Electrocondensation and evaporation of attoliter water droplets: Direct visualization using atomic force microscopy

Working with a biased atomic force microscope (AFM) tip in the tapping mode under ambient atmosphere, attoliter (10⁻¹⁸ L) water droplet patterns have been generated on a patterned carbonaceous surface. This is essentially electrocondensation of water leading to charged droplets, as evidenced from electrostatic force microscopy measurements. The droplets are unusual in that they exhibit a highly corrugated surface and evaporate rather slowly, taking several tens of minutes.      

Reaction of water-stable C60 aggregates with ozone

While the reactivity of C60 has been described in a variety of organic solvents, little information is available regarding aqueous-based reactions due to solubility limitations. In this study, a reaction between C60, as a nanoscale suspension, and dissolved ozone in the aqueous phase was investigated. Findings indicate a facile reaction occurs, resulting in aggregate dissolution concurrent with formation of water-soluble fullerene oxide species. Product analyses, including 13C NMR, MS (LDI), FTIR, UV-Vis, and XPS, indicate highly oxidized fullerene with an average of approximately 29 oxygen additions per molecule, arranged in repeating hydroxyl and hemiketal functionalities. These findings are significant in that they (1) demonstrate the feasibility of other aqueous-based fullerene chemistries, including those for alternative synthesis routes, which might otherwise be considered prohibitive on the basis of solubility limitations, and (2) imply that the aqueous reactivity of fullerene-based materials must be considered appropriately for accurate assessment of their transport, fate, and potential risk(s) in environmental systems.     

Pulsed-mode analysis of soft-X-ray radiation passing through capillary waveguides

Abstract

Soft-X-ray radiation passing through capillary waveguides is theoretically analysed by the pulsed-mode method. We consider the optical guiding by straight and tapered waveguides in the spectral range 100–2000 eV. As an example, we calculate the intensity distribution, transmission coefficient and gain factor for the radiation passing through SiO₂ waveguides.     

Cumulative Effects of Small Reservoirs on Streamflow in Northern Coastal California Catchments

With small reservoirs increasingly employed to meet human water needs, tools that consider cumulative effects of multiple small reservoirs through space and time are essential for understanding impacts of these spatially distributed stresses on catchment hydrology and related ecological processes. We used a GIS-based hydrologic model to predict streamflow impairment caused by 438 small reservoirs in a 743 km² study area in Sonoma County, California, USA. The GIS model was designed to consider the varying effects that these reservoirs have through the project area drainage network, as well as the varying effects they have over time (as reservoirs fill and no longer impair flow downstream). Results indicate that, at the onset of the water year (when reservoirs are assumed to be empty), more than 25 % of the drainage network below reservoirs is impaired by over 50 %. Nine weeks into a normal-type water year, approximately 25 % of the drainage network below reservoirs is impaired by at least 25 %; and at 15 weeks, five percent of the drainage below reservoirs is impaired at least 25 %. Impairment is more persistent in a dry-type year. Nine weeks into a dry year, almost 40 % of the drainage network below reservoirs is impaired by at least 25 %; and at 15 weeks, 25 % of the drainage is impaired by at least 25 %. Results illustrate that impairment caused by reservoirs varies appreciably over space, but as reservoirs fill over time, impairment is lower through most of the drainage network.     

Polyethylene materials with multifunctional surface properties by electrospraying chitosan/vitamin E formulation destined to biomedical and food packaging applications

A dual-bioactive layer based on antimicrobial chitosan and antioxidant vitamin E was immobilized onto PE surface using electrospraying as coating technique. Covalent bonding of the antibacterial/antioxidant layer was achieved through amide bonds or carbamate linkage using both 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysuccinimide or carbonyldiimidazole coupling agents, respectively. The chitosan/vitamin E formulation was characterized by rheological measurements. The vitamin E addition in chitosan matrix leads to changes in chitosan rheological properties, such as viscosity decrease with increasing vitamin E content, change of the gel-like behavior to a fluid-like behavior, which further influences the electrospraying process and deposited coating morphology. The new stratified hybrid materials with improved properties have been characterized by different techniques as attenuated total reflectance-Fourier transform IR spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), polyelectrolyte and potentiometric titration, contact angle titration, scanning electron microscopy (SEM) and antibacterial and antioxidative tests. The electrosprayed bioactive coatings exhibit antibacterial, antioxidant and pH responsive activity. The pH responsiveness was evidenced by switching from hydrophilic to hydrophobic surface at pH ≈ 6. The chitosan/vitamin E modified PE substrate inhibited the growth for three different bacterial strains (Gram-negative and Gram-positive) and presented good antioxidative properties, acting as DPPH radical scavenging surfaces. Moreover, the new obtained materials present good stability and maintain their antioxidative capacity even after subjecting to desorption in harsh medium because of relative strong electrostatic and hydrogen bonds interactions between components of the formulation. The obtained materials can find application in food packaging or in medical field where synergistic action of these bioactive compounds is required.     

Highly photoemissive polymer–transition metal complexes based on poly(2‐hydroxyethyl) methacrylate

The paper presents several new polymer complexes based on poly(2‐hydroxyethyl) methacrylate (P‐HEMA) and transition metals including Y³⁺, Eu³⁺, Tb³⁺ and Dy³⁺. Red‐, green‐, blue‐ and yellow‐emitting polymer complexes with remarkable photoluminescent (PL) properties, high degree of transparency and excellent processability both in bulk and in thin film were prepared and investigated. In the case of the prepared P‐HEMA–Eu³⁺ and P‐HEMA–Tb³⁺ polymer complexes, divinylbenzene was used as a crosslinker resulting a markedly enhanced PL emission, most probably due to the presence of the benzene rings which improve the efficiency of the energy transfer to the cation emissive centres. The prepared polymer complexes were structurally investigated through Fourier transform infrared and X‐ray photoelectron spectroscopies while atomic force microscopy was used to study the morphology of the prepared thin films. Steady‐state fluorescence spectroscopy and absolute PL quantum yield were used for the investigation of the luminescent properties. The impressive PL emission and the convenience of preparation in bulk or thin films could be important arguments for a wide area of applications ranging from photonic conversion materials in optoelectronic devices (light‐emitting diodes, flat‐panel displays) to full‐colour watermarks on special‐purpose papers or PL inks and coatings. © 2019 Society of Chemical Industry     

Surface properties and biocompatibility of cellulose acetates

The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Brief group therapy with low-achieving elementary school children.

The study encompassed 142 low achievers in 2 elementary schools (Grades 2-6) in Israel, all of whom received 4–6 weekly hours' assistance with their academic difficulties in school. After a random division of this sample into experimental and control groups, the former received an additional weekly session of group therapy of an interpersonal nature. The effect of this treatment was examined on 4 dependent variables: academic achievements, self concept, social acceptance, and locus of control. Results indicated significant gains for the experimental group on all these variables—gains that increased over time. Group therapy appears to contribute both to academic progress and to the psychological and social well-being of low-achieving pupils. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exurban development influences woodland bird composition

One of the fastest growing types of land-use change is exurban development—low-density housing outside urban service boundaries. However, how individual species are responding to exurban development remains uncertain. We monitored birds for 5 years across three housing density levels in northern California oak woodlands. We compared community and species responses to exurban development (4–16 ha parcels) with suburban and undeveloped natural areas. We found that individual species and groups of species exhibited variable responses to exurban development. Some species and guilds were impacted by exurban development to the same extent as suburban development while others were less sensitive to this type of land use. For example, the proportion of the bird community composed of tree-and-shrub feeders was similar between exurban and natural areas, whereas proportions of temperate migrants showed significant reductions at both suburban and exurban sites. Similarly, Northern Flicker, Hutton's Vireo, and Orange-crowned Warbler were equally rare in exurban and suburban sites, making large, undeveloped parcels essential for their conservation. By explicitly measuring ecological changes associated with parcel size and density this research provides valuable information to land-use planners on the consequences of zoning for biodiversity conservation.