No abstract

In our discussion of the use of global warming potential (GWP) values in the Howarth et al (2011) paper, our text implies that the GISS group's 2009 and 2010 papers (Shindell et al 2009 andUnger et al 2010) were contradictory. Such an interpretation does not reflect the conclusions of those papers and was not our intention. First, the 2009 and 2010 papers address GWP and radiative forcing, respectively. Our intentions in that paragraph were (a) to illustrate the possible ways that the GWP and radiative forcing discussions in the scientific community were misapplied to lifecycle analysis of greenhouse gas emissions from unconventional gas extraction, and (b) to underscore that the reasonable questions about GWP raised by Shindell et al (2009) are a justification for retaining a broader, rather than narrower, range of GWP possibilities for this calculation.

In our discussion of the use of global warming potential (GWP) values in the Howarth et al (2011) paper, our text implies that the GISS group's 2009 and 2010 papers (Shindell et al 2009 andUnger et al 2010) were contradictory. Such an interpretation does not reflect the conclusions of those papers and was not our intention. First, the 2009 and 2010 papers address GWP and radiative forcing, respectively. Our intentions in that paragraph were (a) to illustrate the possible ways that the GWP and radiative forcing discussions in the scientific community were misapplied to lifecycle analysis of greenhouse gas emissions from unconventional gas extraction, and (b) to underscore that the reasonable questions about GWP raised by Shindell et al (2009) are a justification for retaining a broader, rather than narrower, range of GWP possibilities for this calculation. AbstractNew techniques to extract natural gas from unconventional resources have become economically competitive over the past several years, leading to a rapid and largely unanticipated expansion in natural gas production. The US Energy Information Administration projects that unconventional gas will supply nearly half of US gas production by 2035. In addition, by significantly expanding and diversifying the gas supply internationally, the exploitation of new unconventional gas resources has the potential to reshape energy policy at national and international levels-altering geopolitics and energy security, recasting the economics of energy technology investment decisions, and shifting trends in greenhouse gas (GHG) emissions. In anticipation of this expansion, one of the perceived core advantages of unconventional gas-its relatively moderate GHG impact compared to coal-has recently come under scrutiny. In this paper, we compare the GHG footprints of conventional natural gas, unconventional natural gas (i.e. shale gas that has been produced using the process of hydraulic fracturing, or 'fracking'), and coal in a transparent and consistent way, focusing primarily on the electricity generation sector. We show that for electricity generation the GHG impacts of shale gas are 11% higher than those of conventional gas, and only 56% that of coal for standard assumptions.

Assessment of the surface tension of low-energy solids by means of easy to perform contact angle measurements would be very attractive. Two different approaches are frequently reported to be very promising in this respect. We have evaluated these approaches using mainly apolar surfaces, which present the simplest case possible. The "equation of state" approach, which uses a single parameter, correctly predicts the results on FC722 (perfluoropolyacrylate) and FEP (poly(tetrafluoroethylene-cohexafluoropropylene)), but shows systematic deviations on the surfaces of octyltrichlorosilane (self-assembled on glass) and PE (polyethylene). The "surface tension components" approach uses three parameters. The surface tension is split into a van der Waals component, a Lewis acid component, and a Lewis base component. The determination of the surface tension of apolar surfaces yields reasonably consistent results when using a large set of contact angle data. However, the present results indicate important differences with previously reported values of the van der Waals components of some fluids, i.e., dimethyl sulfoxide (DMSO), formamide, diiodomethane, and 1-bromonaphthalene. The latter two appear not to be apolar in nature when obtained from measurements on FC722 or FEP. The difference with previous reports is due to a discrepancy between the contact angles of diiodomethane and 1-bromonaphthalene measured on either FC722 or PE. It is concluded that neither the "equation of state" nor the "surface tension components" approach can account for all experimental results. The present use of contact angle measurements appears to be limited to the estimation of the surface tension of apolar surfaces, using the "surface tension components" approach.

The etching process of polycrystalline tin-doped indium oxide (ITO) films in HC1 solutions is investigated by kinetic and electrochemical experiments and the patterning characteristics are examined by scanning electron microscopy. The influence of oxidizing agents on the etching behavior is studied. A model is proposed in which ITO is first attacked by undissociated HC1 molecules, forming a surface intermediate which is mobile on the surface. This intermediate can react with HC1 molecules or with the oxidizing agent. The competition between these two reactions determines the kinetics and the patterning characteristics of the dissolution process. A kinetic rate law is derived that predicts the etch rate in FeC1JHC1 solutions. A good agreement between experimental and calculated values is obtained in a wide range of HC1 and FeC13 concentrations.

Tin-doped indium oxide films, prepared by dc magnetron sputtering, have been investigated with respect to their etching behavior in a large number of acids. The etch rate in acids other than the halogen acids is extremely low. The films dissolve at a rate convenient for practical use in concentrated aqueous solutions of halogen acids. Experiments in HC1 solutions diluted with solvents with a low dielectric constant show that the undissociated halogen acid is the active agent for the etching process. A mechanism is proposed to explain the observed results. Addition of I2 or FeC13 to HC1 solutions increases the etch rate substantially. Voltammograms and etching experiments under potentiostatic control show that this is a nonelectrochemical effect.

No abstract

Tin-doped indium oxide (ITO) films, prepared by dc magnetron sputtering, were characterized by (photo ) electrochemical measurements in aqueous H,SO, solutions. Wavelength dependent photocurrent measurements were used to determine the optical band gap energy of these films. Electron excitation from the valence band to localized states in the band gap was observed. The presence of such energy levels resulted in an Urbach tail. Impedance measurements were used to determine the flatband potential and the charge carrier concentration of ITO. A change in the charge carrier concentration due to different deposition conditions resulted in a change of the resistivity and in a shift of the flatband potential. This shift could be explained by a Moss-Burstein-shift of the optical band gap.-