Concentrations and gas-particle partitioning of PCDD/Fs in the urban air of Dalian, China

PCDD/Fs in the urban air of Dalian, China were monitored with high-volume active sampler from November 2009 to October 2010. The concentration of Cl4-8DD/Fs ranged from 3065 to 49538 fg m(-3), with an average of 10249 fg m(-3). The international toxic equivalents (I-TEQ) value of that was 61.8-1182 fg m(-3), with an average of 235 fg m(-3), which was comparable to those in the other urban locations around the world. It was found that the Cl4-8DD/Fs appeared to be present mainly in the particle phase during winter, spring and autumn, while during summer which were dominantly in gas phase. The ratio of Cl4-8DD/Fs present in particle phase increased with the increasing level of chlorination. The concentrations of PCDFs and PCDDs decreased with the increase of chlorinated level, while the concentrations of 2,3,7,8-PCDDs congeners increased with the increase of chlorination level. The homolog profiles of the concentrations of PCDFs presented were higher than those of the PCDDs, which indicated the PCDD/Fs pollution source of the air in Dalian was characteristic for thermal source pollution. The correlation analysis of meteorological parameters with the concentrations of Cl4-8CDD/Fs was conducted using SPSS packages, and it was found that the ambient temperature and atmospheric pressure were important factors influence the concentration of PCDD/Fs in the air. The respiratory risk and intake dioxins of the residents around the sampling sites were studied in the paper. It was found that Junge-Pankow model was much more accurate in predicting the gas-particle partitioning behavior of PCDD/Fs homologues during winter, while the Harner-Bidleman model shows better agreement with the measured data during winter and summer

Refining models of archaic admixture in Eurasia with ArchaicSeeker 2.0

We developed a method, ArchaicSeeker 2.0, to identify introgressed hominin sequences and model multiple-wave admixture. The new method enabled us to discern two waves of introgression from both Denisovan-like and Neanderthal-like hominins in present-day Eurasian populations and an ancient Siberian individual. We estimated that an early Denisovan-like introgression occurred in Eurasia around 118.8–94.0 thousand years ago (kya). In contrast, we detected only one single episode of Denisovan-like admixture in indigenous peoples eastern to the Wallace-Line. Modeling ancient admixtures suggested an early dispersal of modern humans throughout Asia before the Toba volcanic super-eruption 74 kya, predating the initial peopling of Asia as proposed by the traditional Out-of-Africa model. Survived archaic sequences are involved in various phenotypes including immune and body mass (e.g., ZNF169), cardiovascular and lung function (e.g., HHAT), UV response and carbohydrate metabolism (e.g., HYAL1/HYAL2/HYAL3), while “archaic deserts” are enriched with genes associated with skin development and keratinization

Product positioning and pricing decisions in a two-attribute disruptive new market

In disruptive innovation, a new entrant firm with fewer resources challenges the established incumbent firms. The new entrant firm offers an innovative product that is considered superior in new features appealing to a group of new customers, but inferior along the traditional performance attributes valued by mainstream customers. Previous research primarily focuses on the product strategies that could benefit the incumbent firms, thus, it is less unclear how the new entrant firm should strategize the innovative product. This article investigates the product pricing and positioning strategies for the new entrant firms who wholly invest in a single product. Our analytical model incorporates two horizontally distinct product attributes, where potential consumers have different preferences and reservation prices toward the two product attributes. We identify four product pricing and positioning strategies, and their corresponding optimal conditions. Our analysis shows that the product position is closely related to the customer valuation gap between the two attributes. As the innovative product will improve sufficiently on the traditional performance attributes, results from this study can be applied at different stage of product development by the new entrant firm

Application developers’ product offering strategies in multi-platform markets

Mobile application (app) developers usually face challenges in product offering decisions. Our research develops an analytical framework to address a product offering problem that app developers face when introducing paid or free apps in a two-platform market. We provide optimal conditions and platform decisions for each strategy (in single and two platforms) by providing a framework for offering either a paid or a free app. When offering a paid app, we identify platforms’ willingness-to-pays, user densities, and platform-specific app-launching costs as key factors that determine platform selection strategy; if a free app is considered, users’ disutility sensitivity to advertisement is an extra factor for app developers to consider. The developer\u27s intrinsic capability and the app\u27s nature form the quality upper bound for the app. When the quality upper bound is low and users are less sensitive to advertisement, these apps are often offered free in the app market. We find that if users’ disutility sensitivities to advertisements are small, introducing a free app is preferable to a paid app

Recent Advances in the One‐Step Synthesis of Distally Fluorinated Ketones

Fluorinated ketones are intriguing compounds in synthetic chemistry and life science‐related fields. The development of efficient methodologies to obtain these compounds is of significant importance and has therefore attracted considerable attention. This Minireview highlights recent progress made in the synthesis of fluorine‐containing ketones, with an emphasis on those methods in which the construction of carbonyl groups is synergetic with distal (β‐, γ‐, δ‐, etc.) incorporation of fluorine atoms or fluorinated groups.One step to fluorinated ketones: The development of efficient methodologies to obtain distally fluorinated ketones is a rapidly growing area of synthetic chemistry and life‐science‐related fields. In this Minireview, some recent important advances in this area are presented and their reaction mechanisms are also discussed.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137269/1/chem201504036.pd

Polychlorinated dibenzo-p-dioxin and dibenzofuran precursors and formation mechanisms during non-woodpulp chlorine bleaching process

There is great concern about decreasing the amounts of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) that are formed and emitted during the chlorine bleaching of pulp. The formation of PCDD/Fs during non-woodpulp chlorine bleaching was investigated in the study described here. Wheat straw was separated into three components, cellulose, hemicellulose, and lignin. Chlorination experiments were performed, and lignin and hemicellulose contributed more than cellulose to PCDD/F formation when the pulp was bleached using chlorine. The chemical components of lignin were identified by gas chromatography mass spectrometry, and nine possible PCDD/F precursors were quantified by gas chromatography tandem mass spectrometry. Spiked chlorination experiments were performed to investigate the effects of these compounds on PCDD/F formation. 4-Ethyl-2-methoxyphenol had the strongest effect on PCDD/F formation, followed by p-chlorophenol, and guaiacol. All the test compounds promoted polychlorinated dibenzofuran formation but had limited effects on polychlorinated dibenzo-p-dioxin formation. The results allowed mechanisms for the formation of PCDD/Fs from phenol, chlorophenol, catechol, and guaiacol to be proposed. (C) 2018 Elsevier Ltd. All rights reserved

Preparation and Properties of Opaque Polyethylene Terephthalate/TiO2 Filaments

The opaque polyethylene terephthalate (PET) filaments with different mass fractions of TiO2 particles were prepared by low-speed melt spinning and drafting. Basic structures including surface morphology, linear density, orientation degree and crystallinity, and properties including tensile and optical property of the PET/TiO2 filaments were systematically analyzed, especially the visual shielding property. The results showed that TiO2 particles were well-distributed on the filament surface without obvious aggregation, except when the mass fraction of TiO2 exceeded 6%. The addition of TiO2 increased the linear density of the PET filaments. The orientation degree of the filaments was positively correlated with the drafting ratio but hardly influenced by the mass fraction of TiO2. The crystallinity achieved the maximum when the mass fraction of TiO2 was 3% and then decreased gradually. The tenacity of the filaments reduced and the elongation at break enhanced initially and then decreased with the increasing TiO2 content. The opaque effect of the PET filaments improved significantly when the mass fraction of TiO2 was less than 6%, whereas the improvement of the opaque effect slowed down as the mass fraction of TiO2 increased further

Phenyltrichlorosilane-functionalized magnesium oxide microspheres: Preparation, characterization and application for the selective extraction of dioxin-like polycyclic aromatic hydrocarbons in soils with matrix solid-phase dispersion

Magnesium oxide microspheres functionalized with phenyltrichlorosilane (PTS-MgO) were synthesized by surface modification through silanization reaction, which was confirmed by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and N-2 adsorption-desorption. The result indicated that PTS-MgO not only possessed the ability of enhancing the retention with PAHs, but also weakening the interference from chlorinated compounds. As a sorbent for the matrix solid-phase dispersion (MSPD) extraction, PTS-MgO was used to selectively extract seven dioxin-like polycyclic aromatic hydrocarbons (DL-PAHs) from soil samples. Various parameters affecting the recoveries of seven DL-PAHs were investigated and optimized, such as sorbent/sample mass ratio, grinding time, rinsing and eluting conditions. Under the optimized conditions, the developed method combining MSPD with HPLC-FLD exhibited good sensitivity (0.02-0.12 ng g(-1) detection of limits) and linearity (linear correlation coefficient greater than 0.9997). Satisfactory recoveries with DL-PAHs spiked at two levels (10 and 80 ng g-1) were obtained in the range of 72.2-113.1% with RSD < 9.6%, indicating that PTS-MgO had a potential in MSPD extraction of DL-PAHs in soils. Additionally, the proposed MSPD-HPLC-FLD method was also verified by detecting seven DL-PAHs in the standard reference soil. Based on the developed method, DL-PAHs in soil samples were detected with the concentration ranging from 70.08 to 555.05 ng g(-1) dry weight (dw). The total toxic equivalency quotients (TEQ) of seven DL-PAHs varied from 9.93 to 143.94 ng TEQ/g dw. (C) 2017 Elsevier B.V. All rights reserved

Trifluoromethyl Benzoate: A Versatile Trifluoromethoxylation Reagent

Trifluoromethyl benzoate (TFBz) is developed as a new shelf-stable trifluoromethoxylation reagent, which can be easily prepared from inexpensive starting materials using KF as the only fluorine source. The synthetic potency of TFBz is demonstrated by trifluoromethoxylation–halogenation of arynes, nucleophilic substitution of alkyl (pseudo)­halides, cross-coupling with aryl stannanes, and asymmetric difunctionalization of alkenes. The unprecedented trifluoromethoxylation–halogenation of arynes proceeds smoothly at room temperature with the aid of a crown ether-complexed potassium cation, which significantly stabilizes the trifluoromethoxide anion derived from TFBz