Organophosphorus and pyrethroid insecticide urinary metabolite concentrations in young children living in a southeastern United States city

Pesticide metabolites are routinely measured in the urine of children in the United States. Although the sources of these metabolites are believed to include residues in food from agricultural applications and residues from applications in everyday environments (e.g., homes), few studies have been able to demonstrate an association between indoor residential pesticide applications and pesticide metabolite concentrations. To better quantify the effects of potential risk factors related to demographics, household characteristics, occupation, and pesticide use practices on urinary biomarker levels, we performed a study in a city (Jacksonville, Florida) previously determined to have elevated rates of pesticide use. We enrolled a convenience sample of 203 children ranging in age from 4 to 6 years; their caregivers completed a questionnaire and the children provided a urine sample, which was analyzed for a series of organophosphorus and pyrethroid insecticide metabolites. The questionnaire responses substantiated much higher pesticide use for the study participants as compared to other studies. Urinary metabolite concentrations were approximately an order of magnitude higher than concentrations reported for young children in other studies. Few statistically significant differences (at the p < 0.05 level) were observed, however, several trends are worth noting. In general, mean urinary pesticide metabolite concentrations were higher for males, Caucasians, and those children living in homes with an indoor pesticide application occurring within the past four weeks. Comparing the urinary pesticide metabolite concentrations in this study to those reported in the NHANES and GerES studies showed that the children living in Jacksonville had substantially higher pyrethroid pesticide exposures than the general populations of the United States and Germany. Further research is needed in communities where routine pesticide use has been documented to obtain information on the most important routes and pathways of exposure and to develop the most effective strategies for reducing pesticide exposures for children.     

Enhancing and controlling the critical attributes of poly (N-vinylcaprolactam) through electron beam irradiation for biomedical applications

The primary aim of this body of work is to investigate the effect of an industrial scale electron beam sterilization process on novel PNVCL-based smart polymers. There is limited literature available that examines the effects of modifying PNVCL by electron beam irradiation, and as a means of potentially enhancing properties such as the lower critical solution temperature and mechanical behavior. Physically crosslinked poly(N-vinylcaprolactam)–vinyl acetate (PNVCL–VAc) copolymers were prepared by photopolymerization and were subsequently exposed to ionizing radiation via electron beam technology. The mechanical characteristics and phase transitions of the physically crosslinked PNVCL samples were tailored by controlling the electron beam irradiation dose. Importantly, PNVCL and PNVCL–VAc samples (5 wt % in solution) underwent a phase transition between 33.5 and 26.5 °C, following electron beam irradiation. Furthermore, all samples displayed a Young's modulus between 1024.3 and 1516.4 MPa depending on the addition of copolymer and electron beam irradiation dose. The industrial scale electron beam sterilization process proved successful in enhancing/modifying many key smart polymer properties, and this ability to formulate and sterilize in one step could prove a very attractive approach for many biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48639.     

Role and impact of surfactants in carbon nanotube dispersions and sorting

Carbon nanotubes (CNTs) are proving to be versatile nanomaterials that exhibit superior and attractive electrical, optical, chemical, physical, and mechanical properties. Different kinds of CNTs exist, and their associated properties have been actively explored and widely exploited from fundamental studies to practical applications. Obtaining high-quality CNTs in large volumes is desirable, especially for scalable electronic, photonic, chemical, and mechanical systems. At present, abundant but random CNTs are synthesized by various growth methods including arc discharge, chemical vapor deposition, and molecular beam epitaxy. An economical way to secure pristine CNTs is to disperse the raw soot of CNTs in solutions, from which purified CNTs are collected via sorting methods. Individual CNTs are generally hydrophobic, not readily soluble, requiring an agent, known as a surfactant to facilitate effective dispersions. Furthermore, the combination of surfactants, polymers, DNA, and other additives can enhance the purity of specific types of CNTs in confidence dispersions. With highly-pure CNTs, designated functional devices are built to demonstrate improved performance. This review surveys and highlights the essential roles and significant impacts of surfactants in dispersing and sorting CNTs.     

Laser ablative patterning of B4C and MoAlB ceramics for hydrophobic surfaces

Through a novel laser ablative patterning (LAP) process, the present work reported the increase in wetting contact angle of two ceramic materials, boron carbide (B₄C) and molybdenum aluminum boride (MoAlB). The LAP technique employed picosecond laser pulses to form a crosshatch pattern with micropillars on ceramic surfaces. The wetting behavior of both ceramic surfaces was successfully transitioned from hydrophilic (θ < 90°) to hydrophobic (θ > 90°), which was related to Wenzel and Cassie–Baxter mechanisms. Parameters such as laser fluence and number of laser scans were varied to study their effects on ceramic surface characteristics. Lunar dust adhesion experiments were performed on these hydrophobic ceramic surfaces, which showed that the adhesion of lunar soil simulant dust particles was significantly reduced in the patterned B₄C and MoAlB surfaces.     

Solubility and Aging of Calcium Silicate Hydrates in Alkaline Solutions at 25°C

Calcium silicate hydrate (C-S-H) gels are the principal bonding material in portland cement. Their solubility properties have been described, enabling pH and solubilities to be predicted. However, the gels also interact with other components of cements, notably alkalis. C-S-H has been prepared from lime and silicic acid in solutions of sodium hydroxide or potassium hydroxide and by the hydration of tricalcium silicate (C₃S) in sodium hydroxide solutions. Analyses of aqueous phases in equilibrium with 85 gels show that the aqueous calcium and silicon concentrations fit smooth curves over the range of increasing sodium concentrations. Where anomalous data occur, they correspond to solids with low lime contents: such gels are tentatively assumed to fall into a region where the presence of another gel phase influences the aqueous composition. Dimensional changes have been observed in the hydration products of C₃S as a function of alkali content and these may be relevant to the alkali-silica reaction. The significance of this and other data is discussed with reference to real cement systems.     

Effects of variations in incident heat flux when using cone calorimeter test data for prediction of full‐scale heat release rates of polyurethane foam

The development of methods to predict full‐scale fire behaviour using small‐scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data were obtained using cone calorimeter tests and infrared video‐based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests and in predicting results for thinner foams. Results indicated that because of sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Particle surface temperature measurements with multicolor band pyrometry

A noncontact, color‐band pyrometer, based on widely available, inexpensive digital imaging devices, such as commercial color cameras, and capable of pixel‐by‐pixel resolution of particle‐surface temperature and emissivity is demonstrated and described. This diagnostic instrument is ideally suited to many combustion environments. The devices used in this method include color charge‐coupled device (CCD), or complementary metal oxide semiconductor (CMOS) digital camera, or any other color‐rendering camera. The color camera provides spectrally resolved light intensity data of the image, most commonly for three color bands (Red, Green, and Blue,), but in some cases for four or more bands or for a different set of colors. The CCD or CMOS sensor‐mask combination has a specific spectral response curve for each of these color bands that spans the visible and often near infrared spectral range. A theory is developed, based on radiative heat transfer and camera responsivity that allows quantitative surface temperature distribution calculation, based on a photograph of an object in emitted light. Particle surface temperature calculation is corrected by heat transfer analysis with reflection between the particle and reactor wall for particles located in furnace environments, but such corrections lead to useful results only when the particle temperature is near or below the wall temperatures. Wood particle‐surface temperatures were measured with this color‐band pyrometry during pyrolysis and combustion processes, which agree well with thermocouple measured data. Particle‐surface temperature data simultaneously measured from three orthogonal directions were also mapped onto the surface of a computer generated 3‐D (three‐dimensional) particle model. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

Long-term patterns in Lake Champlain's zooplankton: 1992–2010

We examined patterns in Lake Champlain zooplankton abundance from 1992 to 2010 using summer data from five study sites. Rotifer abundance (#/m³) for many common taxa such as Polyarthra, Kellicottia, and Keratella declined lakewide in the mid-1990s which coincided with the invasion of zebra mussels (Dreissena polymorpha) into Lake Champlain. The only rotifer to increase in density following zebra mussel invasion was Conochilus which is a colonial species. Long-term shifts in copepod and cladoceran community composition can be attributed to the arrival of another invasive species in 2004–2005, the alewife (Alosa pseudoharengus). Our results support previous findings that alewife predation can impact larger bodied zooplankton within temperate lake systems. Following alewife invasion into Lake Champlain, body length of Leptodiaptomus and Daphnia retrocurva decreased to a size at or below known alewife feeding preferences. In addition, smaller bodied copepods (primarily Diacyclops thomasi) have increased in abundance since alewife invasion while juvenile copepods have declined. Our results suggest that post-alewife zooplankton patterns are most likely due to alewife size-selective feeding strategies. Observed long-term changes in zooplankton community structure have potential implications for the lake's food web dynamics, particularly recent declines in large bodied zooplankton which may release smaller plankton from top-down control.     

Versatile synthesis of self‐assembling ABA triblock copolymers with polymethyloxazoline A‐blocks and a polysiloxane B‐block decorated with supramolecular receptors

BACKGROUND: Self‐assembling amphiphilic block copolymers with incorporated, biologically relevant functionalities have received limited attention, partly due to the fact that biomolecules are not robust enough to synthetic manipulation, do not lend themselves readily to systematic studies due to their complexity and leach rather quickly from a vesicle or membrane when physically incorporated. Synthetic supramolecules are used as biomolecule mimics in functional membranes. RESULTS: Reaction conditions were established for the synthesis of a tosyl‐terminated siloxane end‐blocker, which serves as molecular weight control in the synthesis of polydimethylsiloxane (PDMS) and poly(dimethylsiloxane‐co‐methylhydrosiloxane) [P(DMS‐co‐MHS)] copolymers. Hydrosilylation reactions were investigated for the covalent coupling of synthetic supramolecules (18‐crown‐6 ether, hydroxybenzoate) to the polymer backbone using the methylhydrosiloxane repeat units as the anchor moiety. Using P(DMS‐co‐MHS) or derivatized P(DMS‐co‐MHS) copolymers as macroinitiator for the ring‐opening polymerization of 2‐methyl‐4‐hydroxy‐oxazoline led to the formation of poly[(dimethylsiloxane‐co‐methylhydrosiloxane)‐block‐oxazoline] [P(DMS‐co‐MHS‐b‐Ox)] ABA triblock copolymers with defined PDMS to PMHS ratios and controlled molecular weights. CONCLUSION: Derivatized P(DMS‐co‐MHS‐b‐Ox) ABA triblock copolymers synthesized using a novel versatile procedure undergo vesicle formation upon electroformation with vesicle diameters ranging from 2 to 10 µm. The size of the vesicle depends on the overall polarity of the macromolecule. Copyright © 2008 Society of Chemical Industry