Electrospinning is a technique used to produce micron to submicron diameter polymeric fibers. The surface of electrospun fibers is important when considering end-use applications. For example, the ability to introduce porous surface features of a known size is required if nanoparticles need to be deposited on the surface of the fiber or if drug molecules are to be incorporated for controlled release. Surface features, or pores, became evident when electrospinning in an atmosphere with more than 30% relative humidity. Increasing humidity causes an increase in the number, diameter, shape, and distribution of the pores. Increasing the molecular weight of the polystyrene (PS) results in larger, less uniform shaped pores. This work includes an investigation of how humidity and molecular weight affect the surface of electrospun PS fibers. The results of varying the humidity and molecular weight on the surface of electrospun PS fibers were studied using optical microscopy, field emission scanning electron micros...

Controlling Surface Morphology of Electrospun Polystyrene Fibers: Effect of Humidity and Molecular Weight in the Electrospinning Process

The study of noble gases in oceanic basalts is central to understanding chemical heterogeneity of the Earth’s mantle and origin of the atmosphere. In the terrestrial environment the abundances of noble gases are quite low because they were excluded from solid materials during planetary formation in the inner solar system. This low background inventory helps to make the noble gases excellent tracers of mantle reservoirs. In this context, mid-ocean ridge and ocean island basalts provide valuable windows into the Earth’s mantle. These oceanic basalts are not prone to the degree of contamination often observed in continental lavas that results from their passage through thick continental lithosphere and crust. Mid-ocean ridge basalts (MORBs) form by partial melting as the ascending mantle beneath spreading ridges reaches its solidus temperature, and MORBs are generally accepted to represent a broad sampling of the convecting upper mantle. Ocean island basalts (OIBs) represent melting ‘anomalies’ that are generally related to mantle upwelling. The extent to which ocean islands are derived from a thermal boundary layer in the deep mantle (e.g., as a mantle plume) or from chemical heterogeneities embedded within the mantle convective flow (e.g., as a mantle ‘blob’) has been debated for decades, and is not currently resolved. The isotope compositions of noble gases in oceanic basalts bear significantly on such debates over the chemical structure of the mantle. When oceanic basalts erupt as submarine lavas, their quenched rims of glass may contain high volatile abundances (especially when they are deeply erupted under elevated hydrostatic pressure), providing the best available opportunity for precisely characterizing the noble gas composition of the Earth’s mantle. In favorable cases, inclusions of melt or fluids trapped within magmatic phenocrysts and mantle xenoliths can also be precisely analyzed for noble gas composition.

Measurable changes in the isotope compositions of noble gases …

Noble Gas Isotope Geochemistry of Mid-Ocean Ridge and Ocean Island Basalts: Characterization of Mantle Source Reservoirs

This paper reports a simple spin-coating technique for rapidly fabricating three types of technologically important materials--colloidal crystal, macroporous polymer, and polymeric nanocomposite, each with high crystalline qualities and wafer-scale sizes. Dispersion of monodisperse silica colloids in triacrylate monomers is spin-coated onto a variety of substrates. Shear-induced ordering and subsequent polymerization lead to the formation of three-dimensionally (3D) ordered colloidal crystals trapped inside a polymer matrix. The thickness of as-synthesized colloidal crystal-polymer nanocomposite is highly uniform and can be controlled simply by changing the spin speed and time. Selective removal of the polymer matrix and silica spheres lead to the formation of large-area colloidal crystals and macroporous polymers, respectively. The wafer-scale process is compatible with standard semiconductor microfabrication, as multiple micrometer-sized patterns can be created simultaneously for potential device applications. Normal-incidence transmission spectra in the visible and near-infrared regions show distinct peaks due to Bragg diffraction from 3D ordered structures. The spin-coating process opens a new route to the fundamental studies of shear-induced crystallization, melting and relaxation.

Large-scale fabrication of wafer-size colloidal crystals, macroporous polymers and nanocomposites by spin-coating.

One century of arsenic exposure in Latin America: a review of history and occurrence from 14 countries

Aerobic methanotrophic bacteria are capable of utilizing methane as their sole energy source. They are commonly found at the oxic/anoxic interfaces of environments such as wetlands, aquatic sediments, and landfills, where they feed on methane produced in anoxic zones of these environments. Until recently, all known species of aerobic methanotrophs belonged to the phylum Proteobacteria, in the classes Gammaproteobacteria and Alphaproteobacteria. However, in 2007-2008 three research groups independently described the isolation of thermoacidophilic methanotrophs that represented a distinct lineage within the bacterial phylum Verrucomicrobia. Isolates were obtained from geothermal areas in Italy, New Zealand and Russia. They are by far the most acidophilic methanotrophs known, with a lower growth limit below pH 1. Here we summarize the properties of these novel methanotrophic Verrucomicrobia, compare them with the proteobacterial methanotrophs, propose a unified taxonomic framework for them and speculate on their potential environmental significance. New genomic and physiological data are combined with existing information to allow detailed comparison of the three strains. We propose the new genus Methylacidiphilum to encompass all three newly discovered bacteria.

Environmental, genomic and taxonomic perspectives on methanotrophic Verrucomicrobia.

Magmatic carbon dioxide (CO2) degassing has been documented before the 31 March 2000 eruption of Usu volcano, Hokkaido, Japan. Six months before the eruption, an increase in CO2 flux was detected on the summit caldera, from 120 (September 1998) to 340 metric tons per day (September 1999), followed by a sudden decrease to 39 metric tons per day in June 2000, 3 months after the eruption. The change in CO2 flux and seismic observations suggests that before the eruption, advective processes controlled gas migration toward the surface. The decrease in flux after the eruption at the summit caldera could be due to a rapid release of CO2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera.

https://science.sciencemag.org/content/sci/292/5514/83.full.pdf

Carbon Dioxide Degassing by Advective Flow from Usu Volcano, Japan

Diffuse emission of CO2, CH4 and ³He was investigated in the summit crater of Teide volcano, Tenerife, Canary Islands The results indicate that Teide volcano releases abundant CO2 not only from its active crater, but also from its flanks as diffuse soil emanations The spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations Our flux measurements indicate a total output of 380 ton·day−1 of CO2 and 16 on·day−1 of CH4 by diffuse degassing From the ³He/CO2 ratios and the CO2 flux we estimate a diffuse ³He flux of 0052 mol·year−1 Isotopic analysis of carbon in soil gas samples from sites of high soil CO2 flux indicates a magmatic origin for the CO2, also reported by high ³He/ 4He ratios of 550 and 587 Ra The origin of methane is more uncertain with low δ13C values suggesting a biogenic contribution

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98GL02561

Diffuse emission of carbon dioxide, methane, and helium-3 from Teide Volcano, Tenerife, Canary Islands

Diffuse emission of CO2 from Miyakejima volcano, Japan

We report the first detailed soil CO2 efflux survey carried out at Cerro Negro volcano, Nicaragua, Central America. Soil CO2 efflux values ranged from 0.5 to 35,000 g m−2 d−1. Spatial distribution of CO2 efflux shows that volcanic gas is mainly released from the summit crater and the fissures opened during the August 1999 eruption. The total CO2 output of Cerro Negro is conservatively estimated to be 2,800 t d−1, based on a study area of 0.58 Km². Contour maps of soil CO2 efflux, ground temperature, and δ13C(CO2) distributions support an important magmatic contribution for the total output of CO2 at Cerro Negro volcano.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001GL013709

Diffuse emission of carbon dioxide from Cerro Negro Volcano, Nicaragua, Central America

The global CO 2 discharge from subaerial volcanism has been estimated at ~300 Mt yr –1 . However, estimates of CO 2 emissions from volcanic lakes have not been considered. In order to improve this information, extensive research on CO 2 emissions of volcanic lakes worldwide has been performed. The observed normalized average CO 2 emission rates increase from alkaline (5.5 t km –2 d –1 ), to neutral (201.2 t km –2 d –1 ), to acid (614.2 t km –2 d –1 ) in volcanic lakes. Taking into account (1) normalized CO 2 emission rates, (2) the number of volcanic lakes in the world (~769), and (3) the fraction and average areas of the investigated alkaline, neutral, and acid volcanic lakes, the estimated global CO 2 emission from volcanic lakes is 117 ± 19 Mt yr –1 , with 94 ± 17 Mt yr –1 as deep-seated CO 2 . This study highlights the importance of a revision of the actual global CO 2 discharge from subaerial volcanism.

Nemesio M. Pérez

Papers

Carbon Dioxide Degassing by Advective Flow from Usu Volcano, Japan

Diffuse emission of carbon dioxide, methane, and helium-3 from Teide Volcano, Tenerife, Canary Islands

Diffuse emission of CO2 from Miyakejima volcano, Japan

Diffuse emission of carbon dioxide from Cerro Negro Volcano, Nicaragua, Central America

Global CO2 emission from volcanic lakes