Phthalocyanines as Sensitive Materials for Chemical Sensors

This paper provides a review of phthalocyan- ines suitable for the development of chemical sensors. Phthalocyanines may be utilized for different types of chemical sensors, including in particular electronic conductance sensors [such as semiconductive, field-effect transistor (FET), solid-state ionic and capacitance sensors], mass-sensitive sensors utilizing a quartz crystal microbalance (QCM) and surface acoustic-wave (SAW) sensors, and optical sensors. The phthalocyanines used are discussed in terms of their physical and chemical properties, as well as their sensitivity, selectivity and reversibility towards the detection of NO₂ and organic solvent vapours. The interaction mechanism between phthalocyanine films and analyte molecules is also discussed.     

Polarization squeezing with cold atoms

We study the interaction of a nearly resonant linearly polarized laser beam with a cloud of cold cesium atoms in a high finesse optical cavity. We show theoretically and experimentally that the cross-Kerr effect due to the saturation of the optical transition produces quadrature squeezing on both the mean field and the orthogonally polarized vacuum mode. An interpretation of this vacuum squeezing as polarization squeezing is given and a method for measuring quantum Stokes parameters for weak beams via a local oscillator is developed.     

Theory and application of a quartz resonator as a sensor for viscous liquids

A comprehensive analysis of the interaction between an AT-cut quartz crystal resonator and a viscous fluid is presented. The analysis, which includes peizoelectric effects, assumes a liquid of finite extent and therefore could also be used to study thin film of viscous liquids. A novel continuous flow cell system was designed and fabricated to monitor viscosity using an 11-MHz quartz crystal resonator. Measured data for frequency shifts of aqueous solutions of alcohols and sugars are in excellent agreement with theory.     

Magnetic behaviour of the MTbF6 fluoroterbates (M=Cd,Ca, Sr, (α/β)-Ba)

Neutron powder diffraction has been performed on the MTbF₆ fluorides (M=Cd, Ca, Sr, (α/β)-Ba). Four of these fluorides (Cd, Ca, Sr, β-Ba) are built of a (pseudo-) tetragonal packing of [TbF₆]^2? chains and only differs by the chains relative orientations. Thus this series represents a valuable opportunity to evaluate the Tb⁴⁺-Tb⁴⁺ magnetic interactions. All the compounds displayed antiferromagnetic order (T_N=2.70 K (Cd), 2.15 K (Ca), 2.60 K (Sr), 2.10 K (β-Ba)), except for the α form of BaTbF₆. The crystal structure of this latter fluoroterbate has also been investigated by means of high-resolution neutron powder diffraction. From Neutron Powder Diffraction data, CdTbF₆ and β-BaTbF₆ magnetic structures were determined, together with the metamagnetic behaviour of β-BaTbF₆ as a function of an external magnetic field. A tentative phase diagram is then given for β-BaTbF₆. Advantage was taken of the polymorphism of the BaTbF₆ fluoroterbate to analyse, on the basis of topological parameters such as bond distances and angles, the magnetic behaviour of its α and β forms. It was shown that superexchange interactions are present in β-BaTbF₆, and that these interactions may also rule the magnetic behaviour of the other MTbF₆ (M=Ca, Sr, Cd) tetravalent terbium fluorides.     

Shedding light on the laser wavelength effect in Raman analysis of skin epidermises

Confocal Raman microspectroscopy is a promising technique which enables measuring the molecular composition of the skin layers, non-destructively and without extrinsic markers. The Raman approach is increasingly used in skin research but with various experimental conditions. In addition to the different skin types, one of the varying parameters is the wavelength of laser excitation. This parameter contributes strongly in the skin Raman response. The present work aimed to evaluate this effect for 3 different wavelengths, 532, 633 and 785 nm, on pig ear skin models. The Raman signal was assessed in the spectral fingerprint region. According to the Raman response for stability, repeatability, variability and fluorescence contribution, the 785 nm excitation wavelength was shown to be the most suitable for epidermis depth profiling in the fingerprint region.     

Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

Combinatorial drug therapies emerge among the most promising strategies to treat complex pathologies such as cancer and severe infections. Biocompatible nanoparticles of mesoporous iron carboxylate metal–organic framework (nanoMOFs) are used here to address the challenging aspects related to the coincorporation of two antibiotics. Amoxicillin and potassium clavulanate, a typical example of drugs used in tandem, are efficiently coincorporated with payloads up to 36 wt%. Due to the occurrence of two distinct pore sizes/apertures within the MOF architecture, each drug is able to infiltrate the porous framework and localize within separate compartments. Molecular simulations predict drug loadings and locations consistent with experimental findings. Drug loaded nanoMOFs that are internalized by Staphylococcus aureus infected macrophages are able to colocalize with the pathogen, which in turn leads to an alleviation of bacterial infection. The data also reveal potential antibacterial properties of nanoMOFs alone as well as their ability to deliver a high payload of drugs to fight intracellular bacteria. These results pave the way toward the design of engineered “all‐in‐one” nanocarriers in which both the loaded drugs and their carrier play a role in fighting intracellular infections.     

A principal component method to impute missing values for mixed data

We propose a new method to impute missing values in mixed data sets. It is based on a principal component method, the factorial analysis for mixed data, which balances the influence of all the variables that are continuous and categorical in the construction of the principal components. Because the imputation uses the principal axes and components, the prediction of the missing values is based on the similarity between individuals and on the relationships between variables. The properties of the method are illustrated via simulations and the quality of the imputation is assessed using real data sets. The method is compared to a recent method (Stekhoven and Buhlmann Bioinformatics 28:113–118, 2011) based on random forest and shows better performance especially for the imputation of categorical variables and situations with highly linear relationships between continuous variables.     

Study on the formation of a supramolecular conjugated graft copolymer in solution

The formation in solution of a supramolecular graft copolymer bearing conjugated blocks is demonstrated using diffusion ordered NMR spectroscopy (DOSY). A tailor‐made poly(3‐(2‐ethylhexyl)thiophene) (P3EHT) with a phenol end group is synthesized. For this purpose, the chain‐growth mechanism of the polymerization of 2‐bromo‐5‐chloromagnesio‐3‐alkylthiophenes in the presence of a Ni(dppp) catalyst (dppp = 1,3‐bis(triphenylphosphino)propane) is exploited, as it enables the use of functionalized initiators to introduce specific end groups. The so‐obtained polythiophene was subsequently mixed in solution with poly(4‐vinylpyridine) (P4VP) to enable phenol‐pyridine hydrogen bonding. The formation of the supramolecular graft copolymer is studied using DOSY‐measurements. Based on the results thereof, the amount of P3EHT attached to the P4VP is calculated and the association constant of the hydrogen bond is estimated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 804–809     

Global air quality and climate

Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH(4)), ozone precursors (O(3)), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O(3) precursor CH(4) would slow near-term warming by decreasing both CH(4) and tropospheric O(3). Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NO(x)) emissions, which increase tropospheric O(3) (warming) but also increase aerosols and decrease CH(4) (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH(4) volatile organic compounds (NMVOC) warm by increasing both O(3) and CH(4). Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O(3) and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O(3) and SOA.