Evaluation of Composition-Dependent Collection Efficiencies for the Aerodyne Aerosol Mass Spectrometer using Field Data

In recent years, Aerodyne aerosol mass spectrometers (AMS) have been used in many locations around the world to study the size-resolved, nonrefractory chemical composition of ambient particles. In order to obtain quantitative data, the mass or (number) of particles detected by the AMS relative to the mass (or number) of particles sampled by the AMS, i.e., the AMS collection efficiency (CE) must be known. Previous studies have proposed and used parameterizations of the AMS CE based on the aerosol composition and sampling line relative humidity. Here, we evaluate these parameterizations by comparing AMS mass concentrations with independent measurements of fine particle volume or particle-into-liquid sampler (PILS) ion chromatography measurements for 3 field campaigns with different dominant aerosol mixtures: (1) acidic sulfate particles, (2) aerosol containing a high mass fraction of ammonium nitrate, and (3) aerosol composed of primarily biomass burning emissions. The use of the default CE of 0.5 for all campaigns resulted in 81–90% of the AMS speciated and total mass concentrations comparing well with fine particle volume or PILS measurements within experimental uncertainties, with positive biases compared with a random error curve. By using composition-dependent CE values (sometimes as a function of size) which increased the CE for the above aerosol types, the fraction of data points within the measurement uncertainties increased to more than 92% and the mass concentrations decreased by ～5–15% on an average. The CE did not appear to be significantly dependent on changes in organic mass fraction although it was substantial in the 3 campaigns (47, 30, and 55%).

Copyright 2012 American Association for Aerosol Research     

Assay of advanced glycation endproducts in selected beverages and food by liquid chromatography with tandem mass spectrometric detection

Food and beverages contain protein glycation adducts--both early-stage adducts and advanced glycation endproducts. We determined the concentrations of glycation adducts in selected food and beverages by liquid chromatography with triple quadrupole mass spectrometric detection. Cola drink contained low concentrations of glycation free adducts, whereas pasteurised and sterilised milk were rich sources of heat-stable glycation adduct residues--Nepsilon-carboxymethyl-lysine and Nepsilon-carboxyethyl-lysine. Laboratory rodent food was a rich source of advanced glycation endproducts. Measurement of glycation adducts in 24 h urine samples of normal and diabetic rats indicated that < 10% of glycation adduct residue consumption was excreted. Induction of diabetes by streptozotocin led to a 2-fold increase in urinary excretion of Nepsilon-carboxymethyl-lysine and a 27-fold increase in urinary excretion of methylglyoxal-derived hydroimidazolone Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine - the latter was decreased by high-dose thiamine therapy that also prevented the development of nephropathy. We conclude that cola drinks are a poor source of glycation adduct whereas thermally processed milk is rich in glycation adducts. Dietary glycation adducts residues probably have low bioavailability. Experimental diabetes is associated with a marked increase in exposure to endogenous formation of methylglyoxal-derived hydroimidazolone which is linked to the development of diabetic nephropathy.     

Defining global leadership in business environments.

Reviews evolutionary models of corporate globalization, distinguishing between international and global firms. To define global leadership, a distinction is made between the content of the activities of leaders in corporations within industries, and the style in which they conduct their affairs. The role of perception in cross-cultural interaction and leadership style is demonstrated by reviewing cross-national research. Alternatives to corporate global leadership are also suggested. Two models of global leadership training designed by multinational corporations are presented. Recommendations for preparing corporate leadership for global business are offered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Group Decision Making and Perceived Decision Success: The Role of Communication Medium.

The authors investigated the role of communication medium on the relationship between team member perceptions and decision success. Seventy-three 3-person groups participated in a consensus intellective task either face-to-face (FTF) or via computer-mediated communication (CMC). The participants also assessed their group's decision success and team member competencies. CMC group members' success perceptions significantly predicted their group's performance, but FTF group members' perceptions did not. Furthermore, only CMC group members' judgments regarding their group's problem-solving ability significantly predicted their decision success. Last, judgments of decision success mediated the relationship between perceptions of members' problem-solving ability and decision success only for CMC group members. Implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The cleanroom-free rapid fabrication of a liquid conductivity sensor for surface water quality monitoring

Conductivity is an important issue of water quality detection. Although there are a number of microfluidic liquid conductivity sensors, most of them were difficult to fabricate and required cleanroom facilities, which significantly increased the cost of sensors. Here, we presented a novel liquid conductivity sensor that was built on interdigitated copper electrodes. Microscale sensor electrodes can be fabricated through the modified microfabrication process without any help of cleanroom facilities. In comparison with FEA simulation and commercial conductivity device, measured results showed that the fabricated liquid conductivity sensor was able to measure a wide range of liquids. Considering the ease of fabrication and its low cost, the cleanroom-free fabricated sensors have much potential for water quality monitoring.     

Microbial and "de novo" transformation of dicarboxylic acids by three airborne fungi

Micro-organisms and organic compounds of biogenic or anthropogenic origins are important constituents of atmospheric aerosols, which are involved in atmospheric processes and climate change. In order to investigate the role of fungi and their metabolisation activity, we collected airborne fungi using a biosampler in an urban location of Montreal, Quebec, Canada (45 degrees 28' N, 73 degrees 45' E). After isolation on Sabouraud dextrose agar, we exposed isolated colonies to dicarboxylic acids (C(2)-C(7)), a major group of organic aerosols and monitored their growth. Depending on the acid, total fungi numbers varied from 35 (oxalic acid) to 180 CFU/mL (glutaric acid). Transformation kinetics of malonic acid, presumably the most abundant dicarboxylic acid, at concentrations of 0.25 and 1.00 mM for isolated airborne fungi belonging to the genera Aspergillus, Penicillium, Eupenicillium, and Thysanophora with the fastest transformation rate are presented. The initial concentration was halved within 4.5 and 11.4 days. Other collected fungi did not show a significant degradation and the malonic acid concentration remained unchanged (0.25 and 1.00 mM) within 20 days. Degradation of acid with formation of metabolites was followed using high performance liquid chromatography-ultraviolet detection (HPLC/UV) and gas chromatography-mass spectrometry (GC/MS), as well as monitoring of (13)C labelled malonic acid degradation with solid-state nuclear magnetic resonance spectroscopy (NMR). Using GC/MS we identified two processes driving chemical modifications of organic aerosol solutions: (I) formation of metabolites within several days, and (II) rapid release (< or =2 min) of organic molecules from fungal species upon the insertion of taxa in organic aerosol solutions. Metabolites included aromatic compounds and alcohols (e.g. trimethylbenzene and butanol). Potential atmospheric implications of our results are discussed.     

Suspended mechanical structures based on elastic silicon nanowire arrays

We demonstrate a bottom-up/top-down combined method for the fabrication of horizontally suspended, well-oriented and size-controlled Si nanowire arrays. Mechanical beamlike structures composed of multiple ordered arrays consecutively linked by transversal microspacers are obtained by this method. Such structures are used to investigate the mechanical elasticity of the nanowire arrays by atomic force microscopy. Our results point out important differences in the morphology and mechanical behavior of the fabricated nanowire-based structures with respect to equivalent bulk material structures.     

Changes in essential oil and physiological parameters of callus and seedlings of <Emphasis Type="Italic">Carum copticum</Emphasis> L. under in vitro drought stress

Drought stress exerts a considerable influence on the production of secondary metabolites, which have interesting biological properties and quite a number are of medicinal importance, in plants. Secondary metabolites also are unique sources for food additives, flavors and industrially important biochemical. They play a major role in the adaptation of plants to the environment and overcoming stress conditions. This study was carried out to elucidate the mechanism of drought stress in seedlings and calli of Carum copticum under in vitro condition by evaluating the physiological and enzymatic activities, and secondary metabolites. Seedlings of C. copticum were cultured in MS medium containing 0, 3 and 6% mannitol and calli were cultured in MS medium containing 1 µM 2,4-d, 4 µM BAP and different levels of mannitol (0, 3 and 6%). After 4 weeks, the enzymatic and physiological parameters were measured by adapting spectrophotometrically and the GC/MS was used for the identification of secondary metabolites. Drought stress induced by mannitol caused a progressive increase of proline and carbohydrates contents in both seedlings and calli and the activation of CAT and SOD enzymes. In addition, drought stress effected the essential oil compounds of seedlings and callus. As compared to the control, mannitol enhanced the percentage of thymol in seedlings and callus under treatment (18.7 and 20.8%) and γ-terpinene (20.0 and 24.6%) as major components. In vitro drought stress induced by mannitol effected the biochemical, physiological and metabolic responses, suggesting that its beneficial effect can be exerted on the main essential oil contents.     

Experimental and computational study of microfluidic flow‐focusing generation of gelatin methacrylate hydrogel droplets

This work presents the experimental and computational study of droplet generation for hydrogel prepolymer solution in oil using a flow‐focusing device. Effects of different parameters on hydrogel droplet generation and droplet sizes in a flow‐focusing device were investigated experimentally and computationally. First, three dimensional (3D) computational simulations were conducted to describe the physics of droplet formation in each regime and mechanism of three different regimes: squeezing, dripping, and jetting regime of hydrogel were investigated. Subsequently, the effects of viscosity, inertia force, and surface tension force on droplet generation, and droplet size were studied through these experiments. The experiments were carried out using different concentration of gelatin methacrylate (GelMA) hydrogel (5 wt % and 8 wt %) as the dispersed phase and two different continuous phase liquids (light mineral oil and hexadecane) with various concentrations of surfactant (0 wt %, 3 wt %, and 20 wt %). All experimental data was summarized by capillary number of dispersed phases and the continuous phases to characterize the different regimes of droplet generation and to predict the transition of dripping to a jetting regime for GelMA solution in flow‐focusing devices. It is shown that the transition of dripping to a jetting regime for GelMA happens at lower capillary numbers compared to aqueous solutions. Moreover, by increasing the viscous force of continuous phase or decreasing the interfacial force, the size of GelMA droplets was decreased. By controlling these parameters, the droplet sizes can be controlled between 30 μm and 200 μm, which are very suitable for cell encapsulation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43701.     

In-Situ Reduction of Promoted Cobalt Oxide Supported on Alumina by Environmental Transmission Electron Microscopy

Abstract  

Reduction of 12wt.%Co/0.5wt.%Re/α-Al₂O₃ Fischer–Tropsch catalyst has been studied in-situ in an environmental transmission electron microscope. Reduction of Co₃O₄ to metallic cobalt was observed dynamically at 360 °C under 3.4 mbar H₂. Structural and morphological changes were observed by high resolution transmission electron microscopy and scanning transmission electron microscopy imaging. The cobalt particles were mainly face centred cubic while some hexagonal close packed particles were also found. Reoxidation of the sample upon cooling to room temperature, still under flowing H₂, underlines the reactivity of the nanoparticles and the importance of controlling the gas composition and specimen temperature during this type of experiment. Similar behaviour was observed for a non-promoted catalyst. Imaging and analysis of the promoted sample before and after reduction indicated a uniform distribution of the promoter.