Permeability control in electro‐sensitive microcapsules with immobilized ferroelectric liquid crystalline segments

Nylon‐polystyrene microcapsules with immobilized ferroelectric liquid crystalline segments were prepared, and permeability control of an encapsulated core material was investigated under an external electric field. A ferroelectric liquid crystal monomer possessing both mesogenicity and chirality responded effectively to the external electrical field. Permeation of the material (oxprenolol) contained in the inner aqueous core of the microcapsules was enhanced under a weak electric field (2 V). Furthermore, the permeability of oxprenolol did not depend on the external electric field in the absence of the ferroelectric liquid crystal segments. To clarify the controlled‐release mechanism of the core material, the light transmittance of the polymer membranes was quantitatively evaluated under an external electric field using a handmade polarized light transmittance apparatus. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1749–1757, 2008     

Point-diffraction interferometer for atmospheric adaptive optics in strong scintillation

This paper evaluates the performance of a point-diffraction interferometer for closed-loop adaptive optics. A point-diffraction interferometer was built using a modified Mach-Zehnder set-up. The system was used in closed-loop using a SLM to implement a square, 12 × 12, piston-only segmented corrector with a stroke of ±π. Its performance was tested for the case of atmospheric turbulence aberrations. The investigation showed, through simulation and experiment, that the point-diffraction interferometer worked in closed-loop operation in both uniform intensity and scintillated aberrations. Its robustness in the presence of phase discontinuities makes it a promising option for wavefront sensing in strong scintillation.     

Experimental study on equilibrium deviations in atmospheric pressure argon/helium surface wave discharges

Atmospheric pressure surface wave discharges generated with Ar–He mixtures with He concentrations up to 99% were studied using spectroscopic techniques. The variation of electron density and linear power density with He concentration and along the plasma column is discussed together with the excitation temperatures derived from the Boltzmann plot of the excited states of Ar I and the values of the b(p) parameters to derive the thermodynamic equilibrium state of the discharge. Important deviations with respect to Local Thermodynamic Equilibrium were observed for He concentrations over 50% as the discharge shifts from a recombining to an ionizing behaviour. Furthermore, the discharge kinetic variations behind these changes are discussed.     

The effect of OH radicals on Cr–I spectral lines emitted by DC glow discharges

The intensity distribution of the Cr–I 428.97 nm resonant and 520.60 nm non-resonant lines was studied as a function of the distance from the anode in a low pressure DC-GD fitted with a Cr metal cathode and operated in various gas atmospheres, including helium (P = 4 mbar), ambient air and water vapor (P = 0.8 mbar). In the helium and ambient air atmospheres, the intensity peaks occurred in the near cathode region (cathode glow) in accordance with the literature. When operated in water vapor, however, the Cr–I 428.97 nm resonant line disappeared, whereas the intensity of the non-resonant 520.60 nm line was enhanced. This result may be attributed to resonant energy transfer collisions taking place between OH radicals excited to the first vibrational level and Cr^*₄₂₈ atoms excited to the z⁷P⁰ upper level of the 428.97 nm transition. The similar gas phase composition encountered with a DC electrolyte cathode atmospheric pressure glow discharge (ELCAD) and the Cr metal cathode GD operating under a low pressure of water vapor suggests that the zero intensity of the Cr resonance lines (428.97 nm, 360.53 nm) produced in the ELCAD may be attributed to similar energy transfer processes. Our results show that the intensity of the Cr–I 520.60 nm line can be used for analytical purposes in the ELCAD.     

Assessment uncertainty associated to the analysis of organic compounds linked to particulate matter of atmospheric aerosols

Current work has evaluated uncertainty associated to quantification of several organic compounds present in particulate matter of atmospheric aerosols, setting out the stages of analytical procedure that contribute most to the global uncertainty. Several sources of uncertainty have been identified, which were clustered into five main contributions: sampling, extraction, clean-up, derivatization and analysis. A discussion of the main contributions to the overall uncertainty is reported, allowing authors to locate the largest ones and plan future improvements. Combined uncertainties ranged between 10-18% (alkanes), 12-16% (PAHs), 10-18% (alcohols) and 9-21% (acids). The analytical procedure was validated by analysing a standard reference material (SRM1649a, urban dust). Also, the proposed method was applied to the analysis of four samples of particulate matter.     

大气气溶胶中溴、碘总量及其形态的提取和测定

比较了超声纯水提取不同时间和多种密封提取条件下大气气溶胶样品滤膜中溴、碘形态稳定性和提取率。结果表明:密封提取方法的提取率高于超声提取方法,但有可能破坏了某种未知的有机碘形态;在长时间纯水超声条件下,醋酸纤维(CF)空白滤膜加标回收中I-形态不稳定。因此,纯水超声提取5 min为最佳提取条件。对比醋酸纤维(CF)和玻璃纤维(GF)空白滤膜加标回收实验发现,各种提取条件下GF材质对样品中溴、碘形态稳定性的干扰比CF材质小。在优化大气气溶胶溴、碘形态提取方法的基础上,建立了HPLC-ICP-MS测定大气气溶胶中BrO3-、Br-、IO3-和I-的方法,并对合肥地区气溶胶样品中溴、碘总量及形态进行测定。合肥地区气溶胶中溴和碘总量浓度分别为883和231 pmol/m3。其中,Br-占总溴的69%,BrO3-未检出;70%的碘为未知形态,包括可溶性有机碘和不可溶性碘。     

New perspective on the determination of flame retardants in sewage sludge by using ultrahigh pressure liquid chromatography–tandem mass spectrometry with different ion sources

Analysis of 11 polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A bis 2,3-dibromopropylether (TBBPA-bis), tetrachlorobisphenol A (TCBPA), tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) was optimized by ultrahigh pressure liquid chromatography/tandem mass spectrometry (UPLC–MS/MS) operating in negative ion (NI) mode. Electrospray ionization (ESI), atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) sources were tested and for PBDEs APCI gave higher sensitivity than APPI while for TBBPA-bis APCI and APPI showed similar performance. ESI was the best option for TCBPA, TBBPA and HBCDs. Detection limits were between 20 and 59 fg for the compounds analyzed by ESI, 0.10 and 0.72 pg for PBDEs and 6 pg for TBBPA-bis. The matrix effect of sewage sludge extract was also tested showing negligible ion suppression for APCI and an increase of the background level of all investigated pollutants leading to a worsening of the limits of quantification by a factor between 1.2 and 3.3. The UPLC-APCI/MS/MS method for PBDEs, after pressurized liquid extraction (PLE), was validated by comparison with the concentration values from the NIST 1944 standard reference material. The advantages of the methods include low detection limits, PBDE congeners specificity using selected multiple reaction monitoring (MRM) transitions, and the absence of thermal degradation of higher PBDE congeners, especially BDE-209. The methods were applied for the determination of the above reported flame retardants in sewage sludge in order to get more information about the degradation on PBDEs (in particular BDE-209) during municipal wastewater treatments.     

Photoluminescence analyses of hydrogenated amorphous silicon nitride thin films

Silicon-rich hydrogenated amorphous silicon nitride (a-SiN_x:H) films were grown by plasma enhanced chemical vapor deposition (PECVD) with different r=NH₃/SiH₄ gas flow ratios. The optical absorption characteristics were analyzed by Fourier transform infrared (FTIR) and UV-visible transmittance spectroscopies. The recombination properties were investigated via photoluminescence (PL) measurements. As r was increased from 2 to 9, the PL emission color could be adjusted from red to blue with the emission intensity high enough to be perceived by naked eye at room temperature. The behaviors of the PL peak energy and the PL band broadness with respect to the optical constants were discussed in the frame of electron-phonon coupling and band tail recombination models. A semiquantitative analysis supported the band tail recombination model, where the recombination was found to be favored when the carriers thermalize to an energy level at which the band tail density of states (DOS) reduces to some fraction of the relevant band edge DOS. For the PL efficiency comparison of the samples with different nitrogen contents, the PL intensity was corrected for the absorbed intensity fraction of the incident PL excitation source. The resulted correlation between the PL efficiency and the subgap absorption tail width further supported the band tail recombination model.     

Observations of the atmospheric boundary layer across the land-sea transition zone using a scanning Mie lidar

Optical properties of the atmospheric boundary layer (ABL) above the land-sea transition interface were measured using a scanning Mie lidar located 30 km away from the Adriatic coast. Based on the two-dimensional range-height-indicator scans, detailed information on the ABL was obtained, including parameters such as atmospheric optical depth, aerosol extinction coefficient and the height of the ABL. The presented case study indicates that the height of the ABL in the land-sea transition zone and the adjacent mountainous region was changing rapidly due to highly variable atmospheric conditions.     

Spectroscopic requirements for ACCURATE, a microwave and infrared-laser occultation satellite mission

The proposed satellite mission ACCURATE consists of a small constellation of satellites in low Earth orbit, combining microwave occultation for thermodynamic state profiling with infrared-laser occultation for greenhouse gas and line-of-sight wind profiling. The mission aims to detect six greenhouse gas molecules with four additional isotopologues (H₂O, CO₂, CH₄, N₂O, O₃, CO, ¹³CO₂, OC¹⁸O, HDO, and H₂¹⁸O) in the upper troposphere and lower stratosphere in the 4000-5000 cm⁻¹ spectral region. Greenhouse gas profiles will be retrieved to within 1-2% accuracy using a ‘differential’ method, requiring two spectral points for each species - one to sample the spectral line and the other nearby to sample the baseline.An estimation of retrieval errors for the ACCURATE mission reveals that errors in spectroscopic line parameters dominate all other error sources. Poor knowledge of the spectroscopy introduces systematic errors into the retrieved greenhouse gas profiles. Using a simple approach, it was shown that the best line parameters currently available are too large to allow retrievals of greenhouse gases to within the stated ACCURATE mission goals of 1% accuracy for CO₂ and 2% for all other species. Therefore, spectroscopic line parameters for targeted lines need to be improved before the ACCURATE mission can be launched. Requirements have been formulated in this direction, and laboratory experiments outlined that could meet these requirements.