaturation and precipitation, toluene helped to destroy lipid structures potentially sequestering CH₃Hg⁺, l-cysteine was used to form water-soluble complexes with Bi³⁺, Hg²⁺ and CH₃Hg⁺. The excess of perchloric acid was eliminated by addition of potassium hydroxide (pH 5 with acetic acid). The obtained extract, was diluted with the mobile phase (1:1) and introduced (20 μl) to the reversed phase HPLC-ICP-MS system. The separation was achieved by isocratic elution (2.5 mmol l⁻¹ cysteine, 12.5 mmol l⁻¹ (NH₄)₂HPO₄, 0.05% triethylamine, pH 7.0:methanol (96:4)) at a flow rate 0.6 ml min⁻¹. Column effluent was on-line introduced to ICP-MS for specific detection of ²⁰²Hg, ²⁰⁰Hg and ²⁰⁹Bi. Analytical signal was defined as the ratio between ²⁰²Hg/²⁰⁹Bi peak areas. The detection limits evaluated for Hg²⁺ and CH₃Hg⁺ were 0.8 and 0.7 μg l⁻¹. Recovery of the procedure, calculated as the sum of species concentrations found in the sample with respect to total ICP-MS-determined Hg was 91.9% for king mackerel muscle and 89.5% for red snapper liver. In the standard addition experiments, the recovery results were 98.9% for Hg²⁺ and 100.6% for CH₃Hg⁺. It should be stressed that the use of Bi³⁺ as IS enabled to improve analytical performance by compensating for incomplete extraction and for imprecision of sample handling during relatively non-rigorous protocol.     

Size and composition control of Pt-In nanoparticles prepared by seed-mediated growth using bimetallic seeds

A two-step method has been developed for precise size and composition control of bimetallic Pt-In nanoparticles. Very small (1.62 nm) PtIn seed nanoparticles with 1:1 metal ratio were prepared in the absence of capping agents followed by growth of Pt on their surface in the presence of oleyl amine as reducing and stabilizing agent. Nanoparticles with bulk compositions of Pt(4)In, Pt(3)In, and Pt(2)In could be synthesized with average diameter smaller than 3 nm. TEM, EDX, and XPS provided evidence for homogeneous growth without separate nucleation of pure platinum nanoparticles in the reaction solution. Pt(3)In nanoparticles were deposited onto SiO(2) surface by incipient wetness impregnation. Temperature-induced changes in the particle surface were monitored by in situ IR spectroscopy and CO adsorption. It was found that surface alloy composition of the particles could be tuned by using oxidizing or reducing atmospheres.     

Efficient Synthesis of Substituted 3‐Azabicyclo[3.1.0]hexan‐2‐ones from 2‐Iodocyclopropanecarboxamides Using a Copper‐Free Sonogashira Coupling

The copper‐free Sonogashira coupling between N‐substituted cis‐ 2‐iodocyclopropanecarboxamides and terminal aryl‐, heteroaryl‐alkynes or enynes, followed by 5‐exo‐dig cyclization of the nitrogen amide onto the carbon–carbon triple bond, provides a remarkably efficient access to a variety of substituted 4‐methylene‐3‐azabicyclo[3.1.0]hexan‐2‐ones in excellent yields. Protonation of these latter enamides generates bicyclic N‐acyliminium ions that can be involved in Pictet–Spengler cyclizations leading to new 3‐azabicyclo[3.1.0]hexan‐2‐ones, possessing a quaternary stereocenter at C4, with high diastereoselectivities. This strategy constitutes an attractive complementary alternative to the classical route that relies on the addition of organometallic reagents to cyclopropyl imides.     

Access to polyfunctionalized diquinanes, hydrindanes, and decalines via TiCl4 promoted Michael-aldol and Baylis-Hillman reactions

The addition of 0.5 equiv of TiCl(4) to (cyclo)alkanones tethered to α,β-unsaturated ketones afforded polyfunctionalized diquinanes, hydrindanes, and decalines. These products, resulting from a Michael-aldol or a Baylis-Hillman reaction, can be obtained with high or total diastereoselectivity in moderate to high yields. These scaffolds represent interesting building blocks for the synthesis of complex natural products.     

Polyacetylenes as enantiodifferentiating alignment media

Orientation help: Valine-derived polyacetylenes are introduced as enantiomer-differentiating alignment media. The F2-coupled HSQC-type NMR spectra of both enantiomers of isopinocampheol (IPC) display narrow line widths allowing for the precise extraction of residual dipolar couplings (black contour plot: (+)-IPC in an isotropic phase, blue: (-)-IPC in an anisotropic phase, and red: (+)-IPC in an anisotropic phase; J=coupling constant).     

Thermodynamics and Kinetics of the Complexation Reaction of Lead by Calix‐DANS4

The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix‐DANS4 are determined to optimize the geometry of the microreactor used for the flow‐injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix‐DANS4) the 1:1 Pb²⁺‐Calix‐DANS4 complex is predominantly formed with a high stability constant (log K_1:1=6.82) and a slow second‐order rate constant (k=9.4×10⁴ L mol^?1 s^?1). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h^?1 to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors.